JP4317563B2 - Gas leak rate measurement method and gas piping maintenance method - Google Patents

Description

  The present invention relates to a measuring method capable of accurately measuring a gas leakage rate at a flange joint portion of a gas pipe, and a gas pipe maintenance method capable of supplying a stable air and being excellent in economy.

  Air, argon, nitrogen, etc. are used as high-pressure gas used in the factory, and these high-pressure gases are supplied to each process from the compressor via the piping network. Will occur.

  Of high-pressure gas, air leakage is permissible as long as it does not affect the process of the supply destination, but leakage of toxic gas and flammable gas is not allowed even in a small amount, and expensive such as argon Gas leaks must be avoided in small quantities due to the large economic losses. For this reason, gas pipes that supply high-pressure gas can be visually checked for gas leaks, or by using a pressure gauge installed in the gas pipes to detect pressure fluctuations, etc. Management is performed.

  However, the visual inspection method has a problem that an error due to the learning of the manager is large, and the inspection method using the pressure gauge has a problem that it is difficult to detect a small amount of gas leakage. In order to solve these problems, various studies have conventionally been made on methods for detecting gas leaks in piping.

  For example, Patent Literature 1 discloses a gas leak detection pigment that changes color by reaction with a combustible gas such as hydrogen, carbon monoxide, acetylene, or methane by causing a specific compound to exist on the particle surface. . By applying the paint blended with this pigment to the surface of a pipe or the like, only the portion where the gas leakage occurs is discolored, so that the leakage of the combustible gas can be accurately detected. However, in the method disclosed in Patent Document 1, there is a problem that it is difficult to detect gases other than combustible gas, and it is necessary to paint all the gas pipes in the factory, which requires equipment costs. There's a problem.

  Patent Document 2 discloses an ultrasonic detector that detects leakage sound, a band-pass filter that inputs an output signal of the ultrasonic detector and passes only a predetermined narrow-band frequency, and an output of the band-pass filter. There has been disclosed an ultrasonic leak detector that includes a detector for detecting a signal and that can easily and accurately inspect leaks in a pipe joint or the like. Since the ultrasonic leak detector detects the frequency of the generated ultrasonic wave, it has an advantage that it can be applied regardless of the type of gas leaking and the equipment cost can be reduced.

  As described above, various techniques have been conventionally developed for detecting a gas leak generated in a pipe.

JP-A-8-129008 JP-A-11-142279

  If an ultrasonic leak detector is used, it is possible to easily detect a gas leak point in a pipe even in a wide range of pipe network surveys. In addition, there are various types of ultrasonic leak detectors that can detect not only the location where gas leaks occur, but also the gas leak rate at that location, that is, gas per unit time (for example, per minute). Detectors that can measure the amount of leakage are also being developed. By using such an ultrasonic leak detector capable of measuring the gas leak rate, it is possible to evaluate the progress of corrosion, perforation, etc. at the detected gas leak location.

  However, the present inventors investigated the piping network using an ultrasonic leak detector capable of measuring the gas leakage rate. Although measurement is possible, it has been confirmed that it is difficult to detect the gas leak point and measure the gas leak rate at the flange joint of the gas pipe. For this reason, when investigating the gas leakage situation in the piping network, it is difficult to accurately grasp the leakage amount of the entire piping network even if an ultrasonic leak detector capable of measuring the gas leakage rate is used.

  On the other hand, in the case of maintenance of gas pipes where the supplied gas is high pressure air, if there is a minute amount of air leak, leave it without repair, or repair or replace the gas pipe where air leak is confirmed each time. There is a case.

