JPH0621836B2 - Gas line abnormality detection device - Google Patents

Description

The present invention relates to a gas line abnormality detection device for detecting an abnormality such as a gas leak in a gas pipe, a plant gas pipeline, or the like, and particularly from a minute pressure fluctuation. The present invention relates to a gas line abnormality detection device capable of reliably detecting an abnormality such as a gas leak.

[Problems to be Solved by Prior Art and Invention]

Fluids that leak due to breakage or destruction of pipelines include liquids and gases. The liquid transfer system related to the former is used when a predetermined pressure is applied to the inside of a pipe to transfer a liquid such as oil to a predetermined place. In this liquid transportation system, various liquid leakage detection devices have been developed for the purpose of detecting oil leakage from the pipeline, and
It is actually installed in the pipeline. By the way, in such a system, when the liquid leaks from the pipeline, pressure fluctuations as shown in FIG. 9 usually occur at the upstream point, the intermediate point, and the downstream point from the leak point. Therefore,
As is clear from the figure, at the upstream point 1, relatively large pressure fluctuations occur at the liquid leakage start st and at the liquid leakage end en, and propagate to the intermediate point 2 and the downstream point 3, which is relatively easy. In addition, the leakage of the liquid can be reliably detected. This is because the liquid is an incompressible fluid, so that the volume is almost constant regardless of the pressure change, in other words, the pressure decreases even with a very slight mass transfer, and thus it is easy to detect. As such a prior art, JP-A-51-15
1180, U.S. Pat. No. 3,962,905 and JP-A-59-24320.

On the other hand, gas leak detection is not so easy. There are two possible reasons. One of them is
This is because the gas is a compressible fluid, and the amount of line pack of the gas dynamically changes inside the pipeline. In other words, the pressure drop is caused by mass transfer because the pressure and the gas density are in a proportional relationship.
This means that even if a gas leak occurs, the pressure does not decrease unless the gas density at the measurement position decreases. Therefore, for example, even if the gas pressure or the gas flow rate changes at one end of the pipeline, it takes a considerable time for the influence to appear at the other end of the pipeline, and
The influence of the change in the pressure and the like is attenuated and diffused while propagating in the pipeline, and arrives in the form of a considerably changed pressure. Furthermore, the effect does not always appear with a fixed time delay. Therefore, detecting gas leakage is very difficult.

The other one is that even if the gas leaks due to the breakage of the pipeline, the change in the gas pressure accompanying it is very small compared to the liquid level in terms of signal level, and the attenuation and diffusion of the gas pressure is severe, It is difficult to distinguish from various changes in gas pressure and the like that occur under normal plant operation.

Therefore, the gas leak detection has the above-mentioned special factors, and therefore, if the liquid leak detection device is directly applied as the gas leak detection device, a false alarm is frequently generated during the operation of the plant. The plant had to be shut down, and there was a risk of causing a major accident by overlooking the gas leak when it actually occurred.

Therefore, conventionally, some gas leakage detection means based on a characteristic peculiar to gas different from the liquid leakage detection have been adopted or proposed. These will be briefly described below.

One of them uses a gas detector that measures a leaked gas component and judges that it is a gas leak, and this is the mainstream of the current gas leak detection method. That is, this gas detector is installed in a place where leakage gas is likely to float in the yard, in a valve house in the case of a gas pipeline, or in a patrol car for patrol. , The presence of gas leakage is detected. However, this gas leakage detection means is problematic in terms of feasibility in the case of a plant, for example, because it is necessary to install a large number of gas detectors except for monitoring by a patrol car, and monitoring by a patrol car is also necessary. It is not suitable for monitoring the entire plant including the above.

The other one is to detect a leak sound in a gas leak hole at the time of gas leak, and to detect this leak sound with a portable microphone. This gas leakage detection means becomes extremely difficult to detect gas leakage as it moves away from the gas leakage hole, regardless of the case where a portable microphone is installed near the gas leakage hole. It is a problem in terms of sex.

