JPS587930B2 - Pipeline damage/leakage detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a pipeline breakage/leakage detection system that detects leakage of transport fluid due to pipe breakage and/or breakage in a double-pipe structure pipeline that transports hazardous substances such as gas and oil. Regarding the method.

Conventionally, the following methods have been considered as methods for detecting pipe breakage and leakage of transport fluid due to breakage in double pipe pipelines.

In other words, a method for detecting damage to the outer tube is to use a pressure gauge to detect a drop in the pressure of the gas filled in the gap between the inner and outer tubes, and a method to detect leakage due to damage to the inner tube is to detect the pressure in the gap between the inner and outer tubes. There is a method of using a pressure gauge to detect the rise in pressure within the transport pipe.

In addition, when the transport fluid is a liquid, there are methods of detecting the liquid flowing into the gap between the inner and outer tubes using a float and a method of detecting using a dielectric constant meter (Japanese Patent Laid-Open No. 74814/1983).

Furthermore, when the transport fluid is oil, there is a method of detecting oil leaked into the gap between the inner and outer pipes using a special cable (Japanese Patent Laid-Open No. 5
0-60822) etc.

However, the conventional detection method that uses the same detector to detect both leakage due to breakage of the outer tube and breakage of the inner tube is to use a pressure gauge to monitor the filling gas pressure in the gap between the inner and outer tubes. only existed.

However, with this method of using a pressure gauge, it takes a considerable amount of time for the pore pressure to rise or fall to the set pressure, requires a lot of maintenance, and if the pressure gauge in one section is broken. However, it has the disadvantage that detection in that section becomes impossible.

The present invention was developed based on extensive research against this background, and uses the same detector to detect leakage of transported fluid due to breakage of the outer pipe and breakage of the inner pipe in a fluid transport pipeline having a double pipe structure. The present invention provides a pipeline damage/leakage detection method that uses the following methods to detect pipeline damage and leakage.

Furthermore, the present invention provides a method for quickly and reliably detecting damage to the outer or inner pipe, so that even if a detector in one section fails, damage to the outer or inner pipe in this section is not detected. Provides a method for detection with detectors in other sections.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of a pipeline with a double pipe structure using the breakage/leakage detection method of the present invention.

In the figure, the pipeline has a double pipe structure consisting of an inner pipe 1 for transporting a desired fluid, and an outer pipe 6 that is sealed and covers the inner pipe 1 and forms a gap 6 between the inner pipe 1 and the inner pipe 1. .

This pipeline is provided with emergency shutoff valves 7 at each predetermined section length.

For example, in oil pipes, it is required by law to provide gaps for emergency shutoff valves at intervals of 1 km in densely populated urban areas, and at 4 km intervals in general urban areas.

In this embodiment, the distance between the emergency shutoff valves is considered as one span.

In the pipeline within one span, partition walls 3 are provided in the inner and outer pipe gaps 6 at predetermined intervals to prevent diffusion of leaked fluid.

In this embodiment, one gap partitioned by a partition wall 3 is
section.

Therefore, in this embodiment, five sections are provided within one span.

The outer tubes on both sides of the partition wall 30 are provided with small diameter tubes, for example, about 1/2 diameter connecting tubes 5, which communicate the sections on both sides, and a flow detector 4 is provided in the middle of the connecting tubes 5.

The flow detector 4 detects the flow of filling gas flowing through the communication pipe 5 and outputs an on or off switching signal.

The switching signal from the flow detector 5 is transmitted through a transmission line to a monitoring device in a predetermined monitoring room (not shown).

As the flow detector 5, a flow switch is used which is activated by the movement of a baffle plate provided in a fluid ventilation section.

There are types of flow switches that are sensitive to flow in both directions and types that are sensitive to flow in only one direction.

The present invention realizes both a method for detecting breakage and leakage using a flow detector that detects flow in both directions, and a method for detecting breakage and leakage when using a flow detector that detects flow in only one direction.

Next, detection of damage to the outer tube and detection of leakage of transport fluid due to damage to the inner tube according to the present invention will be described with reference to FIG.

Figure 2 shows each section in one span as A, B, C,
D and E, and the flow detectors are designated as FS1, FS2, FS3, and FS4.

First, it is assumed that the flow detectors FS1 to FS4 are of a type that detects bidirectional flow directions.

Now, assume that the inner tube is damaged at the cross mark in the center section C, and the transport fluid flows out into the gap between the inner and outer tubes.

The gas filling the gap in section C is discharged to the adjacent sections B and C via the communication pipe by the volume of the outflowing transport fluid.

This flow of fill gas causes flow detectors FS2 and FS
3 are activated and each outputs a switching signal, so that damage to the inner tube in section C is detected.

In addition, if the outer tube breaks at the position indicated by the x mark in section C, the gas that was filled to about 2 kg/cm2 will be released outside the outer tube, so the flow will flow from sections B and D on both sides to section C. Gas flows through FS2 and FS3.

Flow detectors FS2 and FS3 are therefore activated and provide switching signal outputs.

Thus, in response to a breakage of the inner pipe and/or outer pipe, a pipeline breakage/leakage is detected by the operation of the flow detectors FS2 and FS3.

The detection sensitivity of the breakage/leakage detection method of the present invention is such that when an inner pipe breaks, the damage can be detected regardless of the magnitude of the flow rate flowing into the gap between the outer and outer pipes. (Business Law) detection limit: 80 l
/3 It shall have detection sensitivity for leakage of 0 seconds or less.

