JP5711994B2 - Insulation judgment method and insulation judgment system - Google Patents

Description

  The present invention relates to an insulation determination method and an insulation determination system for determining whether or not a riser portion of a submarine pipeline and a surrounding metal object are conductive or a conductive location.

Offshore marine structures such as sea berths that accept crude oil and gas offshore and fixed platforms that produce crude oil and gas contain personnel and equipment on numerous piles that are driven into the seabed and extend to the sea. In general, a deck having a flat surface is mounted on the deck. And these piles are generally made of unpainted steel in the sea or in the seabed soil, and are generally anticorrosive by a sacrificial anode.
In addition, crude oil and gas received at Seaverse, or crude oil and gas produced on a fixed platform are usually transported to an onshore base by a submarine pipeline. In general, this pipeline is covered with an anticorrosion coating in the sea or in the seabed, and is further electrically protected by a sacrificial anode.

Thus, both piles of offshore structures and submarine pipelines are cathodic, but the electrical properties of both differ greatly with respect to leakage resistance. That is, since the pile of an offshore structure is produced | generated with unpainted steel materials, the area which contacts seawater, soil, etc. is large, and leakage resistance is very small. On the other hand, the submarine pipeline is covered with anti-corrosion coating, and touches seawater and soil only through the exposed steel surface and sacrificial anode of the coating damage part, so the contact area is small and the leakage resistance is large compared to the pile of offshore structure .
This difference in leakage resistance has a great influence on the inflow amount of the anticorrosion current to the object to be protected. That is, the amount of inflow of the anticorrosion current is large for the corrosion-protected body having a small leakage resistance, and the amount of the corrosion-preventing current is small for the corrosion-protected body having a large leakage resistance.

  For this reason, when the corrosion protection body having a high leakage resistance and the corrosion protection body having a low leakage resistance are electrically connected to each other, the corrosion protection current of the corrosion protection body having a high leakage resistance is reduced to the corrosion protection body having a low leakage resistance. It flows in and is used for the anticorrosion of the to-be-corroded body having a small leakage resistance. Even when the marine structure pile and the submarine pipeline are connected, the anticorrosion current of the submarine pipeline with high leakage resistance flows into the pile of the offshore structure with low leakage resistance, not the electric protection of the submarine pipeline. Used for cathodic protection of piles of offshore structures.

For this reason, for example, among the sacrificial anodes of the submarine pipeline, sacrificial anodes within a range of several kilometers (km) from the point of conduction with the piles are used for the anticorrosion of the piles and are consumed in a short period of time. Problems arise.
Alternatively, when the seabed pipeline is electrically protected by using an external power supply, a large amount of corrosion protection current also flows into the pile, and even if the rated maximum output current of the external power supply is passed, The problem of not reaching.

As described above, the continuity between the submarine pipeline and the pile of the marine structure having greatly different leakage resistances has a serious adverse effect on the corrosion prevention of the submarine pipeline.
Therefore, it is necessary to make the submarine pipeline and the pile of the offshore structure electrically insulated from each other, and to independently protect each other.

Here, in order to electrically isolate the submarine pipeline and the pile of the offshore structure, the riser rises along the pile of the offshore structure when constructing the offshore structure or the submarine pipeline. It is necessary to work carefully so that the part does not come into contact with the pile.
In addition, the piles of offshore structures, pipe mounts, and on-board equipment are likely to be in contact with the reinforcing bars in the deck and to be connected to the reinforcing bars. For this reason, in the location where the riser portion penetrates the deck, for example, the riser portion is covered with a high-strength insulating material such as pressure-resistant rubber so that the riser portion and the reinforcing bar are not in direct contact.
Furthermore, on the deck, so that the riser portion does not connect with the pile of the marine structure via the pipe mount, the mounting equipment, the reinforcing bar in the deck, for example, between the pipe mount, the mounting equipment and the riser portion, Insert an insulation joint such as a flange type or monoblock type.
By taking these measures, the submarine pipeline and the pile of the offshore structure can be electrically insulated, and each can be independently electrically protected.

However, the insulation of the riser part's insulation joints deteriorates, or the riser part of the submarine pipeline is caused by steel marine dumping, such as marine dumping of remaining materials and other people's marine dumping. Is often connected to the offshore structure pile, and the submarine pipeline and the offshore structure pile are often connected.
Among them, it is conceivable to diagnose the insulation of the insulating joint of the riser portion by combining several methods described in European standards and NACE (National Association Of Corrosion Engineers) standards.

On the other hand, when the seabed pipeline and the pile of the marine structure are conducted via the ocean dumping etc. on the seabed, etc., the investigation of the conduction point is currently conducted by Remotely Operated Vehicle (ROV) The only way to find potential continuity by visual inspection by a diver.
However, if this conduction point is buried in the seabed soil due to the accumulation of dead creatures or changes in the sea floor, the deposit should be removed using a jet to investigate the conduction point. After removal, it is necessary to carry out visual observation with a ROV or a diver. For this reason, the cost and time are required for the investigation, and the burden on the worker is large.

In addition, whether or not the submarine pipeline and the piles of the offshore structure were actually conducted was determined by cutting off the marine dumping that may have caused conduction, before and after the cutting timing. This is done by monitoring changes in the seawater potential of the piles and submarine pipelines of the marine structure, or changes in the output current of the cathodic protection device.
Here, a metal body having a large unpainted surface in seawater, such as a pile of an offshore structure, usually returns to a natural corrosion state from an anticorrosion state (repolarizes). It takes months time. For this reason, monitoring for determining the presence or absence of conduction requires a long period of time.

Therefore, when a technology that can be applied to the determination of the conduction point between the submarine pipeline and the offshore structure is extracted from existing technologies, the technology disclosed in Patent Document 1 is embedded in the ground in parallel with each other. The method of detecting the contact position of the metal tube currently used from the ground surface is mentioned.
FIG. 14 is a diagram showing an example of detecting the contact position of the metal tube using the method of Patent Document 1.
In the figure, a metal tube 1001 to be investigated and a metal tube 1002 parallel to the metal tube 1001 are in contact at a point 1003. Here, the metal tube 1001 and the metal tube 1002 are embedded at a position substantially the same depth from the ground. FIG. 14 shows the positional relationship when the metal tube 1001 and the metal tube 1002 are viewed from above.
In addition, the transmitter 1004 in the figure applies an AC signal voltage having a frequency f1 between a contact 1006 with the metal tube 1001 and a current-carrying anode 1005 buried in the ground. In addition, the transmitter 1009 in the figure applies an AC signal voltage having a frequency f2 between a contact 1006 with the metal tube 1001 and a current-carrying anode 1010 buried in the ground.

  Then, the AC signal current output from the transmitter 1004 is connected to the metal tube 1001 and the metal tube 1002 from the contact point 1003 to the transmitter 1004 side (the left side in the same figure), as indicated by the solid line arrow in FIG. And the metal tube 1001 and the metal tube 1002 flow in the same direction from the contact point 1003 to the transmitter 1009 side (right side in the figure). Moreover, the alternating current signal output from the transmitter 1009 flows in the same direction in the metal tube 1001 and the metal tube 1002 from the contact point 1003 to the transmitter 1004 side, as indicated by the dashed arrow in FIG. On the transmitter 1009 side from the contact point 1003, the metal pipe 1001 and the metal pipe 1002 flow in opposite directions.

Here, when the magnetic sensor 1012 is moved in a direction (Y direction shown in the figure) orthogonal to the extending direction (X direction shown in the figure) of the metal pipe 1001 and the metal tube 1002 on the ground surface, this AC signal The peak position of the output of the magnetic sensor differs depending on the difference in the direction of current flow.
FIG. 15 is a diagram showing the peak position of the output of the magnetic sensor in the method of Patent Document 1.
As indicated by the solid line 1017 in the figure, on the right side (the transmitter 1009 side in FIG. 14) from the point 1003 where the metal tube 1001 and the metal tube 1002 are in contact, the AC signal current output from the transmitter 1004 is the metal tube. Since 1001 and the metal tube 1002 flow in the same direction, the position where the induced voltage generated in the magnetic sensor by these AC signal currents is maximum is between the metal tube 1001 and the metal tube 1002. On the other hand, on the left side of the point 1003 where the metal tube 1001 and the metal tube 1002 are in contact (on the transmitter 1004 side in FIG. 14), the AC signal current output from the transmitter 1004 is reversed between the metal tube 1001 and the metal tube 1002. The position where the induced voltage generated in the magnetic sensor by these AC signal currents is maximized by flowing in the direction is outside the metal tube 1001.

  On the contrary, as indicated by a broken line 1018 in the figure, on the right side of the point 1003 where the metal tube 1001 and the metal tube 1002 are in contact with each other, the AC signal current output from the transmitter 1009 is the metal tube 1001 and the metal tube 1002. , The position where the induced voltage generated in the magnetic sensor by these AC signal currents is maximum is outside the metal tube 1001. On the other hand, on the left side of the point 1003 where the metal tube 1001 and the metal tube 1002 are in contact with each other, the AC signal current output from the transmitter 1009 flows in the same direction in the metal tube 1001 and the metal tube 1002. The position where the induced voltage generated in the magnetic sensor by the current becomes maximum is between the metal tube 1001 and the metal tube 1002.

  Therefore, the magnetic sensor 1012 (FIG. 14) is extended in the extending direction of the metal tube 1001 and the metal tube 1002 at several locations on the ground surface with the metal tube 1001 and the metal tube 1002 considered to be in contact with each other. , And the position where the frequency f1 component of the output voltage of the magnetic sensor is maximized and the position where the frequency f2 component is maximized are measured. Then, based on the measurement result, a point where the position where the frequency f1 component is maximum and the position where the frequency f2 component is maximum of the output voltage of the magnetic sensor 1012 overlaps is acquired or estimated. It is considered that the metal tube 1001 and the metal tube 1002 are in contact at a point where the position where the frequency f1 component is maximum and the position where the frequency f2 component is maximum overlap.

FIG. 16 is a diagram illustrating an example in which the method of Patent Document 1 is applied to the insulation determination between the riser portion of the submarine pipeline and the pile of the offshore structure.
In the figure, a transmitter 1104 includes a contact 1106 on the land side (the side where the pipeline extends to the seabed) of the undersea pipeline 1119 on the marine structure side and the energization suspended in the sea near the sea surface. An AC signal voltage having a frequency f1 is applied between the anode 1105 and the anode 1105. The transmitter 1109 is connected between the contact 1106 on the marine structure side (the side where the pipeline extends to the seabed) of the undersea pipeline 1119 and the insulated anode 1110 hung in the sea. An AC signal voltage having a frequency f2 is applied to.

  And the conduction | electrical_connection position of the riser part 1120 of the submarine pipeline 1119 and the pile 1124 of an offshore structure is orthogonal to the vertical direction which the riser part 1120 extends in the area where the riser part 1120 and the pile 1124 adjoin. In addition, the magnetic sensor is moved in parallel to a virtual plane connecting the riser portion 1120 and the adjacent pile 1124. Then, as described in FIG. 14 and FIG. 15, by acquiring or estimating a point where the position where the frequency f1 component is maximum and the position where the frequency f2 component is maximum overlap in the output voltage of the magnetic sensor. The location where the riser portion 1120 and the pile 1124 are conducted is determined.

JP 2005-134159 A

However, the determination method described in FIG. 16 has the following problems.
The first problem is that the AC signal voltage having the frequency f2 applied from the land side of the submarine pipeline is likely to be almost zero at the riser portion that is the inspection location.
The AC signal voltage applied to the submarine pipeline increases the resistance of the steel pipe of the submarine pipeline. It becomes easy to attenuate. Here, marine structures such as sea berths and fixed platforms are often several kilometers (km) to several tens of kilometers or more away from the land side. For this reason, there is a high possibility that the AC signal voltage applied from the land side will be almost zero at the riser portion which is the inspection location.

