| Standard | Focus | Relationship to RP 551 | | :--- | :--- | :--- | | | Flow measurement by orifice plates | RP 551 references ASME for primary element calculations | | ISA-5.1 | Instrumentation symbols and diagrams | RP 551 assumes you use ISA bubble diagrams | | API RP 552 | Transmission systems (signals) | Companion document – install transmitters (551), then route signals (552) | | API RP 553 | Refinery control valves | Separate but often used in tandem for loop design | | IEC 61511 | Functional safety | RP 551 provides measurement-specific details for SIS |
. Unlike a rigid "standard," an RP acts as a guide to safe engineering practices, helping you balance high performance with long-term maintainability. The Instrumentation Life Cycle
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: It provides criteria for choosing the right technology (e.g., Coriolis vs. Ultrasonic flow meters) based on the specific properties of the process fluid and the environment.
– Defines the boundaries of the recommended practices.