CN103097817A - Line having a safety system - Google Patents

Abstract

The invention relates to a line (1) for a steam power plant comprising an inner pipe (2) and an outer pipe (3), wherein a flow medium present between the inner pipe (2) and the outer pipe (3) as a result of a leakage in the inner pipe (2) can be exhausted and detected by means of an exhaust device (7).

Description

pipeline with safety system

technical field

The invention relates to a pipeline comprising an inner tube and an outer tube arranged around the inner tube, wherein the outer tube surrounds the inner tube in a gas-tight manner, wherein an intermediate space is formed between the inner tube and the outer tube.

Background technique

In thermal power plants, for example, pipes are used which generally have the purpose of transporting a flowing medium safely and without leakage losses. Apart from simple conveying purposes, pipes have to be designed mechanically under high thermal stress. Of course, reliable inferences about service life can become difficult without sufficient knowledge about expected operation. Pipes subjected to multiple temperature cycles are especially highly loaded. These temperature cycles are possible in highly transient operation. Precisely in this highly transiently loaded region, failure of the pipeline must be prevented. Damage to the pipe wall caused by multiple temperature changes must be prevented.

In addition to the high transient operation that results in piping loads, the welds that join the pipes together are also weak points. Damage can occur on the weld seam which can lead to an undesired escape of the flow medium. Therefore, it is also necessary to prevent possible failures in the region of the weld seam.

Especially in steam power plant installations pipes that are extremely thermally loaded are used. Usually, so-called working vapor coolers are used in the pipeline. Working vapor coolers are used for vapor cooling when conventional splash coolers are not or only insufficiently functioning due to difficult operating parameters. Working steam coolers usually consist of a binary nozzle, where the spray steam is discharged from the nozzle mouth at a critical velocity and the sprayed cooling water is atomized into ultra-fine droplets. Therefore, localized cooling of the pipe is possible. It is known to use so-called thermal insulation layers in inner pipes, thus reducing the thermal load on the pipe wall. The shielding layer is a mechanical component or a conical steam jet which conically surrounds the central working steam. The shield prevents water droplets from coming into contact with the pipe wall. Therefore, sudden temperature changes and material fatigue of the pipe wall can be reduced.

Of course, the shielding layer does not always withstand the mechanical demands. The loss of the shielding due to spalling can lead to localized overheating of the pipe wall. In addition, spalling of the shielding layer can also mechanically damage components remote from the fluid through small, worn parts.

Contents of the invention

The object of the invention is to design a pipeline such that a safer operation is possible.

The object is achieved by a pipeline comprising an inner tube and an outer tube arranged around the inner tube, wherein the outer tube surrounds the inner tube in a gas-tight manner, wherein an intermediate space is formed between the inner tube and the outer tube, wherein the pumping The suction device for sucking the flow medium is arranged such that the flow medium located in the intermediate chamber can be sucked, the suction device comprising a detection device which detects the flow of the flow medium. The flow of the flow medium in the suction device almost necessarily leads to the conclusion that there is a leak in the inner pipe. A signal indicative of damage can be output by a suitable detection device, for example a flow measuring counter.

The invention is based on the fact that damages in pipelines can be detected early on according to the invention. In the event of damage, the flow medium can pass into the intermediate space. The suction device, which is designed to suck in the flowing medium, sucks out the flowing medium. Thus, clearly identifiable physical parameters can be determined in order to detect damage in the line, in particular in the inner tube. The flow medium in the suction device has to be detected by means of suitable means in order to ultimately detect damage. For example, flow counters or temperature sensors can be provided in the suction device. The increase in temperature led to the conclusion that there was a leak in the inner tube. The increased flow also leads to the possible conclusion that there is damage in the inner tube.

As soon as a damage occurs in the inner tube and the flow medium in the region of the damage is able to escape from the inner tube, the flow medium flows into the intermediate space, which is located outside the inner tube and is gas-tight relative thereto. closed. This means that the flow medium is located in the intermediate space and cannot flow out. The only outflow possibility is via a suction device. The presence of damage in the inner tube can thus be immediately concluded from the flow medium which can be detected in the suction device. As long as the damage is not excessive, the tubing can still be used.

Advantageous developments are given in the dependent claims. In a first advantageous development, the suction device is therefore developed in such a way that it comprises a line protruding into the intermediate chamber. Thus, a relatively simple mechanism is provided which discharges the flow medium located in the intermediate space. The line must only be connected to devices by means of which a pressure different from, in particular lower than, the pressure in the intermediate chamber can be generated and a flow medium can be received.

In another advantageous development, the detection device has thermocouples. In addition to flow counters, thermocouples can detect damage, since the flow medium in the suction device usually has a high temperature. The occurrence of damage in the inner tube can likewise be concluded from the temperature rise detected by means of thermocouples.

In a particularly advantageous development, the line includes a condenser, wherein the suction device is fluidically connected to the condenser. Provides a closed water steam cycle in steam power plants. This means that at one point the water is converted into steam, which is condensed back into water in the condenser. The pressure in the condenser is very low. When the suction device is fluidically connected to the condenser, a pressure drop occurs from the intermediate chamber to the condenser. The flow medium located in the intermediate space can thus flow directly to the condenser. The flow can be detected by a flow meter. As already mentioned, flows due to temperature rise can also be detected.

In an advantageous development, the outer tube is of thinner-walled design than the inner tube.

