What is High Pressure Butt Welding?
High pressure butt welding calculates the welding force at 3.2 times that used in low pressure welding, and halves the cooling time.
Where is high pressure welding used?
High pressure welding is used exclusively in North America as an ASTM standard, and has been included, at the insistence of the US, in the ISO butt welding standard. Europe does not use high pressure welding, while Australia has taken to it following its introduction on the US controlled coal seam gas project in Queensland.
Which is best?
All British and European authorities use only low pressure welding as they require a 100+ year asset in the ground, so if you want the result to see you out, use low. In North America and the mining industry they seem to be more interested in getting the job done as quickly as possible, and consider 50 years all things being equal to be long enough, so high pressure works for them.
Is there a difference in equipment?
Absolutely. Normal welding equipment from anywhere but North America will be low force, and cost dramatically less than North American made high pressure equipment. The cylinders have to be able to provide 3.2 times the force, the frame wants to bend, the main clamps have to hold the pipes 3.2 times harder, and the reducing liners have to be 2-piece rather than the less expensive layer type, which quickly wear at their interface points under high pressure, causing major alignment issues after only a few months.
Why not use the faster high-pressure method?
Good question. In our opinion low pressure welding provides a much higher factor of safety, and has been tested over 50 years to be more tolerant to things that go on in the field, like dust, wind, slightly dodgy pipe, ambient temperature, operator variables and the like, while high pressure seems to work very well in a laboratory with excellent pipe, a new welding machine in top condition with a perfect heating plate, consistent ambient temperature, the operator is the best possible, no dust and no attitude, so any failure must be operator error. But you did get it done in around half the time.
