RU2306531C1 - Liquid level meter - Google Patents

Abstract

FIELD: measuring technique.

SUBSTANCE: liquid level meter comprises cylindrical housing (2) whose inner space is in communication with the liquid through passages (5). Float (10) mounted in housing (2) is coated with a mirror layer. Emitter (11) and receiver (12) of radiation are connected with the space of cylindrical housing (2) through optical switch (13) made of a disk provided with ports. The surface of the disk is coated with a reflecting layer. The optical switch has corner reflector. Unit (15) is connected with the emitter (11) and receiver (12) of radiation and drive (14) for rotating the optical switch. The liquid level meter is additionally provided with step cylindrical nozzle (6) having base (7) for fastening to the neck of the reservoir, second corner reflector, and glass baffle (8) that separates hollow cylindrical nozzle (6) into stages. The small diameter stage receives tube (1) provided with housing (2) of the liquid level meter. The ring space between the tube and the housing is closed by baffle (3) with reflecting layer (4) on its inner side to prevent a contact with the liquid. The large diameter stage of cylindrical nozzle (6) receives optical switch (13) one port of which receives the first and second corner reflectors. Emitter (11) and receiver (12) of radiation and drive (14) of optical switch (13) are mounted on base (7) of the step cylindrical nozzle (6).

EFFECT: enhanced precision.

3 dwg

Description

The invention relates to liquid level meters for rigid vertical tanks, in particular to liquid level meters using floats, and can be used in the oil and chemical industry mainly to control the level of liquids stored in any vertical tanks having horizontal bottoms.

As the practice of operating vertical rigid tanks has shown, an uncontrolled change in the base height of the tank affects the measurement of the liquid level due to a change in the position of the bottom relative to the roof of the tank during drainage operations and periodic deformations from hydrostatic pressure, and since most level gauges are attached when measuring the level to the base height of the tank, then the reliability of measuring the liquid level is very low due to a change (deflection) in the horizontalness of the bottom.

The authors were faced with the task of developing a level gauge that would reduce the measurement error by taking into account the effect of hydrostatic liquid pressure on the bottom.

When viewing patent and scientific and technical information, technical solutions-analogues were revealed. So, it is known a device for measuring the liquid level in tanks, containing a hydrostatic pressure receiver in the form of a piston, above which are installed emitting and receiving optical fibers, optically coupled respectively to a light source and receiver, electrically connected to a power supply unit, two inputs of an analog-to-digital converter and an indicator (RF patent No. 2064665, G01F 23/14 1996).

The disadvantages of this design are the low accuracy due to the instrumental error of the piston-tube friction pair, the temperature instability of the components of the electrical circuit, the grinding and contamination of the optical surfaces, as well as the small dynamic measurement range due to the large scattering of optical radiation outside the focus of the spherical cavity.

The closest in technical essence to the invention adopted as a prototype is a device for measuring the liquid level in sealed containers, containing a cylindrical hollow body with a piston mounted inside with the possibility of movement in a vertical plane, on the surface of which an angular reflector is placed. In the upper part of the housing, transmitting and receiving fibers are connected through radiation input and output devices and an optical contactor made in the form of a disk with windows, the outer surface of which is covered with a reflective layer, with a radiation source and receiver, electrically connected to the input of the waiting multivibrator, frequency meter and computers (RF patent No. 2084837, G01F 23/22 - prototype).

The disadvantages of this device is the low accuracy due to the influence on the measurement error of the level of uncontrolled changes in the base height of the tank due to a change in the position of the bottom relative to the roof of the tank during drainage operations and periodic deformations from hydrostatic pressure.

The technical result of the invention is improving the accuracy of measuring the liquid level.