It should be noted that the damage leakage detection method of the present invention:
Flow detectors FS2, FS3 adjacent to damaged section C
It is also possible to detect when one or both of the two are out of order.

This is because if the flow detectors FS2 and FS3 are out of order, the flow detectors FS1 and FS4 on both sides will further operate to perform second-stage detection.

The detection pattern when using a bidirectional detection type flow switch for breakage of the inner and outer tubes in section C is shown in the following table.

As is clear from this table, in the present invention, damage to the outer tube and damage to the inner tube can be distinguished from the switching output of the flow detector.

Next, if flow detectors FS1 to FS4 are of a type that detects flow in only one direction, section C
The detection pattern when the pipeline is damaged at the location indicated by the x mark is shown in the following table.

As is clear from this table, even when using a type of flow detector that only senses in one direction, it is possible to detect a damaged leaky section and to identify whether it is an inner tube or an outer tube.

In other embodiments of the invention, flow detectors may be provided at intervals across a desired number of septa.

If a flow detector is attached to each partition wall, the damage location can be determined more accurately, but by lowering the accuracy of damage location recognition, it is possible to set the desired number of partition walls apart and install flow detectors between them as one section. This makes it possible to reduce the number of flow detectors and reduce equipment costs.

In the embodiment shown in FIGS. 1 and 2, the distance between the emergency shutoff valves is one span, but as shown in FIG.
It is also possible to have a structure in which the inner and outer tube gaps of the entire line from the tank or cast holder 10 to the receiving tank or gas tank 11 are integrated by communicating through a communication pipe 5 equipped with the above.

In this way, when filling the gap between the inner and outer tubes with nitrogen, etc., it can be done all at once from the filling port valve 8, and when inspecting each flow detector for failure, the purge valve 9 can be opened and the filling can be carried out at once. By pressurizing gas from the rotary valve 8, it has the advantage that inspection can be easily performed.

In addition, in the present invention, for example, the filling gas in the inner tube gap of section B in FIG.
2 may be activated.

That is, there is a possibility that the flow detector may malfunction due to temperature changes.

In order to avoid this malfunction, a rupture disk (rupture disk or rupture disk) 12 may be provided in the communication pipe 5 in series with the flow detector 4, as shown in FIG.

A rupture disk is one that ruptures when the pressure difference between the front and rear reaches a certain value or more.

By providing the rupture disk 12 in this manner, it is possible to avoid malfunctions of the flow detector due to expansion and contraction of the filled gas due to temperature changes.

Now, considering the difference in burst pressure of the rupture disk 12, when the gas pressure filling the gap between the inner and outer tubes is 2 kg/cm2 gauge, the temperature difference occurring between adjacent sections is at most 10
The pressure difference generated at this time is thought to be about 0.9°C. 1
It is about kg/cm2.

Therefore, by using an aluminum plate rupture disk that ruptures with a pressure difference of about 0.2 kg/cm2, malfunction of the flow detector due to temperature changes can be avoided, and a reliable response to pipe breakage can be achieved.

In the above embodiments, the gap between the inner and outer tubes is filled with an inert gas such as nitrogen gas of about 2 to 3 kg/cm2, but the gap between the inner and outer tubes can also be sealed by reducing the pressure to a value lower than the outside pressure. Of course it's a good thing.

As explained above, the pipeline damage/leakage detection method of the present invention is achieved by providing a flow detector in the connecting pipe that communicates the partition walls between the inner and outer pipes of a pipeline having a double pipe structure. It is possible to quickly and reliably detect leakage of transport fluid due to breakage or breakage of the inner tube.

Furthermore, the same flow detector is used to detect leakage due to breakage of the outer tube and breakage of the inner tube, and it is possible to distinguish between breakage of the outer tube and breakage of the inner tube and to detect the location of the breakage.

Furthermore, in case of failure of the flow detector near the damaged area,
By providing the second-stage detection means, a highly reliable method for detecting damage and leakage in a pipeline with a double pipe structure has been realized.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a pipeline with a double pipe structure showing an embodiment of the present invention, Fig. 2 is an explanatory diagram for explaining the operation of the invention, and Fig. 3 shows another embodiment of the invention. FIG. 4 is a line configuration diagram of a double-pipe structure pipeline, and is an explanatory diagram showing an embodiment of the present invention in which a Lapshire disk is provided to prevent malfunctions due to temperature changes. DESCRIPTION OF SYMBOLS 1... Inner pipe, 2... Outer pipe, 3... Partition wall, 4... Flow detector, 5... Connecting pipe, 6... Outer and outer pipe gap, 7... Emergency shutoff valve, 8... Filling valve, 9... Hershihalb, 10...
...Gas holder, 11...Gas tank, 12...Rupture disk.

Claims (1)

[Scope of Claims] 1. A method for detecting damage and leakage in a fluid transport pipeline having a double pipe structure, in which the gap between the inner and outer pipes of the pipeline is sealed by providing partition walls at appropriate section lengths, and adjacent pipes are connected to each other through the partition walls. A flow detector is provided in a connecting pipe that communicates between the inner and outer pipe gaps, and the flow detector detects the flow through the connecting pipe to detect damage and/or leakage of the pipeline. Damage leakage detection method. 2. The pipeline damage/leakage detection method according to claim 1, wherein a flow detector that detects the direction of flow is used as the flow detector. 3. Claim 2, characterized in that a flow detector that detects bidirectional flow directions is used as the flow detector.
Pipeline damage/leakage detection method described in Section 1. 4. The pipeline damage/leakage detection method according to claim 2, wherein a flow detector that detects only one flow direction is used as the flow detector.