Cleaning device for low-pressure pipeline of cementing truck

Abstract

The utility model relates to a low-pressure pipeline cleaning device of a well cementation cement truck, and relates to the technical field of well cementation equipment. The well cementation cement truck low-pressure pipeline cleaning device comprises a metering tank, a low-pressure pipeline, a slurry mixing pipeline and an injection pump. The metering tank is used for providing clean water; the low-pressure pipeline comprises a first pipeline, a plunger pump and a second pipeline which are connected in sequence, and the first pipeline is communicated with the metering tank; the slurry mixing pipeline is communicated with the plunger pump; the injection pump is respectively communicated with the metering tank and the slurry mixing pipeline; the cleaning device for the low-pressure pipeline of the well cementation cement truck further comprises a cleaning pipeline, and the cleaning pipeline is communicated with the first pipeline and the injection pump so as to clean the low-pressure pipeline. According to the technical scheme, the problems that an existing low-pressure pipeline cannot be cleaned thoroughly, the using amount of clear water is large, and resources are wasted can be solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of cementing equipment, especially to a cementing truck low-pressure pipeline cleaning device. BACKGROUND

[0002] At present, shale oil and gas (shale oil) well becomes the important direction of oilfield exploration and development, with the continuous innovation of well completion technology and the application of new cementing technology, the ability and performance of cementing equipment bring great challenge, among them, the clean water replaces the slurry operation is the important measure of shale gas well (shale oil) saving production time limit and reducing production cost.

[0003] The clean water replaces the slurry operation refers to, in order to avoid the cement slurry deposition, hardening even solidification in the pipeline and cause the pipeline drift reduction until completely blocked, therefore must carry out thorough cleaning to low-pressure pipeline after each time grouting ends. In some cases, the clean water replaces the slurry operation and relies on the height difference of metering tank and slurry mixing tank to drive the clean water flow to clean the pipeline, but such mode not only exists the problem of long time of cleaning the cement slurry and sediment in the low-pressure pipeline at the bottom of plunger pump, but also exists the problems of unclean pipeline, large clean water consumption and resource waste. SUMMARY

[0004] The utility model embodiment provides a kind of cementing truck low-pressure pipeline cleaning device, can solve the problems of unclean, large clean water consumption and resource waste of existing low-pressure pipeline cleaning.

[0005] In a first aspect, the utility model embodiment provides a kind of cementing truck low-pressure pipeline cleaning device, comprising:

[0006] metering tank, for providing clean water;

[0007] low-pressure pipeline, including sequentially connected first pipeline, plunger pump and second pipeline, the first pipeline is communicated with the metering tank;

[0008] slurry mixing pipeline, communicated with the plunger pump;And

[0009] jet pump, respectively communicated with the metering tank, the slurry mixing pipeline;

[0010] Among them, the cementing truck low-pressure pipeline cleaning device further includes cleaning pipeline, the cleaning pipeline is respectively communicated with the first pipeline, the jet pump, to clean the low-pressure pipeline.

[0011] In one embodiment, the cleaning pipeline includes:

[0012] cleaning pipeline, one end is communicated with the first pipeline and the other end is communicated with the outlet of the jet pump;

[0013] At least one cleaning valve is arranged on the cleaning pipeline.

[0014] In one embodiment, the low-pressure pipeline further comprises a gravity water upper valve and a perfusion valve, the gravity water upper valve and the perfusion valve are arranged on the first pipeline and the second pipeline respectively.

[0015] One end of the cleaning pipeline is in communication with the pipeline segment between the gravity water upper valve and the plunger pump of the first pipeline.

[0016] In one embodiment, the cleaning pipeline comprises a connecting pipeline segment, the connecting pipeline segment is connected with the first pipeline, and a preset included angle is formed between the connecting pipeline segment and the first pipeline.

[0017] In one embodiment, the preset included angle is 60°.

[0018] In one embodiment, the mud mixing pipeline comprises:

[0019] A mud tank is provided with a first mud outlet, a second mud outlet, a third mud outlet, a first mud inlet and a second mud inlet.

[0020] A perfusion pipeline is in communication with one end of the first mud outlet and the other end of the second pipeline.

[0021] A perfusion pump is arranged on the perfusion pipeline.