Furthermore, another means is to provide a pressure detector at the gas pipeline's origination point, destination point, or in the middle of the pipeline, and set the pressure detected by this pressure detector and the preset upper and lower limit set values. To detect gas leakage. In addition, US Pat. No. 3,962,905 is a system that determines that a leak has occurred when the pressure drop rate exceeds a predetermined amount from the relationship between the gas leak amount and the pressure drop. Although this gas leakage detection means indirectly determines gas leakage, it has a problem that it cannot be detected unless a large amount of gas leaks.

The present invention has been made in view of the above circumstances, and reliably detects the pressure fluctuation of a minute front wave caused by gas leakage,
It is another object of the present invention to provide a gas line abnormality detection device that accurately and quickly detects gas line abnormality by performing appropriate data processing in consideration of various line states.

[Means for solving problems]

Therefore, the invention according to claim 1 propagates through the gas medium of the gas line from before and after the flow path resistor provided in the gas line due to damage or destruction of the gas line. The differential pressure detector that takes in the pressure fluctuation due to the leading wave to detect the differential pressure, the sampling means that samples the differential pressure detected by this differential pressure detector at a predetermined cycle, and the sampling means Data storing means for storing a predetermined number of the sampling data, a data updating processing means for updating a predetermined number of the sampling data stored by the data storing means, and a data updating processing means for updating the sampling data. Of the data before the given sampling time and at least the data after the sampling time. Of the gas line provided with the calculation means for statistically processing in time series using the data of and the judgment means for judging the presence or absence of gas leakage based on the magnitude of the differential pressure change calculated by the calculation means. It is an abnormality detection device.

Further, the invention corresponding to claims 2 to 4 is a configuration in which the arithmetic means is embodied. That is,
This calculation means is an average value calculation means for calculating respective average values of a plurality of data before a predetermined sampling time point and a plurality of data after the sampling time point, and both of the average values calculated by the average value calculation means. A differential pressure difference calculating means for obtaining a difference between average values, or a maximum value calculating means for calculating a maximum value among a plurality of data within a predetermined time among updated data and a minimum value among the plurality of data And a differential pressure calculation means for calculating the difference between the maximum value and the minimum value calculated by these calculation means.

Further, the calculating means is composed of a selecting means for appropriately selecting a plurality of algorithms for grasping different pressure characteristic changes related to gas leakage, and a means for executing a predetermined calculation based on the selected algorithm. .

[Work]

Therefore, in the invention corresponding to claim 1, since the differential pressure is obtained by sandwiching the flow path low antibody provided in the gas line, the gas in the gas line is damaged due to damage or destruction of the gas line. The pressure fluctuation of the leading wave propagating through the medium can be detected accurately and quickly, and can be detected with high resolution. Then, after the differential pressure data is sampled at a predetermined cycle, a predetermined number of data of the sampling data is updated, and among the updated data, a plurality of data before the predetermined sampling time and the sampling At least the current data from the time point onward is used to perform time-series statistical processing to calculate the change amount, and the presence or absence of gas leakage is determined based on the size of the change amount. Even if the leak is a small leak, the signal due to the gas leak can be extracted and the abnormality of the gas line can be accurately detected without being affected by the noise.

Next, in the invention corresponding to claim 2, the respective average values of a plurality of data before a predetermined sampling time point and a plurality of data after the sampling time point are calculated, and both of them are calculated. If the difference between the average values is obtained, noise can be reliably removed and an abnormality in the gas line due to gas leakage can be accurately detected.

Further, according to the invention corresponding to claim 3, by selecting a plurality of algorithms for grasping different pressure characteristic changes related to gas leakage, and executing a predetermined calculation based on the selected algorithms. It is possible to appropriately detect an abnormality in the gas line due to gas leakage while taking into consideration the components of the gas line, the characteristics of the gas, and the like.

