Closure Mechanism & Slam Prevention
Dual-plate check valves employ two semicircular discs mounted on a central hinge pin with centering torsion springs that actively push the discs toward the closed position. During forward flow, fluid pressure overcomes spring force and folds the discs back parallel to flow direction, creating a streamlined flow path. When forward flow decreases, spring force immediately begins closing the discs—closure initiates before flow reversal develops, unlike swing checks that rely on reverse flow for complete seating.
This spring-assisted closure mechanism delivers 0.1-0.5 second closure time compared to 1-3 seconds for swing checks, preventing water hammer through “non-slam” operation. The discs close gently into the seat before significant reverse velocity develops, eliminating the violent impact and pressure surge characteristic of swing check slam events. For African water pumping stations experiencing frequent power failures or mining operations with unstable electrical supplies, this rapid non-slam closure protects pumps, eliminates piping fatigue damage, and extends system service life from years to decades.
Installation Orientation Requirements
Unlike gravity-dependent swing checks requiring horizontal or vertical-upflow installation, dual-plate check valves install successfully in any orientation: horizontal, vertical upflow, vertical downflow, or inclined angles. Spring force provides closure regardless of gravity direction, eliminating installation restrictions and providing maximum flexibility for complex African piping systems.
Available Configurations: (1) Wafer-style between standard pipe flanges (most compact, requires both flanges for retention), (2) Lug-style with threaded holes for independent flange bolting (enables single-flange removal and deadend service), (3) Double-flanged with integral flanges (eliminates separate gaskets, simplifies installation). For offshore platforms and weight-critical applications, wafer style minimizes installation weight; for African maintenance scenarios requiring single-valve removal without system shutdown, lug style provides superior serviceability.
Cracking Pressure & Pressure Drop
Cracking pressure for dual-plate checks ranges 0.5-1.5 psi depending on valve size and spring selection—lower than lift checks (2-5 psi) but higher than swing checks (0.25-0.5 psi). This moderate cracking pressure ensures positive closure while minimizing pump load penalty. Pressure drop when fully open is 2-5 psi—higher than swing checks (0.2-0.5 psi) due to flow disturbance from the central hinge pin and disc edges, but dramatically lower than lift checks (5-10 psi) or globe valves (15-30 psi).
For African water utilities where energy costs dominate lifecycle expenses, this pressure drop penalty (1.5-2 psi higher than swing checks) must be balanced against benefits: compact installation, water hammer elimination, and any-orientation capability. In many applications, the 2-5% pumping energy increase is justified by eliminating water hammer damage that destroys piping, valves, and equipment costing 100-1000× the energy penalty.