Check valve (non-return valve)

Valve allowing free flow in one direction while blocking reverse flow. Types: ball (simple, economical), disc (low inertia), spring-loaded (cracking pressure 0.3-3 bar), swing check (large diameters). Applications: pump protection, pressure retention, locking circuits. Internal leakage in closed position: ≤5 cm³/min at rated pressure. Brands: Parker, Sun Hydraulics, Bosch Rexroth, SMC.