Further, the invention according to claim 4 calculates a maximum value among a plurality of data within a predetermined time and a minimum value among the plurality of data among the updated data, and calculates these values. By obtaining the difference between the maximum value and the minimum value, the maximum amplitude of the differential pressure can be seen, and when this maximum amplitude exceeds the set value, it can be judged that the gas line is abnormal.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of an abnormality detection device including a gas line 11. Gas leak point 1 in this device
If the pressure detector 13 can be installed at 2, a relatively large pressure fluctuation can be detected at st1 at the start of gas leakage, as shown in FIG. 2, but this pressure fluctuation is propagated and attenuated to cause gas leakage. When the pressure detector 14 is installed at a position distant from the point 12 on the downstream side, the pressure is gradually decreased as shown in FIG. On the other hand, when the differential pressure detector 16 is provided so as to capture the differential pressure from both ends of the valve 15 functioning as a flow path low antibody which is installed on the downstream side of the gas leak point 12, the differential pressure is detected as shown in FIG. As shown in the figure, it was confirmed that a relatively large differential pressure is generated due to the pressure reduction due to the leading wave of the pressure wave at st2 after the start of gas leakage. Therefore, as the gas detecting means in the present device, the pressure detector 14 is installed on either one or both of the upstream side and the downstream side of the gas leak point 12 to detect the gas pressure, or a gas flow meter is installed. Although the flow rate may be detected by the differential pressure detector 16, it is desirable that the differential pressure detector 16 be provided on a line connecting the upstream side and the downstream side of the valve 15 installed on one or both of the upstream side and the downstream side of the gas leak point 12. It is effective to install and to detect the differential pressure.

Reference numeral 17 denotes an A / D conversion means, which amplifies a minute signal related to gas leakage such as pressure and flow rate or a minute differential pressure detection signal output from the differential pressure detector 16 by a predetermined amplification degree, In addition, the signal is converted into a digital signal proportional to the amplified output value, output, and sent to the interface 18. 1
Reference numeral 9 is a sequence program or C for controlling predetermined arithmetic processing and necessary components based on an external command.
It is PU. A bus 20 is derived from this CPU 19, and in addition to the interface 18, a ROM
A (read only memory) 21, a RAM (random access memory) 22, an input / output buffer 23, etc. are connected. The ROM 21 stores, for example, fixed constants for sequence programs and calculations, and, for example, four gas leakage detection algorithms A1 to A4 for grasping different pressure characteristic changes related to gas leakage. Incidentally, if an example is given about each algorithm A1-A4, Is the street. Here, P is a differential pressure detection signal, i is the i-th sampling, Δt is an arbitrary calculation cycle, and C is a set value for judging gas leakage by the judgment means described later. That is, the algorithm A1 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 up to the previous time. Algorithm A2 has been used m times before n times.
This is a comparison between the average value up to the previous time and the average value from (m + 1) times before to the present time, and represents the differential pressure value between the past average value and the current time average value. The algorithm A3 individually compares the sampling data from n times before to the previous time and the sampling data of this time, and performs a logical product (AND) or a logical sum (OR).
Is what you get. Here, _{conjunct, (P in -P i) /} Δt> C AND (P i- (n-1) -P i / Δt> C AND (P i- (n-2) -P i / Δt > C AND ...... AND (P _i-1 −P _i ) / Δt> C, which is the change value of the difference (pressure difference) between a plurality of past individual data and the current data within a certain fixed time. This means that when all the values exceed the set value C, it is judged that there is a gas leak.

On the other hand, the logical sum is (P _in -P _i ) / Δt> C OR (P _{i- (n-1)} -P _i / Δt> C OR (P _{i- (n-2)} -P _i / Δt> C OR …… OR (P _i-1 −P _i ) / Δt> C, which is the change value of the difference (pressure difference) between a plurality of past individual data and the current data within a certain fixed time. ,
This means that gas leakage is judged when any one of the change values exceeds the set value.

The algorithm A4 is a comparison between the maximum value and the minimum value in a plurality of data within a fixed time, and represents the maximum fluctuation range of the differential pressure. And these algorithms A1
A4 is read by the CPU 19 through the input / output buffer 23 from an input key 24 such as a snap switch or other commonly used keyboard, and is selected. R
The AM 22 temporarily stores the data of the arithmetic processing result, the transmission data coming from the partner station, and the like. An output device 25 is a very simple means, for example, provided with a lamp for displaying gas leakage and other abnormalities, and further, a CRT display for displaying images such as characters and figures, and a printing device. Etc. are provided. In short, it is selected and used in consideration of various conditions such as CPU processing capacity, program, and price.

A valve control unit 26 can be connected via an input / output buffer 27 connected to the bus 20, receives control data from the CPU 19, and controls the valve 15 based on this data. In addition, the interface 2 is provided on the bus 20.
Telecontelemeter 30 having the function of a slave station via 8
It is possible to connect. The slave station 30 is installed in each device of the present invention, and the data from each slave station is transmitted to the master station (not shown) or necessary data sent from the master station to each slave station 30. To receive. Although not shown, the master station is connected to a host computer, where the operating status of the entire plant is grasped, necessary data processing is performed, and necessary data and the like are displayed on a display unit provided on the operation panel. In addition to enabling monitoring, the entire line is controlled based on the monitoring result.

Next, the CPU 19 performs the processing shown in FIG. 5 based on the sequence program data. That is, CPU
Reference numeral 19 is composed of a data sampling means A, a data update processing means B, a relative value data calculating means C, etc., and a gas leakage data acquisition means for acquiring relative value data regarding gas leakage, and a gas leakage data acquisition means based on the relative value data. It also has a judging means D for judging the presence or absence of gas and the location of gas leakage, etc., and optionally, the relative value data and the result data judged by the judging means D are transmitted via the telecontelemeter 30 to the master station. Transmission control means E for transmitting to the valve control section 26, and line control means F for performing line control by sending relative value data and judgment result data to the valve control section 26, and diagnostic means for diagnosing whether there is a failure in the pressure or flow rate detection system. G and the like.

Specifically, the sampling means A is the differential pressure detector 1
It is a function of sequentially sampling the digital difference detection signal detected by 6 at a predetermined cycle using a clock. This predetermined cycle is determined as follows, for example. In other words, for pressure detection including differential pressure, it is necessary to "detect transient pressure wave fluctuations that pass in an instant" at the location where the detector is installed, and moreover, the pressure generated during normal operation of a plant or the like. It is necessary to detect the influence of fluctuation as much as possible. The pressure fluctuations that occur when a leak occurs vary depending on the pipeline pressure, inner diameter, leak amount, etc., but by numerically or experimentally comparing the pressure fluctuations during normal operation and gas leakage, It is possible to know the upper limit of the sampling period that is hardly affected by the pressure fluctuation under normal operation and the lower limit of the sampling period that can reliably detect the transient minute pressure fluctuation. Therefore, the sampling cycle is determined in relation to the data processing resolution of the constituent elements in the subsequent stage, but it is desirable to perform sampling with the above sampling cycle as a guide.

Next, the data update processing means B sequentially updates the data sampled by the sampling means A, and RAM
The data is stored in the table 22. The update at that time is determined by the capacity of the data storage area and which leak detection algorithm is used to obtain the relative value data.

The relative value data calculating means C selects the leak detection algorithm desired by the operator from a plurality of leak detection algorithms, and based on this, the ROM 21 and the RAM 2 are selected.
It has a function to read out necessary data from 2 and perform processing according to an algorithm to obtain relative value data.

The determination means D uses the set values of the upper limit and the lower limit determined according to each gas leakage detection algorithm or any one of them, and further compares them with relative value data based on empirical data in the past, Determine if there is a leak. Further, the judging means D receives the diagnostic result data output from the detection system diagnosing means G and sends the necessary data to the transmission control means E and the valve control means F. Furthermore, these data can be used to determine the location of gas leaks as needed. That is, the pressure wave generated by the occurrence of gas leakage propagates to the upstream side and the downstream side of the gas leakage point at approximately (sonic velocity-gas flow velocity) and (sonic velocity + gas flow velocity), respectively. If a pressure or differential pressure detector is installed, L = a + b ΔT = {a / (sonic velocity-gas velocity)}-{b / (sonic velocity + gas velocity) from the pressure wave detection time interval ΔT of each detector. } It is possible to easily estimate the gas leakage occurrence point by the simultaneous equations of. a and b are the distances from the gas leakage point to the detector installation location.

