How to do a better weld
Minor tips on welding
* Set up the equipment. If necessary, erect a welding tent to protect against rainfall, wind and dust, conduct a trial before actual works to ensure the equipment in good working order
* Hold the pipes by clamps, one pipe fixed and one pipe is free to move such that they can be pressed against each other in single direction, then trimming/milling the joint faces
* Stop milling/trimming when joint surfaces are plain, even and crack free
* Check for pipe alignment radially; by bringing the joint faces together. (Max Gap = 0.5mm).
* Check for pipe alignment axially in line with wall thickness.
* Clean heating plate with lint free cloth and water/clear spirits.
* Check the welding temperature. (Recommended by manufacturer)
* Heat up and insert the plate between joint surfaces.
* Exert the heating pressure by the hydraulic unit until a bead is formed along the circumference of the joint faces.
* Reduce pressure to allow for heat dissipation into wall of pipe axially. (Soaking period).
* Remove heating plate over the allocated time and cover it properly to avoid contact with human or any substance,
* Press joint faces together, ensuring that the change-over time is not exceeded.
* Steadily increase the welding pressure to its allocated value.
* Keep at this pressure for the allocated time.
* Allow for cooling down at the welding pressure over the allocated time.
* (Never remove a weld from the machine before the cooling time has elapsed).
* When this cooling time has elapsed, reduce pressure to 0 and remove welded joint from clamps.
* Record the joint vs the pipe number, keep record for the jointing.
* If malpractice happened at any stage of the process, since the pre-heated PE material is not supposed to re-heat, therefore the touch surface of the PE material shall be cut-off (length of cut-off shall be subject to manufacturer recommendation), re-mill and repeat the jointing process.
Safety:
l Do not approach the welding machine when welding in progress, do not touch the materials except trained workers
l The heating plate is hot, do not touch or avoid contact with any material when idle
l Maintain good ventilation
l Aware of electric shock
l Create a good communication including gesture for working
l ventilate the workplace
l Fire extinguisher must be in place when welding in progress, an urgent stop button for power supply shall be established
l Safety induction to workers before works, and assign a person-in-charge to cover all the safety issue
Ivan Wong Sai Wing from Meinhardt