In addition, the attenuation of the AC signal voltage applied from the land side of the submarine pipeline is greatly affected by the leakage resistance of the submarine pipeline, the smaller the leakage resistance, that is, the larger the steel exposed surface of the corrosion-resistant coating damaged part, Also, the greater the number of locations on the exposed steel surface, the easier the AC signal voltage will attenuate. Moreover, in the location where the submarine pipeline is not buried, the exposed steel surface of the damaged portion of the anticorrosion coating is exposed to seawater, so that the AC signal voltage is further easily attenuated.
Here, the submarine pipeline is usually electrically protected by installing sacrificial anodes such as half-bracelet type aluminum alloy anodes at equal intervals in the submarine pipeline. The sacrificial anodes installed at equal intervals cause the AC signal voltage to attenuate, as in the case where the exposed steel surface of the very large anticorrosion coating damage portion is distributed uniformly. Therefore, in a submarine pipeline that has been electrically protected by a sacrificial anode, the applied AC signal voltage is significantly attenuated even if the corrosion protection coating is not damaged.

When the submarine pipeline is not buried and the sacrificial anode is exposed in the seawater, the applied AC signal voltage is further easily attenuated.
As described above, in the method of FIG. 16 in which the method of Patent Document 1 is applied to the insulation determination between the riser portion of the submarine pipeline and the pile of the offshore structure, the AC signal voltage applied from the land side of the submarine pipeline is attenuated. However, it is conceivable that the signal level necessary for the determination cannot be obtained in the riser portion.

As a countermeasure for this problem, it is conceivable to apply an AC signal voltage of frequency f2 to the submarine pipeline at the seabed near the riser portion, not on the land side of the submarine pipeline. In this case, the anticorrosion coating at the location where the AC signal voltage is applied is removed, the cable is connected to the exposed steel surface, and the steel exposed surface to which the cable is connected is further covered with the anticorrosion coating. Then, a transmitter with frequency f2 (1109 in FIG. 16) is installed on the offshore structure, and a cable connected to the steel surface of the submarine pipeline is connected to this transmitter at the bottom of the sea to generate an AC signal voltage with frequency f2. Apply.
However, this method requires a lot of work on the sea floor. The depth of the sea floor is often several tens of meters at sea berths and several tens to three hundreds of meters at fixed platforms, and it is very expensive to perform many tasks on the sea floor, and the burden on workers is large. .

Further, the second problem of the determination method described in FIG. 16 is that the output of the magnetic sensor changes greatly due to a change in the distance between the magnetic sensor and the riser portion or the pile, which may result in erroneous determination. There is a point.
In order to accurately determine the location of conduction between the riser portion and the pile by the method of FIG. 16, the magnetic sensor is parallel to the virtual plane connecting the riser portion and the adjacent pile and the vertical of the riser portion extends. It is necessary to move while maintaining orthogonality to the direction. For this purpose, the distance between the magnetic sensor and the riser part and the distance between the magnetic sensor and the pile are detected, the attitude of the magnetic sensor is controlled based on the detection result, and the distance between the magnetic sensor and the riser part and the pile is corrected. There is a need to do. Adding these functions to a magnetic sensor is very expensive.

  The present invention has been made in consideration of such circumstances, and its purpose is to determine whether or not the riser portion of the submarine pipeline and the surrounding metal objects are conductive and to determine the conductive location. It is to provide a method and an insulation determination system.

[1] The present invention has been made to solve the above-described problems, and an insulation determination method according to an embodiment of the present invention is a submarine terminal provided in the sea and a power source electrically connected to the submarine terminal. The metal tube and the structure by an insulating measurement system including a power source that can be connected to a metal tube that is installed under the sea surface and over the sea and that is electrically protected against the sea surface, and a measurement device that measures current. Alternatively, an insulation determination method for determining insulation between a conductor conducting to a structure, wherein the power source applies a voltage between the underwater terminal and the metal tube, and the measurement is performed. The apparatus measures at least one of a current flowing through the metal tube, a current flowing through the structure, or a current flowing through the conductor, and determines at least one of a magnitude or a direction of the current measured by the measuring apparatus as a predetermined value. Standard By comparison, or, in comparison the current measured by the measuring device size or orientation of at least one in a plurality of locations, and wherein the determining at least one of quality or continuity portion of the insulating.

  [2] The insulation determination method according to an aspect of the present invention is the insulation determination method described above, wherein the structure includes a pile installed over the sea and in the sea and fixed to the seabed, and the measurement is performed. The apparatus is characterized by measuring a current flowing through the pile.

  [3] Moreover, the insulation determination method according to an aspect of the present invention is the insulation determination method described above, wherein the structure includes a plurality of piles installed over the sea and in the sea and fixed to the seabed, The power source applies a voltage between the underwater terminal and the metal pipe, and the measuring device measures a current flowing through the plurality of piles.

[4] Further, the insulation determination method according to an aspect of the present invention is the insulation determination method described above, wherein the structure includes a plurality of piles installed over the sea and in the sea and fixed to the seabed, The power source applies an alternating voltage between the underwater terminal and the metal pipe, and the measuring device measures the phase of the alternating current flowing through the first measurement point of one of the piles, Based on the phase of the measured alternating current, the phase of the alternating current flowing through the second measurement point is measured, the position where the direction of the alternating current is reversed, that is, the position where the phase is reversed , and the phase reversed position is determined. It is determined that the conductor portion is electrically connected to the metal pipe .

  [5] An insulation determination method according to an aspect of the present invention is the above-described insulation determination method, wherein the metal tube is in contact with an insulation joint at an end portion on the sea, and more than on the sea and the insulation joint. A voltage is applied by the power source on the sea surface side, and is supported by a structure on the sea surface side from the place where the voltage is applied to the power source at sea, the insulating joint is in contact with the conductor, and the measuring device is The current value of the current that flows between the portion where the voltage is applied by the power source and the insulating joint of the metal tube, or the metal tube from the location where the voltage is applied by the power source of the metal tube One of the current values of the current flowing through the section between the parts supported by the structure is measured.

  [6] An insulation determination method according to an aspect of the present invention is the insulation determination method described above, wherein the metal tube is applied with a voltage by the power supply at sea, and the voltage is applied to the power supply at sea. The measurement device is supported by the structure on the sea surface side from the place where it is applied, and the measuring device is a current value of the current flowing through the sea surface side and the sea part of the metal tube from the position where the metal tube is supported by the structure. And measuring a current value of a current flowing through a section of the metal tube from a location where the metal tube is supported by the structure to a location where the metal tube is applied with a voltage by the power source. It is characterized by.

[7] An insulation determination method according to an aspect of the present invention is the above-described insulation determination method, wherein the metal tube is applied with a voltage by the power supply at sea, and the voltage is applied to the power supply at sea. It is supported on a structure at sea side than portions to be applied, the measuring device, the metal tube, those gold genus tube current flowing in the sea-side and sea portions than portions to be supported by the structure The current value is measured.

  [8] An insulation determination method according to an embodiment of the present invention is the above-described insulation determination method, wherein the insulation determination method according to [5] is performed, and a measured current value is a predetermined value. If it is less than the threshold value, the insulation determination method according to [6] or [7] is further performed, and the metal tube measured by the insulation determination method according to [6], The current value of the current that flows on the sea surface side and the sea part from the location where the metal tube is supported by the structure, and the metal tube from the location where the metal tube is supported by the structure is the power source. If the difference between the current value of the current flowing through the section up to the location where the voltage is applied is less than a predetermined threshold, or the current value of the power source and the insulation determination method according to [7] above If the difference from the current value measured in is less than the predetermined threshold Furthermore, the insulation determination method by measuring the currents of the plurality of piles as described in [3] above is performed, and the insulation determination method as described in [4] above is further performed on the piles in which the current is confirmed. It is characterized by.

[9] An insulation determination system according to an aspect of the present invention is an insulation determination system that measures current by any one of the insulation determination methods described above, and includes a display unit that displays a message, and the current A control unit that controls the display unit so as to display an instruction to install a sensor for current measurement by the measuring device at the measurement location, and an input unit that obtains a notification that the sensor has been installed. When the input unit obtains the notification , the control unit performs an insulation determination based on a current measured by the measuring device .

  According to the present invention, the presence / absence of conduction between the riser portion of the submarine pipeline and the surrounding metal object can be easily determined.

It is a block diagram which shows the functional block structure of the insulation measuring system in one Embodiment of this invention. It is the schematic which shows the structure of the riser used as the object of insulation determination in the same embodiment, and an offshore structure. In the same embodiment, it is a figure which shows the example of installation of the insulation measurement system 100 in the case of determining the presence or absence of conduction | electrical_connection between the riser 210 and the pile 310-1 by subsurface sea conductors, such as an ocean dumping thing. In the embodiment, it is a figure which shows the example of installation of the insulation measuring system 100 in the case of determining the contact location of the riser 210 and the pile 310-1. In the same embodiment, it is a figure which shows the example of installation of the insulation measuring system 100 in the case of determining the insulation quality of the insulator 220. FIG. In the embodiment, it is a figure which shows the example of installation of the insulation measurement system 100 in the case of determining the insulation quality of the insulated joint 230. FIG. In the same embodiment, it is a block diagram which shows the functional block structure of the insulation measuring system which displays the determination procedure. 4 is a flowchart illustrating a processing procedure performed by a control unit 623 in the embodiment. 4 is a flowchart illustrating a processing procedure performed by a control unit 623 in the embodiment. It is a circuit diagram which shows the structure of the model which conducted the experiment of conduction | electrical_connection determination with a riser and a pile. It is a figure which shows the experimental result of the conduction | electrical_connection determination with a riser and a pile. It is a circuit diagram which shows the part regarding the magnetic sensor of the structure of the model which conducted the experiment of conduction | electrical_connection location detection of a riser and a pile. It is a figure which shows the experimental result of a conduction | electrical_connection location detection with a riser and a pile. It is a figure which shows the example which detects the contact position of a metal tube using the method of patent document 1. FIG. It is a figure which shows the peak position of the output of a magnetic sensor in the method of patent document 1. FIG. It is a figure which shows the example which applies the method of patent document 1 to the insulation determination with the riser part of a submarine pipeline, and the pile of an offshore structure.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram showing a functional block configuration of an insulation measurement system according to an embodiment of the present invention. In the figure, an insulation measurement system 100 includes an AC signal voltage application device 110 and an AC signal current measurement device (measurement device) 120. The AC signal voltage application device 110 includes an AC signal current transmission unit (power source) 111, an AC signal current setting unit 112, an underwater side terminal 113, and a riser side terminal 114. The AC signal current measurement device 120 includes a magnetic sensor 121 and an AC signal current detection unit (current detection unit) 122.

The insulation measurement system 100 is a system used for determining electrical insulation between a metal pipe (hereinafter simply referred to as “riser”) used in a riser portion of a submarine pipeline and a metal object around the riser. The AC signal voltage is applied between the riser and the current-carrying terminal (underwater terminal 113) provided in the sea (that is, the AC signal current is conducted), and the AC at the measurement point set in the riser or the like Measure the signal current.
The AC signal voltage application device 110 applies an AC signal voltage between the riser and a current-carrying terminal provided in the sea.
The AC signal current transmission unit 111 outputs an AC signal current.

The underwater terminal 113 is a terminal installed in the sea. As the underwater terminal 113, for example, a small-diameter bare steel tube, a bare electric wire, or a conductor such as an insoluble anode used in external power supply type anticorrosion is used.
The riser-side terminal 114 is a terminal that is electrically connected to the riser. For example, when the riser is a steel pipe made of a magnetic material, the riser side terminal 114 is generated by a magnet, and the riser side terminal 114 is brought into close contact with the steel surface of the riser by magnetic force. Alternatively, the riser side terminal 114 may be generated by an unmagnetized conductor, and the steel surface of the riser and the riser side terminal 114 may be brought into contact with each other and installed by wrapping with a string or the like. .
The underwater side terminal 113 and the riser side terminal 114 are each connected to the AC signal current transmission unit 111 by a covered electric wire. The AC signal current transmission unit 111 is electrically connected to the undersea terminal 113 via the covered electric wire, and is electrically connected to the riser 210 via the covered electric wire and the riser side terminal 114, and between the underwater side terminal 113 and the riser 210. Apply AC signal voltage.