The specified technical result is achieved by the fact that the known liquid level gauge in rigid vertical tanks, containing a cylindrical body, the internal cavity of which is connected with the measured liquid through channels made in its lower part, is placed with the possibility of vertical movement in the cylindrical body of the float, the upper surface of which is coated with a mirror layer , the source and receiver of radiation associated with the internal cavity of the cylindrical body through an optical contactor, made in the form According to the invention, the disk with windows, on the outer surface of which a reflective layer, an angular reflector and a control unit of a sequence of operations are electrically connected with the radiation source and receiver and with the optical drive of rotation of the optical contactor, further comprises a stepped hollow cylindrical nozzle having a support base for tight mounting on the neck of a rigid vertical tank, a second corner reflector and a glass partition separating the steps of the hollow cylindrical a plate, in a step of a smaller diameter which is fixed with the possibility of limited vertical movement of the pipe with a coaxially mounted cylindrical body of the level gauge, the annular gap between which at the lower ends is hermetically closed from the horizontal wall with a reflection layer on the inner surface with a reflective layer, and in the step of a larger The diameter of the hollow cylindrical nozzle is an optical contactor, in one of the windows of which are installed the first and second corner reflectors, This source and receiver of radiation and the drive of the optical contactor are mounted on the support base of a stepped hollow cylindrical nozzle.

Figure 1 presents the liquid level meter (in the context of the tank);

figure 2 - optical contactor (top view);

figure 3 - optical contactor (view along arrow I-I of figure 2).

The liquid level gauge contains a vertical pipe 1, covering a coaxially mounted cylindrical body 2 with an annular gap (from two to five centimeters). The annular gap is hermetically closed from contact with the measured liquid by a horizontal partition 3, covered with a mirror (reflective) layer 4 from the inside and placed above the channels 5, communicating the internal cavity of the cylindrical body 2 with the measured liquid in the tank. In the upper part of the level gauge there is a stepped hollow nozzle 6, in a smaller diameter step which is fixed with the possibility of limited vertical movement of the pipe 1. The stepped nozzle 6 has a supporting base 7, which is hermetically fixed to the skylight of the vertical tank by means of a bolt connection. The steps of the nozzle 6 are separated by a hermetically sealed glass partition 8, which protects the inner cavity of a larger diameter from the influence of deposits and vapors of the measured liquid on the operation of instrumentation.

The restriction of the vertical movement of the pipe 1 (together with the body 2) is achieved due to the presence of an abutment 9 (in the form of a tenon groove), which provides a range of movement of the pipe 1 in the step nozzle 6. Based on the practice of operating vertical tanks, the maximum deflection of the bottom can reach up to 40 cm in one direction or another, therefore, the range of movement of the pipe in the steps of a smaller diameter is 80 cm.

In the cylindrical body 2 there is a float 10, the upper surface of which is covered with a mirror layer. A source 11 and a radiation receiver 12 (photodiodes) are installed on the supporting base 7. Between the support base 7 and the glass partition 8, an optical contactor 13 is installed, the rotation axis (without position) of which is connected to the rotation drive 14 (stepper motor). The source 11 and the receiver 12 of the radiation, as well as the drive 14 of the rotation of the optical contactor 13 are connected to the block 15 control the sequence of measurement operations.

The optical contactor 13 is in the form of a disk of any durable material (metal, plastic, etc.) with a diameter of five to ten centimeters. The axis of the disk is rigidly connected with the shaft of the drive 14 of rotation of the disk in a horizontal plane. The switch 13 has three equal sectors: "A", "B" and "C" with an angle of 120 ° each.

Sector "A" and its entire external surface (facing the drive 14 of rotation) is covered with a reflective layer.

Sector "B" on its center line has a through hole 16 in the form of a rectangle in which the first 17 and second 18 corner reflectors are located. Corner reflectors 17 and 18 are located in the through hole 16 so as to shift the light flux from the radiation source 11 into the annular gap between the pipe 1 and the cylindrical body 2 and to the radiation receiver 12.

Sector "C" on its center line has a through hole 19 in the form of a circle. The diameter and placement on the axial line is selected from the condition for the passage of the light flux from the source 11 to the radiation receiver 12.

Block 15 control the sequence of operations is made in the form of a microcontroller with software (DS1040 Dallas Semiconductor, ZAO "DODEKA", Reference electronic components, 2003, p.67).

The liquid level gauge works as follows.

To clarify the work, the following conventions are introduced:

- sector “A” conditionally (to explain the operation of the level gauge) is called the sector of the calibration mode;

- sector "B" conditionally (to explain the operation of the level gauge) is called the sector of the mode of measuring the base height of the tank;

- sector "C" is conditionally (to explain the operation of the level gauge) called the sector of the mode of measuring the liquid level in the tank.

