: It supplements API Std 521 (6th edition, 2014).
The standard aims to:
A: No. For steam boilers, refer to ISO 4126 or ASME Section I. ISO 23251 is for petroleum, gas, and chemical process plants. iso 23251 pdf
A: Not if your project requires current compliance. The 2006 edition is withdrawn. Engineering a new plant with a withdrawn standard is a major non-conformity during audits. : It supplements API Std 521 (6th edition, 2014)
When professionals search for they are often looking for the international equivalent of a standard they already know well: API 520 . iso 23251 pdf