Material of steam condensate pipes
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I have a question for everyone. In a recent project, the client requested that steam at 0.4 Mpa be made of SUS304, while the condensate should be made of SUS316L. The condensate needs to be recycled to the boiler room for use as make-up water. Why are the material requirements for condensate pipes higher than those for steam pipes?
We are carbon steel, grade 20 steel.
The iron ion content in carbon steel must be high, right?
I don’t understand; just give it to the client, no need to worry.
The condensate water can exist in a two-phase state (gas and liquid). Erosion and corrosion are severe at elbow sections; in our refinery, many carbon steel elbows used for condensate water have suffered from erosion, thinning, and perforation. However, the use of 316L material is also costly, and it is standard practice to use 316L material for sections at least 10 times the diameter of the pipe downstream of the control valve, including the next elbow after the control valve. Steam pipelines generally do not require such high-grade materials, as corrosion is minimal.
For everything, 304 is sufficient; an L can be added for condensed water.
I forgot to add that this steam is the condensed water from clean steam, which is sent directly back to the deaerator in the boiler room. I wonder if factors related to preventing pipe corrosion have been taken into account?
Refineries use clean steam; if the deoxygenator is removed directly, no impurities can enter. It is not excessive to use stainless steel.