Industrial check valves

Swing check valves use a full-diameter disc that swings open on a top-mounted hinge, offering minimal pressure drop but requiring sufficient flow velocity to hold the disc fully open—suitable for large diameter (DN 100-1200) applications with steady flow like African water mains. Dual-plate (wafer) check valves feature two spring-loaded semi-circular discs that open against centering springs, providing faster closure to prevent slam, compact installation between flanges, and operation at any orientation including vertical downflow. For African mining applications with pulsating pump flow or systems experiencing frequent power interruptions, dual-plate checks reduce water hammer damage. Swing checks suit steady-state municipal water service; dual-plate checks excel in industrial applications with variable flow conditions.

Water hammer (pressure surge from rapid flow deceleration) damages piping, valves, and pumps during check valve closure. Prevention strategies: (1) Use non-slam check valves (dual-plate, tilting disc, or dampered swing checks) that close before reverse flow develops significant velocity, (2) Install external weights or springs on swing checks to accelerate closure in low-velocity applications, (3) Specify dashpot-dampened checks that control closure speed hydraulically, (4) Size check valves properly—oversizing increases closure time and slam intensity, (5) Consider silent check valves with internal springs for instant closure. For African water pumping stations experiencing pump trip events from unstable power grids, silent check valves eliminate destructive pressure surges. For South African slurry pipelines, dual-plate checks withstand abrasive service while preventing reverse flow slam when pumps stop.

Installation orientation critically affects check valve performance: (1) Swing check valves require horizontal installation (flow horizontal, disc swings vertically) or vertical upflow; NEVER install swing checks in vertical downflow where gravity holds the disc open, (2) Dual-plate checks install in any orientation (horizontal, vertical upflow, vertical downflow) due to spring-loaded closure independent of gravity, (3) Lift check valves MUST install in vertical upflow or horizontal pipelines with flow under the seat, (4) Tilting disc checks suit horizontal or vertical upflow installations. For African mining dewatering systems with vertical discharge pipes, specify dual-plate or piston check valves. For Nigerian offshore platform risers with vertical upflow, swing checks or dual-plate designs both function correctly. Always verify manufacturer orientation limits—incorrect installation causes premature wear, chattering, or complete failure to close.

Slurry service (abrasive solids in suspension) requires erosion-resistant materials to achieve acceptable service life: (1) Ni-Hard (martensitic white cast iron) bodies and discs for copper, gold, and iron ore slurries—hardness HRC 58-64 provides 5-10× wear life versus carbon steel, (2) Rubber-lined bodies (natural rubber, polyurethane) with rubber-faced discs for less abrasive services, offering impact resistance and conformable sealing despite wear, (3) High-chrome white iron for extreme abrasion at lower cost than Ni-Hard, (4) Stellite 6 hardfacing on seating surfaces for hybrid designs combining metal strength with wear resistance. For Zambian copper tailings, South African platinum slurry, or DRC cobalt processing, full Ni-Hard construction typically provides best total cost of ownership. For less severe service, rubber-lined checks reduce initial costs. Consult slurry velocity, particle size, and pH to optimize material selection—our mining valve specialists assist with wear life predictions based on African field experience.

Check valves are often mischaracterized as “maintenance-free,” but inspection and servicing extend life and prevent failures: (1) Inspect for disc wear, seat damage, and hinge pin condition every 12-24 months depending on service severity, (2) Clean debris accumulation (scale, weld slag, pipe dope) that prevents full disc opening or sealing, (3) Verify spring function in dual-plate checks—spring fatigue or corrosion causes premature closure or chattering, (4) Re-lap or replace seats showing wire-drawing or erosion damage, (5) Lubricate hinge pins in swing checks operating in abrasive environments. For African slurry service, 3-6 month inspection intervals identify wear before catastrophic failure. For clean water service, annual inspections suffice. Bolted-cover designs enable field service without removing the valve from the line—critical advantage in African installations where valve isolation is difficult. Silent check valves with removable internals simplify maintenance compared to welded-cap swing checks requiring hot work permits.