JP4139908B2 - Gas conduit leak detection method and detection apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for detecting leakage of a gas conduit such as the conduit in a system in which a conduit is connected to a gas main and gas is supplied to each consumer from the conduit.
[0002]
[Prior art]
For example, city gas will be described with reference to FIG. 1 showing an embodiment of the present invention. A gas main 1 embedded in a main road branches a conduit 3 through a supply governor 2 to a consumer group. The branch pipe 3 is supplied to each household H through a lead-in pipe 4, an on-off valve 5, a consumption meter 6, and the like.
[0003]
In this gas supply system, if a gas leak occurs in the branch pipe 3 and the lead-in pipe 4 as well as the gas main pipe 1, a serious accident such as a gas explosion may occur. For this reason, various means have been conventionally used to detect the gas leakage.
[0004]
One of them is called boring survey. A hole with a depth of about 50cm is drilled just above the conduit 3 buried under the road, a pipe is inserted into the hole, and the air in that part is sucked to detect the gas. This is a method of inspecting for leaks with a vessel or odor, and as another means, using a flame ionization gas detector etc., inhaling air near the surface of the route to check for leaks A method is employed, and further, a method of measuring the pressure for a predetermined time after blocking the inflow of gas to the part to be inspected and inspecting for the presence or absence of leakage by the pressure change is employed.
[0005]
[Problems to be solved by the invention]
Boring drills holes every 5 meters, which can damage the road and require a lot of labor and cost. There are many places where it is impossible to drill holes depending on the location. The method of using a hydrogen flame ionization gas detector or the like is a method that can be applied only to a gas having a small specific gravity such as natural gas (gas lighter than air) and cannot be used for a heavy gas such as LP gas. Moreover, it cannot be used in places where humans cannot enter, for example, piping in buildings such as under the floor and pipe shafts. The pressure holding type needs to be implemented after the gas consumption is stopped, and the consumer is inconvenienced that the gas cannot be used for the time during the inspection. In addition, large-scale collective supply facilities not only require enormous effort to stop and restart the gas, but also require careful attention to confirm safety to prevent gas accidents, particularly when the gas is opened.
[0006]
The present invention automatically and unmannedly checks for leaks in city gas and other gas conduits, etc., using a time zone during which no gas is consumed, such as at midnight, and without stopping the gas supply to the consumer. The problem is to get it.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention is directed to inspecting a gas pipe line connected to the gas main pipe by feeding a constant pressure (set pressure) from a conventionally known gas main pipe to the branch pipe and the lead-in pipe. If the target pipe and the lead-in pipe are in a state where gas can be freely introduced from the gas main pipe, for example, if the pressure is reduced to a certain pressure or less, the gas is introduced from the main pipe and the set pressure supplied from the gas main pipe is increased. When the pressure is kept high (pressurized) for a certain period and the high pressure does not decrease over a certain value for a certain period of time, it is determined that there is no leakage in the inspected conduit or the like.
[0008]
On the other hand, if the pressure drop falls below a certain value, the pressure is maintained again, and if it is not possible to determine that the leakage has not occurred for a certain period of time, for example once a month, Judge that there is a possibility of leakage in the conduit.
[0009]
At this time, since the gas can be introduced from the main, the gas is automatically discharged from the main even if the gas consumption starts and the pressure of the pipe to be inspected decreases while maintaining a high pressure. Will not interfere with gas consumption.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
As one embodiment of the present invention, a branch conduit to each consumer is connected to a gas main through a check valve, and a gas having a pressure higher than that of the gas main is connected to the branch conduit after the check valve. Can be injected, and a configuration provided with a gas pressure detector for detecting the pressure of the branch conduit can be adopted. Based on the detection signal of the gas pressure detector, high pressure gas is injected and stopped, Despite trying to maintain the branch conduit at a higher pressure than the gas main, if the pressure drops below a certain value within a certain period of time, it is determined that the conduit is leaking gas and Take appropriate measures.
[0011]
The introduction of high-pressure gas into the branch conduit may be performed by using inspection gas from a high-pressure gas cylinder, etc. The inspection gas can be opened and closed by an on-off valve. The controller controls the detection signal of the gas pressure detector.