The inventive liquid level gauge is a device whose dimensions depend on widespread vertical tanks, the height of which is within the range of Нрз = 12 m, and the diameter of the skylight is 200 mm.

Based on the size of the diameter of the skylight, the larger diameter of the step nozzle 6 is D = 197 mm.

Before starting to measure the liquid level in the tank in the block 15 control the sequence of operations set the following values:

NKZ - the value of the distance from the transmitting 11 and receiving 12 of the radiation source to the surface of the optical contactor 13,

Nbz - the value of the distance from the transmitter 11 and receiver 12 of the radiation source to the reflective layer 4 of the horizontal partition 3,

Нрз - base height of the tank.

The level gauge is installed on the tank so that the end of the pipe 1 touches the bottom of the tank, while checking the perpendicularity of the pipe 1 with respect to the bottom of the tank. When filling the tank in a cylindrical body 2 with the liquid entering through the channels 5, the float 10 is pushed out, while the position of the float 10 corresponds to the liquid level in the tank. The control unit 15 of the sequence of operations, according to the software, by means of a rotation drive 14 rotates the optical contactor 13 so that sector "A" is placed under the transmitting source 11 and radiation receiver 12. Then, the sequence control unit 15 includes a radiation source 11 that delivers a short-term light pulse. The luminous flux from the radiation source 11 is reflected from the surface of the sector "A" of the optical contactor 13 and enters the radiation receiver 12. An electric pulse from the radiation receiver 12 enters the sequence control unit 15, which generates a digital pulse equal to the distance Hk.

In the block 15 control the sequence of operations is the comparison of the set value Nkz with the value of Nk obtained by measurement.

If the specified value of NKZ differs from the value of NK, then this indicates a violation of the perpendicularity of the pipe 1 with respect to the bottom of the tank. Correction of the installation of the pipe 1.

If the set value Нкз corresponds to the obtained value Нк, then the control unit 15 of the sequence of operations, according to the software, by means of the rotation drive 14 rotates the optical contactor 13 so that the through hole 16 of sector "B" is placed under the source 11 and the radiation receiver 12 . Then, the sequence control unit 15 includes a radiation source 11 that generates a short-term light pulse. The luminous flux from the radiation source 11 enters the first 17 corner reflector, from which the corner reflector is transmitted to the second 18 and enters the reflective layer 4 of the horizontal partition 3, is reflected from it and enters the radiation receiver 12 in the same way. There is a measurement of the distance Nb. In the block 15 control the sequence of operations is a comparison of the set value Nbz and the measured value of the distance Nb.

If the measured value of Нб does not correspond to the set value of Нбз, then this indicates that there was a change in the horizontality of the bottom of the tank, while the pipe 1 moved in the stepped nozzle 6 by ΔН equal to the difference between the measured value of Нб and the set value of Нбз. On the control unit 15, the alarm lamp lights up, indicating that for further operation it is necessary to rebuild the tank.

In the current operation of the tank (until the final emptying), this ΔН value will be taken into account as a constant value when the level changes.

If the measured value of Нб corresponds to the set value of Нбз, then the control unit 15 of the sequence of operations, according to the software, by means of a rotation drive 14 rotates the optical contactor 13 so that the through hole 19 of the sector “C” is placed under the source 11 and the radiation receiver 12. Then, the sequence control unit 15 includes a radiation source 11 that generates a short-term light pulse. The luminous flux from the radiation source 11 passes through the through hole 19 in the sector “C”, is reflected from the surface of the float 10 and enters the radiation receiver 12, which corresponds to the Np distance to the float 10, taking into account the obtained ΔН value.

According to the software of the sequence control unit 15, the optical closure 13 rotates at a speed of twenty revolutions per minute by means of the drive 14, which provides continuous monitoring of the liquid level in the tank, taking into account changes in the deformation of the bottom from hydrostatic pressure.

The liquid level in the tank is calculated in the block 15 control the sequence of operations according to the following formula:

Nzh = Nrz-Np,

where NJ is the fluid level,

Нрз - base height of the tank,

Np - the distance from the radiation source 11 to the float 10.