  If there is only a small amount of air leakage, leaving it without repair in the case of a small amount of air leakage will not interfere with production at the supplier, and if the output of the compressor that is the supply source is increased, the pressure will increase. This is because the problem of reduction does not occur. In addition, if the total length of the piping is long, the frequency of occurrence of minute air leaks increases, so repairing or replacing the piping every time an air leak location is detected increases repair costs and increases costs. Is also a factor that neglects a small amount of air leakage. However, even if a small amount of air leaks, the pressure in the piping is lowered when the number of occurrence points is remarkably increased, and if it is left for a long period of time, the adverse effect on the stable air supply becomes obvious, and repair is necessary.

  On the other hand, when repairing or replacing a gas pipe that has been confirmed to have an air leak, it is possible to reliably repair the air leak, but the supply of high-pressure air is stopped while the pipe is being repaired or replaced. However, since the supply amount is reduced, the production of the supply destination is affected. Furthermore, when the total length of the pipe is long, repair cost increases if the pipe is repaired or replaced each time a small amount of air leakage is detected.

  In this way, in the case of maintenance of conventional gas piping, when leaving a small amount of air leakage without repairing, the pressure drop in the piping due to a significant increase in the number of occurrences becomes a problem, and air leakage is confirmed. When repair or replacement is performed for each gas pipe, there is a problem in that the amount of air supply during the repair period is reduced and the repair cost is increased.

  The present invention has been made in view of the above problems, and is capable of accurately measuring the gas leakage rate at the flange joint of the gas pipe, and can supply a stable air and is excellent in economic efficiency. The purpose is to provide a maintenance method for the gas pipe.

  The present inventors use various ultrasonic leak detectors that can measure the gas leak rate, various methods for detecting the gas leak location at the flange joint of the gas pipe, and methods for accurately measuring the gas leak rate. Study was carried out. Examples of the ultrasonic leak detector that can measure the gas leak rate include Plant Walker (registered trademark) LEAK DETECTOR II (hereinafter referred to as “Plant Walker”) manufactured by Yamatake Corporation.

  FIG. 1 is a diagram schematically illustrating a method for detecting a gas leak point in a gas pipe and a method for measuring a gas leak rate using a Plant Walker. The Plant Walker 1 is an ultrasonic leak detector including a parabolic sound collector 2 having sound collection characteristics, an ultrasonic sensor 3, and a display operation panel 4 for setting a signal amplification level.

  When the gas pipe 5 is perforated, the gas flowing through the pipe is released into the atmosphere, so a vortex 6 is generated at the boundary between the stationary atmosphere and the gas with velocity, and ultrasonic waves are generated accordingly. Will occur. In the detection method using the Plant Walker 1, by directing the parabolic sound collector 2 in the ultrasonic flow direction 7, the ultrasonic sensor 3 senses an ultrasonic wave in the vicinity of 40 kHz and can detect a gas leak location. Furthermore, since the Plant Walker 1 can display the leakage level in ten or more stages based on the data recorded on the display operation panel 4, the gas leakage rate can be converted from the display.

  Even if such an ultrasonic leak detector is used, it is difficult to detect the gas leak location at the flange joint and to measure the gas leak speed with high accuracy. The reason for this is that the flange joint has a structure in which a gasket, which is a fixing seal, is sandwiched between two flanges, so that the flange becomes an obstacle and it is difficult to detect the ultrasonic waves generated from the gas leak location. It is done. Further, many gaskets are made of resin, and the fact that the material is different from the holed portion of the pipe is also considered to be a cause of difficulty in detecting ultrasonic waves.

  As a result of repeated studies, the present inventors applied a liquid that forms bubbles along with gas leakage (hereinafter referred to as “foam forming liquid”) to the entire circumference of the gasket at the flange joint, thereby causing gas leakage. Focusing on the repeated formation and rupture of bubbles at the flange joints, the knowledge that the ultrasonic leak detector improves the detection sensitivity of gas leaks by detecting a slight burst sound of bubbles Got.

  Furthermore, the present inventors apply a foam-forming liquid to the entire circumference of the gasket at the flange joint, so that the gas flow leaking from the flange joint is disturbed by the resistance of the liquid that wets the surface, and vortex generation occurs. It was found that the measurement accuracy was improved by performing measurement with the flange joints wet.

