Super Duplex Dual Plate Lug Type Check Valve Manufacturer in Africa 

Pump discharge lines carrying seawater or concentrated brine need a check valve that closes promptly without adding excessive body length. A lugged dual plate design gives spring-assisted closure, while Super Duplex materials protect the body and internals from chloride attack. African Valve is a leading Super Duplex Dual Plate Lug Type Check Valve Manufacturer in Africa, supplying South Africa, Nigeria, Egypt, Angola, other African markets and export projects.

Dual Plate Working Principle

Two semicircular plates rotate around a central hinge pin. Forward flow opens the plates, while torsion springs begin returning them toward the seat as velocity falls. Each plate is lighter and travels a shorter distance than a conventional swing disc.
The shorter closing movement can reduce reverse velocity before shutoff, but it does not remove water hammer from the system. Pump trip time, pipeline length, elevation and fluid velocity still influence the pressure surge.

Why a Lug Body Is Used

Threaded lugs are positioned around the valve body so each flange is bolted independently. This helps with alignment and may simplify maintenance around pumps, strainers or removable pipe sections.
The lug body should not automatically be treated as suitable for retaining full pressure with one flange removed. That condition needs a documented one-sided isolation rating, and the permitted pressure may vary with size, direction and seat design.

Super Duplex Material Arrangement

Cast bodies and plates may use ASTM A995 Grade 5A, while hinge pins, springs and retainers may use compatible F53, F55 or another approved corrosion-resistant material. The internal parts are continuously exposed to the process and should not be downgraded simply because they are smaller.
Super Duplex offers high strength and improved resistance to chloride pitting, crevice corrosion and stress-corrosion cracking. Heat treatment, ferrite balance, spring material and surface condition still affect service life.

Technical Specifications

Size Range: DN50 to DN900
Pressure Ratings: ASME Class 150 to Class 600
Design Standards: API 594 and ASME B16.34 where applicable
Testing Standard: API 598
End Connections: Lug pattern to specified flange drilling
Operation: Automatic, flow actuated
Body Material: ASTM A995 Grade 5A or compatible Super Duplex grade
Plate Design: Dual spring-assisted plates
Seat Options: Metal, PTFE or resilient seat
Installation: Horizontal or vertical upward flow when approved

Seat, Spring and Flow Selection

Metal seats suit higher temperature, abrasive particles and repeated cycling. PTFE or resilient seats may provide tighter shutoff in clean water and chemical service. Seat choice affects leakage, cracking pressure and closing response.
Spring torque should match the installation orientation and operating flow. A spring that is too strong can increase pressure drop, while a weak spring may delay closure. The valve should be sized from normal and minimum velocity rather than nominal pipe size alone.

Industrial Applications

Super Duplex dual plate lug check valves are used in seawater injection, desalination, offshore firewater, produced-water treatment, brine circulation, marine cooling and chloride-bearing chemical systems. They suit compact pump discharge arrangements where lower installed weight is important.

Manufacturing and Inspection

Material certificates and PMI verify the body, plates, pin and spring materials. Ferrite checks and NDT may be added according to project requirements. Dimensional inspection confirms lug drilling, face-to-face length and plate clearance. Hydrostatic shell and seat tests are followed by spring-return and plate-travel checks.