JPS6330737A - Apparatus for detecting abnormality of gas line - Google Patents

Abstract

PURPOSE:To detect minute pressure change generated by the leakage of gas while certainly discriminating from pressure variation, for example, the gas consumption due to the operation of a plant, by providing a differential pressure detection means, a gas leakage data obtaining means and a judging means. CONSTITUTION:Pressure guide piping 13 is provided to a gas line 11 on the upstream or downstream side of a gas leakage point 12 and a differential pressure detection means 14, which is equipped with a capacity element and a resistor element and detects the difference pressure between the specific places of the piping 13, is provided to the pressure guide piping 13. CPU 17 has a gas leakage data obtaining means consisting of a data sampling means, a data renewing means and a relative value data operation means and a judge means. Then, a difference pressure detection signal is successively sampled at a predetermined cycle by the gas leakage data obtained means to obtain relative value data relating to gas leakage on the basis of one or more of gas leakage detection algorithm and the presence of gas leakage or a gas leakage point if necessary is judged by a judging means using said relative value data.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a gas line abnormality detection device that detects abnormalities such as gas leaks in gas piping, plant gas pipelines, etc. This invention relates to a device that can detect abnormalities such as gas leaks.

[Prior Art] Fluid leaked due to damage to a pipeline or the like includes liquid gas and the like. Liquid transport systems related to the former are used when applying a predetermined pressure inside a pipe to transport a liquid such as oil to a predetermined location. In this liquid transport system, various liquid leak detection devices have been developed for the purpose of detecting leaks of oil or the like from pipelines, and are actually installed in vibrator lines. By the way, in such a system, when liquid leaks from the pipeline, pressure fluctuations as shown in FIG. 10 usually occur at a point upstream from the leak point, an intermediate point 8, and a downstream point. Therefore, as is clear from the figure, a relatively large pressure fluctuation occurs at the upstream point 1 at the start of liquid leakage st and at the end of the leakage en, and propagates to the intermediate point 2 and downstream point 3. Liquid leakage can be detected relatively easily and reliably.

On the other hand, gas leak detection is not so simple. There are two possible reasons for this.

One reason is that since gas is a compressible fluid, dynamic fluctuations occur in the line pack amount of gas inside the vibe line. Therefore, for example, even if a change in gas pressure or gas flow rate occurs at one end of the pipeline, it takes a considerable amount of time for the effect to appear at the other end of the pipeline. It is attenuated and diffused as it propagates through the interior, and arrives in the form of a considerably rounded pressure change. Furthermore, the effects do not always appear with a certain time delay.

Therefore, detecting gas leaks is extremely difficult.

The other reason is that even if gas leaks due to pipeline damage, the resulting change in gas pressure, etc. is very small in terms of signal level compared to liquid, and gas pressure, etc. attenuates and diffuses rapidly. It is difficult to distinguish this from the various changes in gas pressure, etc. that occur during normal operation of the plant.

Therefore, gas leak detection involves the above-mentioned special factors, so if the liquid leak detection device is applied as it is as gas leak detection 5Ae, false alarms will occur frequently during plant operation, and each time The plant was forced to shut down without a vote, and there was a risk that if a gas leak actually occurred, it would be overlooked and cause a major accident.

Therefore, conventionally, several gas leakage detection means have been adopted or proposed that take into account the unique properties of gases, which are different from those used for liquid leakage detection. These will be briefly explained below.

(1) One method is to use a gas detector that measures leaked gas components and determines that there is a gas leak, and this is currently the mainstream gas leak detection method. In other words, this gas detector should be installed in a location within the yard where there is a high probability that leaking gas will float.

If it is a gas pipeline, it will be installed inside the valve house, or if it is a patrol car, it will be mounted on it.
It is designed to detect the presence or absence of gas leaks.

(2) The other method focuses on the fact that when gas leaks, a leakage sound is generated at the gas leakage hole, and detects this leakage sound using a portable microphone.

