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Check Valve
The primary function of a check valve is to prevent back pressure in the process. A secondary function can be for isolation. Occasionally, flanged swing check valves are fitted with manual over-ride devices, to allow for positive shut-off without flow pressure assistance. In this case, energisation of the seat to seal interface is by mechanical force applied through an external hand lever
This means flow can only go through the valve one way (uni-directionally). These valves operate principally by directional flow pressure and an some designs this is assisted by gravity. When the flow is in the preferred direction (i.e. in a swing check valve) the pressure will push the disc off the seat and allow the flow through the valve. Should the flow direction change, gravity will return the disc onto its seat and the reverse flow pressure will mechanically force the disc back onto the seat and assist the closure of the valve. Therefore, the more back-pressure applied, the higher the force onto the seat. Check valves often come in wafer pattern to allow reductions in overall length and weight to be built into piping systems. As well as swing type, there are also split disc, ball check, piston check, needle check and nozzle check valves which all operate on the similar principles.
Check Valve Specification
This means flow can only go through the valve one way (uni-directionally). These valves operate principally by directional flow pressure and an some designs this is assisted by gravity. When the flow is in the preferred direction (i.e. in a swing check valve) the pressure will push the disc off the seat and allow the flow through the valve. Should the flow direction change, gravity will return the disc onto its seat and the reverse flow pressure will mechanically force the disc back onto the seat and assist the closure of the valve. Therefore, the more back-pressure applied, the higher the force onto the seat. Check valves often come in wafer pattern to allow reductions in overall length and weight to be built into piping systems. As well as swing type, there are also split disc, ball check, piston check, needle check and nozzle check valves which all operate on the similar principles.
Check Valve Specification
Check Valves - General Design Criteria
- Split Disc, Swing, Piston, Ball, Needle, Nozzle Types
- Full or Reduced Bore
- Special Seat Design Options
- Manual Over-ride Options
- Operating temperature and fluids suitability - further information on request
- Firesafe / Cryogenic / Gas Service certified options
- Modification service available for all stock options
Standard Pressure Class Ratings / End Connections
- ANSI 150, 300, 600, 800, 1500 & 2500lb – Wafer, Flanged RF, RTJ, Socket or Butt-Weld and Hub ends
- PN, API and other Pressure Class Valves available on request
| Common Materials of Construction | Material Specifications |
| Standard Carbon Steel | ASTM A105 A216 WCB WCC |
| Low temperature Carbon Steel | ASTM LF2 A352 LCC LCB |
| Stainless Steel | ASTM A182 F316 ASTM A182 F316L ASTM A182 F304 ASTM A182 F304L ASTM A182 F321 ASTM A182 F347 ASTM A351 CF8M ASTM A351 CF3M |
| Specials | F44 SMO F51 Duplex Super Duplex Monel Hastelloy Titanium Inconel Bronze Alu. Bronze |
| Other |
Soft Seated Metal-to-Metal Seated |