The AC signal current setting unit 112 receives user settings for the magnitude and frequency of the AC signal current, and controls the AC signal current transmission unit 111 to output the AC signal current having the magnitude and frequency set by the user. To do. At that time, the frequency of the AC signal current transmission unit 111 is a frequency excluding the commercial frequency of 50 Hz or 60 Hz and the harmonic frequency thereof, thereby reducing the influence of noise induced by the commercial frequency. It can be suppressed and the risk of erroneous measurement due to noise can be reduced.
The AC signal voltage application device 110 does not include the AC signal current setting unit 112, and the AC signal current transmission unit 111 outputs an AC signal current having a predetermined AC signal current value and a predetermined frequency. May be. Thereby, the apparatus configuration can be simplified. On the other hand, the AC signal voltage application device 110 includes an AC signal current setting unit 112, and the frequency component set by the AC signal current setting unit 112 by synchronizing the AC signal current transmission unit 111 and the AC signal current detection unit 122. Only the AC signal current having the same frequency as that of the AC signal current can be measured by the AC signal current detector 122.
For this reason, even if the energized AC signal current is buried in the noise, only the target component having the exact same frequency as the energized AC signal current can be extracted. It becomes possible.

The AC signal current measuring device 120 measures the magnitude and phase of the AC signal current flowing through the measurement target.
The magnetic sensor 121 detects a magnetic field generated around a measurement target such as a riser by the AC signal current output from the AC signal voltage application device 110. Various types of magnetic sensors can be used as the magnetic sensor 121, which are roughly classified into a type that detects a magnetic field of a closed magnetic path and a type that does not require a closed magnetic path.

As a magnetic sensor for detecting a magnetic field of a closed magnetic circuit, for example, a current transformer (Current Trans-former; CT) in which a winding is wound around an annular iron core can be used. In the method of measuring an alternating current signal in CT, first, a closed magnetic circuit is constituted by an annular iron core so as to surround a measurement object. Then, a magnetic flux is generated in the closed magnetic circuit core due to the AC signal current flowing in the measurement target (primary side), and this magnetic flux crosses the winding (secondary side) applied to the closed magnetic circuit core, thereby the primary current, A principle is used in which a secondary current is measured that is proportional to the signal current flowing through the measurement target and inversely proportional to the number of secondary windings.
In addition, a Hall element type clamp meter is used as the magnetic sensor 121, and a Hall element is arranged in the gap in the magnetic path, and the magnetic flux passing through the Hall element is proportional to the magnitude of the magnetic field component to be detected. You may make it measure by converting into.
On the other hand, as a magnetic sensor that does not require a closed magnetic circuit, an MR sensor using a magnetoresistive effect, an MI sensor using a magnetic impedance effect, or the like can be used. In particular, in the determination of the conduction point between the riser and the pile, which will be described later, the determination can be made more easily by using a magnetic sensor that does not require a closed magnetic path.

The AC signal current detection unit 122 detects and displays the magnitude and phase of the AC signal current output from the AC signal voltage application device 110 that flows through the measurement target such as a riser based on the magnetic field intensity detected by the magnetic sensor 121. . At that time, the AC signal current detector 122 is synchronized with the AC signal current transmitter 111 in order to detect the phase. For example, a lock-in amplifier can be used as the AC signal current detection unit 122 synchronized with the AC signal current transmission unit 111 in this way.
On the other hand, depending on the measurement contents, the AC signal current detection unit 122 may perform measurement without synchronizing with the AC signal current transmission unit 111. As the AC signal current detector 122 that is not synchronized with the AC signal current transmitter 111, for example, a voltmeter such as a digital multimeter can be used.

When a digital multimeter is used as the AC signal current detection unit 122, it is considered that a specific frequency component cannot be extracted, so that if the current to be measured includes noise, the determination accuracy may be reduced, and phase detection may be performed. Although it is not possible, the device configuration can be simplified.
The digital multimeter measures the insulation between the riser 210 and the offshore pipe 240 (measures the insulation quality of the insulation joint) and places where the deck part 320 supports the riser 210 (hereinafter referred to as “deck penetration part”). Measurement that can be performed without using phase information, such as measurement of presence / absence of contact between the reinforcing bar in the deck and the riser, and measurement of presence / absence of conduction between the pile 310 and the riser 210 (conduction location between the pile 310 and the riser 210) It can be used for measurement other than the specific measurement.

In order to measure the magnitude and phase of the AC signal current more accurately, a lock-in amplifier that is a signal processing device that extracts a specific frequency component from the signal to be measured is used as the AC signal current detection unit 122. Can be considered.
The lock-in amplifier uses a target signal that is an AC signal to be measured (in this embodiment, a signal output from the AC signal current transmission unit 111) and noise with a target value at the same frequency as the target signal. By multiplying the reference signal synchronized with the signal, the target signal that is a synchronous component with respect to the reference signal is converted into a DC component, and the noise that is an asynchronous component with respect to the reference signal is converted into an AC component. The lock-in amplifier extracts a target signal that is a direct current component by removing the alternating current component from the converted signal including the direct current component and the alternating current component using a low-pass filter (low-pass filter). More specifically, the lock-in amplifier obtains two DC components proportional to the AC current by multiplying two reference signals having a phase difference of 90 ° with measurement data. Then, the magnitude (amplitude) and phase of the alternating current are calculated and output by performing arithmetic processing on the two DC components.

By using this lock-in amplifier as the AC signal current detection unit 122 and synchronizing with the AC signal current transmission unit 111, among the magnetic fields detected by the magnetic sensor 121, the current output by the AC signal current transmission unit 111 is Only the same frequency component can be extracted. Thereby, even when the AC signal current to be measured is buried in noise, it can be expected that noise can be removed and more accurate determination can be performed. Also, by using a lock-in amplifier, the phase can be measured as a matter of course.
In addition, when using the above-described digital multimeter as the AC signal current detection unit 122, a filter is provided at a stage before the measurement value is input to the digital multimeter, and noise is removed by limiting the noise frequency band. Measurement accuracy can be increased.
However, with the method of providing a filter in front of this digital multimeter, it is difficult to remove noise having a frequency close to the frequency of the target signal. On the other hand, when a lock-in amplifier is used as the AC signal current detection unit 122, the noise component can be separated by changing the frequency band of the AC current by multiplying the measurement signal and the reference signal. Noise having a frequency close to that of the signal can be easily removed.

Here, the synchronization between the AC signal current detection unit 122 (lock-in amplifier) and the AC signal current transmission unit 111 is performed by, for example, passing the AC signal current detection unit 122 and the AC signal current transmission unit 111 through an insulation amplifier. Are connected by a cable, and the output signal of the AC signal power transmitter 111 is input to the AC signal current detector 122 as a reference signal.
Note that the method of synchronizing the AC signal current detection unit 122 and the AC signal current transmission unit 111 is not limited to the method described above. For example, the AC signal current detection unit 122 and the AC signal current transmission unit 111 may include a wireless communication device. In this case, the AC signal current transmitter 111 wirelessly transmits the output signal, and the AC signal current detector 122 synchronizes using the output signal wirelessly transmitted from the AC signal current transmitter 111 as a reference signal. Thereby, it can synchronize, without connecting between the AC signal current detection part 122 and the AC signal current transmission part 111 with a cable.
Alternatively, the AC signal current detection unit 122 may include a transmitter that is independent from the AC signal current transmission unit 111. In this case, the transmitter included in the AC signal current detector 122 outputs a reference signal that approximates the frequency and phase of the output signal of the AC signal current transmitter 111, and the AC signal current detector 122 outputs the reference signal. Use (pseudo) to synchronize. The transmitter included in the AC signal current detector 122 outputs a reference signal that approximates the frequency and phase of the output signal of the AC signal current transmitter 111 with high accuracy, so that the AC signal current detector 122 and the AC signal current are output. Synchronization can be achieved without the need to connect the transmitter 111 with a cable.

  When a lock-in amplifier is used as the AC signal current detection unit 122, in order to synchronize with the AC signal current transmission unit 111, for example, the output of the AC signal current transmission unit 111 is locked in via an insulation amplifier. Input to the amplifier as a reference signal. The reference signal is transmitted using, for example, a BNC cable. Or you may make it synchronize by other methods, such as attaching a radio communication apparatus to AC signal current dispatch part 111 and lock-in amplifier, and transmitting a synchronous signal wirelessly. Alternatively, an oscillator that approximates the frequency of the AC signal current transmission unit 111 may be provided, and a synchronization signal may be obtained from this oscillator in a simulated manner.

Next, with reference to FIG. 2, the structure of the riser and offshore structure which are the objects of insulation determination will be described.
FIG. 2 is a schematic diagram showing the configuration of the riser and the offshore structure.
In the figure, an offshore structure (structure) 300 includes piles 310-1 and 310-2 and a deck portion 320. Further, the offshore structure supports the riser 210 that penetrates the deck portion 320. An insulator 220 is inserted between the riser 210 and the deck unit 320. The riser 210 is connected to the insulating joint 230 at the upper end above the deck penetrating portion where the riser 210 is supported by the deck portion 320, that is, the portion in contact with the insulator 220. (Conductor) 240 is connected.
Moreover, the area | region A of the figure shows the area | region (atmosphere) on the sea, the area | region B of the figure shows the area | region in the sea, and the area | region C of the figure has shown the area | region under the seabed. This area C under the seabed is an area in the seabed soil or where dead creatures or the like are deposited. Hereinafter, the underwater area B and the undersea area C are collectively referred to as “under the sea surface”.

The offshore structure 300 is a structure installed in the ocean, such as a sea berth that accepts crude oil or gas offshore of a harbor or a fixed platform that excavates crude oil or gas from the seabed.
The piles 310-1 and 310-2 are installed over the sea surface and the sea, respectively. Specifically, the piles 310-1 and 310-2 are driven into the seabed at the lower ends, and support the deck portion 320 at the upper ends on the sea. Hereinafter, the piles of the offshore structure 300 are collectively referred to as “pile 310”. The pile 310 is made of unpainted steel under the sea surface, and is generally catalyzed by a sacrificial anode.
Note that the number of piles included in the offshore structure is not limited to two shown in the figure, and may be one or more.
The deck unit 320 is installed on the sea and has a flat surface for accommodating personnel, equipment, and the like. The deck unit 320 supports the riser 210 that penetrates the deck unit 320. The deck part 320 includes a reinforcing bar and is normally connected to each of the piles 310.

The riser 210 is a metal pipe that constitutes a riser portion that is a portion of the submarine pipeline that rises to the sea. The riser 210 has an anticorrosion coating, and the portion having the anticorrosion coating is electrically insulated from surrounding metal objects. The riser 210 is electrically protected by a sacrificial anode installed on the riser or the submarine pipeline.
The insulator 220 is made of a high-strength insulating material such as pressure-resistant rubber, and electrically insulates the riser 210 and the deck unit 320 together with the cover of the riser 210.

The upper sea pipe 240 is installed on the sea and receives crude oil or gas. The crude oil or gas is then transferred to land by the riser 210 and the submarine pipeline.
The insulating joint 230 is installed between the riser 210 and the upper sea pipe 240, and electrically insulates the riser 210 and the upper sea pipe 240 on the pipeline. The insulating joint 230 may be any joint as long as it does not leak crude oil or gas from the upper sea pipe 240 to the riser 210, and electrically insulates the riser 210 and the upper sea pipe 240. A flange-type insulation joint in which an insulation gasket, an insulation sleeve, and an insulation washer are incorporated into a standard flange may be used, or a monoblock insulation joint that has an integrated structure without using any fastening bolts.

Next, with reference to FIGS. 3 to 6, the installation location of the insulation measurement system 100 will be described.
FIG. 3 is a diagram illustrating an installation example of the insulation measurement system 100 in the case where it is determined whether or not the riser 210 and the pile 310-1 are connected by an undersea conductor such as a marine dumped object. In the figure, the same reference numerals (111 to 114, 121, 122, 210, 220, 230, 240, 310-1, 310-2, 320) are assigned to the same parts as those in FIGS. The description is omitted.
In the figure, the riser 210 and the pile 310-1 are both in contact with the steel marine dumping object 400 and are in conduction through the marine dumping object 400. In this figure, the ocean dumping object 400 is under the seabed (region C in FIG. 2), but the current flow is the same as the following description when the marine dumping object 400 is in the sea (region B in FIG. 2). It is.