■ In addition, one other method is to install a pressure detector at the starting and ending base of the gas/vibration line or in the middle of the vibe line, and set the pressure detected by this pressure sensor and the upper and lower limit set values set in advance. This is a means of detecting gas leaks by comparing the

[Problems to be Solved by the Invention] However, each of the above three means has the following problems. That is, in the method (2) above, apart from monitoring by patrol cars, it is necessary to install a large number of gas detectors, so it is difficult to implement, for example, in a plant. However, this method was not suitable for monitoring the entire plant.

In addition, in the method (2) above, regardless of the case where a portable microphone is installed near the gas leak hole, it is extremely difficult to detect gas leaks as the distance from the gas leak hole increases, resulting in problems in terms of practicality and reliability. That was the problem.

Furthermore, in the method (2) above, gas leakage is determined indirectly, and detection is difficult unless a large amount of gas is leaked.

On the other hand, a method has been considered for detecting gas leaks by providing a throttle in the gas line and monitoring the differential pressure before and after the throttle with a differential pressure detector to detect pressure waves that occur when a leak occurs. In this method, in the case of plant piping, a valve that is slightly restricted even in a fully open state may be used, so it is sufficient to monitor the differential pressure before and after the valve. However, in the case of gas pipelines, gas transport energy is lost at the valve part, and
It is difficult to provide a restrictor in the middle of the line because the movement of the VIG inside the pipe is obstructed for purposes such as cleaning the inside of the pipe or inspecting the condition inside the pipe, so there is room for consideration in the application of the above-mentioned method.

The present invention has been made based on these circumstances, and its purpose is to reduce the minute pressure changes caused by gas leaks, for example, by reducing the pressure that occurs during plant operation, even without providing a restriction in the gas line. To provide a gas line leak detection device that can detect gas leaks by reliably distinguishing them from fluctuations, and can accurately and quickly detect gas leaks based on appropriate data while taking various conditions into account. be.

[Means for Solving the Problems] In order to solve the above-mentioned problems and achieve the object, the present invention includes equipping the impulse piping attached to the gas line with at least one of a capacitance element and a resistance element. A differential pressure detection means for detecting a differential pressure between specific points of the pressure piping is provided, and the differential pressure detection signal is sequentially sampled at a predetermined period by a gas leakage data acquisition means to detect at least one gas leakage. Relative value data regarding gas leakage is acquired based on an algorithm, and the determination means uses the acquired relative value data to determine whether or not there is a gas leakage.

[Function] By taking such measures, a differential pressure signal having a relatively large change can be detected by the differential pressure detection means installed in the pressure piping from the gas line without providing a restriction in the gas line. The differential pressure signal is sequentially sampled and updated by a gas leak data acquisition means at a period that is not affected by pressure during plant operation, for example, and the sampling signal is updated using at least one optimal gas leak detection algorithm. By acquiring relative value data regarding gas leakage, the presence or absence of gas leakage is determined.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a system diagram showing the overall configuration of an abnormality detection device including a gas line 11. As shown in FIG. A pressure piping 13 is attached to the gas line 11 on the upstream or downstream side of the gas leak point 1°2, and this pressure piping 13 is equipped with a capacitance element and a resistance element. A differential pressure detection means 14 is provided for detecting a differential pressure between specific locations. 15 in the figure is A/
The D conversion means amplifies the minute differential pressure detection signal output from the differential pressure detection means 14 at a predetermined amplification degree, converts it into a digital signal proportional to the amplified output value, and outputs the signal. , to the interface 16. Reference numeral 17 denotes a CPU (central processing unit) that controls predetermined arithmetic processing and necessary components based on a sequence program or instructions from the outside.

A pass line 18 is led out from this CPU 17, and includes not only the interface 16 but also a ROM (
19. RAM (random access memory) 20 and traffic buffer 21
etc. are connected. The ROM 19 stores fixed constants for sequence programs and calculations, for example, 5
Gas leak detection algorithms A1 to A5 are described.

