Pipe Bursting With HDPE Pipe

Maybe a chemical compatibility issue..you don't say what the pipe contains...

Heat from the cutting of the pipe in the center may have altered the properties of the HDPE. The 600% elongation factor was only good until you cut the hole in it. The center manhole was fitted with some type of fitting to close it off during operation. The chemicals used to adhere the fitting may have cause property change.

Hello, we have allot of underground HDPE pipe in our paper mill. One of the main reasons I see it crack is if you hold it down rigid on both ends when it tries to expand from heat(sunlight, etc) it can crack. I was amazed to see how much that pipe moves from expansion and contraction from the sun heating the ground in a normal weather day. These cracks seem to be linear in nature usually. I have not used the pipe bursting method myself but a few years back did check into it. there is allot of force applied to the pipe in that system could you just be weakening it when it pulls? Or could the pipe be hanging on a branch line from the original pipe? Just some ideas I though about.

pipewelder

I believe you would find with a quick web search that plastic pipes in general have had some history of problems at tapped or hole cut areas, and maybe particularly these problems could be argued most pronounced in areas of pipes that have been incidentally or purposefully bent or pulled? A hole cut in a pipe of course reduces the strength area, and the level of stress can get quite high due to perhaps non-obvious and not advertised "stress concentration factors". I think the level of stress can be analyzed with conventional strength of materials references, at least if you have some idea of actual applied loads, and I wouldn't be surprised that in this case you might come up with stress levels that would be at least uncomfortable to hdpe pipes. A quick search of the literature would also reveal that plastic pipes can be for various reasons be subject to, perhaps some non-obvious nor highly advertised, brittle behaviors, and again I suspect (regardless of elongation claims) a high level of local stress would not be helpful in this regard as well.