Here, the underwater side terminal 113 is suspended and installed at an appropriate depth in the sea, and the riser side terminal 114 is installed in contact with any part between the deck penetration portion of the riser 210 and the insulating joint 230. At that time, since the riser 210 is covered and insulated by the anticorrosion coating, the riser 210 and the riser side terminal 114 are brought into contact with each other by peeling off a part of the anticorrosion coating. Note that a dedicated riser-side terminal may be welded to the riser in advance during construction. Thereby, it is not necessary to remove the riser coating, and the conduction work is facilitated.
Then, when an AC signal voltage is applied between the underwater side terminal 113 and the riser 210 via the riser side terminal 114 by the AC signal current transmission unit 111, an AC signal current flows in the sea. In the following description, as indicated by the arrow of current i _{0 in} FIG. 3, a description will be given based on the timing at which current i ₀ flows in the direction from AC signal current transmission unit 111 to underwater terminal 113. At the timing when the current i ₀ flows in the reverse direction, that is, in the direction from the underwater terminal 113 to the AC signal current transmission unit 111, the AC signal currents (hereinafter simply referred to as currents) i _{1 to} i ₇ shown in FIG. It becomes the direction.

A part of the current flowing from the underwater side terminal 113 into the sea flows into the riser 210 through the anticorrosion coating damaged portion (steel exposed surface) of the riser 210 or the sacrificial anode. In addition, the current flowing from the undersea terminal 113 into the sea flows into the seabed part through the corrosion protection coating damaged part (steel exposed surface) or the sacrificial anode in the seabed part of the pipeline, and enters the riser 210 via the seabed part. Inflow. The current that flows into the riser 210 from the sea or from the bottom of the pipeline flows in the riser 210 toward the riser side terminal 114 (current i ₁ ).
Moreover, the electric current which flows in the sea from the underwater side terminal 113 also flows into each of the piles 310 of an unpainted steel material. Then, the pile 310-1 in contact with the ocean dumping material 400, the current flowing into the pile 310-1 at lower than ocean dumping material 400 flows toward the ocean dumping product 400 (current _i 5). On the other hand, as the pile 310-2, current that has flowed into the pile not in contact with the ocean dumping material 400 flows toward the deck 320 as the current _{i 2.}

The current that has flowed into the rebar of the deck unit 320 from the pile that does not contact the ocean dumping object 400 flows toward the pile 310-1 that contacts the ocean dumping object 400 (current i ₃ ). Then, the current _{i 3} flowing through the reinforcement of the deck portion 320 flows into the pile 310-1 in contact with the ocean dumping material 400 flows toward the ocean dumping product 400 (current _i 4). The current i ₅ flowing into the pile 310-1 below the ocean dumping object 400 below the sea surface and the current i ₄ flowing into the pile 310-1 from the deck part 320 are together with the current flowing into the ocean dumping object 400. And flows in the ocean dumping object 400 toward the riser 210 (current i ₆ ). When the current i ₆ flowing in the ocean dumping object 400 flows into the riser 210, it flows toward the riser side terminal 114 together with the current i ₁ flowing into the riser 210 from the sea or from the bottom of the pipeline (current i ₇ ). Return to the AC signal current transmission unit 111 via the riser side terminal 114.

If there is one or more piles 310-1 that are in conduction with the ocean dumping object 400, current flows through the piles 310-2 that are not in conduction with the ocean dumping object 400 as described above.
In this case, almost all of the current flowing into the plurality of piles 310-2 not connected to the ocean dumping object 400 is the pile 310 in which almost all of the current flowing into the ocean dumping object 400 is connected to the ocean dumping object 400 through the reinforcing bars in the deck portion 320. -1 and a current flows toward the place where the ocean dumping object 400 is conducted under the sea surface of the pile. For this reason, when the magnitude | size of the electric current which flows into each pile is compared, the electric current which flows into the pile 310-1 currently connected with the ocean dumping thing 400 is another pile (the pile 310-2 which is not electrically connected with the marine dumping thing 400). The value is much larger than the current flowing in the current.

  Further, even when there is no conduction between the riser 210 and the pile 310 through the ocean dumping object 400, the riser 210 is electrically connected to the reinforcing bar in the deck part 320 at the place where the deck part 320 supports the riser 210 (deck penetration part). If the insulation performance of the insulating joint 230 inserted between the riser 210 and the upper sea pipe 240 is poor on the deck portion 320, the riser 210 and the pile 310 are disposed via the marine dumped object 400. As in the case where -1 is conducting, current flows through the plurality of piles 310. In this case, the direction of current flows all the way from below the sea surface toward the deck, and if the insulating property of the deck penetration is poor, the current flowing into the pile 310 flows through the reinforcing bar in the deck 320, and from the deck penetration to the riser 210. In addition, if the performance of the insulating joint 230 is poor, a current flows in a direction passing through the insulating joint 230 from the submarine pipe 240 via a conductor such as a gantry connected to the reinforcing bar in the deck portion 320.

The magnitude of the current of each pile 310 at this time shows substantially the same current value, and is different from the case where there is a pile 310-1 that is electrically connected to the ocean dumping object 400.
The riser 210 is not electrically connected to the steel marine dumping 400, and the riser 210 is not electrically connected to the reinforcing bar in the deck portion 320 in the deck penetration portion, and the riser on the deck portion 320 is In the case where the insulation performance of the insulation joint 230 inserted between the 210 and the submarine pipe 240 is good, the current supplied from the submarine side terminal 113 is caused by the corrosion protection coating damage portion (steel) of the submarine pipeline and the riser 210. It flows into only the exposed surface) and the sacrificial anode and flows toward the riser side terminal 114. That is, when the riser 210 is not electrically connected to surrounding metal objects, current flows only through the riser.

Paying attention to these phenomena, when a current is supplied to the riser 210 from the underwater terminal 113, a magnetic sensor is provided at a predetermined position below the deck of the plurality of piles 310 supporting the deck portion 320 around the riser 210 in the upper part of the sea. As a result of installing 121 and measuring the magnitude of the current, if no current is detected in any of the piles 310 or is extremely small, it can be determined that the riser 210 is not electrically connected to the surrounding metal body.
That is, the riser 210 is not electrically connected to the surrounding pile 310 via the ocean dumping object 400, the riser 210 is not electrically connected to the reinforcing bar in the deck portion 320 at the deck penetration portion of the riser 210, and It can be confirmed that the insulation of the insulating joint 230 is good and the riser 210 is not electrically connected to the upper sea pipe 240.

Further, if current is measured by a plurality of piles 310 and there is no significant difference in the magnitude of the current measured by each pile, the measured current is measured by the riser 210 via the ocean dumping object 400 and the surrounding piles 310. Not because it is conducting, but when the riser 210 is connected to the reinforcing bar in the deck part 320 at the deck penetration part of the riser 210, is connected to the riser 210 and the offshore pipe 240, or both are conductive. It can be determined that it depends on the situation.
On the other hand, if the current is measured in the plurality of piles 310 and there is a large difference in the magnitude of the current measured in each pile, any of the piles 310 and the riser 210 are electrically connected via the ocean dumping object 400. It can be judged.
In this case, if the current measured on one or a few piles is greater than the current measured on many other piles, the pile that has a larger current flow than other piles will be dumped in the ocean. 400, the riser 210 is in conduction with the riser 210, and there is no conduction between the riser 210 and the reinforcing bar in the deck 320 at the deck penetration portion of the riser 210, and the insulation of the insulation joint 230 is good. It can be determined that there is no electrical continuity between 210 and the upper sea pipe 240. That is, as shown in FIG. 3, the current that flows into any of the piles 310-2 that are not directly connected to the riser flows into the riser 210 through the piles 310-1 that are connected to the riser 210 and the marine dumped object 400. . Therefore, since the current flowing in from the sea to the pile 310-2 becomes current _{i 4} flowing through the aggregated pile 310-1, so that the large current flows to the pile 310-1.

On the other hand, if the current measured on one or a few piles is smaller than the current measured on many other piles, the pile with the smaller current compared to the other piles is dumped into the ocean. The riser 210 is electrically connected to the riser 210 via the object 400. In addition, the riser 210 is caused by conduction between the riser 210 in the deck penetration portion of the riser 210 and the reinforcing bar in the deck portion 320, and insulation failure of the insulation joint 230. It is possible to determine that there is one or both of the continuity between the pipe and the seaside pipe 240. For example, in FIG. 3, when the insulator 220 is poorly insulated and the riser 210 and the reinforcing bar in the deck portion 320 are electrically connected, the current flowing into the pile 310-2 from the sea is the pile 310-1 and the marine dumped object 400. And flows into the riser 210 from the reinforcing bar in the deck portion 320, which is considered to have a smaller resistance value in the current path than the current path that flows into the riser 210. On the other hand, a part of the current flowing into the pile 310-1 from the sea flows into the riser 210 via the ocean dumping object 400. A part of the remaining current flows from the pile 310-1 toward the deck and flows into the riser 210 via the reinforcing bar in the deck unit 320. Here, in the pile 310-1, the ratio between the current flowing toward the ocean dumping object 400 and the current flowing toward the reinforcing bar in the deck portion 320 is determined according to the ratio of the circuit resistance of both current paths. In any case, the current measured at the pile 310-1 (current of the current _{i 4} and reverse) is to some extent the ocean dumping object 400, since the current is shunted, the current measured at the pile 310-2 (current smaller than i ₂ ).

As described above, the AC signal current transmission unit 111 applies an AC signal voltage between the underwater terminal 113 and the riser 210, and the AC signal current detection unit 122 determines the magnitude of the current flowing through the pile to be measured. By measuring, it can be determined whether or not the riser 210 is electrically connected to surrounding structures and conductors including the pile.
Although FIG. 3 shows the case where the ocean dumping object 400 is in the seabed region, the same determination can be made when the marine dumping object 400 is in the sea region.

Furthermore, the cause of the electrical connection between the riser 210 and another metal body can be obtained by combining the determination of the insulation quality of the insulation joint 230 described later and the determination of the insulation between the riser 210 and the deck portion 320 in the deck penetration portion. It is possible to more reliably determine whether the insulation joint 230 is defective, whether it is a continuity with the rebar in the deck in the deck penetrating portion, or a continuity via a marine dumped object.
In addition, before determining whether or not the riser 210 and the pile 310 are electrically connected, whether the insulation joint 230 installed between the riser 210 and the submarine pipe 240 on the deck is good or bad, The covering of the riser 210 at the deck penetrating portion and the determination of the insulating quality of the insulator 220 installed on the outer periphery thereof are performed by the method described later, and the insulating joint 230 and the insulator 220 of the deck penetrating portion have good insulating properties. If it can be determined, confirmation of the presence or absence of conduction between the riser 210 and the pile 310 can be easily simplified.

That is, as described above, if the insulating joint 230 and the insulator 220 of the deck penetrating portion are both insulative and are not electrically connected to the riser 210 and the pile 310, the AC signal voltage is supplied to the riser 210 and the underwater side terminal 113. When applied to, the AC signal current flows only from the underwater side terminal 113 to the riser via the sea or the submarine soil, and does not flow to the pile 310 at all.
On the other hand, both the insulating joint 230 and the insulator 220 at the deck penetration portion have good insulation. The direction of the current flowing in the upper part of the sea is opposite between the pile 310-1 that is in contact with the ocean dumping object 400 and the pile 310-2 that is not in contact with the ocean dumping object 400. Flowing.

