JPH06221951A - Airtightness testing method for pipe joint section of underground buried pipeline - Google Patents

Abstract

PURPOSE:To enable the inspection of the airtightness of a pipe joint section in a short time by a method wherein the pipe joint section is wrapped airtight with a housing one at a time to reduce or increase a pressure in the housing before the burying of a pipeline part joined and then, changes in the pressure with the passage of time is observed. CONSTITUTION:Each of pipeline joint parts 10 is wrapped airtight with a housing 2 having a pressure gauge 21 before the burying of a pipeline part B arranged based on a working process of one day. The housings 2 are linked to a vacuum pump 3 through a hose 31 and a multiconnector 30. Then, a vacuum pump 3 is driven to reduce the pressure in a space within the housing 2 to a specified negative pressure. Then, the pump 3 is stopped and a valve 22 is closed to observe the condition of the pressure in the housings 2 with a gauge 21. But a transient pressure change is caused in the housings 2 and prevents the judgment of the airtightness until this change ends. This allows the division of the airtight locations at each joint part 10 to reduce individual airtight capacity and the ending of the transient pressure change in a short time thereby enabling the shortening of inspection time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airtightness test method for underground pipes, particularly for vacuum sewage pipes and gas PE pipe pipe joints.

[0002]

2. Description of the Related Art Recently, in a vacuum type sewer system that has been developed, a sewage basin with a vacuum valve is used as a sewage basin that collects the sewage discharged from each location in a residential land through a sewage pipe, A vacuum station equipped with a water collection tank and a pressure pump is installed in the center, and a large number of sewage basins in a certain area are connected to this vacuum station by a vacuum type sewer pipe. A vacuum pump always keeps the pressure reduced, and when sewage is accumulated in the sewage basin and the water level reaches a predetermined water level, the vacuum valve of the sewage basin is automatically opened by air-compression in the water level detection pipe, The collected wastewater in the sewage basin is sucked into the vacuum sewer pipe all at once and collected in the water collection tank of the vacuum station.When the water level in the water collection tank reaches the predetermined water level, the pressure pump is automatically driven to collect the water. water Carrying a tank in sewage to trunk underdrain sewage treatment plant or the public sewer.

In the vacuum sewer system, the pipe joint portion of the vacuum sewer pipe is required to have particularly tight airtightness. Therefore, in the past, normally, after the completion of the construction of the pipeline, the inside of the pipeline is depressurized (or pressurized) to a predetermined negative pressure (or positive pressure) by driving a vacuum pump (or air-compressor), Then, the vacuum pump (or air-compressor) is stopped, the valve between the pipeline and the vacuum pump (or air-compressor) is closed, and the pressure fluctuation in the pipeline thereafter is observed, The airtightness test is performed on the pipe joint part of.

However, in this test method, if the airtightness is found to be poor, it is necessary to detect the poorly airtight pipe joint and to dig up the connection portion, which makes repairing the defective connection difficult.

By the way, the above-mentioned vacuum type sewer pipe is usually constructed by repeating the work of backfilling the pipe portion arranged on that day for each day. In this case, it is possible to perform the airtightness test of the pipe joint portion of the pipe line portion before backfilling the pipe line portion arranged on that day.

For example, as shown in FIG. 3, an air bag 4'is airtightly attached to a predetermined position on the rear side of the pipe line portion B'disposed on the day (the air bag 4'has an air bag 4 '). A hose 40 'with a valve 41' is attached in advance, and an air bag 4'is formed by air-press fitting with this hose 40 '.
To the inner surface of the pipe under pressure, and in this state the air valve 4
1'is closed to maintain its pressure-adhered state), and a vacuum pump 3'is attached to a cap 32 'and a ho
Via a gas pump 31 ', the inside of the pipe line portion B'is depressurized to a constant negative pressure by driving the vacuum pump 3', then the valve 33 'is closed, and the pipe line is formed by a pressure gauge 34'. The pressure condition inside part B'can be observed.

If the indication of the pressure gauge rises, one of the pipe joints in the pipe line portion B'has poor airtightness. In this case, the mounting position of the air back 4'is changed. By moving the pipe joints one by one to the front side and carrying out a test similar to the above-mentioned test each time the pipe joints are moved, the pipe joints with poor airtightness can be detected.

