Wafer Type Dual Plate Check Valve

A wafer type dual plate check valve - also called a double door check valve or dual plate wafer check valve - is an automatic non-return valve with two semicircular spring-loaded half-discs pivoting on a central hinge pin. Forward flow swings both discs roughly 90° open; when flow stops or reverses, the torsion springs return the discs to the seat. It is a wafer check valve in the sense that the thin body clamps directly between two flanges with no dedicated flange ring of its own.

Why it behaves the way it does is a short mechanical chain, and that chain is the whole reason to specify it. Each half-disc has only half the radius of a full swing disc, so its travel arc is roughly half as long and the body face-to-face compresses to about one quarter. Short travel plus spring preload that begins before flow reverses means the discs seat before reverse velocity can build. That is what makes a non-slam check valve non-slam: no reverse flow, no pressure spike. A swing check, by contrast, relies on gravity and waits for reverse flow to push the disc shut - which is exactly when water hammer is born.

Two standards are often confused. API 594 is written specifically for thin-profile wafer and lug check valves; BS 1868 and API 602 cover other valve families and should not be listed against a dual plate design. For pipeline duty the valve is supplied to API 6D; pressure-temperature ratings come from ASME B16.34; testing follows API 598.

Design Standard

Design Features

1. Body slot design to fit the hinge pin
2. Two independent torsion springs ensure quick valve dosing
3. Uninterupted gasketsurface for effectivesealing
4. Lightweight,compact design
5. Two independent seats to ensure consistent sealing even in uneven flow. 

Wafer Type Dual Plate Check Valve drawing

Wafer Type Dual Plate Check Valve Dimension & Weight 

Class 150

Class 300

Class 600

Quality Control and Testing

Every valve is tested before shipment - not sampled. The checkable steps are:

Hydrostatic shell test at 1.5× rated pressure per API 598, with no body seepage.

Seat leakage test at 1.1× (water) and 0.6 MPa air, certified to ISO 5208 Rate A (soft) or Rate D (metal).

Dimensional inspection against API 594 face-to-face and ASME B16.5 flange drilling.

Material verification - spectro PMI on body and trim, with EN 10204 3.1 mill test certificate and full heat traceability.

Functional check - free disc movement and correct spring preload.

Third-party inspection (SGS / TÜV / BV) and witnessed testing available on request; NACE MR0175 documentation where specified.

Packaging, Lead Time and Payment

Packaging. Export plywood cases with internal bracing; valve stems and flange faces protected; clear marking with size, class, material, heat number and flow arrow.

Lead time. Stock configurations from 1–2 weeks; standard production 3–5 weeks; exotic alloys and special materials 8–12 weeks. Confirmed against your line list at quotation.

Payment. T/T and L/C accepted; terms negotiated per order volume.

Warranty. 18–24 months from shipment against documented manufacturing defect; spare discs, springs and seats available.

Logistics. FOB / CIF / CFR to your port; consolidation with other valve and fitting orders supported.

Why Source from GNEE

Integrated manufacturer-supplier. Mill partnerships plus in-house machining, assembly and testing keep specification and quality under one roof.

Standards discipline. Every valve is quoted and built to a named standard (API 594 / API 6D / ASME B16.34 / API 598), with retainerless bodies and documented ISO 5208 seat ratings - no vague "high quality" claims.

Full material and trim range. Carbon, low-temperature, stainless, duplex and bronze bodies with soft or hard seats and NACE MR0175 options.

Documentation and QA. EN 10204 3.1 certificates, shell/seat test reports, PMI and third-party inspection on request.

OEM / ODM and export experience. Private-label and special-material orders supported, shipped to projects across the Middle East, Southeast Asia, Africa and South America.

Valve factory

Send your size × class, body and trim material, end connection, service conditions and destination port - our technical team will confirm the specification and return a quotation with lead time, typically within 24 hours. Contact GNEE today.

FAQ

What is a wafer type dual plate check valve?

A wafer type dual plate check valve is a compact, spring-assisted non-return valve with two half-discs hinged on a central pin. It seats directly between two pipeline flanges, allows one-way flow, and closes before flow reverses to prevent backflow and water hammer. Typical supply is NPS 1/2–24 (DN15–600), Class 150–1500, built to API 594.

Dual plate vs swing check valve - which should I choose?