Incidentally, an example of each of the algorithms A1 to A5 is as follows. Here, P is a differential pressure detection signal, i is the i-th sampling, Δt is a dummy, and C is a set value for determining the presence or absence of gas leakage by a determining means described later. That is, algorithm A1 is a simple comparison between the previous sampling data and the current sampling data, and represents the differential pressure change for each sampling. Algorithm A2 is a comparison between the average value of the sampling data from n times before to the previous time and the current sampling data, and represents the differential pressure deviation of the current data from the average data from the previous time. Algorithm A
3 is a comparison between the average value from n times before to m times and the average value from (m-1) times before to this time, and represents the differential pressure difference between the past average value and the current average value. Algorithm A4 is to individually compare the sampling data from n times before to the previous time with the current data and obtain the logical sum or logical product of the data.
It represents the maximum differential pressure difference (logical sum) or the minimum differential pressure difference (logical product) of sampling data within a certain period of time.

Algorithm A5 is a comparison between the maximum value and the minimum value within a certain period of time, and represents the maximum imaging range of the differential pressure. These algorithms A1 to A5 are read and selected by the CPU 17 through the human output buffer 21 from an input key 22 such as a snap switch or other general keyboard.

The RAM 20 is used to temporarily store data of operation results, transmission data arriving from a slave station on the other side, and the like. Reference numeral 23 is an output device, and as a very simple means, for example, a lamp is provided to indicate a gas leak or other abnormality, and if necessary, a CRT display to display an image such as a character 1 figure, etc., and furthermore a printing device. etc. will be provided.

In short, they are selected and used in consideration of various conditions such as the processing capacity of the CPU 17, programs, and prices.

24 is a line control unit, which can be connected via a human output buffer 25 connected to the pass line 18, receives control data from the CPU 17, and controls the gas line 11 based on the data. be. Further, a teleconmeter 27 having a slave station function can be connected to the path line 18 via an interface 26 . Note that a slave station is installed for each device of the present invention, and data from each slave station is transmitted to the parent 8 (not shown), or necessary data sent from the master station to each slave station is received. It has become. Although not shown, the master station is connected to the host computer, where it grasps the operating status of the entire plant, processes the necessary data, and displays the necessary data on the display section of the operation panel. This allows for monitoring by displaying images and controlling the entire line based on the monitoring results.

FIGS. 2(a) to 2(C) are diagrams showing specific configuration examples of the differential pressure detection means 14. FIG. This detection means 14 is connected to gas lines 11 to 21! Impulse piping 13 having l outlet ports
In the combination of the resistance element 31, the concentrated capacity element 32, and the distributed capacity element 33, the inflow/outflow flow rate of the pressure piping 13 based on the pressure fluctuation of the gas line 11 is reduced.
A time delay element is provided only on one side of the differential pressure converter 34 to create a time lag in the flow rate flowing into and out of the differential pressure converter 34, and a differential pressure signal is extracted from this time lag. There is. That is, FIG. 2(a) shows a configuration in which a lumped capacitance element 32 and a resistance element 31 are provided in series on one side of a differential pressure converter 34, and FIG. A distributed capacitance element 33 and a resistance element 31 are provided in series on one side, and in FIG. 33 and resistance element 31 are provided in series. Due to the time delay circuit constituted by these elements, even if a small pressure fluctuation occurs at the leak point 12 as shown at time st1 in Fig. 3 due to a leakage of about 5% of the line flow rate, for example, the time delay circuit shown in Fig. 4 It can be extracted as a clear differential pressure signal as shown at time st2.

By the way, when a leak occurs in the gas line 11, the pressure fluctuation in the gas line 11 at the location where the detection means 14 shown in FIGS.
Near the leak point 12, the main pressure fluctuation is a combination of step pressure fluctuation and ramp-like or damped wave-like pressure fluctuation, and further away from the leak point 12, the main pressure fluctuation is a ramp-like or damped wave-like pressure fluctuation. Become something. Here, it is assumed that the gas line pressure fluctuations at the gas introduction and outlet ports from the gas line 11 of the pressure piping 13 are almost the same, and that the pressure fluctuations in the gas line 13 are assumed to be almost the same, and that 32. Assuming a temporary delay circuit with the time constant of the impulse piping 13 on the side where the resistance element 31 and the resistance element 31 are provided as a lower value, and assuming that the time delay of the impulse piping 13 on the other side can be ignored, the line pressure This is the differential pressure signal when the pressure changes in a stepwise manner. However, in equation 1), A is a constant representing the magnitude of the step-like pressure fluctuation, A is a constant representing the sensitivity of the differential pressure converter 34, and A is time. Furthermore, the characteristics of the differential pressure converter 34 are taken into consideration under the time constant.