Therefore, the insulation quality of the insulation joint 230 and the insulator 220 of the deck penetration part is determined. If the insulation is a good result, then the AC signal is applied to at least one of the piles 310 around the riser. When the magnitude of the current is measured and the magnitude is zero or below a preset threshold value, it can be determined that there is no conduction between the riser 210 and the pile 310.
On the other hand, when the magnitude of the AC signal current is measured with one or more piles 310 and the magnitude is equal to or greater than a preset threshold value, it can be determined that the riser 210 and the pile 310 are conductive.
In order to detect the pile 310-1 in contact with the riser 210 among the piles 310, as described above, paying attention to the magnitude of the AC signal current, the magnitude of the AC signal current among the plurality of piles 310 is Look for a large pile that protrudes.

Further, in the pile 310-1 in contact with the ocean dumping object 400, the pile 310-1 and the marine dumping object 400 are utilized by utilizing the fact that the direction (phase) of the current is reversed above and below the portion in contact with the marine dumping object 400. Can be determined.
FIG. 4 is a diagram illustrating an installation example of the insulation measurement system 100 in the case where the contact location between the riser 210 and the pile 310-1 is determined. In the figure, the same reference numerals (111 to 114, 121, 122, 210, 220, 230, 240, 310-1, 310-2, 320, 400, i _{0 to} i are used for the same parts as those in FIG. ₇ ) is attached and explanation is omitted.

  In the determination of FIG. 4, the magnetic sensor 121 is suspended along the pile 310-1 in the vicinity of the pile 310-1 to be measured using the magnetic sensor lifting device 510, and the position (water depth) of the magnetic sensor 121 is changed. The phase of the current flowing through the pile 310-1 is measured. Since the current flowing through the pile 310-1 flows toward the ocean dumping object 400, the phase of the current flowing through the pile 310-1 is inverted above and below the portion in contact with the marine dumping object 400. Therefore, based on the magnetic field detected by the magnetic sensor 121, the AC signal current detection unit 122 has a depth at which the phase of the current flowing through the pile 310-1 is reversed, and the location where the pile 310-1 is in contact with the ocean dumping object 400. Judge as the depth of water.

In more detail, the magnetic sensor 121 is installed in the upper part of the sea below the deck part 320 of the pile 310-1 in contact with the ocean dumping object 400, and the magnitude and phase of the current (i ₄ ) are determined by the AC signal current detection part 122. After the measurement, the phase of the measured current is set to, for example, 90 ° on the positive side (plus) by a phase adjuster built in the AC signal current detector 122 or attached externally. After that, when the magnetic sensor 121 is moved along the pile 310-1 from the sea side toward the sea bottom and the magnetic sensor passes through a place where the pile 310-1 is in contact with the marine dumped object 400, the marine dumped object 400 is moved. The phase of the current (i ₄ ) to be measured is reversed from 90 ° on the positive side (plus) to 90 ° on the negative side (minus) with the contact point as a boundary.
In the above, the phase of the current (i ₄ ) measured at the sea level below the deck portion 320 of the pile 310-1 is set to the plus side, but even on the minus side, and within the adjustment range of the phase adjuster Any phase value may be set.

  When the magnetic sensor lifting device 510 suspends the magnetic sensor 121, it is easy to change the position of the magnetic sensor 121 by using a relatively lightweight magnetic sensor that does not require a closed magnetic path as the magnetic sensor 121. At this time, in order to prevent the magnetic sensor 121 from flowing into the ocean current, a pipe 520 made of a non-magnetic material such as a resin pipe is driven along the pile 310-1 to be measured, and the magnetic sensor 121 is suspended in the pipe 520. Lower. Thereby, since the magnetic sensor 121 can be surely laid along the pile 310-1, the magnetic sensor 121 and the cable for suspending the magnetic sensor 121 are prevented from flowing into the ocean current, and the water depth at which the phase is reversed is more accurately detected. Can be determined. Further, when the ocean dumping object 400 is in the seabed area by driving the pipe 520 to the seabed area so that the magnetic sensor 121 can be suspended in the seabed area (for example, the marine dumping object 400 is In the case where the pile 310-1 is buried in a dead body or the like, the location where the pile 310-1 is in contact with the ocean dumping object 400 can be determined.

As described above, the AC signal current transmission unit 111 applies an AC signal voltage between the underwater terminal 113 and the riser 210, and the AC signal current detection unit 122 has two or more locations on the pile to be measured. By detecting the phase of the current flowing through the location, when the phase detected at the first measurement location is opposite to the phase detected at the second measurement location, the vicinity of the second measurement location It can be determined that there is a portion that is electrically connected to the riser 210 due to contact with the ocean dumping object 400 (between the first measurement location and the second measurement location).
Although FIG. 4 shows the case where the ocean dumping object 400 is in the seabed area, the same determination can be made when the marine dumping object 400 is in the sea area.

In addition, about the area | region in the sea, even if a diver moves with the magnetic sensor 121 and raises / lowers the magnetic sensor 121, the conduction | electrical_connection location of the pile 310-1 and the riser 210 can be determined. In this case, it is not necessary to prepare the pipe 520.
In the determination of the conduction point between the pile 310-1 and the riser 210 described above, it is only necessary to detect the phase of the current flowing through the pile 310-1, so the magnetic sensor 121 and the pile 310-1 can be moved up and down. Even when the distance changes and the amount of magnetic flux detected by the magnetic sensor 121 changes, it can be expected that the determination can be made accurately.
In addition, when performing determination using the pipe 520, what is necessary is just to install the pipe 520, after specifying the pile which has touched the ocean dumping thing etc. in the determination demonstrated in FIG. Therefore, it is not necessary to install the pipe 520 in advance for each pile.

Further, by using the insulation measurement system 100, it is possible to determine whether the insulation of the insulator 220 is good, that is, whether or not the riser 210 in the deck penetrating portion is electrically connected to the reinforcing bar in the deck portion 320.
FIG. 5 is a diagram illustrating an installation example of the insulation measurement system 100 when determining whether the insulation of the insulator 220 is good or bad. In this figure, it is assumed that the insulation performance of the insulating joint 230 is good and that the pile 310-1 and the riser 210 are not in contact with the marine dumped object 400.
In the figure, same reference numerals refer to like parts as those in FIG. _{3 (111~114,121,122,210,220,230,240,310-1,310-2,320, i 0 ~i 3} , i ₇ ) is attached, and the description is omitted. In addition, in the example of the figure, as described above, the pile 310-1 is not in contact with the marine dumped material, and the current flowing into the pile 310-1 from the sea flows into the deck section 320, as with the pile 310-2. Since this current flows, this current is also indicated by i ₂ like the current of the pile 310-2.

When the insulating property of the insulator 220 is good, no current flows from the reinforcing bar in the deck portion 320 to the riser 210 in the deck penetration portion, and i ₁₁ = 0. Here, the same reference numerals as those for current indicate the magnitude of the current (AC signal current value) (the same applies hereinafter).
On the other hand, when the insulating property of the insulator 220 is poor, current flows from the deck unit 320 to the riser 210 (i ₁₁ ). Here, the magnitude of the current i _{11 and} the magnitude of the current i ₇ flowing through the riser 210 below the deck penetration (on the side opposite to the riser side terminal 114) and above the deck penetration (on the riser side terminal 114 side). Since i ₇ + i ₁₁ = i ₁₂ , the relationship with the magnitude of the current i ₁₂ flowing through the riser 210 is i ₇ <i ₁₂ . Therefore, using an AC signal current measuring device 120, and the magnitude of the current i _7, and measuring the magnitude of the current i _12, the smaller the difference between the two, specifically, if it is less than the predetermined threshold The insulation of the insulator 220 is determined to be good, and if it is equal to or greater than the threshold value, the insulation of the insulator 220 is determined to be defective.

The determination as to whether or not the current difference is less than the threshold may be made by the user based on the current measurement value of the AC signal current measurement device 120, or the AC signal current detection unit 122 of the AC signal current measurement device 120 may be You may make it perform. Moreover, the magnitude of the threshold value used for the determination is, for example, 1/100 of the magnitude of the current i ₀ output by the AC signal current transmission unit 111, and the current i ₀ output by the AC signal current transmission unit 111. Can be determined based on size.

As shown in FIG. 5, by the AC signal current measuring device 120 comprises a plurality of magnetic sensors 121 may measure the magnitude of the current i _7, the magnitude of the current i ₁₂ simultaneously. Alternatively, the magnitude of the current i _{7 and} the magnitude of the current i ₁₂ may be individually measured using the same magnetic sensor 121. In this case, only one magnetic sensor 121 included in the AC signal current measuring device 120 is sufficient.

When the insulation of the insulating joint 230 is good, the magnitude of the current i ₁₂ flowing through the riser 210 above the deck penetration (the riser side terminal 114 side) and the current i output from the AC signal current transmission unit 111 The magnitude of ₀ is equal, i.e. i ₁₂ = i ₀ . Therefore, after determining that the insulation performance of the insulation joint described below is good in the insulation determination of the insulation joint described below, whether or not the difference between the magnitude of the current i _{7 and} the magnitude of the current i ₀ is equal to or less than a threshold value. May be determined. At this time, when the output current can be measured by the AC signal current transmission unit and the current value display function is provided, it is not necessary to measure the magnitude of the current i ₀ anew. On the other hand, when the AC signal current transmission unit 111 does not have a current measurement function, a shunt resistor is inserted, and a voltage drop at the shunt is measured with a lock-in amplifier synchronized with the AC signal current transmission unit. The current i ₀ may be calculated by dividing the measured value by the shunt resistance. Note that the lock-in amplifier need not be prepared separately for measuring the current i ₀ , as long as the AC signal current detection unit 122 can input multiple channels, and may be measured by the AC signal current detection unit 122. .

Note that FIG. 5 shows an example in which the pile 310-1 and the riser 210 are not electrically connected, but the insulation 220 is poorly insulated even when the pile 310-1 and the riser 210 are electrically connected. Occurs, the current i ₁₁ flows from the deck unit 320 to the riser 210. Therefore, regardless of the presence or absence of conduction between the pile 310 and the riser 210, the insulation quality of the insulator 220 can be determined by the above-described determination.
Part of the current flowing into the pile 310-1 from the sea flows into the riser 210 via the ocean dumping object 400. A part of the remaining current flows from the pile 310-1 toward the deck and flows into the riser 210 via the reinforcing bar in the deck unit 320. Here, in the pile 310-1, the ratio between the current flowing toward the ocean dumping object 400 and the current flowing toward the reinforcing bar in the deck portion 320 is determined according to the ratio of the circuit resistance of both current paths.

When the path of the current flowing into the pile 310-1 is examined in detail, generally, a part of the current flowing into the pile 310-1 from the sea flows into the riser 210 via the ocean dumping object 400. A part of the remaining current flows from the pile 310-1 toward the deck and flows into the riser 210 via the reinforcing bar in the deck unit 320. However, in the pile 310-1, the ratio of the current flowing toward the ocean dumping object 400 and the current flowing toward the reinforcing bar in the deck portion 320 is determined according to the ratio of the circuit resistance of both current paths. When FIG. 4 where the pile 310-1 and the riser 210 are in contact is explained, a part of the current (i ₅ ) flowing into the pile 310-1 flows into the ocean dumping object 400, and a part of the remaining current flows. Since the current flows toward the deck section 320 on the sea, the current (i ₄ ) flowing from the deck section 320 on the sea side toward the sea does not occur (a current in the reverse direction occurs).
Further, even if the pile 310-1 and the riser 210 are electrically connected and the insulation joint 230 is poorly insulated, if the insulation failure occurs in the insulator 220, the current i ₁₁ flows from the deck portion 320 to the riser 210. Therefore, regardless of the presence or absence of conduction between the pile 310 and the riser 210, the insulation quality of the insulator 220 can be determined by the above-described determination.

