HDPE Liner
HDPE Liner
(OP)
Is there a method of chemically attacking an HDPE liner that is stuck in a pipeline and can not be removed mechanically?
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RE: HDPE Liner
HDPE melts around what, 130°C? I guess that would also depend on the grade. You would probably have to check the melting point with the manufacturer?
How long of a piece are you looking at?
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RE: HDPE Liner
You do not say what the pipe is made of.
If the co-efficient of thermal expansion of the PE is higher than the pipe material, which I guess it most probably is, it can then be withdrawn as it contracts away. It could also be broken into smaller pieces as it em-brittles. The effect of temperature on the impact strength of the pipe vs the liner would need to be considered to determine the optimum temperature.
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RE: HDPE Liner
RE: HDPE Liner
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: HDPE Liner
The resin is Dow DGBD-2480 BK.
We have heated the pipeline to 70C and attempted to pull with no success.
RE: HDPE Liner
If you heat it up too much, is there sufficient tensile strength to mechanically "pull it out"?
Even if you melt it, getting the melted plastic out would be tough too!
I was thinking like 20 feet when I suggested melting it. I don't know about 1/2 mile.
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RE: HDPE Liner
Regards
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RE: HDPE Liner
How would you burn it out?
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RE: HDPE Liner
It all depends on whether or not you can get straight access to each end.
Maybe get it burning and pump some oxygen in there to enhance the flamibility and purge the byproducts of combustion. I am presuming both ends are open so that and purge air or oxygen in from one end and exhaust out the other end.
I have no idea how much trouble and cost it can stand vs removing and replacing the entire pipe. You do have a very unique and difficult problem.
If you go the burning route, the biggest problem will be exhausting the smoke. If the pipe has fall, start the fire at the low end and exhaust out the high end.
I am also presuming this is a straight pipe.
Chemically PE is very similar to petrol and burns with a similar reaction. It just takes a lot more heat to vaporise it.
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RE: HDPE Liner
Have you done this before? With what size pipe?
ootpik did not mention size of pipe. I don't know if that would make a difference.
You are right, this is an unique problem.
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RE: HDPE Liner
If this has to be done, and the burning does not work, another method to simplify removal after shrinking it with liquid nitrogen would be to use something like a pipe cutter that expands out from the inside rather than squeezing down from the outside. Cut of a workable section of the liner and then freeze that section.
If you can get a short section of an identical pipe, you can do lab tests to see how much clearance and how each component em brittles at various temperatures.
I do not know if you can get internal expanding pipe cutters, but a half competent fitter should be able to knock one up for you.
HDPE should soften in the range of 110 to 130 deg C.
What is the internal finish. What is the ID. What is the access to each end. Is it straight and is there good straight access to each end
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RE: HDPE Liner
RE: HDPE Liner
We use this system to clean polymer (Nylon) piping and equipment on a routine basis as part of general maintenance and overhauls.
The first four are people that can supply portable gas burners and the last one is a description of the process.
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