Valves

Check valves: swing, dual-plate, lift and piston

Check (non-return) valves stop reverse flow on pump discharges, compressor outlets and process lines. CRS PLUS sources swing check valves, dual-plate wafer check valves, forged lift and piston check valves for small-bore lines, and axial nozzle check valves for high-flow service, quoted by size, class, type, end connection and material.

Check valves we quote

Sourced through the qualified supplier base. Sizes, ratings and grades are shown as ranges; send your bill of materials and every line is quoted against its exact specification.

Check valves we quote
Product	Standard	Sizes	Rating / class	Materials
Swing check valve, bolted cover	API 6D / BS 1868 / ASME B16.34	NPS 2 to 48	Class 150 to 2500	A216 WCB, A352 LCC, A351 CF8M
Dual-plate wafer check valve	API 594	NPS 2 to 48	Class 150 to 2500	A216 WCB, A105N, A351 CF8M; Inconel or SS springs
Lift / piston check valve, forged	API 602 / BS 5352	NPS ½ to 2	Class 800 to 1500	A105N, A350 LF2, A182 F316
Ball check valve	ASME B16.34	NPS ½ to 4	Class 150 to 600	A105N, A351 CF8M
Axial (nozzle) check valve	API 6D	NPS 2 to 48	Class 150 to 2500	A216 WCB, A105N, A352 LCC

How a check valve is specified

A check valve line states size, class, type, end connection, body and trim materials and installation orientation — for example "6 in class 150 swing check valve, RF flanged, A216 WCB, trim 8". Swing and lift checks are normally installed in horizontal lines; dual-plate and axial checks can be fitted horizontally or in vertical upward flow. The orientation is stated on the order so the right design is supplied.

Swing or dual-plate

A swing check has a hinged disc that swings open with flow and closes under gravity and back-flow. It has low pressure drop but is long and heavy, and can slam on rapid flow reversal. A dual-plate check uses two spring-loaded half-discs in a short wafer body clamped between flanges; it closes quickly, reduces slam and saves weight and space, which makes it common on pump discharges.

Documentation and supply terms

Mill test certificate: EN 10204 3.1 certificate for every line, traceable to the heat number marked on the item. EN 10204 3.2 with third-party witness on request.
Marking: Material grade, size, rating and heat number marked on each item to the governing standard (MSS SP-25 for valves, flanges and fittings).
Inspection: Positive material identification, dimensional checks and third-party inspection arranged where the project specifies them.
Sour and low-temperature service: NACE MR0175 / ISO 15156 hardness limits and impact testing applied where the piping class calls for them, and stated on the certificate.
Quotation: Each line states the standard, grade, origin, lead time and certification before you commit. Listing does not indicate stock held by CRS PLUS.

Frequently asked questions

What is a check valve?

A check valve (non-return valve) allows flow in one direction and closes automatically to prevent reverse flow. It needs no operator; flow opens it and back-pressure, gravity or a spring closes it.

What is API 594?

API 594 is the standard for check valves of the flanged, lug, wafer and butt-welding types, covering dual-plate wafer and swing designs with dimensions, materials and testing requirements.

Which check valve for a pump discharge?

Dual-plate or non-slam axial check valves are usually preferred because they close before significant reverse flow develops, limiting water hammer. The choice depends on line size, flow rate and how quickly the flow reverses.

What does "trim 8" mean?

Trim numbers are defined in API 600 and API 602 and describe the materials of the seating surfaces and internal parts. Trim 8 is 13% chromium stainless with hard-faced seats, a common general-purpose trim for carbon steel valves.

How are check valves tested?

Each valve is shell and seat tested to API 598 or API 6D and supplied with a test certificate and material certificates for pressure-containing parts.

Request a check valve quotation

A structured offer follows within 72 hours.