As described above, the AC signal current transmission unit 111 applies an AC signal voltage between the underwater terminal 113 and the riser 210, and the AC signal current detection unit 122 is connected to the sea surface side of the riser 210 from the deck penetration portion. Measured by measuring the magnitude of the current i ₇ flowing through the sea part and measuring the current value of the current i ₁₂ flowing through the section of the riser 210 between the deck penetration and the location where the riser side terminal 114 contacts. Based on the current value, it is possible to determine whether the insulation of the insulator 220 is good, that is, the insulation between the riser 210 and the deck portion 320 at the deck penetration portion.
Alternatively, when the insulation of the insulating joint 230 is good, the AC signal current transmission unit 111 applies an AC signal voltage between the undersea terminal 113 and the riser 210, and the AC signal current detection unit 122 By measuring the current value of the current i ₇ flowing through the sea side from the deck through-hole 210, the measured current value is compared with the output current value (i ₀ ) of the AC signal current transmission unit 111, thereby insulating the current. It is possible to determine whether the insulation of the object 220 is good, that is, the insulation between the riser 210 and the deck part 320 at the deck penetration part.
That is, if there is no difference between the current flowing in the sea side from the deck penetration part of the riser 210 and the output current of the AC signal current transmission part 111, the insulation between the riser 210 and the deck part 320 in the deck penetration part is It can be judged that it is good.
Moreover, although it is indirect, it can be judged that the insulation performance of the insulation coupling 230 is also favorable.

Further, the insulation measurement system 100 can be used to determine the insulation quality of the insulation joint 230, that is, the presence or absence of conduction between the riser 210 and the offshore pipe 240.
FIG. 6 is a diagram illustrating an installation example of the insulation measurement system 100 in the case where the insulation quality of the insulation joint 230 is determined. In the figure, the same reference numerals (111 to 114, 121, 122, 210, 220, 230, 240, 310-1, 310-2, 320, i ₀ , i ₁ , i ₇ , i ₁₂ ) are attached, and the description is omitted.
When the insulation of the insulating joint 230 is good, no current flows from the upper sea pipe 240 to the riser 210, i ₂₁ = 0.
On the other hand, when the insulation of the insulating joint 230 is poor, current flows from the offshore pipe 240 into the riser 210 (i ₂₁ ). The current i ₂₁ is a part of the current flowing from the underwater side terminal 113 through the pile 310 and the deck part 320 or the part where the submarine pipe 240 directly or indirectly contacts the deck part 320. 240 flows into 240.

Here, the magnitude of the current i _21, the magnitude of the current i ₁₂ flowing through the riser 210 above the deck penetration (the riser side terminal 114 side), and the output current (from the riser side terminal 114) of the AC signal current transmission unit 111. relationship between the magnitude of the alternating signal current current flowing through the transmitting unit 111) _{i 0 is} a _{i 21 + i 12 = i 0} . Therefore, the AC signal current measuring device 120 is used to measure the magnitude of the current i _{21 and} the magnitude of the current i _{12. If} the current i ₂₁ is very small with respect to the current i ₁₂ , specifically, If i ₂₁ is less than a predetermined threshold value, it is determined that the insulation of the insulating joint is good, and if it is equal to or greater than the threshold value, it is determined that the insulation is poor. The determination as to whether or not the current i ₂₁ is less than the threshold may be made by the user based on the current measurement value of the AC signal current measurement device 120, or the AC signal current detection unit 122 of the AC signal current measurement device 120 may be used. You may make it perform. The size of the threshold value used for determination, for example, the magnitude of the current i ₀ which like hundredths the magnitude of the current i ₀ output from the alternating signal current transmission unit 111, the AC signal current transmission unit 111 outputs Can be determined based on Further, even if the current i ₂₁ is not measured, if the current i ₁₂ and the current i ₀ are substantially equal, it can be determined that the insulation of the insulating joint 230 is good. As for the current i ₀ , when the output current can be measured by the AC signal current transmission unit 111 and the current value display function is provided, it is not necessary to measure the magnitude of the current i ₀ anew. On the other hand, when the AC signal current transmission unit 111 does not have a current measurement function, a shunt resistor is inserted, and a voltage drop at the shunt is measured with a lock-in amplifier synchronized with the AC signal current transmission unit. The current value may be calculated by dividing the measured value by the shunt resistance. Here, the lock-in amplifier does not need to be separately prepared for the measurement of the current i ₀ , as long as the AC signal current detection unit 122 can input multiple channels. good.

Even when the insulating property of the insulator 220 is poor, the current i ₁₂ flowing through the riser 210 above the deck penetration portion is the sum of the current flowing into the riser 210 from the sea level (i ₇ ) and the deck portion 320. Since the current flowing into the riser 210 (i _{11 in} FIG. 5) is combined, the relationship between the magnitude of the current i _{12 and} the magnitude of the current i ₀ of the AC signal current transmission unit 111 is as follows. The same as in the case of good insulation. Therefore, regardless of whether the insulation of the insulator 220 is good or bad, the insulation quality of the insulating joint 230 can be determined by the above-described determination. Similarly, whether the insulation joint 230 is insulated or not can be determined by the above-described determination regardless of whether the pile 310 and the riser 210 are electrically connected.

As described above, the AC signal current transmission unit 111 applies an AC signal voltage between the underwater terminal 113 and the riser 210, and the AC signal current detection unit 122 is operated by the AC signal current transmission unit 111 of the riser 210. The current value of the current i ₂₁ that flows between the location where the current is output (that is, the location where the riser-side terminal 114 contacts) and the insulating joint 230, or the current is output by the AC signal current transmission unit 111 of the riser 210. Current value of the current i ₁₂ flowing through the section from the location where the riser 210 is supported by the deck portion 320 of the offshore structure (ie, the deck penetration portion), or the output current i _{0 of the} AC signal current transmission portion 111 By measuring either of the above, based on the measurement result, the insulation quality of the insulating joint 230, that is, the riser 210 and the offshore pipe 240 It is possible to determine the insulation. As described above, when the output current can be measured by the AC signal current transmission unit and the current value display function is provided, there is no need to measure the magnitude of the current i ₀ anew.

The principle of the measurement method described above is not limited to the case where an AC signal voltage is applied between the underwater terminal 113 and the riser 210, but a DC signal voltage is applied between the underwater terminal 113 and the riser 210. This is also the case. When using an AC signal current, as described above, even if the energized AC signal current is buried in noise, only the same frequency component as the energized AC signal current can be extracted. It can be performed.
When DC signal current is used, phase information cannot be obtained, but without using phase information, such as measurement of the presence / absence of conduction between pile 310 and riser 210 or measurement of insulation between riser 210 and offshore pipe 240. The DC signal current can be used for measurements that can be performed (measurements other than specifying the conduction point between the pile 310 and the riser 210). As the DC signal current for measurement, for example, a pulsating current (a current whose direction is constant but whose magnitude changes) may be used.
When measuring using a DC signal current, connect the + (plus) pole of the power supply (corresponding to the AC signal current transmitter 111) to the underwater terminal and connect the-(minus) pole to the riser 210. By doing so, corrosion of the damaged part of the pile or riser or the sacrificial anode is prevented.

As described above, the insulation quality of the insulation joint 230 can be determined regardless of the insulation quality of the insulator 220 and whether or not the pile 310 and the riser 210 are electrically connected. Regardless of whether or not 310 and the riser 210 are electrically connected, it is possible to determine whether the insulation of the insulator 220 is good or bad. Therefore, first, it is determined whether the insulation of the insulating joint 230 is good or not, next, the quality of the insulation of the insulator 220 is determined, and then the presence or absence of conduction between the pile 310 and the riser 210 is determined. When it determines, the determination result can be confirmed for every determination by determining the conduction | electrical_connection location (the location where the pile 310 contacts the marine dumping thing 400) of the pile 310 and the riser 210 further.
Then, the insulation measurement system can display this determination procedure.
Hereinafter, with reference to FIG. 7 to FIG. 9, an insulating measurement system that displays the above determination procedure will be described.

  FIG. 7 is a configuration diagram showing a functional block configuration of the insulation measurement system displaying the determination procedure. In the figure, an insulation measurement system 600 includes an AC signal voltage application device 110 and an AC signal current measurement device 620. The AC signal voltage application device 110 includes an AC signal current transmission unit 111, an AC signal current setting unit 112, an underwater side terminal 113, and a riser side terminal 114. The AC signal current measurement device 620 includes a magnetic sensor 121, an AC signal current detection unit 122, a control unit 623, a storage unit 624, a display unit 625, an input unit 626, and a sensor lifting / lowering unit 627. In the figure, the same reference numerals (110 to 114, 121, 122) are assigned to the same parts as those in FIG.

The AC signal current measuring device 620 measures the magnitude and phase of the current flowing through the measurement object, like the AC signal current measuring device 120. In addition, the AC signal current measuring device 620 determines insulation based on the measurement result.
The storage unit 624 stores a determination procedure performed by the insulation measurement system 600, a message displayed on the display unit 625 by the control unit 623, and a threshold value used when the control unit 623 performs determination. The storage unit 624 functions as a working memory when the control unit 623 performs a determination process.
The input unit 626 has a push button indicating the determination start timing (hereinafter referred to as “measurement start button”), and accepts a user operation input by pressing the measurement start button.

The control unit 623 reads the determination procedure from the storage unit 624 and controls the display unit 625 to display a message indicating the operation to be performed by the user. In addition, the control unit 623 determines information indicating the magnitude and phase of the detection result of the AC signal current detection unit 122, the magnitude of the output current of the AC signal current transmission unit 111, and the like according to the operation input received by the input unit 626. Based on the information indicating the phase, the insulation is determined, and the display unit 625 is controlled to display the determination result.
In order to synchronize the AC signal voltage application device 110 and the AC signal current measurement device 620, the output of the AC signal current transmission unit 111 is input to the AC signal current detection unit 122 of the AC signal current measurement device 620 as a reference signal. .
The display unit 625 has a display surface such as a liquid crystal display, and displays a message under the control of the control unit 623.
The sensor lifting / lowering unit 627 changes the position (water depth) of the magnetic sensor 121 according to the control of the control unit 623, similarly to the magnetic sensor lifting / lowering device 510 described in FIG. 4.

8 and 9 are flowcharts showing a processing procedure performed by the control unit 623.
In the process of FIG. 6, the control unit 623 first installs the magnetic sensor 121 at a position where the current i ₁₂ (FIG. 6) flowing through the riser 210 is measured above the deck penetration (on the riser side terminal 114 side). The display unit 625 is controlled to display a message for instructing. Then, the control unit 623 waits for a signal indicating that the determination start button is pressed to be output from the input unit 626 (step S11).
When a signal indicating that the determination start button has been pressed is output from the input unit 626, the control unit 623 acquires information indicating the magnitude of the current i ₀ of the AC signal current transmission unit 111 from the AC signal current setting unit 112 (step) S12). In addition, the control unit 623 acquires information indicating the magnitude of the current i ₁₂ output from the AC signal current detection unit 122 (step S13). Then, the control unit 623 reads out the threshold value from the storage unit 624, and determines whether or not the difference (i ₀ −i ₁₂ ) between the magnitude of the current i _{0 and} the magnitude of the current i ₁₂ is less than the read threshold value.

If the difference between the magnitude of the magnitude of the current i ₀ and the current i ₁₂ is equal to or more than the threshold (step S14: NO), the control unit 623 displays a message indicating that the insulating joint 230 is defective insulation Thus, the display unit 625 is controlled (step S15). Thereafter, the control unit 623 waits for the user to repair or replace the insulating joint 230 and press the determination start button (step S16). When a signal indicating that the determination start button is pressed is output from the input unit 626, the control unit 623 returns to step S12.
Since repair or replacement of the insulation joint 230 can only be performed after the fluid has been removed, it is often impossible to repair or replace the insulation joint 230 immediately after measurement. Therefore, after the message that the insulation joint needs to be repaired or replaced is displayed, it is possible to go to the next step by the reset function.

On the other hand, at step S14, if the difference between the magnitude of the magnitude and the current _{i 12} of the current _{i 0} is determined to be less than the threshold value (step S14: YES), the control unit 623, the insulating joint 230 is good insulation The display unit 625 is controlled to display a message indicating this. Further, the control unit 623 displays a message instructing to install the magnetic sensor 121 at a position where the current i ₇ (FIG. 5) flowing through the riser 210 is measured below the deck penetration (on the side opposite to the riser side terminal 114). The display unit 625 is controlled to do so. Then, the control unit 623 waits for a signal indicating that the determination start button is pressed to be output from the input unit 626 (step S17).