[0012]
At this time, even if trying to maintain the above-mentioned inspection target pipe (branch pipe) at a high pressure, if the pressure does not become high, the maintenance action is stopped, and after a certain period of time, the maintenance action is performed again, and a leak inspection is performed. It is good to do. The high pressure cannot usually be maintained when there is a large consumption, in which case the gas pressure in the pipe to be inspected does not increase until the gas consumption stops, and the gas for inspection is wasted. Will end up. For this reason, after the valve is opened, the gas pressure in the inspected conduit does not increase after a certain period of time (usually, if there is no consumption, the pressure in the inspected conduit rises for about 5 minutes) In this case, once the automatic opening / closing valve is closed, the valve is opened again after a certain period of time (usually about 15 minutes for gas consumption per hot water supply).
[0013]
【Example】
An embodiment is shown in FIG. 1, which, as described above, branches a conduit 3 from a gas main pipe 1 embedded in a main road to a consumer group via a supply governor 2, and this branched conduit. The gas b is supplied from 3 to each household H through the intake pipe 4, the on-off valve 5, the consumption meter 6, and the like. The supply governor 2 has a check valve function (blocking function) and depressurizes the gas b from the gas main 1 to a constant value while preventing the gas backflow from the branch conduit 3 to the gas main 1. For example, the pressure is reduced from 0.1 MPa to 2.0 KPa and fed into the branch conduit 3. The gas in the branch conduit 3 is at a required pressure, for example, 1. Set to 5 to 2.0 KPa.
[0014]
An inspection gas cylinder 11 in which an inspection gas cylinder 11 is provided with a pressure reducing adjustment valve 12, an inspection governor 13, and an automatic open / close valve (electromagnetic valve) 14 is connected to the branch conduit 3. A similar gas a that is the same as the supply gas b from the main pipe 1 or that does not hinder combustion is filled. For this reason, when the automatic opening / closing valve 14 is opened, the inspection gas a in the cylinder 11 is depressurized to a constant value, for example, 10 KPa, by the pressure reducing valve 12, and further depressurized by the governor 13, for example, 2.5 KPa, to branch. At this time, the pressure of the introduced gas is set higher than that of the supply gas b from the gas main pipe 1 through the governor 2, so that the branch pipe 3 has a pressure higher than that of the supply gas b.
[0015]
Further, a pressure recording device 15 is attached to the branch conduit 3, and this pressure recording device measures the pressure of the branch conduit 3 and records the change. Further, the branch conduit 3 is provided with a pressure measuring device 16 with an external output such as a pressure switch, the automatic open / close valve 14 is opened, the inspection gas a is introduced, and the pressure of the branch conduit 3 rises to a predetermined value. When the pressure P ₁ (for example, 2.4 KPa) is reached, a signal to that effect is generated, and when the automatic open / close valve is closed and the branch conduit 3 is leaking and when the gas is consumed, the pressure decreases. When it falls to P ₂ (for example, 2.1 KPa), a signal to that effect is sent to the controller 17.
[0016]
The controller 17 outputs a signal from the pressure measuring device 16 with an external output as an input, and issues an opening / closing command to the automatic opening / closing valve 14 as an output. The controller 17 outputs a signal increased from the pressure measuring device 16 with an external output to the set pressure P _1. receiving the, close to the automatic opening and closing valve 14 instruction, it generates a signal to open when subjected to reduced signal to a set pressure P ₂ are reversed. Although the automatic opening / closing valve 14 is installed on the outlet side of the inspection governor 13, there is no problem even if it is in the vicinity of the inspection governor 13.
