API 6A Check Valve

SVR Global manufacturers API 6A check valves engineered for wellhead and surface flow control assemblies across the United States. Each valve is designed, manufactured, and monogrammed in accordance with API Specification 6A (21st Edition), the standard adopted globally as ISO 10423 for wellhead and Christmas tree equipment. 

What is an API 6A Check Valve?

An API 6A check valve is a directional valve used for controlling the flow in one direction only, while restricting the opposite direction, to avoid backflow of produced fluids, drilling mud, cement slurry, or completion fluids into upstream lines.

• Prevents backflow of produced fluids, drilling mud, cement slurry, and completion fluids

• Qualified under a Product Specification Level (PSL) and Performance Requirement (PR) framework

• Framework governs material traceability, NDT scope, and hydrostatic test protocols

• Distinguished from general industrial check valves by certification depth and documentation

Valve Design Types:

Swing Check Valve-

A hinged disc on a rocker arm or trunnion pin lifts off the seat along an arc under flow pressure and returns on reversal.

• Low flow resistance in the open position

• Suited to larger bore sizes

• Matched to clean or moderately particulate media

Lift / Piston Check Valve-

A guided poppet or piston travels a linear, vertical path, lifting off the seat under flow and reseating by spring or gravity return.

• Compact footprint relative to swing designs

• Orientation flexible in select configurations

• Specified for manifold and choke line assemblies with limited space

API 6A Classification Parameters:

Pressure Rating-

API 6A check valves are rated across standard working pressure classes from 2,000 psi through 20,000 psi, matching the pressure rated connections used on wellheads, tubing heads, and Christmas tree spools.

• Working pressure range: 2,000 psi to 20,000 psi

• Rating matched to the mating wellhead, tubing head, or tree spool connection

• Pressure class ties directly into body and bonnet stress calculations

Material Class-

The material classification system uses letters AA, BB, CC, DD, EE, FF, and HH to classify the materials suitable for sweet or sour service due to exposure to hydrogen sulfide (H2S), carbon dioxide (CO2), and chloride levels.

• Classes AA through HH span sweet to sour service metallurgy

• Selection driven by H2S partial pressure, CO2 content, and chloride exposure

• Sour service classes require NACE MR0175 / ISO 15156 sulfide stress cracking compliance

Temperature Class-

Qualifying temperature range is specified by the classification of temperatures from K to V that range between -60°F and 350°F and determine the choice of the material for body, bonnet, and seats construction.

• Temperature classes K through V, roughly -60°F to 350°F

• Governs elastomer and seal material selection

• Affects body, bonnet, and seat metallurgy choices

Product Specification Level (PSL)-

PSL 1 through PSL 4 define escalating requirements for material certification, dimensional verification, NDT scope, and documentation.

• PSL 1: baseline material and dimensional requirements

• PSL 2: added NDT and documentation requirements

• PSL 3 / PSL 4: specified for wellbore annulus, production tubing interface, HPHT, and sour gas applications

• Higher PSL levels expand traceability and inspection scope

Performance Requirement (PR)-

PR1 and PR2 designate the validation testing regime applied to the design, including pressure cycling and seat leakage verification under rated differential pressure.

• PR1: standard design validation testing

• PR2: extended cycle testing and seat leakage verification at full rated differential pressure

Construction and Materials:

SVR Global API 6A check valves are built from forged carbon steel, low alloy steel, or corrosion resistant alloy bodies, machined to API 6A dimensional and stress limit requirements under ASME/API allowable stress calculations.

• Body materials: forged carbon steel, low alloy steel, or corrosion resistant alloy

• Machined to API 6A dimensional and allowable stress requirements

• End connections: flanged (RF, RTJ per API 6BX), threaded, or hub type

• Seating surfaces hardfaced with cobalt based alloy overlay for wear and sour service resistance

• Bonnet and body joints sealed with metal ring gaskets or API specified sealing rings

Testing and Quality Assurance:

Every API 6A check valve undergoes hydrostatic shell testing, seat leakage testing, and, where specified, fire safe qualification under API 6FA.

• Hydrostatic shell testing on every valve

• Seat leakage testing under rated differential pressure

• Optional fire safe qualification per API 6FA

• Material test report (MTR) traceability per API 6A

• NDT scope (ultrasonic, magnetic particle, radiographic) scaled to assigned PSL

• ISO 9001 quality management with API monogram documentation support

API 6A Check Valve Applications:

• Choke manifold and flowback equipment assemblies

• Cementing and fracturing back pressure lines

• Gas gathering and injection flowlines

• Sour-gas and H2S bearing production systems requiring NACE MR0175 compliant materials