The thermally loaded parts of the line are therefore designed according to the invention with a thin-walled tube surrounding the inner tube, which is formed as an elastically closed container. The region can be, for example, in the region of the weld seam or in the region of the mixing path downstream of the working steam cooler. The different thermal expansions of the inner tube and the outer tube lead to tensions which can be compensated by the thin-walled outer tube. The outer tube is therefore designed to withstand said tension. Therefore, the outer tube is formed thinner than the inner tube. Since only slight leaks can be detected, the outer tube does not have to be designed against the total live steam pressure, which allows a thin-walled and thus elastic construction. Due to the thin-walled construction, it must be designed against indentation when vacuum loads occur.

In order for the intermediate space to be as airtight as possible, in another advantageous development the inner tube is welded to the outer tube. In a further advantageous development, the line includes a working steam cooler which protrudes and is guided through the outer tube and the inner tube in a gas-tight manner. This means that the working gas cooler vapor is guided through the inner tube and the outer tube in a tight manner.

The present invention will now be further elucidated on the basis of examples. Components with the same reference number generally show the same properties.

Description of drawings

The accompanying drawings show:

Figure 1 shows a cross-sectional view of the pipeline,

Figure 2 shows a cross-sectional view of the pipeline in the direction of flow.

Detailed ways

FIG. 1 shows a cross section of a line 1 . The pipeline 1 includes an inner tube 2 and an outer tube 3 . Line 1 is suitable for steam delivery of relatively hot steam (>600°C). The outer tube 3 is arranged on the inner tube 2 in an airtight manner. For this purpose, the outer tube 3 has a weld seam 4 which is formed in the circumferential direction relative to the axis of rotation 5 . An intermediate chamber 6 is formed between the outer tube 3 and the inner tube 2 . The line 1 is designed with an outer tube 3 , in particular at locations that are subjected to high thermal loads. The outer tube 3 is thin-walled in relation to the inner tube 2 . This means that the wall of the outer tube 3 is thinner than the inner tube 2 . The inner tube 2 and the outer tube 3 are made of steel. The wall thickness of the outer tube 3 is between 10% and 80% of the thickness of the inner tube 2 . The thickness of the outer tube 3 can also adopt the following ranges: 20%-70%, 20%-60%, and 20%-50% of the wall thickness of the inner tube 2 .

The wall thickness of the outer tube 3 is therefore made thinner than the inner tube 2, so that the different thermal expansions of the inner tube 2 and the outer tube 3 that occur during operation can lead to tensions that can be caused by the thin-walled outer tube 3 Compensation. Additional flexible elements (e.g. bellows-like structures) must be considered as required. The outer tube 3 is designed to resist indentation. If a leak occurs, the intermediate space 6 can be detected by the suction device 7 as a result of the leak flowing through the intermediate space 6 . In the simplest case, the suction device 7 is designed as a line 8 which protrudes into the intermediate space 6 . Said line 8 is fluidically connected to a condenser, not further shown. This means that the low pressure in the condenser causes the flow medium in the intermediate space, where the pressure is higher than in the condenser, to be able to flow out.

The outer tube 3 surrounds the inner tube airtightly. The suction device 7 is designed for suctioning the flow medium located in the intermediate chamber 6 . The suction device 7 includes a detection device, not further shown, which detects the flow of the medium. In the simplest case, a flow measuring counter can be provided in the pipe 8 , which can detect a sudden increase in the flow in the pipe 8 as a leak in the inner pipe 2 .

Alternatively or additionally to the flow measurement counter, a thermocouple 9 can be arranged in the line 8 . A sudden increase in temperature detected by the thermocouple 9 can be concluded as a leak in the inner tube 2 .

The inner tube 2 is particularly highly transiently loaded. This means that varying temperature cycles occur at these locations. In an alternative embodiment, the line 1 is designed with a working steam cooler 10 which is arranged in a gas-tight or steam-tight manner through the inner tube 2 and the outer tube 3 . Especially in the region of the working steam cooler 10 the inner tube 2 is exposed to high thermal loads. Through the working steam cooler 10, the spray steam is discharged from the nozzle nozzle at a critical speed and the cooling water sprayed along the rotation axis direction 5 is atomized into ultra-fine droplets.

FIG. 2 shows a cross-sectional view of the line 1 (seen in the direction of the axis of rotation 5 ). As can be clearly seen in FIG. 2 , the intermediate chamber 6 is an air-tight or vapor-tight chamber in which leaks occurring in the inner tube 2 can be detected and detected. The suction device 7 is not further shown.

Claims (8)

1. pipeline (1), described pipeline comprise inner tube (2) and the outer tube (3) that arranges around described inner tube (2),

Wherein said outer tube (3) surrounds described inner tube (2) airtightly,

Wherein form intermediate cavity (6) between described inner tube (2) and described outer tube (3),

The aspirator (7) that wherein is used for the suction streams moving medium is arranged to aspirate the flow media that is positioned at described intermediate cavity (6),

It is characterized in that,

Described aspirator (7) has checkout gear, and described checkout gear identifies flowing of described flow media.

2. pipeline according to claim 1 (1),

Wherein said aspirator (7) comprises pipeline (8), and described pipeline extend in described intermediate cavity (6).

3. pipeline according to claim 1 (1),

Wherein said checkout gear has thermocouple (9).

4. pipeline described according to one of the claims (1), described pipeline comprises condenser,

Wherein said aspirator (7) is connected with described condenser fluid.

5. pipeline described according to one of the claims (1),

Wherein said outer tube (3) constitutes than described inner tube (2) thin-walled more.

6. pipeline described according to one of the claims (1),

Wherein said outer tube (3) is welded on described inner tube (2).

7. pipeline described according to one of the claims (1),

Described pipeline has working steam cooler (10), and described working steam cooler stretches into and passes described outer tube (3) and described inner tube (2).

8. pipeline according to claim 7 (1),

Wherein said working steam cooler (10) airtightly or steam seal pass described outer tube (3) and described inner tube (2).

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