API STD 594-2010 pdf free download

API STD 594-2010 pdf free download.Check Valves: Flanged, Lug, Wafer, and Butt-welding.
3 Terms and Definitions For the purposes of this document, the following definitions apply. 3.1 class An alphanumeric designation that is used for reference purposes relating to valve pressure/temperature capability, taking into account valve material mechanical properties and valve dimensional characteristics. It comprises “Class” followed by a dimensionless whole number. The number following “Class” does not represent a measurable value and is not used for calculation purposes except where specified in this International standard. The allowable pressure for a valve having a class number depends on the valve material and its application temperature and is to be found in tables of pressure/temperature ratings. 3.2 dimension number DN An alpha numeric designation of size that is common for components used in a piping system, used for reference purposes, comprising the letters “DN” followed by a dimensionless number indirectly related to the physical size of the bore or outside diameter of the end connection as appropriate. The dimensionless number following “DN” does not represent a measurable value and is not used for calculation purposes except where specified. 3.3 nominal pipe size NPS An alpha numeric designation of size that is common for components used in a piping system, used for reference purposes, comprising the letters “NPS” followed by a dimensionless number indirectly related to the physical size of the bore or outside diameter of the end connection as appropriate. The dimensionless number may be used as a valve size identifier without the prefix “NPS.” The dimensionless size identification number does not represent a measurable value and is not used for calculation purposes.
4 Pressure-temperature Ratings 4.1 Valve Rating 4.1.1 The pressure-temperature rating of the valve for various body materials shall be as follows: — Type ‘A’ valves only: a) gray iron: the pressure-temperature rating for the applicable flange class as specified in ASME B16.1; b) ductile iron: the pressure-temperature rating for the applicable flange class as specified in ASME B16.42. — Type ‘A’ and Type ‘B’ valves: a)steel, nickel alloy, and other alloy: The pressure-temperature rating shall be in accordance with Standard Class ratings of ASME B16.34, Table 2, for the applicable Group 1, 2, or 3 material of ASME B16.34, Table 1. b)special materials: The pressure-temperature rating for materials not covered by ASME B16.34 shall be determined by the procedures in ASME B16.34, Appendix B. 4.2 Temperature Restrictions 4.2.1 Restrictions of temperature and concurrent pressure, or pressure and concurrent temperature, (e.g. those imposed by special soft seals or special trim materials), shall be marked on the valve identification plate (see Section 8). 4.2.2 The temperature for a corresponding pressure rating is the maximum temperature of the pressure-containing shell of the valve. In general, this temperature is the same as that of the contained fluid. The use of a pressure rating corresponding to a temperature other than that of the contained fluid is the responsibility of the user. 4.2.3 For temperatures below the lowest temperature listed in the pressure/temperature tables the service pressure shall be no greater than the pressure for the lowest listed temperature. The use of valves at lower temperatures is the responsibility of the user. Consideration should be given to the loss of ductility and impact strength of many materials at low temperature.
5.1.2 The face-to-face dimensions shall be as follows: Type ‘A’ valves (including valves with ring-joint facings) shall conform to those shown in Table 3 and Table 4. Type ‘B’ valves shall conform to ASME B16.10. Short pattern or special lengths are not permitted unless by agreement between purchaser and manufacturer. 5.1.3 The purchase order shall specify for Type ‘A’ valves whether the body type shall be wafer, lug or double flanged and for Type ‘B’ valves whether the body type shall be flanged or butt-welding. Type ‘A’ double-flanged valves will only be supplied where nut space between flanges is adequate. End and cover flanges of steel, nickel alloy and other alloy valves shall be integrally cast or forged with the body. However, flanges may be attached by full penetration butt-welding if agreed to by the purchaser. Flanges shall conform to ASME B16.5 and have butt-welding ends for use without backing rings. Flanges for iron valves shall only be the integral type.