  As described above, when the flange joint was kept wet and an ultrasonic leak detector was applied, it was confirmed that not only gas leak was detected, but also the leak rate could be measured with high accuracy.

  Furthermore, the present inventors tried to use the value of the measured leakage rate for a maintenance method of gas piping in which the supplied gas is high-pressure air. Considering the loss of air due to leakage and the repair costs required for repairs, as well as the reduction in production efficiency due to leakage and the reduction in production efficiency during the repair period, etc., comprehensive adjustment between stable air supply and economic efficiency investigated. As a result, periodically check the occurrence of air leaks in the piping network with a detector, and based on the measured leak rate, repair only those areas that were determined to have a large problem due to air leaks, and trace air leaks. It was learned that it is an economical maintenance method to watch the progress of the leak rate without repairing the part.

The present invention has been completed on the basis of the above findings, and has the gist of the following (1) and (2) gas leak rate measuring method and the following (3) gas pipe maintenance method.
(1) A method for measuring a gas leakage rate at a flange joint portion of a gas pipe using an ultrasonic leak detector capable of measuring a gas leak amount per unit time, the fixing seal for the flange joint portion After the gasket portion is wetted by applying a foam-forming liquid, the gas leak rate of the flange joint is measured using the ultrasonic leak detector. Method.
(2) In the method for measuring a gas leakage rate described in (1) above, by using an aqueous solution of a surfactant as the foam-forming liquid, the generation of foam is promoted, and a fine burst sound of foam is detected. Therefore, it is desirable because the gas leak detection sensitivity is improved.
(3) A gas pipe maintenance method in which the gas supplied into the pipe is high-pressure air and has a plurality of flange joints, wherein the air leakage rate at the flange joints is set to the above (1) or (2 ) To determine whether or not the flange joint needs to be repaired based on the obtained leak rate value, and determine whether or not the measured flange joint needs repair. The maintenance method of the gas piping characterized by the above-mentioned.

  In the present invention, “gas” means various gases including industrially used air, non-combustible gas such as argon and nitrogen, and combustible gas such as hydrogen.

  Further, the “foam forming liquid” means a liquid having a surface tension enough to generate bubbles when a gas is blown and swells along with leakage of a gas pipe. For example, an aqueous solution of a surfactant such as soapy water or an aqueous solution of a detergent can be used.

  According to the gas leak rate measuring method of the present invention, after the flange joint is wetted by applying a foam-forming liquid, the gas leak rate of the flange joint is measured using an ultrasonic leak detector. As a result, it is possible to detect the gas leak location at the flange joint of the gas pipe, which has been difficult in the past, and to measure the leak rate with high accuracy.

  Furthermore, according to the maintenance method of the gas pipe of the present invention, since the air leak speed at the flange joint portion of the gas pipe can be grasped by adopting the gas leak rate measuring method, it is necessary to repair the air leak location. Can be objectively determined based on the measured leak rate, so that a stable supply of air can be performed and the repair cost can be minimized. As a result, loss due to air leakage can be reduced, and repair costs can be reduced, so that maintenance of gas piping with excellent economic efficiency becomes possible.

  According to the gas leak rate measuring method of the present invention, it is possible to detect the gas leak location of the flange joint portion of the gas pipe, which has been difficult in the past, and to accurately measure the leak rate. The detection of the gas leak location and the measurement of the gas leak rate at the flange joint are difficult to carry out with high accuracy because the flange becomes an obstacle and the ultrasonic waves generated from the gas leak location are difficult to detect.

  For this reason, the method for measuring the gas leakage rate of the present invention employs a configuration in which the gas leakage rate is measured after the pretreatment so that the gas leakage detection sensitivity is improved. Specifically, after the gasket portion, which is a fixing seal for the flange joint, is wetted by applying a foam-forming liquid, an ultrasonic leak detector is used to detect the gas leak location and the gas leak rate. Measure. Since the foam-forming liquid may be a liquid having a surface tension such that bubbles are generated when gas is blown, an aqueous solution of a surfactant such as soapy water is applicable.

  The reason why the flange joint is wetted with the foam-forming liquid in this way is that, since foam is repeatedly formed and ruptured, a fine burst sound of the foam is detected, so that the gas leak detection sensitivity is improved. In addition, it is considered that the flow of gas leaking from the flange joint is disturbed by the resistance of the liquid that wets the surface, thereby promoting the generation of vortices and improving the measurement accuracy.

  In the gas leak rate measuring method of the present invention, an ultrasonic leak detector capable of measuring the gas leak rate at the location where the gas leak occurs is used. As an ultrasonic leak detector having such a function, for example, the above-mentioned Plant Walker can be mentioned.

  Next, the maintenance method of the gas piping of the present invention will be described.

  The gas pipe maintenance method of the present invention is a gas pipe maintenance method in which the gas supplied into the pipe is high-pressure air and has a plurality of flange joints, and the air leakage rate at the flange joints is determined. Measure using the measurement method specified in the invention, determine whether or not the flange joint needs to be repaired based on the obtained leak rate value, and determine whether the measured flange joint needs repair or not It is characterized by that.

  In this way, pipes that are supplied with high-pressure air in the pipes are targeted for leaks of toxic gases and flammable gases even in small quantities, and leaks of expensive gases such as argon are This is because even a small amount must be avoided because the economic loss is large.

  In the gas pipe maintenance method of the present invention, it is determined whether the flange joint is repaired or not repaired based on the measured value of the leakage rate. As described above, based on the actually measured data, it is possible to objectively determine whether or not the air leaking portion needs to be repaired. Therefore, it is possible to supply a stable air and to minimize the repair cost.

  As a specific determination method, a specified value for the allowable leak rate is determined, and if the leak rate exceeds the specified value for each flange joint, it is determined that repair is necessary, and the leak rate is less than the specified value. In this case, there is a method for determining that repair is unnecessary.

  In addition, the leak rate of all flange joints is measured and accumulated from the top in the order of the leak rate, and it is determined that repair is necessary as a group of points where the accumulated leak rate falls within the set tolerance. The remaining portion may be determined as not requiring repair. For example, if a method of determining that the top 2% of the measured leak rate in the flange joint is repaired is required, the loss due to the amount of gas leakage can be reduced and the repair cost can be suppressed as will be described later. .

In order to confirm the effects of the gas leak rate measuring method and the gas pipe maintenance method of the present invention, the air leak rate of all flange joints of the pipe supplied with air was measured in the factory.
(Test conditions)
An example of the present invention in which the leakage rate was measured by the method defined in the present invention and a comparative example in which the leakage rate was measured by a conventional method were performed on 1000 flange joints, respectively.

  In the measurement of the air leak rate, Plant Walker was used as an ultrasonic leak detector, and soap water was used as a foam forming liquid.

  Regarding the maintenance method of gas piping, based on the measured air leak rate at each location, the top 2% with the highest leak rate, that is, the 20 locations with the highest leak rate in 1000 locations are selected and determined to be repaired. The method was adopted. When there were a plurality of places corresponding to the 20th place from the top, the number of places required at random was selected from the places corresponding to the 20th place, and the top 20 places were determined.

  In the comparative example, air leak detection and air leak rate measurement were performed by Plant Walker in a dry state without pretreatment, that is, without wet by applying soapy water to the flange joint before measurement. did. All locations were measured, but no air leak was detected in the first measurement.