[0017]
This embodiment has the above-described configuration, and is configured for each of the inspected conduit ranges (conduit 3 after supply governor 2 and lead-in tube 4) A indicated by a chain line frame in FIG. A valve opening signal is issued to the valve 14 and the inspection gas a is introduced into the branch conduit 3. When the pressure rises to a predetermined upper limit pressure (a pressure higher than the closing pressure of the supply governor and does not interfere with gas consumption) P _{1, the} pressure measuring device 16 with an external output transmits a message to that effect to the controller 17. The automatic opening / closing valve 14 is closed. Although the pressure drop in the case of the automatic opening and closing valve 14 is closed branch line 3 a case and gas consumption leaky, drops to a predetermined pressure P _2, the external output with a pressure measuring device 16 is the controller 17 The automatic open / close valve 14 is opened again, and the inspection gas a is introduced into the branch conduit 3. Thereafter, the repetition is performed.
[0018]
If gas consumption exceeding the gas supply from the inspection gas side occurs during this leakage inspection, the gas is automatically supplied from the supply governor 2 and the gas consumption is not hindered.
[0019]
The pressure fluctuation recorded by the pressure recording device 15 during that time is read, and if the upper limit pressure does not decrease for a certain period of time (normally 5 minutes if the volume of the branch conduit 3 is 10 m ³ or less), there is no leakage. to decide. On the other hand, if the pressure drop is below a certain value, it is determined that a leak has occurred in the inspection target conduit or the like.
[0020]
At the time of this inspection, a clock is built in the controller 17, and the leakage inspection time is limited to a time zone where gas consumption is low (usually a time zone from midnight to early morning) by the timer, thereby reducing the waste of the inspection gas a. If the gas pressure in the branch conduit 3 does not increase even after about 5 minutes have elapsed after the valve is opened, the automatic open / close valve 14 is once closed, and after about 15 minutes, the valve is opened again. Furthermore, when the pressure drops due to gas consumption after the pressure rises, the automatic opening / closing valve 14 is not opened immediately, but is opened after 15 minutes to reduce the waste of the inspection gas a.
[0021]
The pressure change in the branch conduit 3 described above is recorded in the pressure recording device 15, and the change is read to determine the presence or absence of leakage. At this time, the enclosed pressure and the elapsed time are automatically read, and if the enclosed pressure does not change for a predetermined fixed time, for example, if the volume of the branch conduit 3 is 10 m ³ or less, normally, the fact that there is no change (the leakage is They occur not that) can be displayed in a lamp or the like.
In addition, when it cannot be determined that the above leakage has not occurred even for a certain period of time, for example, one month, it is determined that there is a possibility that leakage has occurred in the inspection target conduit or the like.
[0022]
When the gas pressure of the main pipe 1 is equal to that of the branch conduit 3, a check valve 18 can be employed instead of the supply governor 2 of the branch conduit 3, as shown in FIG. Instead of the stop valve 18, a large-diameter governor having a check function with a small pressure loss can be used. Further, if there upstream pressure of the supply governor 2 (the pressure of the gas mains 1) is predetermined pressure P ₁ or more, as shown in FIG. 3, gas a for checking the delivery gas b of the upstream side Can be used as Furthermore, as shown in FIG. 4, even when the pressure of the supply gas b is equal to or lower than the predetermined pressure P ₁ , the pressure can be increased through the booster 19 to the set pressure P ₁ and used as the inspection gas a. In FIG. 1, a mobile gas generation facility can be used instead of the inspection gas cylinder 11.
[0023]
In addition, when the volume of the branch conduit 3 is small, it is conceivable that the pressure of the branch conduit 3 exceeds a predetermined pressure due to a delay in tracking of the automatic opening / closing valve 14. For this reason, it is preferable to provide a constant flow valve or a throttle in the middle of the inspection governor 13 and the branch conduit 3 to limit the amount of gas introduced from the inspection governor 13 to the branch conduit 3 to compensate for the follow-up delay. . Further, when the pressure measuring device 16 with external output reaches the set pressure, the controller 17 is notified of this, but the pressure sensor is attached to the inspection target conduit 3 and the controller 17 reads the pressure to determine the set pressure. Can be done automatically. The pressure detector (pressure measuring device) 16 can be provided between the automatic opening / closing valve 14 of the detection gas pipe 10 and the conduit 3.
