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PE pipe, PE water supply pipe in the construction of the need to pay attention to things


Release time:

Jun 04,2019

In the application of various buried polyethylene pipelines, the laying quality is the key factor for the pipeline to achieve the required long-term service life. High-density polyethylene (HDPE) pipes have many unique properties that make pipe laying safer and faster. At the same time, the correct construction design and installation specifications will make these advantages of the pipeline play a greater role. (I) technical preparation before construction must be familiar with and master the construction drawings before construction; B. prepare the corresponding construction equipment; C. on-the-job training for operators, training qualified, can carry out construction; D. pipelines and pipe fittings shall be accepted according to standards.

In the application of various buried polyethylene pipelines, the laying quality is the key factor for the pipeline to achieve the required long-term service life. High-density polyethylene (HDPE) pipes have many unique properties that make pipe laying safer and faster. At the same time, the correct construction design and installation specifications will make these advantages of the pipeline play a greater role.
Technical preparation before (I) construction
Must be familiar with and master the construction drawing before construction;
B. Prepare corresponding construction equipment;
C. on-the-job training for operators, training qualified, can carry out construction;
d. Pipes and pipe fittings shall be accepted according to standards.
(2) Excavation of pipe trench
Pipe trench excavation must be carried out in strict accordance with the design drawings or the excavation route and excavation depth guided by the project supervisor, and shall not be changed without the consent of relevant departments.
High-density polyethylene (HDPE) pipes have good flexibility and light weight, and can be prefabricated on the ground for longer pipes. Where local shape conditions permit, ground welding of the pipeline can reduce the excavation width of the pipeline trench. Excavating tools such as rotary excavators, plows or buckets can be used for the excavation of narrow pipe trenches. Generally, the minimum cover thickness of polyethylene pipe is:
The burial depth of the pipe top (I) buried under the driveway shall not be less than 0.9 m;
B. Should be buried under the sidewalk or pipe support shall not be less than 0.75 meters;
c. The branches under the green belt or residential area should not be less than 0.6 meters.
In sandy or muddy ditches, if it is not easy to make the upright side walls of the ditch, you can make a 45-degree slope or a slope that supports the ditch wall material. If the trench is wide, the initial landfill material must be compacted to support the final landfill weight.
Preparation of (III) Single Tube Trench Bottom
For pressure systems such as water supply, drainage or long-distance pipelines, unless there are special requirements in the design drawings, the horizontal accuracy of the bottom of the pipe trench is generally not very high. For gravity drainage systems, the slope must meet the specified requirements.
If the bottom of the ditch is fairly straight, and there are basically no large stones in the soil, then there is no need for leveling. Of course, it would be better if it were an undisturbed bottom of the pipe. However, if the bottom of the trench is disturbed or must be disturbed during excavation, its density shall be at least that of the surrounding landfill material. The bottom of the excavated trench is usually flattened with small stones, without sharp edges and corners, no more than 50mm in diameter, and some sand and clay materials. All specifications of HDPE pipes can generally adapt to a small amount of uneven bottom of local pipe grooves, but if the backfill material contains sharp edges or hard shale stone, it may produce stress concentration areas on the surface of the pipe and damage the pipe.
For excavation of shale and loose rock and soil, a uniform grooved bed must be provided for PE pipe to avoid contact with loose rock. The usual practice is to dig deeper than the specified level when opening the bottom of the pipe. At least 150mm, then backfill to the specified height with appropriate landfill material and compact to a density of 90% or higher.
For similar unstable soils, such as wet clay or sandy soil, the support strength is low and the trench excavation depth is 100-150mm deeper than the specified value. It shall then be backfilled with specified or original excavated material to ensure uniform support for HDPE pipes. In unstable organic soils, if the groundwater level of the installation site is high enough to flood the pipeline, additional weight can be added to the pipeline to resist the buoyancy of the pipeline, but this additional design weight should not exceed the support strength of the foundation.
