thermoplastic polymer for very cold weather

[suzanparvez]

Hi, We are manufacturing at present pipe for oil and gas industry. Guys can you suggest me which thermoplastic materials will be good at -150F. We will make pipe from these materials.

Also please suggest about thermoset polymer.
thx a lot.

 

[Demon3]

-150°F is almost exactly -100°C for those like me living outside the US.

You will need to specify your material requirements more closely. For example, will the pipe always be at low temperature or will the same material be expected to take temperature cylcing between -100°C and 20°C for example? What is the highest temperature it will see?

The reason I ask is that any polymer that retains impact resistance at -100°C is likely to be a soft rubbery material with poor modulus (stifness) at room temperature. See this article for some hints

http://www.zeusinc.com/pdf/Zeus_Low_Temp.pdf

A good way to solve your demands would be to use a cheaper polymer for the core of the pipe, to give stifness and keep costs down and then have an outer coating of some rubbery material to give impact resistance.

 

[suzanparvez]

Thx Demon for your inputs. Temperature will be between between -100°C and 20°C. Ambient temperature will be the highest.

This will be a composite pipe. So there will be liner, then fiber then the coating and it will be inserted through a steel pipe.

So I think rubbery material will be ok. I thought it before but you provided good description.
My question : what kind of rubbery material will be good ?
How about Nylon
thx

 

[Ashereng]

suzanparvez,

I just came across this post, which is a duplicat of the one in piping and fluid mechanics, in which there are already many replies:

thermoplastic materials at -150F
thread378-155895

It is usually preferred that multiple posts be avoided - now you have 2 threads on the same topic that people may need to go back and forth with.

"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?

 

[suzanparvez]

Ashereng

I thought people at mechanical forum on piping do not come here so I posted in two senctions.
This is my 1st post. I think I will not do this mistake again. sorry for the inconveniences.

 

[Ashereng]

No worries.

A single post with all the responses makes for easier reading.

If you think people in other forum/fora would benefit, you can post a link in the other forum/fora to direct them to the primary post.

"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?

 

[Demon3]

Now I am really confused. If this plastic pipe will be inside a steel pipe the what is the function of the plastic?

You can tell whether a polymer is soft and impact resistant at the temperature by checking its glass transition temperauture (Tg). The Tg of nylon is way too high so it wil be brittle at -100°C. For something rubbery at -100 you'll need for example a silicone rubber.

 

[suzanparvez]

Hi Demon, Your last mail was very helpfull. Steel pipe corrodes and thats why the Pipe will act as a Liner. Now about the temperature it is LNG/CNG will be transporting through the pipe and it is very tough to plough the steel pipe so they want to have the plastic pipe inside.

The project is clearly defined actually. I am being only asked to find a material which will work at -165F. Going through your article and few more I think fluorocarbon is the only choice but expansive.

Anyway thx a lot for the help man.

 

[suzanparvez]

Hi Demon, There are few mistakes in my last reply. The plastic pipe will act as a liner and the project is not clearly defined yet.

 

[Demon3]

Usually for low temperatures fluorocarbons and silicones are the obviousl choices. If you need to increase the stiffness then adding some glass fiber will help. It's very hard to make pipes because they have to last for many years without failure under pressure. To be sure of a new material you would need some years of accelerated pressure testing.

 

[thermcool]

Ultra High Weight Polyethylene is a good thermoplastic for low temperature applications.

 

[metron]

I agree with thermcool,
Polyethylene is the choice for this application. The company I work for mould thermal cylinder covers in HDPE for LPG cylinders that get buried underground for a large gas supply company here in Australia. Many of these are used in underground mines, and Hydro power plants around Australia.

 

[Diwoaux]

I would look on

http://www.matereality.com

they have a really comprehensive characterization for a lot of materials.