[0024]
【The invention's effect】
According to the present invention, as described above, since the leakage is detected by the pressure change of the inspection target conduit while supplying the original gas, (1) it is not necessary to stop the consumer's gas consumption. 2) If the device is set, there is an effect such that inspection can be performed unattended, (3) it can be surely inspected where no one can enter, and (4) light or heavy gas can be used.
[Brief description of the drawings]
FIG. 1 is a gas inspection circuit diagram of another embodiment. FIG. 2 is a gas inspection circuit diagram of another embodiment. FIG. 3 is a gas inspection circuit diagram of another embodiment. Figure [Explanation of symbols]
1 Gas main 2 Governor for supply 3 Inspected pipe (branch pipe)
4 Lead-in pipe 5 Opening / closing valve 6 Consumption meter 10 Inspection gas pipe 11 Inspection gas cylinder 12 Depressurization adjusting valve 13 Inspection governor 14 Automatic opening / closing valve 15 Pressure recording device 16 Pressure measuring device 17 Controller 18 Check valve 19 Booster a Inspection gas b Supply gas H Household

Claims (4)

Connected to the gas main (1) through a branch valve (3) to each consumer via a check valve (2, 18) that prevents gas backflow from the branch conduit (3) to the gas main (1) Then, each consumer's lead-in pipe (4) is connected to the branch pipe (3) after the check valve, and from the gas main pipe (1) to the branch pipe (3) and the lead-in pipe (4). A gas conduit leakage detection method for a branch conduit (3) and a lead-in tube (4) after the check valve in a gas conduit for feeding gas under pressure ,
An inspection gas pipe (10) is connected to the branch conduit (3) via an on-off valve (14), and a gas pressure detector (16) is provided, and a detection signal from the gas pressure detector (16) is provided. The controller (17) controls the opening and closing of the on- off valve (14), and the on-off valve (14) is opened in a time zone in which the consumer consumes less gas. 3) and a gas (a) having a pressure higher than the above-mentioned constant pressure within a range that does not impede gas consumption into the inlet pipe (4), and the inside of the branch pipe (3) and the inlet pipe (4) The open / close valve (14) is pressurized by pressurizing the gas (b) from the gas main (1) to a pressure (P ₁ ) somewhat higher than the constant pressure supplied from the gas main (1) in a state where the gas (b) can be introduced freely. Close and maintain its high pressure (P ₁ ), even with the gas pressure detector (16) And perform a leak inspection based on the presence or absence of a decrease in the constant pressure,
In that leakage inspection, if the predetermined time, it does not decrease the high pressure than a predetermined value, a leak in the upper Symbol branch line (3) and lead-in tube (4) does not occur, whereas, the high pressure (P ₁₎ is If it falls below a certain value, the leakage is occurring,
After pressurized to the branch conduit (3) and lead-in tube (4) the high pressure (P _1), if it is more gas consumption of consumer its high pressure (P ₁₎ can not be maintained, or, the high If you can not pressurized to a pressure (P _1), after a certain time, once again, the high pressure by the pressure effect it has to perform leak test gas conduit leak detection, wherein the (P ₁₎ to Method. 2. The pressure recording device (15) is attached to the branch conduit (3) according to claim 1, and the leakage occurs for a certain period of time based on a record of the pressure change in the branch conduit (3) of the pressure recording device (15). If it cannot be determined that the gas pipe has not been leaked, it is determined that there is a possibility of leakage in the branch pipe (3) and the lead-in pipe (4) . A gas detector (1) according to claim 1, wherein the gas main pipe (1) is connected to a branch pipe (3) from the branch pipe (3) to the gas main pipe (1). prevents gas backflow through the check valve (2, 18) connected to, on the non-return valve following the branch conduit (3), the gas main pipe (1) higher than the pressure of the gas (a) test gas tube for injecting (10) as well as connected via the on-off valve (14), a gas pressure detector (16) for pressure detection of the branch conduit (3) provided, the on-off valve (14 features and Suruga scan conduit leakage detection device that the closing and to control with the controller (17) by the detection signal of the gas pressure detector (16)).   The gas conduit detection device according to claim 3, wherein a pressure recording device (15) is attached to the branch conduit (3) to form the gas conduit leakage detection method according to claim 2.

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