Alloy 20 Swing Check Valve Manufacturer  in Africa

Reverse flow through an acid-transfer pump can damage equipment, contaminate storage vessels and disturb process stability. An Alloy 20 swing check valve prevents this movement through a hinged disc that closes automatically as forward velocity falls. The Alloy 20 pressure parts resist many sulphuric acid and chloride-bearing fluids. African Valve is a leading Alloy 20 Swing Check Valve Manufacturer  in Africa, supplying Nigeria, Egypt, South Africa, Kenya and Ghana and supporting exports to the Middle East, Europe and other international industrial markets.

What Moves the Disc?

During normal operation, forward flow pushes the disc away from the body seat. The disc rotates around a hinge pin and remains open while sufficient fluid velocity is available.When the pump stops or the pressure balance changes, gravity and reverse pressure move the disc back toward the seat. No actuator is required. The valve reacts entirely to the hydraulic conditions in the pipeline.A swing disc travels farther than the plates in a dual plate check valve. If reverse velocity develops quickly, the disc may strike the seat with considerable force. The resulting pressure wave is commonly referred to as check valve slam.

When Is a Swing Check Valve Appropriate?

The design performs well in systems with steady flow and gradual pump deceleration. Its open disc creates a broad flow path and generally lower pressure loss than spring-loaded check valves.It may not be the best choice for short pump discharge lines, pulsating flow or systems where rapid shutdown is expected. In those cases, an axial or dual plate check valve may respond faster.Correct sizing is important. An oversized valve can leave the disc partially open during normal operation, causing repeated movement of the disc and accelerated wear of the hinge pin.

Installation Direction

Horizontal installation is common, with the valve cover facing upward. Vertical installation is possible where the fluid travels upward and gravity can return the disc toward the seat.

Downward vertical flow is normally unsuitable because gravity holds the disc away from the closed position. The flow arrow marked on the body must always match the intended pipeline direction.

Alloy 20 Body and Internal Parts

ASTM A351 CN7M is typically used for cast bodies, covers and discs. Forged trim components may be produced in ASTM A182 F20.

The hinge pin, disc arm and seat ring remain exposed to the process fluid. They should therefore be manufactured from Alloy 20 or another material proven compatible with the chemical. Metal seats are commonly used, although a soft insert can be provided for lower leakage in clean, moderate-temperature service.

Technical Specifications

Size Range: DN50 to DN900
Pressure Ratings: Class 150 to Class 600; PN10 to PN100
Design Standards: BS 1868, API 6D or ASME B16.34
Testing Standard: API 598 or API 6D
End Connections: Flanged RF, RTJ or butt-weld
Operation: Automatic swing-disc closure

Engineering Characteristics

• A full-opening disc limits restriction during forward flow.

• Alloy 20 supports many acid and chloride services.

• Bolted covers provide access to the hinge and disc.

• External counterweights may modify closing behaviour.

• Renewable seat rings can simplify maintenance.

• No external power source is required.

Applications

The valve is used in sulphuric acid plants, fertilizer units, chemical transfer lines, acid storage, pickling plants and corrosive pump systems. The piping engineer should evaluate flow velocity and pump shutdown time before selecting it.

Inspection Process

Hinge clearance, disc alignment and seat contact are checked during assembly. Hydrostatic shell testing verifies pressure integrity, followed by reverse-seat testing. PMI, NDT and MTC review can be included according to project requirements.