On the other hand, under the same assumption, the differential pressure signal ΔP2 when the line pressure fluctuates in a ramp-like manner is -H ΔP2-BkT(1-e)
-(2). However, B is a constant indicating the magnitude of the ramp-like pressure fluctuation.

Also, the differential pressure signal △P3 when the pressure fluctuates in a damped waveform
Hato becomes. However, C and D are constants indicating the magnitude of the attenuated wave and the state of attenuation. Note that this is the case of CT.

Therefore, using these equations (1) to (4), characteristics A, 8. By considering C and D, the sensitivity constant and time constant T of the detection circuit 14 can be estimated.

Next, the CPU 17 performs processing as shown in FIG. 5 based on the sequence program data.

That is, the CPU 17 has a gas leakage data acquisition means consisting of a data sampling means 41, a data updating means 42, and a relative value data calculating means 43, and based on the relative value data, determines whether or not there is a gas leak and, if necessary, the location of the gas leak. It has a judgment means 44 for making a judgment, and additionally includes a detection system diagnosis means 45 for diagnosing the presence or absence of a failure in the pressure detection system. A transmission control means 46 transmits the relative value data and the result determined by the determination means 44 to the master station via the telecontelemeter 27, and a transmission control means 46 transmits the relative value data and the result determined by the determination means 44 to the line control section 24. It has a line control means 47 for controlling and discharging.

Specifically, the sampling means 41 has a function of sequentially sampling the digital differential pressure detection signal detected by the differential pressure detection signal 14 at a predetermined period using a clock. This predetermined period is determined, for example, as follows. In other words, pressure detection including differential pressure must detect transient pressure wave fluctuations that momentarily pass through the location where the detector is installed, and the influence of pressure fluctuations that normally occur under m-beams in plants, etc. must be detected by reducing it as much as possible. The pressure fluctuations that occur when a leak occurs are the pipeline pressure, internal diameter, l! There are differences depending on the amount of leakage, etc., but by numerically or experimentally comparing the pressure fluctuations during normal operation and during gas leakage, we have determined that the sampling period is almost unaffected by pressure fluctuations under normal operation. It is possible to know the upper limit of the sampling period and the lower limit of the sampling period at which transient minute pressure fluctuations can be reliably detected. Therefore, although the sampling period is also related to the data processing resolution of the subsequent component, it is preferable to sample using the above-mentioned sampling period as a guide.

Next, the data update F'r processing means 42 sequentially updates the data sampled by the sampling means 41 and stores it in the table of the RAM 20. It is determined by whether relative value data is obtained using leakage detection algorithms A1 to A5.

The relative value data calculating means 43 selects the leak detection algorithm desired by the operator from among the plurality of leak detection algorithms A1 to A5, and based on this selects the leak detection algorithm desired by the operator.
It has a function of reading necessary data from AM20, processing it according to an algorithm, and obtaining relative value data.

The determining means 44 uses each gas leak detection algorithm A1 to A.
The presence or absence of gas leakage is determined by using the upper and lower limit set values or any one of them determined according to No. 5, and by comparing the relative field data based on past empirical data. Further, this judgment means 44 receives the data of the diagnosis result outputted from the detection system diagnosis means 45 and transmits it to the transmission control means 46.
and sends necessary data to the line control means 47. Furthermore, using these data, the location of the gas leak can be determined as necessary.

