If you'd like to access the full text of the standard, I recommend:
: While earlier versions were nearly identical to API RP 521, the current ISO 23251:2019 provides additional clarifications and requirements specific to international and European practices. Standard Content & Structure iso 23251 pdf
Most international regulations (OSHA in the US, PED in Europe, and local HSE laws) require adherence to recognized standards. In a lawsuit or incident investigation, citing a "summary" is insufficient. You must demonstrate that your engineering decisions followed the exact wording of ISO 23251. If you'd like to access the full text
ISO 23251 is a standard related to the petroleum, petrochemical, and natural gas industries - Drilling and production equipment - Subsurface sucker rod pumps and fittings. Primarily utilized in oil refineries, it also governs
is the definitive international standard for pressure-relieving and depressuring systems within the petroleum, petrochemical, and natural gas industries. Primarily utilized in oil refineries, it also governs safety protocols for gas plants, Liquefied Natural Gas (LNG) facilities, and upstream production sites. Scope and Technical Application
This standard covers the design, materials, testing, and documentation of subsurface sucker rod pumps and fittings. It includes: