Safety valve rules, i.e., rules for overpressure protection by the use of various pressure-relieving devices, vary somewhat among the five book sections of the ASME Boiler & Pressure Vessel Code which require such protection. This paper reviews those rules by discussing the following topics: Pressure relief device terminology and function. The problem of overpressure protection. Code rules for overpressure protection: rules for determining required relieving capacity; for allowable overpressure; for set pressure and set pressure tolerance; for blowdown. The various pressure relief devices permitted by the Code. Design of pressure relief valves. How relieving capacities are established and certified. The qualification of pressure relief device manufacturers. Installation guidelines. Concluding remarks.

1.
ASME N626.3, Qualifications and Duties of Specialized Professional Engineers, 1993. (Note: Soon to be incorporated into Section III.)
2.
Harrison, S. F., History of Safety Values and Safety Relief Values, National Board of Boiler & Pressure Vessel Inspectors, Columbus, Ohio, 1982.
3.
Pressre Relief Devices, ASME Performance Test Code PTC 25, 1994.
4.
ASME Boiler & Pressure Vessel Code, 1992 Edition with 1993 Addenda.
5.
Pressure Relief Device Certifications, National Board of Boiler & Pressure Vessel Inspectors, Columbus, Ohio.
6.
Power Piping, ASME B31.1, 1992 Edition.
7.
National Board “VR” Repair Symbol Administrative Rules and Procedures, Repair of ASME and National Board Stamped Pressure Relief Values, NB-65, National Board of Boiler & Pressure Vessel Inspectors. (Note: Soon to be incorporated into National Board Inspection Code, ANSI/NB-23.)
8.
Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries, RP 520, Part 1—Sizing & Selection, American Petroleum Institute, 6th Edition, Mar. 1993.
9.
Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries, RP 520, Part II—Installation, American Petroleum Institute, 3rd Edition, Nov. 1988.
10.
Guide for Pressure-Relieving & Depressuring Systems, RP 521, American Petroleum Institute, 3rd Edition, Nov. 1990.
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