JPS61165099A - Method for sensing leakage of gas pipe line and its device - Google Patents

Abstract

PURPOSE:To sense leakage of gas surely by disposing a plurality of pressure gauges on a gas pipe line at a predetermined interval and judging occurrence of gas leakage when pressure difference before upper and lower stream sides shows a predetermined value. CONSTITUTION:In measurement positions S1-S3 in a certain fixed section of a gas pipe line, S1 is considered to be located on the upper stream side S3 on lower stream side, and S2 in a position of gas leakage. When no leakage occurs in a normal gas flow, a convex curve is given from S1 toward S2 by pressure drop, therefore pressure gradient is almost equal between L1 and L2, or that of L2 is larger. When gas leakage occurs in S2, pressure gradient is changed between L1 and L2. Therefore, gas leakage of a certain fixed section on the gas pipe line can be sensed by obtaining the difference between pressure gradients at L1 and L2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas pipeline leakage detection method and apparatus for detecting gas leakage in a gas pipeline.

[Conventional technology]

Conventionally, various leakage detection methods have been proposed for liquid transportation pipelines, but there are major differences between liquid transportation pipelines and gas pipelines, so leak detection methods have been proposed for liquid transportation pipelines. Leak detection methods cannot be directly applied to gas pipelines.

First, since gas is a compressible fluid, there are dynamic fluctuations in the amount of gas packed in the line.

This causes an arrow-like phenomenon that does not occur in liquid pipelines.

For example, the effects of changes in pressure, flow rate, etc. at one end take a considerable amount of time to appear at the other end. Moreover, the shadow IIQ is attenuated and diffused while propagating through the pipeline, and arrives in a considerably distorted form. Naturally, the period between the two cannot be determined, and they do not simply appear with a fixed time delay.

Next, changes in pressure, flow rate, etc. caused by leakage are much smaller than in the case of liquids, and the attenuation is large, making it extremely difficult to distinguish them from the various fluctuations that constantly occur during normal operation. Also, the propagation time of changes is much slower than in liquids.

The current status of gas pipeline leak detection is as follows.

Conventionally, the mainstream method for gas leak detection has been to use a gas detector that directly detects the leaked gas components using a senna.In a yard, the gas detector is installed in a location where there is a high probability that leaked gas will float. In the case of gas pipelines, gas detectors are currently installed inside the pulp house, or patrol cars equipped with gas detectors are patrolled and monitored.

Furthermore, a method has been reported in which a portable microphone is used to capture the amount of gas leaking from a leak hole.

In the operation of gas pipelines, the pressure is measured at the origin, destination, or midway through the pipeline, and its upper limit is measured.

Leakage is only indirectly determined when an abnormality is found by comparing it with the lower limit set value, and it is usually not possible to detect it unless there is a large amount of leakage.

Further, in many cases, the set value depends on the experience of the individual operator.

[Problem that the invention seeks to solve]

In the conventional methods described above, in the case of direct detection of leakage gas using a sensor or capture of the amount of leakage, a great deal of effort is required for detection, and continuous monitoring of the entire pipeline cannot be performed. In addition, a problem has arisen in that the amount of leakage that can be detected by monitoring the lower limit of pressure is extremely limited to leakage from large bones.

The present invention was made to solve such problems, and an object of the present invention is to provide a gas pipeline leak detection method and device that can reliably detect gas leaks in a gas pipeline.

[Means for solving problems]

The gas pipeline leak detection according to the present invention includes providing a plurality of pressure gauges at predetermined intervals in the gas pipeline.
The pressure gradient from the measured values by the two upstream pressure gauges and the measured value by the two downstream pressure gauges in any section selected by the input circuit connected to these pressure gauges. In this invention, when the pressure gradient is calculated by two calculation circuits, it is determined that there is a gas leak.In this invention, when gas leaks in the middle of the gas pipeline, the upstream center around the leak point is determined to be a gas leak. The pressure gradient in the side tubing increases, the pressure gradient in the downstream tubing decreases, and the overall pressure gradient curves downward. This phenomenon is detected from the difference in pressure gradient and it is determined that there is a gas leak.

〔Example〕

FIGS. 1 to 7 are diagrams showing one embodiment of the present invention.

In FIG. 1, (1) is a gas pipeline through which gas flows, and (21) to (21) are pressure gauges provided at predetermined intervals in the gas pipeline (1).

Figure 2 shows each measurement point S in the gas pipeline (
A graph showing the gas pressure of ~S, where the horizontal axis represents the length L of the gas pipeline (1), and the vertical axis represents the gas pipeline (1).
), it can be seen that when gas is flowing normally in the gas pipeline (1) and there is no leakage, the gas pressure draws an upwardly convex curve as it goes from the inflow side to the outflow side. It can be seen that it is decreasing.

