A155-66 means ASTM standard nº A155, 1966 edition (42 years old).
ASTM standard A155, related to "Electric fusion welded steel pipe for high pressure service" was discontinued in 1978 and replaced by three standards: A671, A672 and A691.
From this 3 standards, A691 includes a grade CM75 welded pipe which is a low alloy C-Mo steel with a nominal Mo content of about 0,5%, which is equivalent to seamless pipe P11 material that you mention.
I think you can use P11 if minimum thickness required is maintained.
Kind regards
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ASTM A155-66 GRADE CM75 CLASS 1 PIPE
Re: ASTM A155-66 GRADE CM75 CLASS 1 PIPE