Next, the operation of the apparatus configured as described above will be described.
When the differential pressure detection signal across the valve 15 detected by the differential pressure detector 16 is sent to the A / D conversion means 17, it is amplified by a predetermined amplification degree and converted into digital data, and then a plurality of bit lines are used. And is sent to the bus 20 via the interface 18. At this time, the CPU 19 samples the differential pressure detection data on the bus 20 by using, for example, a clock having a cycle of 1 sec, and sequentially stores the known data stored in the table of the RAM 22 while updating the known data.
Therefore, normally, when a raw signal is detected by a differential pressure detector installed upstream of the gas leak point 12, a signal including noise shown in FIG. 6 is detected, but the sampling means A thins it out. Processing is also done at the same time.

Then, the CPU 19 sequentially samples the differential pressure detection data at a predetermined cycle, and performs the following processing for each sampling data. A desired gas leakage algorithm is designated in advance from the input key 24, but the algorithm may be designated in the middle of the data processing process. In this designation, for example, the algorithm A1 has a relatively short processing time for presence / absence of leakage. Algorithm A2 is resistant to noise, but requires processing time. In this way, the algorithm is specified based on past experience and the like while considering the state of the line and the importance of the plant. Then,
For example, the CPU 19 reads out and selects a gas leakage algorithm such as A2 from the ROM 21 according to the designation,
For each sampling, the average value from n times before to m times before and the average value from (m + 1) times before until this time are compared to obtain the differential pressure difference between the past average value and this time average value. FIG. 7 is a diagram obtained by sequentially plotting the relative value data obtained by the algorithm A2 as an example. Then, the relative value data thus obtained is judged by the judging means D. The determination means D has an upper limit set value Vu and a lower limit set value Vd as the leak determination set value c, and compares the set value Vu with the relative value data obtained for each sampling.
When u and Vd are exceeded, it is determined that the gas is leaking, a necessary component such as the output device 25 is displayed, or the line control means F including the valve control 26 through the input / output buffer 27 controls the valve 15 And the like, and gives a command from the input / output buffer 27 to the telecontelemeter 30. In response to this, the telecontelemeter 30 takes in the data from the judging means D via the interface 28, and the master station (not shown). ) Is converted into a desired signal and transmitted. It should be noted that FIG. 8 is a diagram in which relative value data obtained by arithmetic processing by the algorithm A4 is sequentially plotted for each sampling data, and in this case, one set value V _s is set.
If it exceeds, it is judged that there is a gas leak.

〔The invention's effect〕

Therefore, according to the first aspect of the invention, since the pressure difference is obtained by sandwiching the flow path resistor installed on the gas line, the gas line inside the gas line is damaged due to an abnormality such as breakage or destruction of the gas line. The pressure fluctuation of the first wave propagating through the gas medium can be detected accurately and quickly, and can be detected with high resolution. Moreover, since the signal related to the gas leakage is sampled at a predetermined cycle, it can be captured separately from the pressure fluctuation of a relatively large cycle during normal operation. Furthermore, time-series statistical processing is performed to calculate the amount of change, and the presence or absence of gas leakage is determined based on the amount of change, so even small leaks that include noise will affect the noise. Instead, the signal due to the gas leakage can be extracted to accurately detect the abnormality in the gas line.

Further, in the inventions of claims 2 and 4, it is possible to reliably remove noise and accurately detect an abnormality in the gas line due to gas leakage, and to see the maximum amplitude of the differential pressure. And when this maximum amplitude exceeds the set value,
It can be determined that the gas line is abnormal.