In other words, the pressure waves generated by the occurrence of a gas leak propagate to the upstream and downstream sides of the gas leak point 12 at (sonic velocity - gas flow velocity) and (sonic gas flow velocity), respectively, so that the pressure waves are propagated at intervals that can be known in advance. If you install additional pressure or differential pressure detectors, the pressure wave detection time interval ΔT of each detector
From the following equations, the gas leakage point can be easily estimated using the following simultaneous equations: 1=a+b ΔT=[a/(sonic velocity−gas flow velocity)]−[b/(sonic velocity+gas flow velocity)]. However, a and b are the distances from the gas 31 leak point 12 to the detector installation location.

Next, the operation of the device configured as described above will be explained. When the differential pressure detection signal between specific points of the pressure piping 13 detected by the differential pressure detection means 14 is sent to the A/D conversion means 15, it is amplified at a predetermined amplification degree and converted into digital data. , from interface 16 to pass line 18 via multiple bit lines.

At this time, CP'U17, for example, l sea li1
The differential pressure detection data on the pass line 18 is sampled using the periodic clock, and the known data stored in the table in RA~120 is stored while being updated sequentially.

Therefore, normally, when a raw signal is captured by the differential pressure detection means 14 installed upstream of the gas leak point 12, a signal containing noise as shown in FIG. 6 is detected, but the sampling means 41 detects it. A thinning process is also being performed at the same time.

The CPU 17 sequentially samples the differential pressure detection data at a predetermined period, and performs the following processing for each sampled data.

That is, a desired gas leakage algorithm is specified in advance using the input key 22, but the algorithm may be changed during the data processing process. For example, when a simple comparison between the previous sampling data and the current sampling data is desired, that is, the differential pressure change (relative value data) for each time, algorithm A1 is specified. However, since this one result cannot be used as is unless the differential pressure change is extremely large, it is effective to make a decision in the determination means 44 based on data from a plurality of times. Algorithm A2. A3 is superior to A1 in terms of accuracy. In addition, algorithm A2 has a relatively fast processing time for determining the presence or absence of leakage, and algorithm A3 is resistant to noise. However, this algorithm A3 requires processing time. In this way, the algorithms A1 to A5 are specified based on past experience and the like while taking into consideration the importance of the line bottom and the plant. Then, for example, the CPU 17 selects and reads the gas leakage algorithm, for example A3, from the ROM 19 according to the specification, and for each sampling, calculates the average value from n times before to m times and the average value from (m-1> times before to this time). A comparison is made to find the differential pressure difference between the past average value and the current average value.

As an example, FIG. 7 is a diagram obtained by sequentially plotting relative value data obtained by algorithm A3.

Then, the relative value data obtained in this manner is used to determine whether there is a gas leak or not by the determining means 44. This judgment means 44 has an upper limit setting value Vu and a lower limit setting value Vd as leak judgment setting fields, and compares it with the relative value data obtained for each sampling, and when the gas exceeds each setting value VU, Vd. It is determined that there is a leak, and a necessary component such as the output device 23 displays this fact, or
Line control means 47 including line control unit 24 through 5
The input/output buffer 25 sends a command to the telecontelemeter 27, and in response to this, the telecontelemeter 27 takes in the data from the determining means 44 via the interface 26 and sends it to the master station. Convert and transmit the desired signal. Note that FIG. 8 is a diagram in which each sampled data is sequentially plotted using algorithm A5, and in this case, if one set value VS is exceeded, it is determined that there is a gas leak.

Thus, according to this embodiment, the gas pressure difference is detected using the differential pressure detection means 14 without providing a restriction in the gas line 11, so that gas leakage can be accurately detected based on the pressure change at the start of gas leakage. The presence or absence of a gas leak can be accurately and quickly determined by selecting at least one desired algorithm from a plurality of predetermined algorithms for each sampling data and determining relative value data. If this information is transmitted using a telemeter, it will be useful for the operation management of the entire plant. Further, since the configuration is such that it is possible to determine whether the detection system related to gas leakage is good or not, it is possible to distinguish between gas leakage and the detection system, and to further improve reliability.

Furthermore, since there is no need to provide a restriction in the gas line 11, there is no loss of gas transport energy due to the restriction.