  For this reason, all locations were carefully measured over a sufficient time again. The detection of the air leak location was not stable, and the reproducibility of the measured value of the leak rate was poor, so that the measurement time required about five times as long as that of the present invention example. As a result, since it was possible to barely detect 32 leak points, the top 20 points were identified from among them, and it was determined that repair of the flange joint was necessary. The total leak rate of 20 flange joints determined to be repaired was calculated and repaired.

Following the comparative example, the inventive example was carried out. First, the entire circumference of the gasket at the flange joint was wetted by applying soapy water, and the air leakage rate at the flange joint was measured using a Plant Walker. As a result of carrying out this operation for all locations, 720 leak locations were detected in 1000 locations. Twenty locations where the measured leakage rate was high were selected, and it was determined that repair of the flange joint was necessary. A total value P (m ³ / min) of gas leakage rates at 20 flange joints determined to be repaired was calculated for repair.

For each of the inventive examples and the comparative examples, the air use conditions were substantially the same, and the average value of the amount of air supplied from the compressor before and after repair was calculated per day. Based on this calculated value, a decrease R (m ³ / min) of the air supply amount from the compressor after repair was calculated. If the effect of reducing the air leakage rate by repairing the piping is large, the amount of air sent from the compressor can be reduced. It becomes an index of the speed reduction effect.
(Test results)
As a result of comparing the reduction amount R of the air supply amount after repair in the inventive example and the comparative example, in the inventive example, the air supply amount corresponding to about 8 times that of the comparative example was reduced. That is, it was confirmed that the effect of reducing the air leakage rate of the example of the present invention was about 8 times that of the comparative example.

  Furthermore, in the example of the present invention, the total value P of the air leakage speeds of the 20 flange joints determined to be repaired was within a range of ± 50% of the reduction amount R of the air supply amount from the compressor. . From this, it was confirmed that the measurement method of the leak rate according to the present invention has good measurement accuracy.

  According to the gas leak rate measuring method of the present invention, after the flange joint is wetted by applying a foam-forming liquid, the gas leak rate of the flange joint is measured using an ultrasonic leak detector. As a result, it is possible to detect the gas leak location at the flange joint of the gas pipe, which has been difficult in the past, and to measure the leak rate with high accuracy.

  Furthermore, according to the maintenance method of the gas pipe of the present invention, since the air leak speed at the flange joint portion of the gas pipe can be grasped by adopting the gas leak rate measuring method, it is necessary to repair the air leak location. Can be objectively determined based on the measured leak rate, so that a stable supply of air can be performed and the repair cost can be minimized. As a result, loss due to air leakage can be reduced, and repair costs can be reduced, so that maintenance of gas piping with excellent economic efficiency becomes possible.

  Thus, the gas leak rate measuring method and gas pipe maintenance method of the present invention can be widely applied as a method that enables facility management with excellent economic efficiency.

It is a figure which illustrates typically the detection method of the gas leak location in gas piping, and the measuring method of a gas leak rate using Plantwalker.

Explanation of symbols

1. Plantwalker 1. 2. Parabolic sound collector Ultrasonic sensor 4. 4. Display operation panel Gas piping 6. Vortex 7. Ultrasonic flow direction

Claims (3)

A method for measuring a gas leak rate at a flange joint of a gas pipe using an ultrasonic leak detector capable of measuring a gas leak amount per unit time,
Gas leakage rate of the flange joint after wetting the gasket part, which is a sealing seal for the flange joint, by applying a liquid that forms bubbles with gas leakage (hereinafter referred to as “foam forming liquid”) Is measured by using the ultrasonic leak detector.   The method for measuring a gas leakage rate according to claim 1, wherein the foam forming liquid is an aqueous solution of a surfactant. The gas supplied into the pipe is high-pressure air, and a maintenance method for the gas pipe having a plurality of flange joints,
The air leakage rate at the flange joint is measured using the measurement method according to claim 1 or 2, and the necessity of repair of the flange joint is determined based on the obtained leak rate value. A maintenance method for gas piping, characterized by determining whether or not repair of a flange joint is necessary.

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