Alloy 20 Dual Plate Check Valve

Limited piping space can make a full-bodied check valve difficult to install, especially in chemical skids and pump discharge assemblies. An Alloy 20 dual plate wafer check valve fits between two flanges while providing spring-assisted protection against reverse flow. Its two-part disc responds faster than a heavy swing disc, and the Alloy 20 wetted construction suits many sulphuric acid and chloride-containing services. African Valve is a prominent Alloy 20 Dual Plate Check Valve Manufacturer and Supplier in Africa, serving Nigeria, Egypt, South Africa, Kenya and Ghana and exporting to the Middle East, Europe and other project locations.

How Do the Two Plates Close?

The disc is divided into two semicircular sections mounted on a common hinge. Forward flow opens both plates, compressing the torsion springs. When flow velocity begins to fall, stored spring force starts moving the plates toward the seat.

The plates do not need to travel through a wide arc. Their lower weight and shorter stroke allow the valve to react before a large volume of fluid reverses direction. This is why dual plate check valves are frequently considered for pump systems where pressure surge is a concern.

The valve must still be selected from actual flow data. Excessive line velocity can damage hinge components, while very low velocity may prevent the plates from reaching a stable open position.

Selecting Alloy 20 Components

ASTM A351 CN7M is normally used for cast Alloy 20 bodies and plates, while forged components can be supplied in ASTM A182 F20. The alloy was developed for corrosive chemical service and contains copper in addition to nickel, chromium and molybdenum.

Spring and hinge materials require close attention because they are smaller stressed components. Depending on the fluid, they may be produced from Alloy 20 or another compatible nickel-based alloy.

PTFE and reinforced PTFE seats are suitable for many clean chemical fluids. A metal-seated arrangement may be selected for higher temperature, abrasive particles or services where polymer degradation cannot be accepted.

Technical Specifications

Size Range: DN40 to DN1200
Pressure Ratings: Class 150 to Class 600; PN10 to PN100
Design Standards: API 594 and ASME B16.34
Testing Standard: API 598
End Connections: Wafer type between ASME B16.5 or EN flanges
Operation: Automatic, spring-assisted non-return action

Practical Advantages

• The short body suits restricted equipment layouts.

• Lower disc mass improves closing response.

• Spring assistance limits delayed closure at falling flow.

• Alloy 20 withstands many acidic and chloride-bearing media.

• The open plates create a comparatively direct flow passage.

• Installation weight is lower than that of a conventional flanged valve.