PE gas case
PE gas pipe connection
1. Technology before PE gas pipe construction
a.Be familiar with and master the construction drawings before construction; b. Prepare the corresponding construction equipment;
c. On-the-job training for operators, construction can be carried out after the training is qualified; d. Acceptance of pipes and fittings according to standards.
2.Excavation of PE gas pipe trench
The excavation of the pipe trench must be carried out in strict accordance with the design drawings or the excavation route and excavation depth guided by the project supervision, and it must not be altered without the consent of the relevant departments. In general, the minimum buried polyethylene pipeline is The thickness of soil cover on the pipe top is: A. The buried depth of the pipe top buried under the roadway shall not be less than 0.9 meters; B. The buried pipe under the sidewalk or the pipe branch shall not be less than 0.75 meters; C, the branch pipe under the green belt or the residential area shall not be less than 0.6 meters ;
D. In the permafrost or seasonal frozen ground layer, the top of the pipe should be buried below the freezing line. At the bottom of the sturdy and stable trench, the width of the trench is determined by the operating space required for construction, and the size of the space must allow The proper preparation of the bottom of the trench and the landfill and compaction of the trench filling materials are normally carried out, and the economics of the cost of trench trench excavation and the purchase of landfill materials must also be considered.
3. Preparation of the bottom of the PE gas pipe trench
For pressure systems like water supply, sewage or long-distance pipelines, unless the design drawings have special requirements, generally, the horizontal accuracy of the bottom of the trench is not very high. For gravity drainage systems, the grade of the slope must reach the specified level Claim.
If the bottom of the trench is fairly straight, and there are basically no large stones in the soil, then no leveling is necessary. Of course, it is better if the bottom of the trench is not disturbed, but if the bottom of the trench is better Has been disturbed or must be disturbed during the excavation process, then its compactness should at least reach the compactness of the surrounding landfill materials. Generally, the bottom of the trenches to be excavated should be small stones with no sharp edges and no more than 50mm in diameter. Then mix some materials such as sand and clay to level it. HDPE pipes of all specifications can generally adapt to a small amount of unevenness at the bottom of the trench, but if the backfill material contains sharp-edged stones or hard shale, then A stress concentration zone may be created on the surface of the pipeline to damage the pipeline. For excavation in shale and loose rock soil, in order to avoid contact with loose rocks, a uniform trench bed must be provided for HDPE pipelines. The general approach is When opening the bottom of the control trench, it should be excavated at least 150mm deeper than the specified grade, and then backfilled to the prescribed height with appropriate landfill materials, and compacted to a density of 90% or higher.
4.Laying of pipes in the trench of PE gas pipe
Before the pipeline is placed in the trench, the pipeline should be thoroughly inspected. The pipeline is only allowed to be hoisted or rolled into the trench if no defects are found. The pipeline is usually pre-connected on the ground, and sometimes the pipeline may It will be pre-connected into many 150-meter-long pipe sections and stored in a certain place.When it needs to be lowered and connected, it will be transported to the installation site, and then these pipe sections will be connected by hot-melt or mechanical connection.The nominal diameter is less than 20mm pipes can be dragged into the pipe trench manually; for all large pipes, pipe fittings, valves, fire hydrants and accessories, they should be carefully placed into the pipe trench with appropriate tools; for long-distance pipe lifting
, nylon is recommended rope.
5.The final pipeline 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 it must be ensured that the connected pipes must be cooled to the ambient temperature of the soil before connecting. When connecting to metal pipes, water tanks
or pumps, the method is generally used Blue connection. If it is not convenient to use hot-melt connection, flange connection can also be used. When flange connection, the bolts should be evenly tightened in advance, wait 8 hours before re-tightening. 
6. Stress test
The pressure test can be performed before or after the pipeline is backfilled. The pipeline should be covered with soil at a certain interval, especially for snake pipelines. During the pressure test, the pipeline should be fixed in place. The flange connection should be exposed to check for leaks.
The test pressure of the pressure test should not exceed 1.5 times of the pressure level of the pipe or the lowest pressure level of the fittings in the system.At the beginning, the pressure should be raised to the specified test pressure value and stay for a sufficient time to ensure that the pipe is fully expanded. The process takes 2-3 hours. When the system is stable, increase the pressure to 1.5 times the working pressure, stabilize the voltage for 1 hour, carefully observe the pressure gauge, and patrol along the line. If there is no visible leakage or occurrence during the test, If there is a significant pressure drop, the pipeline passes the pressure test.
During the pressure test, the continuous expansion of the pipe will cause a pressure drop to occur.It is normal for a certain pressure drop to occur during the test, and it cannot be proved that the pipeline system must have leaked or damaged.
7.Backfill and compaction
In general, the axillary angle and initial backfill requirements must be at least 90%, and the compacted layer should be at least 150mm from the top of the pipe, and direct compaction should be avoided for places less than 300mm from the top of the pipe. The final backfill may use the original Excavate soil or other materials, but they must not contain frozen soil, agglomerated clay, and stones with a maximum diameter of 200 mm.