Description of pipe installation by PE:
1. Connection technology.
Large diameter HDPE pipe pressure system mainly USES the hot melt docking way to connect, to undertake small USES the hot melt connection, when connected to the metal pipe and other pipe flange connection must be used, small diameter pipe steel-plastic transition connection is also available.
1. Hot melt butt:
The hot melt docking is to use hot melt welder to heat side (hot melt docking for 210 + 10 ℃ temperature), after being melt pipe end, its joint rapidly, maintain a certain pressure, the cooling to achieve the purpose of welding. Refer to the following table for hot melt docking process. The HDPE tube with a size greater than 90mm can be connected by a hot-melt butt joint. The method is reliable, and the bearing and pressure of the interface have higher strength than the pipe material itself.
2. Electric fusion welding: the connection requirement can be easily realized after the use of a special electric fusion welding machine.
3. Steel plastic flange connection.
PE water supply pipe and steel pipe and valve connection while the steel-plastic flange connection: HDPE pipe and the corresponding plastic hot melt docking way can be used for connection between support ring, steel pipe end and metal flange connection, should comply with the provisions of the corresponding pipe welding; Then the connection of HDPE pipe and steel pipe can be completed by using flange film. The flange connection also applies to the connection between the HDPE tube and the HDPE tube. In general, there is no need for sealing ring between HDPE support ring and HDPE support ring, but the sealing ring needs to be added under the working condition of large size and high pressure. When the HDPE support ring is connected with other materials (steel tube, galvanized iron pipe, etc.), the sealing ring must be used.
Ii. Excavation of the trench.
1. The excavation of the narrow trench can be excavated with rotary excavator, plow or shovel. In solid, solid groove, the width of the trench is decided by construction need operating space, the space must be allowed to function at the bottom of the trench to the size of the correct preparation and trench landfill landfill materials and cement, but also to consider the cost of pipe trench excavation and buying landfill materials and other costs of the economy. The width of the trench should generally be considered the specification of the pipe and the compaction tool used. When the ground connection, furrow width is + 0.3 D, when installed in a ditch or open trench backfill have difficulty, can not meet the requirement of the backfill soil compactness, furrow width for D + 0.5, and the total width of not less than 0.7 meters. In sand or mud trench, if is not easy to make a vertical pipe trench wall, you can do a 45 ° or capable of supporting a slope of trench wall materials. If the trench is wider, the initial filling material must be compacted to support the final filling weight.
2. Laying of pipes in pipe trench.
The pipe should be thoroughly checked before the pipe is put into the pipe, and the pipe is allowed to be hoisted or rolled into the pipe without any defects found. Pipelines are usually in good ground connection in advance, sometimes pipe may be connected into about 150 meters long in advance many section, stored in a certain place, when to delegating and connection, to be transported to installation site, and then USES the hot melt connection or mechanical connection way to connect these section. A pipe with a nominal diameter of less than 20mm can be drawn into a trench by hand. For all large pipes, fittings, valves, fire hydrants and accessories, appropriate tools should be used to carefully place them in the trench; Nylon rope is recommended for long distance piping.
3, in the end of pipe connection with assembly inside the pipeline pipe hot melt connection piping hot melt connection in the same way on the ground, but must ensure that the connected piping must be cooled to the ambient temperature of the soil before connection. When the PE water supply pipe is connected with metal pipe, water tank or pump, flange connection is generally adopted. For PE water supply pipe, the flange connection can be used when it is not easy to connect with the hot melt. When the flange is connected, the bolts should be tightened up in advance, and then re-fastened after 8 hours.
4. Pressure test of PE water supply pipeline.
Strength test: in addition to the air in the pipe to be tested, the pressure should be raised to the required pressure value with a steady rate of pressure, and the pressure gauge should be placed at the lowest point of the pipe. The pressure test can be carried out before or after the pipe is backfilled. The pipe should be covered with a certain interval, especially for the snake line. When the pressure test is conducted, the pipe should be fixed in place. Flange connection should be exposed to check for leakage. Pressure test of the test pressure shall not exceed minimum pressure in the pipe pressure level or system level of accessories pressure level of 1.5 times, at the start of the test pressure value of the pressure should be up to and keep enough time to ensure the pipe full expansion, the process will take 2 to 3 hours, after the system is stable, the pressure to rise to 1.5 times the working pressure, voltage regulator for 1 hour, carefully observe the pressure gauge, and along the tour, if there is no visible leakage in the process of testing or obvious pressure drop, the pipe through the pressure test. In the process of pressure test, pressure drop due to continuous expansion pipe will produce, produce certain pressure test process, force down is normal, do not so to prove that the pipeline system must leak or damage.
5. Backfill and tamping.
The following three kinds of materials can be used as backfilling materials for PE water supply pipes; The first category: 5-40mm angular stones, including a large number of locally accessible materials such as coral, broken slag, crushed rock, and broken shells; Type ii: coarse sand and gravel with a maximum diameter of 40mm, including sand or gravel with a small amount of powder, usually granular and non-stick, which can be wet or dry; Third category: fine sand and clay gravel, including fine sand, sand and clay gravel mixtures. If the original excavation soil or other materials are used, no permafrost, lump clay and no more than 200mm of stone shall be allowed.
PE water supply and drainage pipeline.
PE protection measures for water pipes:
1. Always put the largest pile on the bottom surface.
2. The inside of the pipe is very smooth. To prevent slipping, it should be securely fixed when loading.
3. Small diameter straight pipe or light pipe can be handled by hand.
4. PE water supply pipe shall be kept in a clean place.
5. In order to prevent direct light rays, it should be placed indoors or covered with a cover.
6. For buried pipes, the trench should be dug to clear the rocks and other hard objects in the groove.
7. Ensure that there is no special high temperature equipment around the pipe, so as to prevent heat distortion of pipe material.
8. Large weight should not be piled on top of the pipe to prevent the pipe from being damaged by such a large external force.