Double Flanged Dual Plate Check Valve

Size: 2" - 48" (DN50 - DN1200)

Pressure: Class 150 - 600 / PN 10-100

Standard: API 6D, ASME B16.34, MSS SP-126, AWWA C508

Body Materials: A216 WCB, A351 CF8M, A351 CF8, ductile iron (GGG40)

Seat: Metal-to-metal or soft seated (elastomer/PTFE seal on plate edge)

Plates: Two semicircular plates on central hinge pin with torsion spring assist

Design: Double flanged body — full flanged connections on both inlet and outlet sides (ASME B16.5)

Maximum Structural Integrity for Large Lines

Wafer and lug dual plate check valves work well for most applications — they sandwich between pipeline flanges and the flange bolts hold everything in position. But at large diameters and high pressures, pipeline forces become serious. A 48" Class 600 wafer body has a thin face-to-face dimension. The body wall between the flanges has minimal structural depth. Under pipeline bending loads, thermal expansion forces, and hydraulic surges at that size and pressure, a wafer body is structurally marginal.

Double flanged design solves this by providing full flanged connections on both sides — two independent flange attachment points with a full valve body between them. The structural depth is real. The body resists bending loads from the pipeline. The flanges distribute bolt loading across two dedicated connection surfaces rather than relying on through-bolts clamping a thin wafer. For 24" through 48" lines at Class 300 and above, that structural difference matters.

Why You Pay More — and When It's Worth It

Double flanged dual plate check valves cost more than wafer and lug formats at the same size. The body is heavier, the face-to-face dimension is longer, and you're buying two full flanges instead of a thin wafer disc. The weight difference is significant at large sizes — a 36" double flanged body weighs considerably more than a 36" wafer body.

You pay that premium when structural security matters more than compact installation. Waterworks applications following AWWA C508 often specify double flanged because large-diameter water mains operate under sustained pressure with potential surge events. Petrochemical isolation points on critical pipelines at Class 600 need the structural depth for long-term reliability. If you're running a 6" Class 150 HVAC line, a wafer dual plate does the job at lower cost. If you're running a 36" Class 600 crude oil pipeline, double flanged is the appropriate choice.

The Dual Plate Mechanism — Same Proven Design

The internal mechanism is the same as lug and wafer dual plate check valves. Two semicircular plates hang on a central hinge pin. Torsion springs on the pin assist plate closing. Forward flow pushes both plates open — the plates fold back against the body wall and leave the bore mostly clear for flow passage. When forward flow stops, the torsion springs start closing the plates immediately, and backpressure finishes the job. Spring assist means the plates begin closing before backpressure develops — faster closure than gravity-only single disc swing checks.

Metal-to-metal seats handle steam, high temperature, and abrasive service. Soft seated versions with elastomer or PTFE seals on the plate edge give bubble-tight shutoff for water, chemical, and low-temperature process applications. Same seat options, same closing mechanism — the double flanged format just wraps that proven mechanism in a more robust body.

Installation Reality — Longer Face-to-Face, More Bolt Work

Double flanged valves have a longer face-to-face dimension than wafer and lug formats. You need more pipe length between the two pipeline flanges to accommodate the valve body. That matters in tight installation spaces — if you're retrofitting a wafer check valve with a double flanged valve, the piping layout may need modification.

Bolt work is also more involved. Wafer and lug valves use through-bolts that pass across the valve body. Double flanged valves bolt on each side independently — two sets of flange bolts, two gasket surfaces, two bolt-tightening sequences. More labor per installation. At large sizes where you're handling heavy flanges and long bolts, that labor adds up.

A: At sizes above 24" and pressures Class 300 and above where pipeline structural loads are significant. Also for AWWA C508 waterworks applications and critical petrochemical isolation points where long-term structural reliability matters more than compact installation and lower cost.

A: Yes. The full flanges on both sides allow independent bolt-up on each side. You can bolt a blind flange on one side for dead-end isolation. Wafer bodies cannot handle dead-end service because they rely on through-bolts.

A: No. The internal flow path and plate mechanism are the same as wafer and lug dual plate check valves. Pressure drop through the valve is determined by the plate geometry and seat design, not the body format.

A: Significant at larger sizes. A 24" double flanged body weighs roughly 30-40% more than a 24" wafer body. The difference increases with size. Consider weight in your installation planning — handling equipment, support structures, and freight costs all increase.

A: Yes. AWWA C508 covers double flanged check valves for waterworks service. Manufacturers offering double flanged dual plate check valves for water utility applications typically design and test to AWWA C508 requirements.