In Fig. 6, (3) is a pressure control valve installed on the inflow side of the gas pipeline (1), (4) is a pressure control valve installed on the outflow side of the gas pipeline (1), and (5) is a gas pipe This is the gas leak point in line (1). Figure 4 is a graph showing the change in gas pressure at each point when gas is leaking from the gas leakage point (5) of the gas pipeline (1).The length L of the gas pipeline (1) is shown horizontally at 1111. and the vertical axis is the gas pipeline (pressure P in υ
is taking. In the graph, the solid line is the pressure distribution e when there is no leakage.
ff, and the broken line represents the pressure distribution and its time change at the time of gas leakage. That is, from this graph, it can be seen that the -vertical pressure decreases at the gas leak point (5), and the pressure gradients on the upstream and downstream sides differ from those when there is no leak. Figure 5 is a graph similar to Figure 4 when gas is leaking from a gas pipeline (1) equipped with a flow control valve on the outflow side, and the pressure gradient on the upstream side is higher than when there is no leakage. It can be seen that the pressure gradient on the downstream side is not much different than when there is no leakage.

Figure 6 is an explanatory diagram for expressing the gas pressure gradient in the gas pipeline (1) using a mathematical formula. side, S, pipe downstream side, S! is the gas leak point. Also, the section between L, U8° and S, L is S! The interval between and and S is shown. Furthermore, P and ~P indicate, as an example, the pressure at each measurement point S and ~Ss when a pressure control valve is provided on the gas outflow side, where the solid line is the pressure distribution when there is no leak, and the broken line is the pressure distribution when there is a gas leak. shows the pressure distribution.

The pressure gradients in the sections of the gas pipeline (υ) can be expressed by the following equations.

As is clear from the graphs in Figures 4 and 6, when the gas flow is normal and there is no leakage, the pressure decreases in an upwardly convex curve as you go from SI to S. ,
It can be seen that the pressure gradients are almost equal or larger in the sections L and .

Next, gas leakage is S! As shown in the graphs of Figures 4 and 6, [L, and L! It can be seen that the pressure gradient changes in the section.

In addition, if a flow rate control valve is provided on the gas outflow side, the fifth
From the graph in the figure, it can be seen that the pressure gradient changes clearly in the section.

Therefore, by determining the difference in the pressure gradient between L and T, it is possible to detect gas leakage in a certain section of the gas pipeline (1).

The difference in pressure gradient between Ll and Ll is expressed by the following equation.

ε is an allowable value that takes into account the dynamics of the gas pipeline.

From equation (3), gas is leaking between S and S8 when the difference in pressure gradient between L and Ll becomes larger than 6, and the larger the difference in pressure gradient, the more leakage occurs. , it can be seen that there is a large amount of gas leaking.

As a method of comparing pressure gradients, four pressure gauges are used as shown in Figure 8, and the pressure gradients of pressure p, , p between the two pressure gauges (21) (2,) on the upstream side and the pressure gradient on the downstream side are Between the two pressure gauges (
21) and (24) using the pressure gradient of pressure PS * P4 and performing the same calculation as before. If a leak occurs in the middle of the section between these, it can be detected with higher accuracy.

FIG. 7 is a block diagram of a gas leak detection device used when carrying out the method of this invention.

This gas leak detection device detects the difference in pressure gradient between a certain arbitrary section of the gas pipeline (1), for example, sections S and -S, calculates the difference, and outputs a gas leak signal.

In the figure, (2+) to (2,) are gas pipelines (
1) are five pressure gauges installed at predetermined intervals, (B) is an input circuit into which the measured values measured by the pressure gauges (21) to (2s) are input, and (2) and (TO) are The A/l) converter that converts the analog signal from the input circuit αa into a digital signal, α◆, (to) calculates the pressure gradient of the gas connected to the A/D converters (2) and (6), respectively. The arithmetic circuit is connected to the arithmetic circuit α→, (g) is a comparator that determines gas leakage, and (lη is the output device that outputs a leakage signal that is connected to the comparator q→.0 Camphor is an arithmetic circuit (L4.
(g) and comparator α time.

Next, a case will be described in which gas leakage is detected by the method of the present invention.

Gas leaks in gas pipelines are detected using the gas leak detection device described above.

Pressure gauges (2,) to (2,) are installed at five measurement points S, to S, in the gas pipeline (1). For example, if there is a gas leak in a certain section of the measurement points S and ~S in the gas pipeline (1), for example, between the measurement points S and ~S, Measurement point S by the input circuit α force that selected that section.