[0022] A mud mixing and stirring pipeline is in communication with the second mud outlet, the second pipeline and the jet pump respectively, and the mud mixing and stirring pipeline is configured to inject the mixed and stirred cement slurry into the mud tank.

[0023] In one embodiment, the mud mixing and stirring pipeline comprises:

[0024] A mixer is used to mix the cement slurry and inject the mixed and stirred cement slurry into the mud tank.

[0025] A water injection pipeline is in communication with one end of the jet pump and the other end of the mixer.

[0026] A circulation pipeline is in communication with one end of the second mud outlet and the other end of the first mud inlet.

[0027] A circulation pump is arranged on the circulation pipeline.

[0028] In one embodiment, the mud mixing and stirring pipeline further comprises:

[0029] A densimeter is arranged on the circulation pipeline.

[0030] A flow meter is arranged on the water injection pipe.

[0031] At least one first valve is arranged on the water injection pipe.

[0032] At least one second valve is arranged on the circulation pipe.

[0033] In one embodiment, the metering tank is provided with a first water outlet and a second water outlet; the first pipeline is connected to the first water outlet through a gravity water pipeline, and the injection pump is connected to the second water outlet through a water supply pipeline.

[0034] In one embodiment, the first water outlet and the second water outlet are respectively provided with a first water valve and a second water valve; and the water supply pipeline is provided with at least one third valve.

[0035] Compared with the prior art, the advantages of the embodiments of the present application are that the cleaning pipeline connected to the first pipeline and the injection pump is arranged, the clean water provided by the metering tank is pressurized by the injection pump and then flows into the cleaning pipeline to form high-pressure water, the high-pressure water is used to quickly flush the cement slurry deposits in the low-pressure pipeline, the cleaning effect is good, and the water consumption and the cleaning time are effectively reduced; in addition, the cleaning pipeline can also pressurize and supply water for the plunger pump, and the water supply efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0036] The present application will be described in more detail below based on the embodiments and with reference to the drawings.

[0037] Figure 1 is a main structure schematic diagram of a low-pressure pipeline cleaning device of a cementing cement truck provided by an embodiment of the present application;

[0038] Figure 2 is Figure 1 a structure schematic diagram of a cleaning pipeline provided by an embodiment of the present application.

[0039] REFERENCE NUMERALS:

[0040] 10, metering tank; 110, first water outlet; 120, second water outlet; 130, first water valve; 140, second water valve;

[0041] 20, low-pressure pipeline; 210, first pipeline; 220, plunger pump; 230, second pipeline; 240, gravity water valve; 250, perf valve;

[0042] 30, slurry mixing pipeline; 310, slurry tank; 320, grouting pipe; 330, grouting pump; 3401, mixer; 3402, water injection pipe; 3403, circulation pipe; 3404, circulation pump; 3405, density meter; 3406, flow meter; 3407, first valve; 3408, second valve;

[0043] 40, jet pump; 410, water supply pipe; 420, water outlet valve;

[0044] 50, cleaning pipeline; 510, cleaning pipe; 5101, connecting pipe section; 520, cleaning valve. DETAILED DESCRIPTION

[0045] The utility model will be described further below with reference to the drawings.

[0046] At present, shale oil and gas (shale oil) well becomes the important direction of oil field exploration and development, along with the well completion technology continuous innovation and the application of new cementing technology, the ability and performance of cementing equipment bring great challenge, and the clean water replaces the slurry operation is the important measure of shale gas well (shale oil) saving production time limit and reducing production cost.

[0047] The clean water replaces the slurry operation refers to, in order to avoid cement slurry deposition, concretion and even solidification hardening in the pipeline and cause the pipeline drift diameter to reduce until completely blocked, so must carry out thorough cleaning to low pressure pipeline after each time grouting ends.In some cases, the clean water replaces the slurry operation relies on the height difference of metering tank and slurry mixing tank to drive clean water flow to clean the pipeline, but such mode not only exists cement slurry and sediment in the cleaning piston pump bottom low pressure pipeline for a long time, but also exists the problems of pipeline cleaning not clean, clean water consumption is large and resource waste.

