Technical Instructions
HDPE
Joining of HDPE pipes
Site Pipeline Pressure And Leakage Testing
Joining of HDPE pipes
Butt-Fusion Jointing
- Butt-Fusion Jointing is normally used for pipe sizes over 90 mm. this jointing method combines the advantage of simplicity and effectiveness.
- The Butt-Fusion procedure:
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- Clean pipe ends.
- Clamp pipes ends tightly into the fusion machine .
- trim both surfaces squarely by rotating the double-edged trimmer.
- Remove trimmer and check for square uniform alignment by pressing the pipe ends together.
- With pipe ends properly faced, insert the heater plate at 205° C and compress the pipe ends against the plate at the specified pressure. Watch for a proper melt bead formation uniformly around the circumference of both pipe ends.
- Once the heating process is complete, quickly withdraw the heater plate ensuring that the plate does not rub against the molten pipe ends.
- Press the melted pipe ends together using the specified joining pressure forming a twin roll-back fusion bead. Maintain pressure for sufficient time and further allow the joint to cool.
Electro-Fusion Jointing:
- Electro-Fusion Jointing of PE pipes is done with an integral electrical heating coil embedded in the fitting. Welding is carried out by passing a current through the coils. The coils, acting as resistors, dissipate heat and melt the surrounding material which expands causing the fittings to be fully fused to the pipe.
Flanged Connection of PE pipes:
- It is common to use a flanged connection to join HDPE pipe to PE pipe when a piping section will require removal in the future. Flanged joints are also used to connect PE pipe to other type of pipes or fittings.
Site Pipeline Pressure And Leakage Testing
The purpose of the site pressure is to ensure that the installed section of line under test and all joints and fittings included in the section will withstand the design working pressure plus a safety margin without leakage.
A. Before pressure testing the following guidelines should be observed:
- End caps are mounted on all ends of the pipeline.
- Insert air bleed valves at all the highest points along the pipeline.
- Allow 24 hours after welding before test.
- The line should be filled with water 24 hours Prior to the start of the test.
- Ensure that the system is entirely ventilated.
- Backfill the pipeline before test
- Leave joints exposed
- Test with all valves fully open
B. During pressure testing the following should be observed:
- Ensure that all air bleed valves are open and working.
- Slowly fill the pipeline with water avoid damage due to pressure surge.
- Gradually raise the pressure to a pressure corresponding to 1.5 times the nominal pressure class the pressure is maintained for 2 hours.
- Supplementary filling of water allowed. During the following 60 minutes water should not be added. After 60 minutes the pressure is measured and the water is added until the pressure is again 1.5 times the nominal pressure class.
- The fall in pressure and the amount of water added should not exceed the following limits:
- Pressure drop in percentage of he initial pressure = 2%
- Water quantity in liters/ meter = 0.2 Di – 0.001 + DV
- Where DV = 0.05 x d2
- Di is the inside diameter