S! The measured pressure values measured by the pressure gauges (2+) and (2t) are sent to one A/D converter (2) as an analog signal, and
), (2M) The pressure measurement value measured by the VC is sent as an analog signal to the other A/'D converter (2). Each A/1) converter (b) (to) converts an analog signal into a digital signal.

Send digital signals to arithmetic circuits α→ and (g), respectively.

One calculation circuit α◆ calculates the pressure distribution of gas between measurement points S1 and S using the above-mentioned equation (1), and the other calculation circuit (2) calculates the pressure distribution between measurement points S and S. The pressure gradient of the gas between is calculated using the above-mentioned equation (2). These calculation circuits (14 (1cJ) send the calculated pressure gradient values to the comparator a→, and the comparator CL determines whether gas is leaking between the measurement points S and S3 based on the above-mentioned equation (3). If there is a leak, send the leak signal to the output device (
Send to (b). The output device αη outputs a signal indicating whether or not there is a ti leakage to an external VC, and the display signal is displayed as a numerical value or symbol on an appropriate display. Note that when the amount of gas leakage is large, the output of the leakage signal sent from the output device anvc becomes large, so that the degree of leakage can be determined to some extent.

In addition, in this example, there are 8 measurement points in a certain section.
Although the explanation was limited to 1% S, the input circuit Ql)
For example, the measurement points are ~S, , S, ~SS s
, IS, S5, etc., it goes without saying that gas leakage in any given section of the gas pipeline can be detected.

〔Effect of the invention〕

As explained above, this invention measures the pressure gradient between the upstream side and the downstream side in any section of the gas pipeline where a plurality of pressure gauges are placed at predetermined intervals in the gas pipeline and has four pressure gauges. Compare the difference between the two (upstream side -
When the downstream side) is 〉ε, it is determined that there is a gas leak.

The change in pressure gradient that always occurs in VC when a gas leaks in a gas pipeline can be ascertained, making it possible to continuously monitor the entire pipeline area unlike before, making it possible to reliably detect gas leaks. It also has the effect of being able to recognize the location of gas leaks within a certain area.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a gas pipeline according to an embodiment of the present invention, Fig. 2 is a graph showing gas pressure at various points in the gas pipeline, and Fig. 6 is a diagram showing a gas pipeline equipped with a pressure control valve. Figure 4 is a graph showing the pressure distribution and its time change when there is no leakage and when there is a gas leak in a gas pipeline equipped with a pressure control valve on the gas outflow side, and Figure 5 is a diagram showing the gas outflow. A graph similar to Figure 4 of a gas pipeline with a flow control valve on the side, Figure 6 is an explanatory diagram for expressing the gas pressure gradient in a gas pipeline using a mathematical formula, and Figure 7 is a block diagram of a gas leak detection device. FIG. 8 is an explanatory diagram of the case where a gas pressure gradient is detected by the method of the present invention using four pressure gauges. In the figure, (1) is a gas pipeline, (21) to (
Measure 2s) with a pressure gauge. In each figure, the same reference numerals indicate the same or corresponding parts. Agent: Patent Attorney Sanro Kimura 1, Case Display Patent Application No. 59-275255 2, Name of Invention Method and Device for Leak Detection of Gas Pipeline Name (
412) Nippon Kokan Co., Ltd. (name) 4. On the "Detailed Description of the Invention" column and drawings in the agent's specification - Funachiko Kano Hidden & Contents of the amendment (1) Page 2, line 6 of the specification ``Gas pipe price'' of ``
"Gas pipeline". (2) "Summary" on page 2, line 14 is amended to read "application." (3) On page 3, lines 7 and 8, “The attenuation is also large.
," is deleted. (4) Add the following sentence after "..." on page 7, line 18. "Of course, S does not have to coincide with the gas leak location,
The same thing can be said if there is a leakage point between 81 and 83. (5) Figure 5 of the drawings shall be amended as a corrected drawing. that's all

Claims (2)

[Claims] (1) A plurality of pressure gauges are installed in a gas pipeline at predetermined intervals, and the pressure gradients on the upstream and downstream sides of any section of the gas pipeline with three or four pressure gauges are compared. A leak in a gas pipeline is determined to be a gas leak when the difference (upstream side - downstream side) is > ε with respect to a predetermined value ε of the pressure gradient. Detection method. (2) A plurality of pressure gauges installed at predetermined intervals in the gas pipeline, an input circuit into which the measured values of the pressure gauges are input, and two pressure gauges on the upstream side in any section selected by the input circuit. A calculation circuit that calculates a pressure gradient from the measurement values measured by the two pressure gauges on the downstream side, and a pressure gradient calculated by these calculation circuits. When the difference between the pressure gradients on the upstream and downstream sides is >ε for a given value ε,
A gas pipeline leak detection device comprising a comparator that determines that there is a gas leak.