A dual plate valve closes by spring force in milliseconds and is the right choice for pump and compressor discharge, water-hammer-sensitive lines, vertical-up installation and space-limited layouts. A swing check relies on gravity and reverse flow, can slam at high velocity, and suits large-bore, low-cost water service where surge is not a concern. For a full decision table, see our dual plate vs swing check valve guide.

Which standard governs dual plate wafer check valves?

API 594 is the governing standard written specifically for thin-profile wafer and lug type check valves, setting face-to-face to the ASME B16.10 short pattern. API 6D applies where the valve serves a pipeline; ASME B16.34 sets the pressure-temperature ratings; API 598 covers testing. When a purchase order cites more than one standard, the order governs.

What does non-slam mean and how does it prevent water hammer?

Non-slam means the spring starts returning the discs as forward velocity falls, so the valve seats before flow actually reverses. Because reverse velocity never builds, the pressure surge (water hammer) that cracks pumps, piping and instruments never forms. The short disc travel - each half-disc has half the radius of a swing disc - is what makes fast closure physically possible.

What pressure classes and sizes can you supply?

Standard supply is NPS 1/2–24 (DN15–600) in Class 150, 300, 600, 900 and 1500. Larger sizes and Class 2500 are available on enquiry. Face-to-face conforms to API 594 / ASME B16.10 short pattern.

What body and trim materials are available?

Body materials include A216 WCB carbon steel, A351 CF8 and CF8M (304 and 316 stainless), A351 CF3M for low temperature, A352 LCB and LCC for cryogenic duty down to −46 °C, A182 F51 duplex 2205, and aluminium bronze. Trim options cover Stellite 6 hard-faced or soft seats (PTFE, NBR, EPDM, Viton) with Inconel X-750 or SS316 springs, plus NACE MR0175 sour-service trim.

What is a retainerless design and why does it matter?

Retainerless means the hinge and stop pins are supported from inside the body with no holes drilled through the wall. A conventional design drills through the body and seals the pins with external plugs - each plug is a fugitive-emission path. API 594 requires the absence of through-body holes, so retainerless construction removes that leak path at source. It is not visible externally, so confirm it on the inspection documentation.

What seat leakage rate applies - is it "Class VI per API 598"?

Seat leakage is rated to ISO 5208: Rate A (zero visible leakage) for soft seats and Rate D for metal-to-metal seats. The phrase "Class VI per API 598" is incorrect - Class VI belongs to ANSI/FCI 70-2, the control-valve leakage system, and API 598 does not define a Class VI. We certify seat tightness against ISO 5208 on every valve.

What is the cracking pressure of a dual plate check valve?

Cracking pressure - the differential needed to start opening the discs - is typically 0.03–0.2 bar (about 0.4–3 psi), set by the spring. A stronger spring closes sooner and protects the system better but adds a small head loss to the pump, so spring rate is selected against the service velocity (usually 2–4 m/s through the valve).

Can a dual plate check valve be installed in vertical piping?

Yes, but only with flow upward (bottom to top). On horizontal lines the hinge pin must stay horizontal so debris does not collect at the seat. Never install the valve with flow downward - gravity then works against the spring and reseating cannot be guaranteed, so the valve will leak.

What is the face-to-face dimension of a wafer check valve?

Face-to-face follows the API 594 / ASME B16.10 short pattern and is typically 1/4 to 1/5 the length of a comparably rated flanged swing check. Exact millimetres are quoted per size and pressure class at order entry rather than as a single fixed figure.

Is a dual plate check valve full bore and piggable?

No. The central hinge pin and the two springs sit in the bore, so a dual plate valve is not full bore and will not pass a pig. For pigging or full-bore service specify a full-opening swing check built to API 6D, whose disc swings clear of the pipe ID.

What documents and inspection certificates do you provide?

Every valve ships with an EN 10204 3.1 mill test certificate, shell and seat test reports, and full material traceability. Third-party inspection by SGS, TÜV or BV and witnessed testing are available on request, and NACE MR0175 compliance is documented where specified.

What is your minimum order quantity, lead time and OEM capability?

Minimum order is 1 piece for stock configurations. Standard lead time is 3–5 weeks and 8–12 weeks for exotic alloys; OEM/ODM and special materials are supported. Exact lead time is confirmed against your line list at quotation.