Underground Gas Polyethylene Piping System

HDPE Gas Pipe Connection

1. Technology before construction of HDPE gas pipe

a. Be familiar with and master the construction drawings before construction;

b. Prepare the corresponding construction equipment;

c. On-the-job training for operators, and construction can only 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 HDPE gas pipe trench must be carried out in strict accordance with the excavation route and excavation depth guided by the design drawings or engineering supervision, and no modification shall be made without the consent of the relevant departments. Generally speaking, the minimum buried polyethylene pipe is required. The thickness of the cover soil on the top of the pipe is:

A. The buried depth of the pipe top buried under the roadway shall not be less than 0.9 meters;

B. Buried under the sidewalk or pipeline branch shall not be less than 0.75 meters;

C. The branch pipe under the green belt or in the residential area shall not be less than 0.6 meters;

D. In permafrost or seasonally frozen ground, the depth of the pipe top should be below the freezing line. At the bottom of a sturdy and stable trench, the width of the pipe trench is determined by the operating space required for construction, and the size of the space must allow The correct preparation of the bottom of the HDPE gas pipe trench and the burial and compaction of the pipe trench landfill materials should be carried out normally, and the cost of excavation of the pipe trench and the cost of purchasing landfill materials should also be considered.

HDPE Gas Pipe Package

3. Preparation of HDPE gas pipe trench bottom

For pressure systems such as water supply, sewage or long-distance pipelines, unless the design drawings have special requirements, generally speaking, the horizontal accuracy of the bottom of the pipe trench is not very high. For gravity drainage systems, the grade of slope must reach the specified level. Require.

If the trench bottom is fairly straight and there are basically no large rocks in the soil, then leveling is not necessary. Of course, it is better if it is an undisturbed trench bottom. But if the trench bottom If it has been disturbed or must be disturbed in the process of excavation, its compactness should at least reach the compactness of the surrounding landfill materials. The bottom of the excavated pipe trench is generally made of small stones with a diameter of no more than 50mm without sharp edges and corners. Mix some materials such as sand and clay to level it. HDPE gas pipe of all sizes can generally adapt to a small amount of local 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 rock, a uniform trench bed must be provided for the HDPE pipeline. The general practice is When the bottom of the trench is opened and controlled, it shall be dug at least 150mm deeper than the specified grade, and then backfilled to the specified height with appropriate landfill materials, and compacted to a density of 90% or higher.

4. Laying of pipes in PE gas pipe trenches

Before the pipe is placed in the trench, it should first be fully inspected, and only if no defects are found, the pipe is allowed to be hoisted or rolled into the trench. The pipe is usually pre-connected at the ground, and sometimes the pipe may be It will be pre-connected into many HDPE natural gas pipe sections about 150 meters long, stored in a certain place, and when it needs to be lowered and connected, it will be transported to the installation site, and then these HDPE natural gas pipe sections will be connected by hot melt connection or mechanical connection. The nominal diameter is less than 20mm pipes can be manually dragged into the trench; for all large pipes, fittings, valves, fire hydrants and accessories, appropriate tools should be used to carefully place them into the trench; for long-distance pipe hoisting, nylon is recommended rope.

HDPE Gas Pipe Production Process

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 it must be ensured that the connected pipes must be cooled to the ambient temperature of the soil before connecting. When connecting with metal pipes, water tanks or water pumps, the method is generally used. Flange 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, and then re-tighten after 8 hours.

6. Stress test

The pressure test can be carried out before or after the pipeline is backfilled. The pipeline should be covered with soil at certain intervals. Especially for the meandering pipeline, the pipeline should be fixed in place during the pressure test. The flange connection should be exposed to check for leaks.

The test pressure of the pressure test should not exceed 1.5 times the pressure level of the pipe or the fittings with the lowest pressure level in the system. At the beginning, the pressure should be raised to the specified test pressure value and held for a sufficient time to ensure that the pipe is fully expanded. A process takes 2-3 hours, when the system is stable, increase the pressure to 1.5 times the working pressure, stabilize the pressure 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 lead to a pressure drop. It is normal for a certain pressure drop to occur during the test, and this does not prove that the pipeline system must be leaked or damaged.

7. Backfill and compaction

Under normal circumstances, the requirements for the axillary angle and initial backfilling should be at least 90%, and the tamping layer should be at least 150mm from the top of the pipe. For places less than 300mm from the top of the HDPE natural gas pipe, direct tamping should be avoided. The final backfill may use the original Excavation of soil or other materials, but it shall not contain frozen soil, agglomerated clay and stones with a maximum diameter of not more than 200mm.

HDPE Gas Pipe Factory

1. After the HDPE gas pipe is installed, it should be properly protected (especially when tiling tiles), and the HDPE natural gas pipe should not be disassembled, moved, touched, smashed, squeezed, or pressed without permission to ensure that the gas pipe is intact and not damaged.

2. Remember not to seal the HDPE gas pipe, especially the main valve of the whole building and the gas meter in each user's home. If you need to decorate it, you can make it into a valve cabinet or leave a ventilation hole, and reserve enough space for maintenance and security inspection.

3. Do not disassemble or assemble gas pipelines (including pipeline fixing hooks or pipe clamps) and water heaters without permission. They should be installed by professional technicians of relevant gas companies to ensure safety.

4. A room with a gas pipeline cannot be used as a bedroom, so as to avoid gas leakage and fire, which may endanger life and safety. At the same time, the kitchen or room through which the gas pipeline passes shall not be stacked with inflammable and explosive materials.

5. The HDPE gas pipeline cannot be buried in the wall and is not less than 10cm from the ground. The HDPE natural gas pipe is not allowed to pass through the wall and should not be too long, and the hose of the stove should not exceed 2 meters.

6. If the indoor pipeline is already carrying gas, and the indoor gas leakage is found, first close the gas valve in front of the meter, open the indoor doors and windows for ventilation, and prohibit opening electrical switches and other behaviors that may cause sparks.