API Standard 621 is a Recommended Practice (RP) that describes guidelines for reconditioning metallic gate, globe, and check valves.
API 621 RP provides guidelines for reconditioning heavy wall carbon steel, ferritic alloy, stainless steel, and nickel alloy gate, globe, and check valves for ASME pressure classes up to 2500. The guidelines apply to flanged and butt weld cast or forged valves.
The standard describes specifications pertaining to the repair of the following valve parts:
- Handwheel nut
- Stem nut and stem nut housing
- Stem nut retainer
- Packing gland flange
- Packing gland
- Back seat bushing
- Body and bonnet
- Bonnet stuffing box
- Body-to-bonnet flanges and gasket surfaces
- Body end flanges, gasket surfaces, and face-to-face dimensions
- Body guides
- Body seat rings
- Wedge guides
- Wedge, globe, disc, and clapper
- Body-to-bonnet joint bolting
- Packing gland eye bolts
- Body-to-bonnet joint gasket
The standard also provides guidelines for post-repair assembly, pressure testing, and shipping.
A full copy of API 621, with complete recommendations for reconditioning metallic gate, globe, and check valves, can be purchased from the American Petroleum Institute.