API St 526-2009 pdf download.Flanged Steel Pressure-relief Valves.
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. 7.2 Determination of Orifice Area The minimum required effective orifice area shall be determined in accordance with API 520, Part I. 7.3 Valve Selection For valves described in this standard, inlet and outlet flange sizes and pressure-temperature ratings shall conform to the data in Table 3 through Table 16 for spring-loaded valves and Table 17 through Table 30 for pilot-operated valves. Inlet and outlet pressure limits are governed by the flange pressure-temperature limits or by the manufacturer’s design limits, whichever is lower. 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.
8.2 Spring-loaded Pressure-relief Valves The body and bonnet materials shall be in accordance with Table 3 through Table 16 for the required temperature range. The body and bonnet may be of different materials but must meet the minimum pressure-temperature requirement. The body and bonnet materials shall be equivalent to or better than the following types and grades: — carbon steel, ASME SA-216, Grade WCB; — austenitic stainless steel, ASME SA-351 Grade CF8M; — chromium molybdenum steel, ASME SA-217, Grade WC6; — nickel/copper alloy, ASME SA-494 Grade M35-1; — alloy 20, ASME SA-351 Grade CN7M. Materials for springs shall be selected per Table 2 on the basis of the operating temperature of the process fluid unless an analysis of the ambient or relieving conditions indicates a spring requiring a different material. Material for the internal parts of the valve shall be in accordance with the manufacturer’s standards for the temperature and service or as indicated on the purchaser’s specification sheet.