API 594:2004 pdf free download.Check Valves: Flanged, Lug, Wafer and Butt-welding
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 rinjoint 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.
4.1.10 For Type ‘A’ valves a tapped hole shall be provided in the body of valves which are either NPS 10 or larger, or which weigh more than 50 lb. (23 kg), for attachment of an eye bolt or equivalent lifting device. The hole shall be tapped with a coarse (UNC) Class 2B thread, conforming to ASME B1.1. If an eyebolt is specified in the purchase order, it shall conform to ASME B18.15.
4.1.11 Unless otherwise specified in the purchase order, for Type ‘A’ valves the lugs of lug type valves and flanges of dou- ble-flanged type valves shall be provided with non-threaded (drilled) bolt clearance holes.
4.1.12 Butt-welding ends shall conform to the require- ments of ASME B16.25 for the bore specified for use without backing rings.
4.1.13 Conversion of a flanged end to a butt-welding end is not permitted except by agreement between the purchaser and manufacturer.
4.1.14 Type ‘B’ valves shall have a bolted cover design that meets the requirements of ASME BPVC, Section VIII, flat covers shall conform to UG 34 and dished covers shall conform to Appendix I-6. Cover and cover flanges shall be circular except NPS 2 and NPS 2 1 / 2 . Body-to-cover joint shall be flanged with a flat face (Class 150 only), raised face, tongue and groove, spigot and recess, or ring joint per ASME B16.5.
4.1.16 When valve design utilizes a stem that extends beyond the pressure boundary, it shall be provided with a means so that, in the event of a structural failure of stem-to- closure attachment items, the stem will not be ejected through the pressure boundary while the valve is under pressure.
4.2 PLATES AND DISC Valves are classified as follows:
a. A single-plate valve has a plate or disc that closes the valve when flow reversal or gravity forces the plate or disc against the valve-body seat. This closure may be aided by the use of springs or other devices.
b. A dual-plate valve has plates that close the valve with the assistance of one or more springs, when flow reversal forces the plates against the valve-body seat. c. For Type ‘A’ single-plate valves and Type ‘B’ valves, when a nut is used to assemble the disc or plate to the hinge arm, the nut shall be secured to prevent separation; the use of a single tack weld, lock washer or lock nut are not acceptable means.API 594 pdf download.API 594:2004 pdf free download
