PE water supply pipes due to its own advantages are widely used in construction water supply and drainage, underground sewage pipeline, building heating, industrial pipeline and other field. The connection method includes butt fusion and electrofusion, we usually use butt fusion to connection. Regarding to the specific connection mode, we summarized as the following points.
1. Preparation: place the pipe or pipe fitting in a flat position on the butt fusion welding machine, leaving enough cutting allowance of 10-20mm.
2. Clamping: according to the welded pipe, pipe fitting to selection the appropriate slip fixture, clamping pipe and ready for cutting.
3. Cutting: Cutting welding pipe section, pipe end surface impurities and oxide layer, ensure that two butt fusion surface smooth and no impurities.
4. Alignment: the end face of the two welding sections shall be completely aligned. The smaller the wrong side, the better. Otherwise, the fusion quality will be affected.
5. Heating: butt fusion temperature generally between 210-230°C advisable, heating plate heating time will be different in winter and summer, with two end surface melting length for 1-2mm is better.
6. Switching: remove the heating plate quickly and make the two hot melt ends stick and pressurize. In order to ensure the quality of butt fusion, the shorter the switching period, the better.
7. Butt fusion: it is the key of welding. The butt fusion should always be carried out under the melting pressure, and the width of rolled 2 edges should be 2-4mm.
8. Cooling: keep the butt pressure unchanged, and allow the interface to cool slowly. The time of cooling shall be subject to the stiff of the welding beads as the hand touches and the heat cannot be felt.
9. Completion of docking: release the slip after cooling, remove the welding machine and re-prepare the next interface connection.
Note: due to the good flexibility of PE pipes itself, all pipe installation is not considered expansion coupling installation.
The excavation and backfill of pipe groove are very important when PE water supply pipe is installed. Whether the standard of excavation and backfill directly affects the installation effect and the service life of PE water supply pipe. Therefore, it is necessary to implement it in accordance with the construction specifications as far as possible.
Pipes groove excavation
1. Straight line is advisable for pipes groove excavation, and the width of groove bottom excavation is DN+0.30m. When the pipes are connected underground, the width of groove bottom at the junction should be appropriately increased, the width of groove bottom should not be less than DN+0.50m, so as to facilitate installation and butt fusion.
2. When the pipes are buried, the minimum pipe top covering depth should meet the following requirements: ①it should not be less than 0.80m, when buried under the roadway. ② it should not be less than 0.60m when buried under sidewalk.
3. When crossing the roadway and failing to reach the design depth, steel casing should be laid for protection.
4. When the pipes groove must make a turn, the turning angle shall not be too large, and the bend radius shall comply with the following requirements: PE pipes bending radius allowed R(mm) D≤50 30D; 50D≤160 50D; 160D≤250 75D; D≤250 100D.
5. When manually digging pipe grooves, the bottom of the grooves shall be flat and dense without sharp objects. Ditch bottom can have ups and downs, but must be smooth support pipes, if there is overexcavation, need to be backfill immediately.
Upon completion of installation and laying of pipelines, backfill shall be carried out immediately upon acceptance of concealed works. Backfilling shall comply with the following requirement:
1. Prevent pipes from floating due to water in the tank. If there is water, try to dtain it.
2. When backfilling the pipes groove in the mixed sections of stone, earthwork and stone, the clay or sand should be first shipped and backfilled to the top of the pipes 200-300mm, then backfilled with other miscellaneous soil after compaction.
3. Backfill must be started from both sides of the pipes at the same time, backfill and tamp one layer and another.
4. Before pressure testing, backfill should not be less than 500mm under normal circumstances.
5. Large area backfilling after pressure testing should be carried out under the condition that the pipeline is filled with water. After pipes laying, it should not be in the state of empty pipe for a long time.