Plastic Lined Steel pipe issues. 6

[DjazAutomation]

Hello,

I would like to know how to install plastic lined steel pipe in a typical process.

Is it true that Lined pipes must be purchased premanufactured by specifying precisely the lenght of each unit, beacause it is impossible to cut the pipe the right lenght on site (Can Affect the plastic internal coating in the cutted section.)

If it's true, it would be really a problem for me since it's quiet difficult in my project to have exact lenghts (no precise Isometric pipe drawings available). I guess in this case we have to have very precise isometric drawings. Is there any other way?

Do you think that, like conventionnal steel pipes, plastic lined steel pipes lenghts can be ajusted on site to match each installation case?

Thank you very much.

Djaz.

 

[micalbrch]

The problem is welding. You cannot weld a plastic coated flange to a plastic coated pipe. The heat will destroy the coating. So, you must get most of the piping completely welded and coated. Assume that a certain percentage (perhaps 10 %) of the piping must be made on site so that everything matches. These remaining 10 % must be coated after finishing.

 

[C2it]

It is common to have plastic lined pipe supplied in exact dimensions with flanged ends on spools. The plastic internal coating then extends over the flange face to provide a gasket.

A pain in the butt dimensionally however. Can't really see a good way around that.

 

[cvg]

you could use insitu lining after the pipe is completely installed.

http://www.insituform.com/

http://www.naplinc.com/

 

[tr1ntx]

"Is there any other way?"

If you have enough money to spend, you can buy a bunch of assorted length spools, assuming they are allowed on your project. And if your length variation increments aren't too small.

 

[brimmer]

Remember you can construct the steel pipeline and pull a "liner" of plastic pipe through, either tight (same diameter) or free standing (smaller diameter), then you don't have to worry about pre fabricating lenghts.

 

[moltenmetal]

See my post under Chem Eng other topics, and please don't cross-post!

 

[tr6]

There are two ways to accommodate situations where your field measurements are not quite accurate:

1. Design into your pipe "spacers" at strategic points, say 1/2" thick, that can be machined to whatever thickness you need to make up for gaps. Spacers can be made out of polypropylene.

2.Resistoflex provides a "Field kit" with dies and mandrels where you can cut the pipe to length (leaving a length of liner extending past the face), thread the flange onto the pipe, and then heat the end to flare the liner onto the flange face.

A long time ago, when Dow made lined pipe and fittings, pipe spools were field made up by cutting the liner flush with the end of the pipe, thread on the flange so that the face of the flange was flush with the face of the liner and pipe, and then machine a small groove into the end of the pipe and flange face. A gasket, which looked like an over-sized o-ring, would be installed to mate up to a lined fitting or another spool.

 

[Ashereng]

If you are thinking of something like Flex Pipe or Flex Steel, they come off rolls as they are laid. In the field, they are can be cut, and I believe compression type fittings are used to connect them.

"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?

 

[DjazAutomation]

Great!

I would like to thank you all for these valuable information.
I am studying all these possibilities (Using Spacers, pull a liner through the pipe, Resistoflex Field kit, etc.) to understand the pros and cons for each solution.

After that, I think that I will probably have more questions about these solutions.

Please feel free to add any suggestion.

Thanks again and sorry for cross-posting!

Djaz.