When a signal indicating the determination start button is pressed is output from the input unit 626, the control unit 623 is output from the AC signal current detection unit 122 acquires information indicating the magnitude of current i ₇ (step S21). Then, the control unit 623 reads out the threshold value from the storage unit 624, and whether the difference (i ₁₂ −i ₇ ) between the magnitude of the current i ₁₂ acquired in step S13 and the magnitude of the current i ₇ is less than the read threshold value. It is determined whether or not (step S22). Note that the threshold used by the control unit 623 in step S22 and the threshold used in step S14 may be the same threshold or different thresholds. The same applies to the threshold value used in step S32 described later. It can be expected that the determination can be made more accurately by using a different threshold value for each determination location. On the other hand, by using the same threshold value, the storage area required for the storage unit 624 to store the threshold value can be reduced.

When it is determined that the difference between the magnitude of the current i _{12 and} the magnitude of the current i ₇ is greater than or equal to the threshold (step S22: NO), the control unit 623 displays a message indicating that the insulator 220 is defective in insulation. Thus, the display unit 625 is controlled (step S23). Thereafter, the control unit 623 allows the user to electrically insulate the riser 210 and the deck unit 320 by, for example, replacing the insulator 220 by scraping (shaving) the concrete of the deck unit 320 around the deck penetration portion. Secured and waits for the determination start button to be pressed (step S24). When a signal indicating that the determination start button is pressed is output from the input unit 626, the control unit 623 returns to step S21.
Since the work to hang the concrete of the deck part 320 for repairing or replacing the insulator 220 may not be performed immediately after the measurement, a message indicating that repair or replacement of the insulator is actually required was displayed. It is possible to go to the next step later by the reset function.

On the other hand, when it is determined in step S22 that the difference between the magnitude of the current i _{12 and} the magnitude of the current i ₇ is less than the threshold (step S22: YES), the control unit 623 indicates that the insulator 220 has good insulation. The display unit 625 is controlled to display a message indicating this. Further, the control unit 623 installs the magnetic sensor 121 at a position for measuring the current flowing through the pile 310 shown in FIG. 4 (i ₂ or i ₄ (it cannot be determined whether the current is i ₂ or i ₄ at this time)). The display unit 625 is controlled to display a message instructing to do so. Then, the control unit 623 waits for a signal indicating that the determination start button is pressed to be output from the input unit 626 (step S25). Here, if there are a plurality of piles 310, the user selects any one pile and installs the magnetic sensor 121. For example, the user selects a pile with the shortest distance from the riser 210 and installs the magnetic sensor 121 on the selected pile.

When a signal indicating that the determination start button is pressed is output from the input unit 626, the control unit 623 indicates the magnitude of the current (i ₂ or i ₄ ) of the selected pile output from the AC signal current detection unit 122. Information is acquired and written in the storage unit 624 (step S31). Then, the control unit 623 reads the threshold from the storage unit 624, determines the size of the selected pile of current _{(i 2} or _{i 4)} is, whether less than the read threshold value (step S32).

Selected, when the size of the pile closer to the riser 210 current _{(i 2} or _{i 4)} is determined to be less than the threshold value (step S32: YES), the riser 210 and all pile 310, conduction is not the Determined. Therefore, the control unit 623 controls the display unit 625 so as to display a message indicating that there is no conduction between the riser 210 and the pile 310 (step S33). Thereafter, the control unit 623 ends the processing illustrated in FIGS. 8 and 9. In this case, for confirmation, it is desirable to confirm that the same result can be obtained with other piles selected (a few in number).
On the other hand, when the size of the selected pile of current _{(i 2} or _{i 4)} is equal to or more than the threshold (step S32: NO), the control unit 623, either pile riser 210 and ocean dumping was 400 The display unit 625 is controlled so as to display a message indicating that it is conducting through, for example (step S41).

Next, in order to identify the pile 310-1 which is conducted through the riser 210 and the ocean dumping object 400 shown in FIG. 4, it is necessary to similarly measure the current (i ₂ or i ₄ ) in the surrounding piles. . For this reason, the control unit 623 displays a message instructing the magnetic sensor 121 to be installed at a predetermined position of the other pile in order to measure the current in another pile (pile for which the magnitude of the current has not yet been measured). The display unit 625 is controlled. Then, after the magnetic sensor 121 is installed, the control unit 623 waits for a signal indicating that the determination start button is pressed to be output from the input unit 626 (step S42). Hereinafter, the pile on which the magnetic sensor 121 is installed is referred to as a “current pile”.
When a signal indicating that the determination start button is pressed is output from the input unit 626, the control unit 623 indicates the current pile current (i ₂ or i ₄ ) output from the AC signal current detection unit 122. Information is acquired and written in the storage unit 624 (step S43).

And the control part 623 reads the magnitude | size of the measured pile electric current from the memory | storage part 624, each of the magnitude | size of the read electric current, and the magnitude | size of the electric current which flows through the newly measured pile acquired in step S43. Compare Compared to any of the read current magnitudes, there is no significant difference in the magnitude of the current flowing through the newly measured pile (specifically, the current magnitude difference is less than a predetermined threshold). If it is determined that there is a), the control unit 623 determines that the measured pile and the current pile are not piles in contact with the riser.
For example, when the determination in step S44 is performed for the first time, the piles whose current magnitude has been measured are only the piles measured in step S31. In this case, the control unit 623 reads the magnitude of the current flowing through the pile 310 measured at step 31 from the storage unit 624, and the magnitude of the read current and the magnitude of the current flowing through the pile 310 measured at step S43. Compare. If there is not a big difference in the magnitude | size of an electric current, the control part 623 is that the pile 310 measured at step 31 and the pile (present pile) measured at step S42 are not the pile which is in contact with a riser. judge.

  Moreover, when performing determination of step S44 for the 2nd time, the pile which has measured the magnitude | size of an electric current is the pile (henceforth "the pile measured first") 310 measured by step S31, and step S43. This is a pile (hereinafter referred to as “second measured pile”) 310 measured at the first execution. In this case, the control unit 623 reads out the first measured pile current magnitude and the second measured pile current magnitude from the storage section 624, each of the read current magnitudes, and step S43. The magnitude of the current flowing in the pile 310 (hereinafter referred to as “the third measured pile”) 310 is compared. If there is no significant difference in the magnitude of the current measured in the third pile compared to any of the first measured pile and the second measured pile, the control unit 623 The second measured pile and the third measured pile (current pile) are determined not to be in contact with the riser (step S44).

If it is determined in step 44 that there is no significant difference in current magnitude in comparison between the current pile and the pile measured so far (step S44: NO), the process returns to step S41, The process (the loop of step S41-S44) which selects an other pile and measures an inflow electric current is repeated until the pile from which a magnitude | size differs produces is detected.
On the other hand, if it is determined that there is a large difference in current magnitude (step S44: YES), the control unit 623 has conduction between the current pile (pile showing the protruding current) and the riser 210. and a message indicating, for detecting the conduction position between the riser 210 and the pile 310-1, a message indicating to adjust the phase of the current i ₄ obtained in step S45, the magnetic sensor 121, described in FIG. 4 As described above, the display unit 625 is controlled so as to display a message instructing to prepare to be able to move up and down along the pile (step S45).

  At that time, phase adjustment is performed on the output voltage from the magnetic sensor 121 as necessary. For example, it is adjusted to 90 ° on the positive side (plus side) so that the phase change of the output voltage from the magnetic sensor 121 can be easily captured (for example, easy to monitor with an oscilloscope). For this phase adjustment, for example, the AC signal current detection unit 121 includes a phase adjuster, or the output voltage of the magnetic sensor 121 is input to the phase adjuster using an external phase adjuster, and the user (measurement) This is done by rotating the phase adjustment dial of the phase adjuster while checking the phase of the output voltage of the phase adjuster at the site. Alternatively, the AC signal current detection unit 121 may include a phase adjuster and automatically change to a preset phase.

Then, the control unit 623 performs phase adjustment and preparation for enabling the magnetic sensor 121 to move up and down, and presses the determination start button (a signal indicating that the determination start button is pressed is output from the input unit 626). (Step S51).
When a signal indicating that the determination start button is pressed is output from the input unit 626, the control unit 623 lowers the magnetic sensor 121 to a predetermined measurement start water depth. Then, the control unit 623 obtains output from the AC signal current detection unit 122, a current i ₄ flowing through the pile (phase after adjustment) current having a magnitude and phase, and the information indicating the current position of the magnetic sensor Then, the acquired information is displayed on the display unit 625. In addition, the control unit 623 performs measurement preparation such as generating a file for storing measurement data in the storage unit 624 (step S52).

Then, the control unit 623 lowers the magnetic sensor 121 by a predetermined water depth interval or continuously and outputs the magnitude of the current i ₄ flowing through the pile output from the AC signal current detection unit 122. The phase and position (water depth) of the magnetic sensor are displayed on the display unit 625 in real time and written to the storage unit 624 (step S53).
Then, the control unit 623 is output from the AC signal current detecting section 122, (prior to detecting the contact position) information indicating the phase of the current i ₄ flowing through the pile, (set by the phase adjustment) measured at the start In comparison with the phase of the AC signal current in real time (step S55), when it is determined that the phase is reversed (step S55: YES), a contact point detection signal (such as a pulse signal) is transmitted to the display unit 625. . Further, the control unit 623 may write information indicating that the position where the phase is reversed is detected in the storage unit 624 together with the water depth when the phase is reversed (step S56).
On the other hand, when it is determined in step S55 that the phase is not reversed (step S55: NO), the control unit 623 returns to step S53 and continues the process of measuring the current and determining the phase.

  If the phase is determined to be an opposite phase (step S55: YES), the control unit 623 will further describe the depth of the magnetic sensor 121 at the time of the current determination and the pile to be determined at this depth. The display unit 625 is controlled to display a message indicating that is electrically connected to the riser 210 and a message instructing to cancel the conduction (step S56). Thereafter, the control unit 623 waits for the user to cancel the conduction between the pile and the riser 210 by, for example, removing the marine dumping in contact with the pile and press the determination start button (step S57). When a signal indicating that the determination start button is pressed is output from the input unit 626, the control unit 623 returns to step S31.

Note that the removal work of the ocean dumping object 400 may not be performed immediately after the measurement work. Therefore, the display unit 625 may display a message that the ocean dumping object 400 needs to be removed, and the AC signal current measurement device 620 may wait for a user's reset operation. The user's reset operation is performed, for example, when the AC signal current measuring device 620 includes reset operation input means such as a reset button, and the user operates the reset operation input means. When the reset operation is performed, the AC signal current measurement device 620 (control unit 623) returns to Step S31.
In addition, although the case where it returns to step S31 after step S57 and the determination of conduction | electrical_connection with a riser 210 and a pile is performed again was demonstrated above, conduction | electrical_connection does not arise between a riser and several piles. Conceivable. Therefore, the AC signal current measuring device 620 (control unit 623) may end the process of FIG. 9 after step S57 is ended.

  As described above, the insulation quality of the insulation joint described in FIG. 6 is determined. When it is determined that the insulation is good, the insulation in the deck portion described in FIG. 5 is determined and the insulation is determined to be good. In the case of determining the presence or absence of conduction between the pile described in FIG. 3 and the riser 210, when determining that there is conduction, by determining the conduction location between the pile described in FIG. 4 and the riser 210, As described above, the quality of insulation can be determined for each determination. That is, first, the insulation quality of the insulation joint can be determined, then the insulation quality at the deck penetration can be determined, then the presence / absence of conduction in the pile can be determined, and if there is conduction in the pile, the conduction is established The location can be identified.

  Note that only part of the determination described with reference to FIGS. 8 and 9 may be performed by the insulation measurement system 600. For example, the insulation measurement system 600 instructs only to perform the determinations of steps S11 to S16 (determination of the insulation of the insulation joint 230), and performs determination according to this instruction. May be performed. Also in this case, it is possible to determine the insulating property to be determined.

