Stainless Steel and Carbon Steel Welding

I don't know why you do what you do. Perhaps your standards are telling you to do that. Why don't you talk to the individuals who wrote and published your standards?

If we can weld both materials and technically it is correct than we can change or modify our standard drawings as per technical clarification to reduce cost.

Then you need to be talking to the authors of your standard drawings and selling the idea to them instead of wasting time here. Perhaps they don't want rusty pipe supports under their stainless steel pipes - I don't know!

That is a good illustration as to why standards are necessary. Have a Team-point.

As JNB pointed out, rust will be an issue and rust is not the same as corrosion.

I agree supports should not be welded, but I would certainly paint all the CS used.

so the as- built drawings must show what was actually used if the prints aren't revised.

(Sent from my phart smone)

It not common practice to weld piping to supports due to the expansion/contraction differences of the different metals.

If the carbon steel and the stainless steel must be welded to each other, it is common practice to weld these with a stainless steel rod of the same alloy as the stainless steel piece. For example if carbon steel is welded to 304 stainless steel a 304, 308 or 316 rod would be used. If it CS to 316 Stainless, a 316 stainless rod would be used.

If a patch is to be made on the wall of the pipe, stainless can be used for the patch material on either CS or Stainless pipe.

This method can also be used for CS patches on CS pipe only in situations where CS is compatible with the material within the pipe, does not rust and put steel rust particles in the transferred materials.

Good Luck, Old Salt

A very simple reason appears to me. A little common sense will tell you that the most likely reason for the use of SS is corrosion resistance. When you weld it with CS, you've destroyed the corrosion resistance in that area. If this is a sanitary application, you will totally destroy that function and make the process people very unkind to you.