CS flange and SS flange connection

What does the end Client's P&ID and piping standards have to say on the subject?

Er, nuts, bolts and gaskets don't do gas liquid separation without being assembled onto a piece of process equipment....

AT PIPING, SS304 MATERIAL

AT SEPERATOR (VESSEL) , CS MATERIAL

FOR PIPING, WE SHOULD USE SS FLANGE AND

FOR FLANGE OF NOZZLE OF VESSEL , CS FLANGE.

PLEASE EXPLAIN DISSIMILAR MATERIAL JOINING TOGETHER, WHAT WILL HAPPEN AT CS FLANGE? IT WOULD BE SPOILED EASILY WHEN WE USE SS B&N&GASKET?

The problem that you may face is Galvanic Corrosion on Carbon Steel. This can be an issue both for itnernal and/or external surfaces.

Internal: It depends on the fluid, if it's a good electrolyte (water, seawater...) then it's higly probable that you'll have corrosion on carbon steel. If the fluid is not a electrolyte then you'll not have to worry.

External: It depends on the exposure, if it's in marine environemnts with humidity condernsation then the possbiility are higher, if it's a dry environments (desert..) then it will be less probable.

The best thing you can do is to use isolating bolts and nuts.

this MIL standard is a good guidelines:

Please STOP SHOUTING! People round here are trying to get some sleep.

It is best to use SS bolts/nuts with SS washers

I gave Kev a good answer vote, but have one issue with his answer. How do you take unknowns into account?

I read that through after posting it and realised I should have written 'variables' and not 'unknowns'. Thought I would just leave it in to see how many people would read through that without nodding off!!

Gold star for being eagle-eyed.

Thanks for the 'good answer' award. Much appreciated.

Kev Brown

I have an opinion on the choice of bolting material. I am not usually involved in the specification of materials, but my company manufactures pressure vessels, so I see what many companies choose.

It seems that the external environment is more important in choosing bolt material than the internal process conditions. An exception to this is consideration for the risk of rapid bolt corrosion and failure due to leakage.

In the absence of a corrosive (or wet) external environment, I would think that low alloy bolting (B7 or B16 with 2H nuts) would be most preferrable.

Austenitic stainless bolting (B8, B8M) are subject to the same stress corrosion cracking issues that 304 and 316 stainlesses are and even more so becuase they are so highly stressed. If you are in a marine (salt spray) atmosphere, these would be definitely not recommended. Go for PTFE coated alloy bolts instead. (That's what all of our coastal / offshore customers do.)

Hello Lawrence,

Refer to your comment and advice, your company is a pressure vessels manufacturer. Could you please tell me your company contact person and email in order to enquiry pressure vessels for gas compressor packages. what informations do you need for enquiry and vessel sizing?

Do you mean PTFE coated alloy bolts&nuts(low alloy bolting) than SS is suitable for saliferous (corrosive high CO2>52%) environment? In that case, how about gasket material?

Thanks & regards,

Sincerely yours,

Cherry

Cherry,

Let's take the commercial question off the discussion. Email me at lbower@josephoat.com.

On your CO2>52% environment, that sounds like internal bolting. Consult a metallurgist and gasket manufacturer for recommendations. My comments were directed at external bolting.

Lawrence

Thank you for an outstanding resource! Excellent contribution.

I think the point is getting diverted. The problem is to join dissimilar material....i.e CS with SS.....how to join....& what to use.....

I know what you are saying there Mannu but you still need to take into consideration the various areas I mentioned. All these go towards deciding the material to use as well as the problems with interaction between dissimilar grades of metal.

I'm no metalurgist so those sorts of problems would have to be directed elsewhere I'm afraid.

We need to look at both the forces coming from the joint which would affect the strength requirements of the bolts and the interaction between the material grades.

Go to gasket manufacturer Pikotek

Tugrul