Stainless Steel Piping

[Charan5]

Hello,

What is experience on 18" stainless steel pipe sitting on carbon steel support steel with U bolts around it. The pipe wall thickness is 0.25" carrying DNCG gas. Is that okay to let the pipe sit on carbon steel structure. Do we need posion pad? The pipe is at 200F.

 

[flash3780]

You're worried about galvanic corrosion? I'll need a metallurgical guy to back me up, but I'm pretty sure that 300 series stainless steel on steel isn't an issue. The chromium oxide form the stainless forms a barrier.

Here's the chart the metals guys always hand me when I ask about galvanic corrosion:

http://www.corrosionist.com/Galvanic_Series_of_Metal_in_Seawater.htm

 

[unclesyd]

We do have some SS on m CS supports but now require a SS lining for contact with the SS pipe, everything else is CS. I can't recall any problems other than rust stains on the SS piping so someone decided to change this.
In pipes using a SS clamp type guide with a lot of axial movement and/or vibration I've seen a lot of galling and wear with some metal loss. On heavier piping we use the roller type supports and depend on design to get vibration out. We use both SS and CS rollers.

 

[Charan5]

Thanks for the feedback both of you. Load on support I am expecting less than 1000lbs and 2" of insulation. Carbon steel member and U-bolt will be in insulation, with very small axial movement. I will look into this.

 

[europipe]

It not a good design to support insulated lines this way.
You should use a shoe in case of hot insul. and wood or strong foam in case of cold insul.

Greetings

 

[moltenmetal]

I agree with Europipe. There's no problem with the carbon/stainless contact, for either material, but it's the wrong way to do the job. Keeping water out is very tough this way.

 

[europipe]

Moltenmetal....and conduction from the line to the supporting steel.