What are the considerations for using stainless steel in heat exchanger tubes?

[m.a.tarafdar]

We have 3 interstage coolers for a Synthesis gas compressor.Synthesis gas is mostly H2 & N2 with small Ar & CH4.Tube side fluid is water & shell side fluid is Syn.gas.The heat exchangers are made of carbon steel.Now due to corrosion in tube to tubesheet joint we like to use SS for tubes.But our vendor dont' agree & mentioned that there will be a chance of crevice corrosion.Is there any real reason for vendor's concern?

 

[Enthalpy]

You don't plan to weld stainless on carbon steel, do you? This wouldn't work.

Generally, I expect stainless to perform better than carbon steel, BUT stainless isn't a general guarantee! Corrosion depends on the chemicals and the temperature, for instance water composition changes everything. The material and quality of the welds, even their heat history, are important. Hundreds of different stainless compositions are used, with very different corrosion properties.

For instance, stainless scissors in sea water would last few weeks. Or weld joints in normal 10-8 stainless would corrode in sweet water, but low-carbon variants improve it.

So you can't avoid the full check of alloy compatibility with your fluids and your welding method.