[0048] Embodiment one

[0049] In order to solve the above technical problems, the utility model embodiment provides a kind of cementing cement truck low pressure pipeline cleaning device, including metering tank 10, low pressure pipeline 20, slurry mixing pipeline 30 and jet pump 40;Metering tank 10 is used to provide clean water;Low pressure pipeline 20 includes sequentially connected first pipe 210, piston pump 220 and second pipe 230, and first pipe 210 is communicated with metering tank 10;Slurry mixing pipeline 30 is communicated with piston pump 220;Jet pump 40 is communicated with metering tank 10, slurry mixing pipeline 30 respectively;Wherein, cementing cement truck low pressure pipeline cleaning device further includes cleaning pipeline 50, and cleaning pipeline 50 is communicated with first pipe 210, jet pump 40 respectively, to clean low pressure pipeline 20.

[0050] As can be seen from the above, by arranging the cleaning pipeline 50 communicated with the first pipeline 210 and the jet pump 40, the clean water provided by the metering tank 10 is pressurized by the jet pump 40 and then flows into the cleaning pipeline 50 to form high-pressure water, and the high-pressure water is used to quickly flush the cement slurry deposits in the low-pressure pipeline 20, which not only has a good cleaning effect, but also effectively reduces the water consumption and cleaning time; in addition, the cleaning pipeline 50 can also pressurize the water supply for the plunger pump 220, thereby providing the water supply efficiency.

[0051] It should be noted that the discharge port of the plunger pump 220 is connected with a high-pressure pipeline to inject water or slurry into the well.

[0052] It should be further noted that the water of the metering tank 10 comes from an external water source, and the external water source can be communicated with the metering tank 10 through a water delivery pipe, and a plurality of water delivery valves are arranged on the water delivery pipe, so as to input clean water into the metering tank 10.

[0053] Embodiment Two

[0054] As shown in Figure 1 and Figure 2 , the cementing cement truck low-pressure pipeline cleaning device includes a metering tank 10, a low-pressure pipeline 20, a slurry mixing pipeline 30, and a jet pump 40; the metering tank 10 is used to provide clean water; the low-pressure pipeline 20 includes a first pipeline 210, a plunger pump 220, and a second pipeline 230 connected in sequence, and the first pipeline 210 is communicated with the metering tank 10; the slurry mixing pipeline 30 is communicated with the plunger pump 220; the jet pump 40 is communicated with the metering tank 10 and the slurry mixing pipeline 30, respectively; wherein the cementing cement truck low-pressure pipeline cleaning device further includes a cleaning pipeline 50, and the cleaning pipeline 50 is communicated with the first pipeline 210 and the jet pump 40, respectively, to clean the low-pressure pipeline 20.

[0055] As can be seen from the above, by arranging the cleaning pipeline 50 communicated with the first pipeline 210 and the jet pump 40, the clean water provided by the metering tank 10 is pressurized by the jet pump 40 and then flows into the cleaning pipeline 50 to form high-pressure water, and the high-pressure water is used to quickly flush the cement slurry deposits in the low-pressure pipeline 20, which not only has a good cleaning effect, but also effectively reduces the water consumption and cleaning time; in addition, the cleaning pipeline 50 can also pressurize the water supply for the plunger pump 220, thereby providing the water supply efficiency.

[0056] It should be noted that the discharge port of the plunger pump 220 is connected with a high-pressure pipeline to inject water or slurry into the well.

[0057] It should be further noted that the water of the metering tank 10 comes from an external water source, and the external water source can be communicated with the metering tank 10 through a water delivery pipe, and a plurality of water delivery valves are arranged on the water delivery pipe, so as to input clean water into the metering tank 10.

[0058] In some embodiments, the cleaning pipeline 50 comprises a cleaning pipeline 510 and at least one cleaning valve 520; one end of the cleaning pipeline 510 is in communication with the first pipeline 210 and the other end is in communication with the outlet of the jet pump 40; and the at least one cleaning valve 520 is arranged on the cleaning pipeline 510.

[0059] By setting the cleaning valve 520 to control the opening and closing of the cleaning pipeline 510, the cleaning function is ensured while avoiding affecting the water injection and grouting work of the cementing truck when not cleaning.

[0060] It should be noted that the cleaning valve 520 includes but is not limited to an electrically controlled pneumatic butterfly valve.

