pipeline elongation
pipeline elongation
(OP)
My question is about pipeline elongation & contraction for underground condition.
We are designing a drinking water pipeline. The type of the pipe is HDPE (polythene) and the transport water line length is 2500 m, dia of pipe is 630 mm. Pipe will be buried in nearly 1,5 m. depth. Installation weather temperature is nearly 40C and drinking water temp will be 20C; therefore we are assuming that there will be a 20 C temp. difference.
The line is almost straight and no direction change.
Here is the formula;
ΔL= k.ΔT.L where L=length of pipe :2500 m
k=elongation coeff. (0,18 for HDPE)
ΔT= temperature change (20)
ΔL=0,18.20.2500= 9000 mm = 9 m.
There shall be 9 m. contraction. The question is what type of precautions must we considered to compensate such a contraction?
I think laying the pipe in a "snake shape" will be enough but I am not sure.
Thanks for the replies...
We are designing a drinking water pipeline. The type of the pipe is HDPE (polythene) and the transport water line length is 2500 m, dia of pipe is 630 mm. Pipe will be buried in nearly 1,5 m. depth. Installation weather temperature is nearly 40C and drinking water temp will be 20C; therefore we are assuming that there will be a 20 C temp. difference.
The line is almost straight and no direction change.
Here is the formula;
ΔL= k.ΔT.L where L=length of pipe :2500 m
k=elongation coeff. (0,18 for HDPE)
ΔT= temperature change (20)
ΔL=0,18.20.2500= 9000 mm = 9 m.
There shall be 9 m. contraction. The question is what type of precautions must we considered to compensate such a contraction?
I think laying the pipe in a "snake shape" will be enough but I am not sure.
Thanks for the replies...





RE: pipeline elongation
Verify the expected elengotion against a couple of HDPE manufaturers and make sure the expected elongation parameteres meet those by the agency that is reviewing your plans.
That is quite a susbtantial elongation, I would suggest looking into using Expansion/Contraction joints at certain intervals. The number of these will depend on their expansion/contraction ability. An example is the EBBA Iron EX-TEND 200. Search fot it at http://www.ebaa.com. Verify that it can be used on HDPE pipe. You are using metric units, so it sounds like you may outside the United States (just my gut feeling), so if this is the case look for similar products from pipe manufacturers in your area if the EBBA product is not available. Hope this helps.
RE: pipeline elongation
RE: pipeline elongation
HDPE is buried all the time. Often it will sit in the sun and heat up to over 50C and then be buried in the 15C earth without problems.
Whatever you do, don't install an expansion loop underground. The constraining action of the ground will keep more than a few dozen meters from benefiting from it and the loops often cause low points or high points to trap liquid in a gas line or gas in a liquid line. They do a lot of harm and no good whatsoever.
David
RE: pipeline elongation
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RE: pipeline elongation
As a result, I understand that, for a buried PE pipe system, there is no need to take special precautions for elongation of the pipe. Up to certain temperature change, restriction of the soil is enough. But, If temperature change is extreme, low thrust capacity (unrestrained) connections to manholes may require longitudinal force thrust block (in-line anchor) protection (puddle flange application.)
Additionally, connections between other type of pipe (pvc,ductile etc.)might be a problem. When transitioning from PE pipe to bell and spigot style pipes, the combination of thermal change and thrust load from internal pressure may cause sufficient contraction to pull apart the transition joint or other bell and spigot joints in the pipeline.
The most satisfactory explanation that I can found is here;
(thanks for bimr)
http://w
RE: pipeline elongation