There is no risk of disturbing the running of the VIG, and it is very suitable as a gas leak detection device not only for plant piping but also for gas vibe lines.

Note that the present invention is not limited to the above embodiments.

For example, in the embodiment described above, the differential pressure detection means 14 shown in FIGS.
As shown in FIGS. (a) to (C), the resistance element 31. Even if only one of the lumped capacitive element 32 or the distributed capacitive element 33 is provided on one side of the differential pressure converter 34, it is possible to obtain a differential pressure signal, although it is inaccurate. Also, the same figure (d)
As shown in (e), it is also possible to have one gas outlet for the gas line 11. In this case, the flow rate flowing into and out of the impulse piping 13 is halved because it passes through the common outlet. Although the detection sensitivity of the differential pressure signal is slightly reduced, a sufficiently accurate differential pressure signal can be detected. It goes without saying that various other modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As described in detail above, according to the present invention, minute pressure changes caused by gas leakage can be reliably identified as pressure changes occurring during Plan 1 to operation, even without providing a restriction in the gas line. It is possible to provide a gas line leak detection device that can distinguish and detect gas leaks, and can accurately and quickly detect gas leaks based on appropriate data while taking various conditions into account.

[Brief explanation of the drawing]

1 to 8 are diagrams showing an embodiment of the present invention, in which FIG. 1 is a schematic configuration diagram of the entire device, and FIGS. 2(a) to (
C) is a specific configuration diagram of the differential pressure detection means, FIGS. 3 and 4.
The figure shows the pressure fluctuation at the leak point and the differential pressure detection signal of the differential pressure detection means in response to this pressure fluctuation, Figure 5 is a block diagram showing the functional configuration of the CPU, and Figure 6 shows the differential pressure at the time of gas leak. Raw data diagrams, Figures 7 and 8 are relative value data diagrams obtained by different leak detection algorithms, Figures 9 (a) to (e) are diagrams showing modified examples of differential pressure detection means, and Figure 1
Figure 0 is a pressure fluctuation diagram at the time of liquid leakage. 11...Gas line, 12...Gas leak point, 13.
...Pressure piping, 14...Pressure detection means, 17...C
PU, 19...ROM, 20...RAM, 22...
- Input key 123... Output device, 24... Line control unit, 27... Telecontelemeter, 41... Sampling means, 42... Data update processing means, 43
... Relative value data calculation means, 44 ... Judgment means, 4
5...Detection system diagnostic means, 46...Transmission control means, 4
7...Line ill m means. Applicant's representative Patent attorney Takehiko Suzue Figure 2 Stl □ Time f'ifl Figure 3 Figure 4 - Opening Figure 6 Temporary P old -11 Figure 7 Figure 8 Figure 9 Figure 10 Procedure amendment document Showa ψ1. January. 20th, Commissioner of the Patent Office Kuro 1) Mr. Akio 1, Indication of the case, Patent Application No. 174561/1982, Name of the invention: Gas line abnormality detection device 36 Person making the amendment Relationship with the case Patent applicant (412) Mouth Honkoukan Co., Ltd. 4, agent: UBE Building 7, 3-g7-2 Kasumigaseki, Chiyoda-ku, Tokyo;
Contents of amendment (1) “One other means” in page 5, line 6 of the specification
Correct the statement by saying, ``What is another method?'' (2) Correct the statement on page 9, line 19 of the same book. (3) In the same book, page 24, line 18, "Figure 8" is corrected to "Figure 9."

Claims (1)

[Claims] A differential pressure detection means that includes at least one of a capacitance element and a resistance element in a pressure piping attached to a gas line, and detects a differential pressure between specific points of the pressure piping, and one or more gas leak detection means in advance. An algorithm is stored, and the detection signal from the differential pressure detection means is sequentially sampled at a predetermined period, and relative value data regarding gas leakage is obtained from this sampling data based on one or more appropriate gas leakage detection algorithms. and a determination means for determining whether or not gas is leaking from the gas line using the relative value data acquired by the gas leakage data acquisition means. Gas line abnormality detection device.