Further, the invention of claim 3 can appropriately detect the abnormality of the gas line due to the gas leakage, while considering the constituent elements of the gas line, the characteristics of the gas, and the like.

Therefore, it is possible to provide a gas leak detection device for a gas line which is very effective in terms of safety measures for a plant having a gas line and environmental aspects.

[Brief description of drawings]

1 to 8 are shown to explain one embodiment of the device of the present invention, and FIG. 1 is a schematic configuration diagram of the entire device,
2 to 4 are pressure fluctuation detection diagrams that differ depending on the installation location and detection method of the detector, FIG. 5 is a functional block diagram of the device, FIG. 6 is a raw data diagram of differential pressure at gas leakage, and FIG. FIG. 8 and FIG. 8 are relative value data diagrams obtained by different leak detection algorithms, and FIG. 9 is a pressure fluctuation diagram at the time of liquid leakage. 11 ... Gas line, 12 ... Gas leak point, 13, 14
...... Pressure detector, 15 …… Valve, 16 …… Differential pressure detector, 1
9 ... CPU, 21 ... ROM, 22 ... RAM, 24
...... Input key, 25 …… Output device, 26 …… Valve control unit,
30 ... telecon telemeter, A-sampling means,
B ... Data update processing means, C ... Relative value data calculation means, D ... Judgment means, E ... Transmission control means, F ... Line control means, G ... Detection system diagnostic means.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-51-151180 (JP, A) JP-A-56-162029 (JP, A) JP-B-59-24302 (JP, B2) US Patent 3962905 (US , A)

Claims (4)

[Claims] 1. A device for detecting an abnormality of a gas line from a gas leak caused by damage or destruction of the gas line, wherein damage or destruction of the gas line is detected before or after a flow path resistor provided in the gas line. Due to this, the differential pressure detector that takes in the pressure fluctuation due to the leading wave propagating through the gas medium of the gas line to detect the differential pressure, and the differential pressure detected by this differential pressure detector is set to a predetermined cycle. Sampling means for sampling at, a data storage means for storing a predetermined number of data among the sampling data obtained by the sampling means, and a data for updating a predetermined number of data among the sampling data stored by the data storage means The update processing means and the data updated by the data update processing means before the predetermined sampling time. An arithmetic means for statistically processing in time series using a plurality of data and at least the present data of the data after the sampling time and two arithmetic values calculated by this arithmetic means are compared to calculate the change amount. An abnormality detection device for a gas line, comprising: a determination unit that determines the presence or absence of gas leakage based on the size. 2. The calculation means calculates an average value of a plurality of data before a predetermined sampling time point and a plurality of data after the sampling time point, and an average value calculation means. The gas line abnormality detecting device according to claim 1, further comprising: a differential pressure difference calculating means for obtaining a difference between the average values of the two. 3. The calculating means has a selecting means for appropriately selecting a plurality of algorithms for grasping different pressure characteristic changes related to gas leakage, and a means for executing a predetermined calculation based on the selected algorithm. The gas line abnormality detection device according to claim 1. 4. A device for detecting an abnormality of a gas line from a gas leak caused by damage or destruction of the gas line, wherein the gas line is protected from damage before and after the low antibody in the gas line is provided. Due to this, the differential pressure detector that takes in the pressure fluctuation due to the leading wave propagating through the gas medium of the gas line to detect the differential pressure, and the differential pressure detected by this differential pressure detector is set to a predetermined cycle. Sampling means for sampling at, a data storage means for storing a predetermined number of data among the sampling data obtained by the sampling means, and a data for updating a predetermined number of data among the sampling data stored by the data storage means Among the data updated by the update processing means and the data updated by this data update processing means, Maximum value calculating means for calculating a large value, minimum value calculating means for calculating a minimum value among the plurality of data, and differential pressure difference calculating means for obtaining a difference between the maximum value and the minimum value calculated by these calculating means. And a determination unit that determines whether or not there is a gas leak based on the magnitude of the differential pressure difference calculated by the differential pressure difference calculation unit.