[0061] It should also be noted that the cleaning pipeline 510 can be connected by multiple pipe sections, which can be elbow pipes or straight pipes, depending on the on-site installation, and the present application does not make specific limitations.

[0062] In some embodiments, the low-pressure pipeline 20 further comprises a gravity water valve 240 and a grouting valve 250, and the gravity water valve 240 and the grouting valve 250 are arranged on the first pipeline 210 and the second pipeline 230, respectively; and one end of the cleaning pipeline is in communication with the pipe section between the gravity water valve 240 and the plunger pump 220 of the first pipeline 210.

[0063] By connecting one end of the cleaning pipeline to the pipe section between the gravity water valve 240 and the plunger pump 220 of the first pipeline 210, the high-pressure water can thoroughly clean the pipe section between the gravity water valve 240 and the plunger pump 220 of the first pipeline 210, effectively preventing the cement slurry from solidifying.

[0064] It should be noted that the gravity water valve 240 and the grouting valve 250 include but are not limited to an electrically controlled pneumatic butterfly valve.

[0065] It should also be noted that when grouting into the well through the grouting pump 330 and the plunger pump 220, although the gravity water valve 240 is in a closed state, the cement slurry will squeeze into the pipe section between the gravity water valve 240 and the plunger pump 220 of the first pipeline 210 because the cement slurry has a certain pressure after being pumped by the grouting pump 330.

[0066] In some embodiments, the cleaning pipeline comprises a connecting pipe section 5101, the connecting pipe section 5101 is connected to the first pipeline 210, and the connecting pipe section 5101 and the first pipeline 210 have a preset included angle therebetween.

[0067] By setting the connecting pipe section 5101 having a preset included angle with the first pipe 210, the high-pressure water flow conveyed by the cleaning pipe can lift the cement slurry sediment in the low-pressure pipeline 20, and quickly suck it away by the plunger pump 220, which not only further improves the cleaning effect, but also further reduces the water consumption and cleaning time required for cleaning the low-pressure pipeline 20.

[0068] It should be noted that, in actual production, the cleaning device provided by the utility model reduces the time for cleaning the low-pressure pipeline 20 from the original 5 minutes to 1 minute, and reduces the water consumption from the original 1.0 cubic meters to 0.5 cubic meters. In addition, compared with the existing metering tank 10 gravity water mode, the utility model utilizes the jet pump 40 to suck clean water in the metering tank 10 and pressurize the plunger pump 220 with water through the cleaning pipe, which improves the water efficiency of the plunger pump 220. When the clean water displacement pressure is 45-50MPA, the water efficiency of the plunger pump 220 is improved from the original 88% to 99%.

[0069] In some embodiments, the preset included angle is 60°.

[0070] In some embodiments, the slurry pipeline 30 comprises a slurry tank 310, a perfusion pipe 320, a perfusion pump 330, and a slurry mixing pipeline; the slurry tank 310 is provided with a first slurry outlet, a second slurry outlet, a third slurry outlet, a first slurry inlet, and a second slurry inlet; one end of the perfusion pipe 320 is in communication with the first slurry outlet, and the other end is in communication with the second pipe 230; the perfusion pump 330 is arranged on the perfusion pipe 320; the slurry mixing pipeline is in communication with the second slurry outlet, the second pipe 230, and the jet pump 40, respectively, and is configured to inject the mixed cement slurry into the slurry tank 310.

[0071] By setting the slurry mixing pipeline in communication with the second slurry outlet, the second pipe 230, and the jet pump 40, respectively, the jet pump 40 is used to suck clean water in the metering tank 10 to supply water for cement slurry mixing; the slurry tank 310 receives the mixed cement slurry output by the slurry mixing pipeline, and the perfusion pipe 320 and the perfusion pump 330 are used to convey the cement slurry to the plunger pump 220 to inject the cement slurry into the well. In addition, by providing multiple slurry outlets and slurry inlets on the slurry tank 310, a structural basis is provided for connection with different pipes, avoiding the use of a slurry outlet or a slurry inlet for pipes with different functions, which causes inconvenience in use.

[0072] It should be noted that the first slurry outlet, the second slurry outlet, and the third slurry outlet are respectively provided with a slurry valve, which includes but is not limited to an electrically controlled pneumatic butterfly valve.