The inventive level gauge was tested on a reservoir of the RVS-3000 brand, the height of which is Нз = 1226 cm, therefore, taking into account the distance to the mirror surface 4 of the partition 3 Нбз = 1216 cm. The aim of the experiment was to verify the adequacy of the level gauge in comparison with manual means of measuring the level of TS-kerosene 1 in RVS-3000. The level gauge measured the distance from the transmitter 11 and receiver 12 of the radiation source to the reflective layer 4 of the horizontal partition 3, which coincided with the specified one and amounted to Нб = 1216 cm. The level of aviation kerosene ТС-1, located in the tank, amounted to Нж = 889 cm, which corresponds to calibration table of the tank with a volume of 2510.121 m ³ .

After a technological operation was carried out to receive 380.06 m ^{3 of} kerosene into the tank through a reference meter, the control unit 15 gave a mismatch signal (Нб amounted to 1218.7 cm) equal to the distance difference ΔН = Нб-Нбз = 1218.7-1216 = 2.7 cm, which indicates the deformation of the bottom. At the level gauge control unit 15, an alarm lamp illuminated, requiring a tank re-calibration.

Having measured the level with the help of an exemplary roulette, we got Нж = 1025 cm, and according to the calibration table the volume of kerosene was 2892.987 m ³ .

When comparing data on the volume of kerosene that passed through the reference meter and measured using a level gauge, we obtained the difference ΔV = (2892,987-2510,121) -380.06 = 2.806 m ³ .

Analysis of the study showed:

- when using manual level measuring instruments, the deformation of the tank bottom was ΔН = 2.7 cm, therefore, the unaccounted systematic component of the level measurement error will lead to a lack of kerosene equal to 2.806 m ³ ;

- the liquid level meter, taking into account the influence of the systematic component of the level measurement error (ΔН = 2.7 cm), allows you to reliably measure the level of oil in the tank, thereby solving the problem of improving the accuracy of level measurement.

The application of the invention will allow due to the combination of known structural units: a cylindrical body 2 with channels 5, and distinguishing features: a vertical pipe 1 with a horizontal partition 3, covered with a mirror (reflective) layer 4, forming a sealed cavity for measuring the base height of the tank, as well as the combination of applications structural units: float 10, source 11 and radiation receiver 12, optical closure 13 with drive 14 rotation, control unit 15, first 17 and second 18 corner reflectors, data in a step nozzle 6, the steps of which are separated by a glass partition 8 to protect the instrumentation from the effects of factors such as tarring, oxidation, etc., and mounted on a support base 7, which allows hermetic installation of the entire level gauge on the tank skylight , to increase the accuracy of measuring the liquid level in vertical tanks by eliminating the systematic component of the error from the deformation of the tank bottom, and also to quickly make a decision on the rebuilding Application reservoir.

Claims (1)

A liquid level gauge in rigid vertical tanks, containing a cylindrical body, the inner cavity of which is connected through the channels made in its lower part to the tank cavity, placed with the possibility of vertical movement in the cylindrical body of the float, the upper surface of which is coated with a mirror layer, the radiation source and receiver associated with the internal cavity of the cylindrical body through an optical contactor, made in the form of a disk with windows, on the outer surface of which is reflected the second layer, an angle reflector and a control unit of a sequence of operations, electrically connected with a radiation source and receiver and with an optical contact rotation drive, characterized in that it further comprises a stepped hollow cylindrical nozzle having a support base for tight mounting on the neck of a rigid vertical tank, the second corner a reflector and a glass partition separating the steps of the hollow cylindrical nozzle, in a step of a smaller diameter which is fixed with the possibility of for limited vertical movement of the pipe with a coaxially mounted cylindrical body of the level gauge, the annular gap between which at the lower ends is hermetically closed from the horizontal partition with a reflective layer on the inner surface, and an optical contactor is placed in the step of a larger diameter of the hollow cylindrical nozzle, in one of the windows of which the first and second corner reflectors are installed in the opposite direction, while the radiation source and receiver and the optical closure drive A mounted on the support base of the hollow stepped cylindrical nozzle.

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