Hello all

I have a design and build application with r407C. The system will have 150mmOD suction lines and will need to use carbon steel.

In literature(american) it is suggested to use SCH40(similar to natural gas pipes interms of pipe thickness). I check the pipe properties and find out that the operational allowed pressure is 45Bar,testing pressure is 70Bar for Schedule40 pipes.

I do not want to use an overqualified piping for the job, but do not want to underestimate the job either. Highest pressure r407C will go in the system is 8-10bar max. Standard Electric Resistance Welded pipes in the market have properties of 25Bar operational pressure allowances(which seems more than enough.

I read that in ammonia systems most of the time suction and discharge lines are used with seamless carbon steel. I do not understand why especially seamless .

My questions are:

1)Can i use ERW(electric resistance welded) carbon steel pipes instead of seamless carbon steel pipes?.(I am worried if sudden changes in the temperature may create microcracks on the welded area after a period of time maybe?)
2)Should i use regular thickness (25bar) pipes instead of 40bar pipes.

Thank you for your time.