A pressure method may be used instead of the pressure reduction method. For example, as shown in FIG. 4, the rear end of the pipeline under construction is sealed with a cap 5 ', and before the pipeline portion B'disposed on that day is backfilled, the pipeline portion B' Air is attached to the tip through cap 32 'and hose 31'.
Compressor-3 'is connected, and the air-compressor is driven to increase the pressure in the pipeline to a constant pressure.
The air-compressor-3 'is stopped, the valve 33' is closed, the pressure state in the pipeline thereafter is observed by the pressure gauge 34 ', and if the indication of the pressure gauge 34' drops, the pipeline Detecting a poorly airtight pipe joint by applying soapy water to the pipe joint existing in the part B'and repairing the defective joint,
After that, it is possible to backfill the pipe line portion B ′ arranged on that day.

[0009]

By the way, in the airtightness test method shown in FIG. 3, it is necessary to depressurize the inner space of the pipe line portion arranged on that day to a predetermined negative pressure by evacuation by a vacuum pump. Further, in the airtightness test method shown in FIG. 4, it is necessary to pressurize the maximum internal space of the entire pipe length to a predetermined positive pressure by press-fitting air by the air-compressor.

As is clear from the viewpoint of thermodynamics, a space having a constant volume is depressurized or pressurized by vacuuming or air-pressing,
Until a certain negative pressure or positive pressure is reached, the energy lost due to the friction of the gas flow and the turbulence of the gas flow is given to the gas again as heat, and is internally irreversible adiabatic change. Therefore, the change in the gas state during that period is evaluated by the polytropic change, and on the other hand, when the steady state is reached after the constant negative pressure or the positive pressure is reached, the change in volume becomes equal. However, as shown in FIG. 5, during the transition from the polytropic change a to the equal volume change b, a transient pressure fluctuation c occurs over a certain period.

Therefore, this transient pressure fluctuation period t is
The greater the flow of gas during depressurization (or pressurization), and therefore the larger the capacity of the vacuum pump (or air-compressor), the longer the gas flow becomes. When the airtightness test is performed by the test method shown in FIG. 3, the transient pressure fluctuation period t is 1
It can reach hours.

Since this transient pressure fluctuation is similar to the pressure fluctuation when there is a leak, it is necessary to wait for the transient pressure fluctuation period to judge whether the airtightness is acceptable or not. , I have to spend a considerable amount of time on the test.

In the above, if the vacuum pump or the air-compressor has a small capacity and the flow of gas at the time of depressurization or pressurization is made gentle, the above transient pressure fluctuation period can be shortened. However, it takes a long time to reach a predetermined negative pressure or positive pressure in the pipeline, and in the end, a long time is required for the airtight test.

An object of the present invention is to provide an airtightness test method for pipe joints of underground buried pipes, which allows the airtightness test of pipe joints to be performed in a sufficiently short time during construction of a vacuum sewer pipe. To do.

[0015]

A method for testing the airtightness of a pipe joint of an underground buried pipeline according to the present invention is a method for testing the airtightness of a pipe joint of an underground buried pipeline. Before embedding the pipe line portion joined by the above, the pipe joint portions are individually air-tightly enclosed by a housing, and the inside of the housing is depressurized or pressurized to a predetermined pressure, and then the inside of the housing with the passage of time. The configuration is characterized by observing the pressure state of.

[0016]

The space between the pipe joint and the housing is decompressed or pressurized by a vacuum pump or air-compressor. Since the space volume is small, use a small vacuum pump or air-compressor. However, the space can reach a predetermined negative pressure or positive pressure in a short time.

Since the evacuation speed or the air-press-fitting speed is low, the vacuum pump or the air-compressor is used.
It is possible to sufficiently shorten the transient pressure fluctuation period between the change in the polytropy during driving and the change in the isovolume in the steady state after the vacuum pump or the air-compressor is stopped. It is possible to judge whether the airtightness of the pipe joint is good or not from the pressure state in the housing sufficiently early after the stop of-.

Therefore, the airtightness test of the pipe joint can be performed in a sufficiently short time as a whole.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. Figure 1 (a) shows the vacuum type sewer pipe under construction,
Indicates a pipeline portion that has already been buried, and B indicates a pipeline portion that has not been backfilled.

In this pipe line, a plastic pipe, for example, a high density polyethylene pipe is used as the pipe 1.
A heat fusion method is used for joining the tubes. For example, after inserting the tube insertion port 12 into the tube receiving port 11 containing the heating wire, the heating wire is energized and heated to generate heat. A method of heat-sealing the contact surface with the insertion port can be used.

In order to test the airtightness of the pipe joint portion of the pipeline during construction shown in FIG. 1 (a) according to the present invention, the pipe portion B in which the pipes are joined and arranged according to the working process of one day is used. Before performing the backfilling of the pipes, as shown in FIG.
0 is hermetically enclosed by a housing 2 with a pressure gauge 21, and each housing 2 is connected to a vacuum pump 3 via a hose 31 and a multi-connector 30.

After that, the vacuum pump 3 is driven to cause a predetermined negative pressure (usually -0.7 kg / cm ² ) in the space inside each housing 2.
After that, the vacuum pump 3 is stopped, the valve 22 of each housing 2 is closed, and each housing 2 thereafter.
The pressure state inside is observed by the pressure gauge 21.

During the evacuation by the vacuum pump 3, the pressure in the housing 2 fluctuates due to the polytropic change, and after the vacuum pump 3 is stopped, when the steady state is reached, an equal volume change occurs and the polytropic change occurs. As described above, the transient pressure fluctuation occurs during the transition from the period to the equal volume change period.Since this transient pressure change has the same aspect as the pressure change due to the leakage of the pipe joint, In order to judge whether the airtightness of the pipe joint is acceptable or not based on the pressure change in the housing, it is necessary to wait for the end of the transient pressure change period.If this period is long, it is necessary to extend the airtightness test. It

However, in the present invention, the space volume in the housing 2 for evacuation is small, and even if the vacuum pump 3 having a small capacity is used, decompression to a predetermined negative pressure is performed in a sufficiently short time. Further, since the vacuuming speed is low and the transient pressure change period can be shortened sufficiently, the airtightness test as a whole can be conducted in a sufficiently short time.

In this way, if the airtightness test of the pipe joint is carried out before the backfilling by using the working process of one day as a unit, the backfilling is performed as the final process of the working process of one day. After completing the daily work process, the work process will be repeated on a daily basis to proceed with the construction.

In the present invention, the housing 2 has a structure shown in FIG.
(A) and (b) of FIG. 2 [Rolled sectional view of (a) of FIG. 2], horizontal ears 23, 23 are provided at both ends of the width.
Elastic packing 25 of rubber or the like shown in FIG. 2C over the inner rims of the ears 23, 23 and the end plates 24, 24 of the split cylinder having the end plates 24, 24 at both ends in the length direction. It is possible to use the one in which the ears are fastened and the ears are fastened with the bolts and nuts 26. It is also possible to use a 30% cylindrical body instead of the 20% cylindrical body, and a liquid sealant (butyl or silicone type etc.) is used instead of the elastic packing 25 such as rubber. You can also

In the above-mentioned embodiment, the airtightness test is conducted on all the joints of the work process unit for one day at a time, but it is also possible to test each joint immediately after the completion of the joining work. Further, in the above embodiment, the vacuum pump is used to evacuate the inside of the housing, but an air-compressor is used instead of the vacuum pump to pressurize the inside of each housing to a predetermined positive pressure, and then The present invention can also be realized by shutting off the air-compressor, shutting off the space between the housing and the air-compressor by closing a valve, and then observing the pressure state in each housing by the pressure gauge of each housing. Can be implemented.

[0028]

As described above, according to the method for testing the airtightness of the pipe joint portion of the underground buried pipe of the present invention, whether the airtightness of the pipe joint portion is acceptable or not before the backfilling is performed during the construction of the pipe passage. The test can be performed in a short time, and a large amount of time can be allocated to general work other than the airtightness test during the daily work process, and the entire pipeline can be constructed in a short time.

Needless to say, since the airtightness of the pipe joint can be detected before the backfilling and the joint can be repaired, an airtight test is conducted after the pipeline is constructed. Unlike the conventional example in which the position of the defective joint is dug up, the defective joint can be easily repaired.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention, (a) of FIG. 1 shows before an airtight test, and (b) of FIG. 1 shows an airtight test.

2 (a) is a longitudinal cross-sectional explanatory view of a housing used in the present invention, and FIG. 2 (b) is a cross-sectional view taken along the line of FIG. 2 (a). FIG. 2C is a perspective explanatory view showing packing of the housing.

FIG. 3 is an explanatory diagram showing a conventional example.

FIG. 4 is an explanatory diagram showing another conventional example.

FIG. 5 is an explanatory diagram showing a pressure fluctuation state when the space having a constant volume is evacuated to a constant negative pressure and then the evacuation is stopped.

[Explanation of symbols]

 A backfilled pipeline part B backfilling incomplete pipeline part 10 pipe joint part 2 housing 21 pressure gauge 22 valve 3 vacuum pump

Claims (1)

[Claims] 1. A method for testing the airtightness of a pipe joint portion of an underground buried pipe, wherein the pipe joint portions are joined to the housing one by one before the pipe portion joined by the pipe joint portion to be tested is buried. Airtightly enclosing the inside of the housing, reducing or pressurizing the inside of the housing to a predetermined pressure, and observing the pressure state inside the housing with the passage of time thereafter. Test method.