As described with reference to FIG. 5, even if it is determined in step S22 in FIG. 8 whether the difference between the magnitude of the current i _{7 and} the magnitude of the current i ₀ is equal to or less than a threshold value, the insulation of the insulator 220 is performed. It is possible to determine whether or not the property is good, that is, whether or not the riser 210 in the deck penetrating portion is electrically connected to the reinforcing bar in the deck portion 320. Further, as described in FIG. 6, the magnitude of the current i ₂₁ is measured in steps S12 to S13 in FIG. 8, and it is determined in step S14 whether the current i ₂₁ is less than a predetermined threshold value. Even in this case, the insulation of the insulating joint 230 can be determined.

Next, an experiment using a model for determining the presence / absence of conduction between the riser 210 and the pile 310-1 described in FIG. 3 will be described.
FIG. 10 is a circuit diagram showing a configuration of a model for which an experiment was performed.
The experimental circuit of the figure includes a transmitter 711 corresponding to the AC signal current transmitter 111, a stainless steel electrode 713 corresponding to the underwater terminal, a magnetic sensor 721 corresponding to the magnetic sensor 121, and an AC signal current detector. 122, three lock-in amplifiers 722, a BNC cable 751 for synchronizing the transmitter 711 and the lock-in amplifier 722, two shunts 752 for current measurement, a current adjustment resistor 753, and a riser 210 Covered bar steel 810 provided with an insulation coating corresponding to the above, a bare bar steel 811-1 corresponding to the pile 310-1, a bare bar steel 811-2 corresponding to the pile 310-2, and a conductor corresponding to the reinforcing bar of the deck portion 320 820, a conductor 840 corresponding to the ocean dumping object 400, and a switch 841 that simulates contact and removal of the marine dumping object 400. Further, the stainless steel electrode 713, the covered steel bar 810, and the bare steel bars 811-1 and 811-2 are immersed in a 3% saline solution corresponding to seawater in the container 851. In addition, all the conducting wires 840 used for the experiment were covered electric wires in order to prevent corrosion.

Since each of the piles 310 is electrically connected to each other via the reinforcing bars in the deck portion 320, the bare steel bars 811-1 and 811-2 are connected to each other by a conducting wire 820 in the atmosphere.
Further, when the riser 210 and the pile 310-1 are conducted in the sea, a shunt 752 is inserted into the conductor 820 connecting the bare steel bars 811-1 and 811-2 in order to measure the current flowing in the deck portion 320. The lock-in amplifier 722 was connected to the voltage terminals on both sides of the inserted shunt 752.
In addition, the coated steel bar 810 and the conductive wire 820 are not in contact with each other, simulating a state where the riser 210 and the deck portion 320 are insulated by the insulator 220.

Moreover, the bare steel bar 811-1 and the conducting wire 840 are connected in water, imitating the contact between the pile 310-1 and the ocean dumping object 400. In addition, a part of the insulation coating of the covered steel bar 810 is peeled off in a manner similar to the contact between the riser 210 and the marine dumped object 400 and connected to the conducting wire 840 in water. And the switch 841 which simulates the contact and removal of a marine dumping thing is inserted in the conducting wire 840 in air | atmosphere.
Moreover, since the alternating current signal transmission part 111 and the riser 210 are connected by the riser side terminal 114, the transmitter 711 and the covered steel bar 810 are electrically connected by a conducting wire. A current adjusting resistor 753 and a current measuring shunt 752 are inserted in series into this conducting wire, and a lock-in amplifier 722 is connected to the voltage terminals on both sides of the shunt 752. In addition, the transmitter 711 and the stainless steel electrode 713 are electrically connected by a conducting wire.
Further, a magnetic sensor 721 is installed on the conducting wire 840 and a lock-in amplifier 722 is connected. Thereby, a current corresponding to the current detected by the magnetic sensor 121 is detected.
Further, by inputting the output from the transmitter 711 to the reference signal terminal of the lock-in amplifier 722 via the insulation amplifier through the BNC cable 751, each of the lock-in amplifiers 722 and the current output from the transmitter 711 Only the same frequency component was detected.

And the frequency of the transmitter 711 was changed into 220 hertz (Hz), 760 hertz, and 1 kilohertz (kHz), and the measurement result shown in FIG. 11 was obtained.
As shown by the measurement results in the figure, in a state where the coated steel bar 810 and the bare steel bar 811-1 are not conductive, that is, in a state where the switch 841 is opened, the bare steel bar 811-2 and the bare steel bar at any frequency. The current flowing between 811-1 and the current flowing between the bare steel bar 811-1 and the covered steel bar 810 were almost zero, and no current flowed into the covered steel bar 810 corresponding to the riser 210. On the other hand, in a state where the coated steel bar 810 and the bare steel bar 811-1 are conductive, that is, in a state where the switch 841 is closed, the bare steel bar 811-2 and the bare steel bar 811-1 are interposed at any frequency. , And the magnitude of the current flowing through the bare steel bar 811-1 and the coated steel bar 810 were measured to be about one fifth of the output current of the transmitter 711. At any frequency, the direction of the current measured with the switch 841 closed was downward corresponding to the direction from the deck unit 320 toward the sea.
From this experimental result, it was shown that the present invention can detect whether the riser 210 and the pile 310 are electrically connected to each other by steel marine dumping or the like.
In addition, it was shown that the same experimental result was obtained irrespective of the frequency of the transmitter 711, so that the determination of the present invention can be performed using an appropriate frequency other than the commercial frequency and its harmonics.

Next, in addition to the above-described experiment, a detection experiment was performed on the location where the coated steel bar 810 and the bare steel bar 811-1 are conducting. In the experiment, as shown in FIG. 12, a magnetic sensor 900-1 is arranged outside the container 851, power is supplied to the magnetic sensor from a power supply 900-2 for driving the magnetic sensor, and the output of the magnetic sensor 900-1 is output. Is input to the lock-in amplifier 722 synchronized with the transmitter 711. As the lock-in amplifier 722, one having a built-in phase adjustment function was used.
And after fixing the magnetic sensor 900-1 to the position of the water surface side of the container 851, the alternating current which flows into the covered steel bar 811-1 from the conducting wire 820 is measured, and the phase of this current is set to + 90 ° by the phase adjuster. did. Then, the magnetic sensor 900-1 was moved downward along the container 851, and the phase output at that time was monitored by the lock-in amplifier 722.
As a result, as shown in FIG. 13, the phase output changed from + 90 ° to −90 ° at the location where the conducting wire 840 was connected to the coated steel bar 811-1.
From this experimental result, it was shown by this invention that the location where the riser 210 and the pile 310 are conducted by a steel marine dumping object or the like can be detected.
In addition, it was shown that the same experimental result was obtained irrespective of the frequency of the transmitter 711, so that the determination of the present invention can be performed using an appropriate frequency other than the commercial frequency and its harmonics.

A program for realizing all or part of the functions of the AC signal current detection unit 122, the control unit 623, the display unit 625, and the input unit 626 is recorded on a computer-readable recording medium. Processing of each unit may be performed by reading a recorded program into a computer system and executing the program. Here, the “computer system” includes an OS and hardware such as peripheral devices.
Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a holding device such as a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a hard disk built in the computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.

  INDUSTRIAL APPLICABILITY The present invention is suitable for use in an insulation determination method and an insulation determination system that determine the presence or absence of a conduction between a riser portion of a submarine pipeline and a surrounding other metal body or a conduction location.

100, 600 Insulation measurement system 110 AC signal voltage application device 111 AC signal current transmission unit 112 AC signal current setting unit 113 Underwater side terminal 114 Riser side terminal 120, 620 AC signal current measurement device 121 Magnetic sensor 122 AC signal current detection unit 510 Magnetic Sensor Lifting Device 520 Pipe 623 Control Unit 624 Storage Unit 625 Display Unit 626 Input Unit 627 Sensor Lifting Unit 210 Riser 220 Insulator 230 Insulation Joint 240 Upper Marine Pipe 300 Offshore Structure 310, 310-1, 310-2 Pile 320 Deck part

Claims (9)

An underwater terminal provided in the sea,
A power source that is electrically connected to the undersea terminal, and a power source that can be electrically connected to a metal pipe that is installed under the sea surface and under the sea surface and is electrically protected.
A measuring device for measuring current;
Insulating measurement system including
An insulation determination method for determining insulation between the metal tube and a structure or a conductor conducting to the structure,
The power source applies a voltage between the underwater terminal and the metal tube,
The measuring device measures at least one of a current flowing through the metal tube, a current flowing through the structure, or a current flowing through the conductor ;
Compare at least one of the magnitude or direction of the current measured with the measuring device with a predetermined reference, or compare at least one of the magnitude or direction of the current measured with the measuring device at a plurality of locations. An insulation determination method comprising: determining at least one of insulation quality and conduction location . The structure comprises a pile installed over the sea and under the sea and fixed to the sea floor,
The insulation measuring method according to claim 1, wherein the measuring device measures a current flowing through the pile. The structure includes a plurality of piles installed over the sea and under the sea and fixed to the sea floor,
The power source applies a voltage between the underwater terminal and the metal tube,
The insulation measuring method according to claim 1, wherein the measuring device measures a current flowing through the plurality of piles. The structure includes a plurality of piles installed over the sea and under the sea and fixed to the sea floor,
The power source applies an alternating voltage between the underwater terminal and the metal tube,
The measuring device measures the phase of the alternating current flowing through the first measurement point of one of the piles, and uses the phase of the measured alternating current as a reference for the alternating current flowing through the second measuring point. Measure the phase and detect the position where the direction of the alternating current is reversed, that is, the position where the phase is reversed ,
The insulation determination method according to claim 1, wherein the phase reversal position is determined as a conduction point that is conducted to the metal pipe . The metal pipe is in contact with the insulating joint at an end portion at sea, and is applied with a voltage by the power source at sea and on the sea surface side than the insulating joint, and is at sea surface side from the place where the voltage is applied to the sea and the power source. Supported by the structure at
The insulating joint is in contact with the conductor;
The measuring device may be configured such that the current value of the current flowing between the location where the voltage is applied by the power source and the insulation joint of the metal tube, or the location where the voltage is applied by the power source of the metal tube. 2. The insulation determination method according to claim 1, wherein one of current values of a current flowing through a section between the metal tube and a portion supported by the structure is measured. The metal tube is applied with a voltage by the power source at sea, and is supported by the structure on the sea surface side of the sea and a place where the voltage is applied to the power source,
The measuring device measures a current value of a current flowing on a sea surface side and on a sea part from a portion of the metal tube where the metal tube is supported by the structure, and the metal tube of the metal tube is the structure. The insulation determination method according to claim 1, wherein a current value of a current flowing through a section between a place supported by the metal pipe and a place where the voltage is applied to the metal tube by the power source is measured. The metal tube is applied with a voltage by the power source at sea, and is supported by the structure on the sea surface side of the sea and a place where the voltage is applied to the power source,
It said measuring device, of the metal tube, according to claim 1, those gold genus tube and measuring the current value of the current flowing in the sea-side and sea portions than portions to be supported by the structure Insulation judgment method.   When the insulation determination method according to claim 5 is performed and the current value of the measured current is less than a predetermined threshold, the insulation determination method according to claim 6 or 7 is further performed. The current value of the current flowing through the sea surface side and the sea part of the metal tube, measured from the insulation determination method according to claim 6, of the metal tube, The difference between the current value of the current flowing through the section from the location where the metal tube is supported by the structure to the location where the voltage is applied by the power source is less than a predetermined threshold, or If the difference between the current value of the power source and the current value measured by the insulation determination method according to claim 7 is less than a predetermined threshold, the plurality of piles according to claim 3 Perform insulation judgment method by measuring the presence or absence of current and confirm current For the piles which, further insulating determination method which is characterized in that the insulating determination method according to claim 4. An insulation determination system that measures current by the insulation determination method according to any one of claims 1 to 8,
A display for displaying a message;
A control unit that controls the display unit so as to display an instruction to install a sensor for current measurement by the measuring device at the measurement point of the current;
An input unit for obtaining a notification that the sensor is installed;
Comprising
Wherein, when the input unit acquires the notification, insulating determination system, characterized in that a determination of the insulation on the basis of the current which the measuring device is measured.

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