API 526-2017 pdf download.Flanged Steel Pressure-relief Valves.
1 Scope This standard is a purchase specification for flanged steel pressure-relief valves. Basic requirements are given for direct spring-loaded pressure-relief valves and pilot-operated pressure-relief valves as follows: — orifice designation and area; — valve size and pressure rating, inlet and outlet; — materials; — pressure-temperature limits; — center-to-face dimensions, inlet and outlet. Nameplate nomenclature and requirements for stamping are detailed in Annex A. 2 Normative References The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. API Recommended Practice 520 (all parts), Sizing, Selection, and Installation of Pressure-relieving Devices in Refineries API Standard 527, Seat Tightness of Pressure Relief Valves ASME B16.5, Pipe Flanges and Flanged Fittings ASME B16.34, Valves-Flanged, Threaded and Welding End ASME Boiler and Pressure Vessel Code (BPVC), Section VIII: Pressure Vessels, Division 1 and Division 2 ASME BPVC, Section II: Materials: ASME SA-216, Carbon-Steel Castings Suitable for Fusion Welding for High-Temperature Service ASME SA-217, Martensitic Stainless Steel and Alloy Steel Castings for Pressure-Containing Parts, Suitable for High-Temperature Service ASME SA-351, Specification for Castings, Austenitic, Austenitic-Ferritic (Duplex), for Pressure-Containing Parts ASME SA-494, Specification for Castings, Nickel and Nickel Alloy
4 Responsibility 4.1 The purchaser is primarily responsible for the following: a) selecting the type of pressure-relief valve and the required pressure-temperature ratings; b) specifying materials that will satisfactorily resist corrosion from the process fluid and environmental conditions; c) selecting the minimum required orifice area based upon relieving conditions derived from full knowledge of the pressure-relieving system and the requirements of the applicable codes and regulations; d) providing data for sizing and selection. 4.2 The manufacturer is primarily responsible for the following: a) designing and manufacturing pressure-relief valves to satisfy the requirements of this standard and the purchaser’s specification; b) publishing relieving capacities based upon certified test data; c) advising the purchaser of any nonconformance to the purchaser’s specification; d) final sizing verification using the manufacturer’s actual orifice area and certified coefficient of discharge. 5 Conflicting Requirements Whenever the information included on the purchaser’s specification sheet or purchase order conflicts with the provisions of this standard, the purchaser’s specification sheet or purchase order shall govern. Where conflicting requirements exist, the manufacturer shall call them to the attention of the purchaser. 6 Orifice Areas and Designations The standard effective orifice areas and the corresponding letter designations are listed in Table 1. These effective areas are valid only when used with the sizing equations contained in API 520, Part I. 7 Design 7.1 General Pressure-relief valves discussed in this standard shall be designed and manufactured in accordance with the applicable requirements of ASME BPVC, Section VIII for pressure-relief devices.
7.4 Dimensions Center-to-face dimensions shall be in accordance with Table 3 through Table 16 for spring-loaded valves and Table 16 through Table 29 for pilot-operated valves, with tolerances of ± 1 / 16 in. for valve inlet sizes up to and including 4 in., and ± 1 / 8 in. for valve inlet sizes larger than 4 in. Flange facings and dimensions shall be in accordance with ASME B16.5. For some valve designs, the inlet raised face height may substantially exceed the nominal dimension specified in ASME B16.5. Consult the manufacturer for exact dimensions. 7.5 Lifting Levers Lifting levers shall be provided when required by ASME BPVC or when designated on the purchaser’s specification sheet. As allowed by code for pilot-operated pressure-relief valves, means in lieu of lifting levers may be specified for connecting and applying adequate pressure to the pilot to verify that the moving parts critical to proper operation are free to move. 7.6 Special Construction Features Construction features beyond the scope of this standard shall be provided as agreed upon by the manufacturer and the purchaser and shall be designated on the drawings provided to the purchaser. 7.7 Restricted Lift Pressure-Relief Valves a) Table 1 shows a 21 % to 78 % increase in effective orifice area from one lettered orifice to the next lettered orifice. In some applications, the user may desire a smaller increase so that the resulting rated capacity is lower.