[0073] It should be noted that the second pipeline 230 is provided with at least one fourth valve, which is arranged on the pipeline segment of the second pipeline 230 between the plunger pump 220 and the perfusion pipe 320.

[0074] In some embodiments, the mud mixing and stirring pipeline comprises a mixer 3401, a water injection pipe 3402, a circulation pipe 3403, and a circulation pump 3404; the mixer 3401 is used for stirring and mixing the cement slurry and injecting the stirred and mixed cement slurry into the mud tank 310; one end of the water injection pipe 3402 is in communication with the jet pump 40 and the other end is in communication with the mixer 3401; one end of the circulation pipe 3403 is in communication with the second mud outlet and the other end is in communication with the first mud inlet; and the circulation pump 3404 is arranged on the circulation pipe 3403.

[0075] The mixer 3401 is arranged to complete the work of stirring and mixing the cement slurry, and the mixer 3401 is used to directly inject the stirred and mixed cement slurry into the mud tank 310; the circulation pipe 3403 and the circulation pump 3404 are arranged to suck the cement slurry in the mud tank 310 and re-inject it into the mud tank 310, thereby playing a role of secondary stirring and mixing.

[0076] It should be noted that the specific structure and working principle of the mixer 3401 are prior art, and will not be described herein.

[0077] In some embodiments, the mud mixing and stirring pipeline further comprises a densimeter 3405, a flowmeter 3406, at least one first valve 3407, and at least one second valve 3408; the densimeter 3405 is arranged on the circulation pipe 3403; the flowmeter 3406 is arranged on the water injection pipe 3402; the at least one first valve 3407 is arranged on the water injection pipe 3402; and the at least one second valve 3408 is arranged on the circulation pipe 3403.

[0078] The densimeter 3405 is arranged on the circulation pipe 3403 to detect whether the mixing is up to standard, thereby ensuring that the cement slurry in the mud tank 310 is stirred uniformly; and the flowmeter 3406 is arranged on the water injection pipe 3402 to measure the flow of fluid in the water injection pipe 3402, thereby controlling the amount of water injected into the mixer 3401.

[0079] It should be noted that the specific structure and working principle of the densimeter 3405 and the flowmeter 3406 are prior art, and will not be described herein.

[0080] It should be noted that the first valve 3407 includes but is not limited to an electrically controlled pneumatic butterfly valve, and the second valve 3408 includes but is not limited to a manual butterfly valve.

[0081] In some embodiments, the metering tank 10 is provided with a first water outlet 110 and a second water outlet 120; wherein the first pipeline 210 is connected to the first water outlet 110 through a gravity water pipeline, and the jet pump 40 is connected to the second water outlet 120 through a water supply pipeline 410.

[0082] By providing multiple water outlets on the metering tank 10, a structural basis is provided for connecting to different pipelines, avoiding the use of a single water outlet for pipelines with different functions, which causes inconvenience in use.

[0083] In some embodiments, the first water outlet 110 and the second water outlet 120 are respectively provided with a first water valve 130 and a second water valve 140; and the water supply pipeline 410 is provided with at least one third valve.

[0084] By providing the first water valve 130, the second water valve 140, and the third valve, the flow of fluid is controlled to ensure the normal operation of the entire device.

[0085] It should be noted that the first water valve 130, the second water valve 140, and the third valve include but are not limited to electrically controlled pneumatic butterfly valves, and the present application does not make specific limitations.

[0086] During the cementing process, when water is injected into the well, the first water valve 130, the gravity water valve, and the clean water valve are opened, the third valve and the fourth valve are closed, and the water in the metering tank 10 enters the plunger pump 220 under the action of gravity, and then enters the well through the high-pressure pipe. Of course, the second water valve 140, the third valve, and the cleaning valve 520 can also be opened, and the jet pump 40 can be used to suck clean water in the metering tank 10 and supply it to the plunger pump 220, and then enter the well through the high-pressure pipe.

[0087] During the cementing process, when mixing the slurry, the gravity water valve, the fourth valve, and the clean water valve are closed, the second water valve 140 and the third valve are opened, and the jet pump 40 is used to suck clean water in the metering tank 10 and inject it into the mixer 3401 through the water injection pipe 3402. After the mixing of the cement slurry is completed in the mixer 3401, the cement slurry is injected into the slurry tank 310; the circulating pump 3404 sucks the cement slurry in the slurry tank 310 and injects it into the slurry tank 310 through the circulating pipe 3403, and the density meter 3405 on the circulating pipe 3403 is used to detect the mixing result; after the mixing of the slurry is completed, the injection pump 330 sucks the cement slurry in the slurry tank 310 and injects it into the well through the injection pipe 320, the second pipeline 230, the plunger pump 220, and then the high-pressure pipe;

[0088] When the low-pressure pipeline 20 needs to be cleaned, the clean water provided by the metering tank 10 is pressurized by the jet pump 40 and flows into the cleaning pipeline 50 to form high-pressure water, the high-pressure water is used to quickly flush the cement slurry deposits in the low-pressure pipeline 20, the cement slurry deposits in the low-pressure pipeline 20 are lifted, and the plunger pump 220 quickly sucks them away, thereby improving the cleaning effect, reducing the water consumption and the cleaning time.

[0089] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to the present application and equivalents thereof without departing from the scope of the present application. In particular, the technical features mentioned in each of the embodiments can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A cement truck low pressure line cleaning apparatus, comprising: The cementing truck comprises: a metering tank for providing clean water; a low-pressure pipeline comprising a first pipe, a plunger pump and a second pipe connected in sequence, the first pipe being in communication with the metering tank; a mud mixing pipeline in communication with the plunger pump; and a jet pump in communication with the metering tank and the mud mixing pipeline respectively. The low-pressure pipeline cleaning device of the cementing truck further comprises a cleaning pipeline in communication with the first pipe and the jet pump, so as to clean the low-pressure pipeline.

2. The low pressure line cleaning device for cementing trucks of claim 1, wherein, The cleaning pipeline comprises: a cleaning pipe in communication with the first pipe at one end and the outlet of the jet pump at the other end; at least one cleaning valve arranged on the cleaning pipe.

3. The low pressure line cleaning device of claim 2, wherein, The low-pressure pipeline further comprises a gravity water upper valve and a perfusion valve arranged on the first pipe and the second pipe respectively. The cleaning pipe is in communication with the pipe section between the gravity water upper valve and the plunger pump of the first pipe.

4. The low pressure line cleaning device of claim 3, wherein, The cleaning pipe comprises a connecting pipe section connected with the first pipe, and a preset included angle is formed between the connecting pipe section and the first pipe.

5. The low pressure line cleaning device of claim 4, wherein, The preset included angle is 60°.

6. The cement truck low pressure line cleaning apparatus of any one of claims 1-5, wherein, The mud mixing pipeline comprises: a mud tank provided with a first mud outlet, a second mud outlet, a third mud outlet, a first mud inlet and a second mud inlet; a perfusion pipe in communication with the first mud outlet at one end and the second pipe at the other end; a perfusion pump arranged on the perfusion pipe; a mud mixing and stirring pipeline in communication with the second mud outlet, the second pipe and the jet pump respectively, and configured to inject the mixed and stirred cement slurry into the mud tank.

7. The low pressure line cleaning device of claim 6, wherein, The mud mixing and stirring pipeline comprises: a mixer for mixing the cement slurry and injecting the mixed and stirred cement slurry into the mud tank; a water injection pipe in communication with the jet pump at one end and the mixer at the other end; a circulation pipe in communication with the second mud outlet at one end and the first mud inlet at the other end; and a circulation pump arranged on the circulation pipe.

8. The cement truck low pressure line cleaning apparatus of claim 7, wherein, The mud mixing and stirring pipeline further comprises: a densimeter arranged on the circulation pipe; a flow meter arranged on the water injection pipe; at least one first valve arranged on the water injection pipe; and at least one second valve arranged on the circulation pipe.

9. The cement truck low pressure line cleaning apparatus of any one of claims 1-5, wherein, The metering tank is provided with a first water outlet and a second water outlet; the first pipe is in communication with the first water outlet through a gravity water upper pipe, and the jet pump is in communication with the second water outlet through a water supply pipe.

10. The cement truck low pressure line cleaning apparatus of claim 9, wherein, The first water outlet and the second water outlet are respectively provided with a first water valve and a second water valve; and the water supply pipe is provided with at least one third valve.

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