McElroy Discussion Forums

I have noticed that some pipe manufacturers use inter-facial pressures as low as 25 lbs/in^2 up to 75 lbs/in^2. This obviously makes bead up and soak times vary to establish "the proper" melt bead finished look. ( artistic really ) Is there any scientific evidence that would define the "perfect weld pressure" or is the gamut of possibilities so large that everyone is comfortable with such huge variances? i.e. minimum touching two molten surfaces together OR up to the point where you press all the molten material from the joint. Testing methods such as ASTM, ISO, etc. do not seem to agree.

There are some variations and differing theories about how best to fuse plastic pipes. Some of the variances are due to different materials but as you point out there are some variations even for HDPE. There has also been a large amount of testing done for the different standards. The different practice are probably a result of different theories and the evolution of the process over time. Obviously ASTM uses 60-90 PSI interfacial pressure which is a substantial range. There are some other standards that use a lower range. There are benefits to different standards but in general you just want to make sure you're using a good standard that is accepted and tested so you can point to parameters that make sense. If you need some more information or more depth information shoot us an e-mail at techsupport@mcelroy.com or give us a call. Thanks.