A best practice is to design to the stricter requirement of the two documents.
A common point of confusion is the difference between and API Standard 556 (or API 556). It is critical to clarify this for anyone searching for the api rp 556 pdf . api rp 556 pdf
: It typically does not cover oil-fired heaters, utility water tube boilers, or specialty heaters like CO boilers or ethylene furnaces, which may fall under other standards like Safety and Compliance Evolution A best practice is to design to the
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