(IV) laying pipes in the ditch
Before putting the pipe into the pipe ditch, the pipe should be thoroughly inspected, and only if no defects are found, the pipe should be allowed to hang or roll into the pipe ditch.
Pipes are usually pre-connected to the ground. Sometimes pipes may be pre-connected into many sections of about 150 meters long, stored in a certain place, and transported to the installation site when they need to be handed over and connected. The segments are then joined by hot melt joining or mechanical joining.
Pipes with a nominal diameter of less than 20mm can be manually pulled into the pipe groove; all large pipes, fittings, valves, fire hydrants and accessories should be carefully placed into the pipe groove using appropriate tools; for long-distance pipe hoisting, nylon rope is recommended.
(5) Final pipe connection and assembly
The hot melt connection of the pipes in the trench is the same as the hot melt connection of the pipes on the ground, but the connected pipes must be cooled to the ambient temperature of the soil before connecting.
When HDPE pipes are connected to metal pipes, water tanks or water pumps, flange connections are usually used. For high-density polyethylene (HDPE) pipes, flange connections can also be used when hot melt connections are not easy. When connecting the flange, the bolts should be tightened evenly in advance, and then tightened after 8 hours.
(6)PE pipeline pressure test
The HDPE piping system shall be pressure tested before being put into operation. The pressure test includes two parts: strength test and water tightness test. Water is usually recommended as the test medium for the test.
Strength test
After removing the air in the pipeline to be tested, the pressure is increased to the required pressure value at a stable pressurization speed, and the pressure gauge should be placed at the lowest point of the pipeline as much as possible.
The pressure test may be performed before or after the pipeline is backfilled. Pipes shall be covered with soil at certain intervals. Especially for snake pipes, the pipes should be fixed in place during pressure testing. Flanged joints shall be exposed to check for leaks.
The test pressure of the pressure test shall not exceed 1.5 times the pressure rating of the pipeline in the system or the fitted pressure level of the lowest pressure rating. The pressure shall be increased to the specified test pressure at the beginning and maintained for a sufficient time to ensure that the pipeline is fully expanded. This process takes 2 to 3 hours. When the system is stable, the pressure is increased to 1.5 times the working pressure, and the pressure is stable for 1 hour. Carefully observe the pressure gauge and check the line. If there is no obvious leakage or obvious pressure drop during the test, the pipeline will pass the pressure test.
During the pressure test, the continuous expansion of the pipeline will cause pressure drop. It is normal to generate a certain pressure drop during the test, which cannot prove that the pipeline system will leak or be damaged.
Water tightness test
HDPE pipes are connected by electric melting, which makes HDPE pipes have better waterproof performance compared with traditional pipes.
The test pressure for the water tightness test shall not exceed 1.15 times the pressure rating of the pipeline or the lowest pressure rating of the fittings in the system. When the pipeline pressure reaches the test pressure, the temperature of the test medium in the pipeline should be consistent with the ambient temperature of the pipeline for a certain period of time. When the temperature and pressure are stable, the timing should be started. Generally, the water tightness test shall be stable for 24 times. After the test, if there is no obvious leakage or pressure drop, the water tightness test shall be carried out.
(7) Backfilling and Compaction
In general, the following three materials can be used as backfill materials for hdpe pipes;
The first category: 5-40mm boulder, including a large number of locally readily available materials, such as coral, broken slag, gravel and broken shells;
The second category: coarse sand and gravel with a maximum diameter of 40mm, including different grades of sand or gravel containing a small amount of powder, usually granular and non-stick, either wet or dry;
The third category: high-quality sand and clay gravel, including fine sand, clay sand and clay gravel mixture.
In general, the haunch angle and initial backfilling shall be at least 90%, the compacted layer shall be at least 150 mm from the top of the pipe, and direct compaction shall be avoided at less than 300 mm from the top of the pipe.
The final backfill may be made of original excavated earth or other material, but shall not contain frozen earth, agglomerated clay and stones with a maximum diameter not exceeding 200mm.








































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