API 6A Swing Check Valve

SVR Global manufacturers API 6A swing check valves for wellhead, manifold, and flowline systems across the United States, designed and tested to API Specification 6A (21st Edition) / ISO 10423 across PSL 1-PSL 4 and PR1/PR2 requirements. 

How an API 6A Swing Check Valve Operates?

A swing check valve uses a hinged disc mounted on a trunnion or rocker arm. Forward flow swings the disc off its seat for near unobstructed passage on flow reversal, the disc swings back under its own weight and reverse differential pressure, sealing the bore against backflow into the wellbore, flowline, or upstream vessel.

• Disc to seat sealing geometry: spherical hinge connection lets the disc self align with the seat across a full range of motion, compensating for minor eccentricity in flow.

• Non slam closing action: the swing geometry reduces disc velocity near the seat, limiting water hammer effects and seat impact fatigue compared to lift type designs.

• Full bore flow path: an open disc geometry produces a lower pressure drop than lift or piston type check valves, which benefits high throughput gathering lines and multiphase flow service.

• Bolted bonnet construction: the body to bonnet joint is sealed with a metal ring gasket, keeping the internal trim externally serviceable without removing the valve from the line.

Design and Material Specifications:

Material Class Selection for Sour and Corrosive Service:

• Material class governs resistance to hydrogen sulfide (H2S), carbon dioxide (CO2), and chloride bearing fluids encountered in production streams. 

• SVR Global selects material class per API 6A Annex tables based on the partial pressure of H2S, in-situ pH, and chloride concentration reported for the well or facility, aligning trim hardness and body chemistry with NACE MR0175/ISO 15156 sulfide stress cracking resistance requirements.

Standards and Certifications:

• API Specification 6A (21st Edition) - design, material, and testing baseline for wellhead equipment.

• ISO 10423 - international equivalent standard for cross border project specification.

• API 6FA - fire tested and qualified design option for fire safe shutoff requirements.

• NACE MR0175 / ISO 15156 - sulfide stress cracking resistance for sour service material classes (EE, FF, HH).

• API 6A Annex F/G - hydrostatic shell and seat leakage test protocols applied prior to dispatch.

• PSL 1-PSL 4 documentation - material test reports, NDT records, and dimensional verification scaled to project-specified PSL level.

API 6A Swing Check Valve Applications:

• Wellhead and Christmas Tree Systems - Blocks reverse flow of crude oil, natural gas, condensate, and formation water downstream of master and wing valves during shut-in or workover.

• Manifold and Flowline Assemblies - Isolates individual wells on gathering headers, preventing cross-flow between wellbores on a shared trunk line.

• Injection and Disposal Systems - Prevents backflow into supply pumps/compressors on water injection, gas lift, and saltwater disposal lines during pressure loss or shutdown.

• Choke and Kill Manifolds - Maintains directional flow control per API 16C during well control operations and pressure testing.

• Sour Gas and HPHT Wells - Specified in NACE material classes (EE, FF, HH) for elevated H2S, deepwater tie backs, and PSL 3/PSL 4 completions.

• Pipeline Pump and Compressor Stations - Prevents reverse rotation and backflow on discharge piping when units trip or shut down.