API 594 pdf download.Check Valves: Flanged, Lug, Wafer and Butt-welding
1.1 SCOPE This standard covers design, material, face-to-face dimen- sions, pressure-temperature ratings, and examination, inspec- tion, and test requirements for two types of check valves. 1.1.1 Type ‘A’ check valves are short face-to-face as defined in Tables 2A and 2B and can be: wafer, lug, or double flanged; single plate or dual plate; gray iron, ductile iron, steel, nickel alloy or other alloy designed for installation between Class 125 and 250 cast iron flanges as specified in ASME B16.1, between Class 150 and 300 ductile iron flanges as specified in ASME B16.42, between Class 150 – 2500 steel flanges as specified in ASME B16.5, and between Class 150 – 600 steel pipeline flanges as specified in MSS SP-44 or carbon steel flanges as specified in ASME B16.47. 1.1.2 Type ‘B’ check valves are long face-to-face as defined in 4.1.2 and can be: flanged or butt-welding; steel, nickel alloy or other alloy designed for installation between Class 150 – 2500 steel flanges as specified in ASME B16.5 or for butt-welding into industry accepted piping systems.
4.1 BODY AND COVER 4.1.1 The minimum body wall thickness for various mate- rials shall be as follows: Type ‘A’ valves only: a. Gray iron: as shown in Tables 1A and 1B for Class 125 and Class 250 only. b. Ductile iron: as shown in Tables 1A and 1B for Class 150 and Class 300 only. Type ‘A’ and Type ‘B’ valves: c. Steel and chrome-moly steels per ASME B16.34, Table 1, Group 1: as shown in Tables 1A and 1B, for Classes 150, 300, 600, 900, 1500 and 2500 d. Nickel-base alloys per ASME B16.34, Table 1, Group 2 and other alloys per ASME B16.34, Table 1, Group 3: 1. For Classes 150, 300 and 600 only: as shown in ASME B16.34, Table 3. 2. For Classes 900, 1500 and 2500: as shown in Tables 1A and 1B. e. Special materials: The minimum body wall thickness for materials not covered by ASME B16.34 shall be as agreed between the purchaser and manufacturer. 4.1.2 The face-to-face dimensions shall be as follows: Type ‘A’ valves (including valves with ring-joint facings) shall con- form to those shown in Tables 2A and 2B. Type ‘B’ valves shall conform to ASME B16.10. Short pattern or special lengths are not permitted unless by agreement between pur- chaser and manufacturer.4.1.3 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 ade- quate. 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. Welding and examination shall conform to ASME B31.3 for Normal Fluid Service, unless otherwise specified, including qualifications for the weld procedure and welder or welding operator. The finished weld thickness shall not be less than the minimum body wall thickness. Heat treat- ment shall be performed in accordance with the material specification and shall be done prior to required valve pres- sure testing. 4.1.4 Type ‘A’ valves larger than NPS 24 in Classes 150, 300, and 600 shall have body-flange bolt patterns suitable for the lug or double-flanged type, outside diameters suitable for the wafer type, and gasket surface dimensions compatible with the flange standards specified in the purchase order. 4.1.5 Flange faces with ring-joint grooves shall conform to the dimensions shown in either ASME B16.5 or ASME B16.47, as applicable. 4.1.6 Flange facing finishes shall be: Type ‘A’ valves only: Gray iron and ductile iron valves shall be finished as specified in MSS SP-6. Type ‘A’ and Type ‘B’ valves: Steel, nickel-alloy and other alloy valves shall be finished as specified in ASME B16.5. 4.1.7 Auxiliary connections are required only when speci- fied by the purchaser: Type ‘A’ valves only: For gray iron and ductile iron valves the size, type and location of auxiliary connections shall be the manufacturer’s standard unless otherwise agreed by the manufacturer and the purchaser. Type ‘A’ and Type ‘B’ valves: For steel, nickel alloy and other alloy valves auxiliary connections shall comply with the requirements of ASME B16.34, Section 6.3. The location and designation of auxiliary connections shall be: a) manufac- turer’s standard for Type ‘A’ valves and b) per ASME B16.34, Figure 1(b) for Type ‘B’ valves. 4.1.8 The valve may have either an integral or a removable seat ring. Sealing compounds or greases shall not be used when assembling seat rings, however, a light lubricant having a viscosity no greater than kerosene may be used to prevent galling of mating threaded surfaces. 4.1.9 Tapped test openings are permitted only if specified in the purchase order. If a tap is made in the body for testing the valve, the tap shall not be larger than NPS 1 / 2 . After test- ing, the tapped hole shall be fitted with an ASME B16.11 or ASME B16.14 threaded solid round or hex-head plug. The test tap may require a boss to provide the minimum thread engagement, as specified in ASME B16.34.