General steam (10barg) material.

[superpiper]

A client is changing over his general steam/condensate distrubution slowly to Stainless Steel (316l)

This for some reason is concerning me.
What are the risks and benefits of such a course?

The system will be a mixture of carbon steel/Stainless steel
Under 185c temp.

Any answers???

 

[NozzleTwister]

superpiper,

The first thing that comes to my mind is the difference in thermal expansion. Stainless steel has a significantly greater coefficient of thermal expansion than carbon steel.

With the piping routings the same, you will see increased thermal movement, higher equipment nozzle and restraint loads, and any existing springs in the system may need to be replaced or load settings revised.

I recommend a flexibility review or analysis for the entire system considering stainless piping.

Good luck,


NozzleTwister
Houston, Texas

 

[zdas04]

You might also want to look at corrosion effects. The threashold for stress-corrossion cracking of stainless steel is a very low chloride level (I don't have that reference any more but I recall it is in the ppb range).


David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[TD2K]

Why is the client considering this? At 10 barg and under 185C, I've seen CS specified for steam systems.

 

[superpiper]

Hello again with respect to my post

The reason is that corrosion (from the outside -in) is rotting the pipework.

It IS currently cheaper to use S/S pipework, rather than paint Carbon steel pipework.

My question is aimed at the material side of things.ie

1.will trace C/S in the steam/condensate from the existing pipework, comprimise the new S/S pipework
2.What (if any) effect will stress corrosion cracking have?
3. Are Steam systems usually saturated with clorides?
4.Is Non-Chloride foamglass alot more expensive than fibreglass?
5. Is S/S suitable due to work hardening /creep/brittleness?

Etc etc.
I am comfortable with the analysis side of the equation.