Check Valve Selection: Swing, Lift, Dual-Plate, and Nozzle Types

Check valves prevent reverse flow automatically. This guide covers swing, lift, dual-plate, and nozzle check valve designs, their advantages, and selection criteria per API 594 and API 6D.

Swing check valves use a hinged disc that swings open with forward flow and closes under gravity and backflow. The disc is not spring-loaded, so closure depends on flow reversal.

Advantages: Low pressure drop. Simple design. Suitable for water and wastewater. Sizes 2 to 60 inch. Cost-effective for large sizes.

Disadvantages: Slow closure (disc must travel full arc). Water hammer risk in rapid flow reversal. Not suitable for pulsating flow. Requires horizontal installation (disc hinge at top).

Lift check valves use a disc or piston that lifts vertically with forward flow. The disc is guided by a stem or cage. Closure is faster than swing check because the disc travels a shorter distance.

Advantages: Fast closure. Suitable for high pressure. Can be installed horizontally or vertically (depending on design). Good for pulsating flow.

Disadvantages: Higher pressure drop than swing check (flow is redirected through seat). Not suitable for viscous fluids. More expensive than swing check.

Dual-plate (wafer) check valves use two spring-loaded plates that open with forward flow and snap closed on flow reversal. The wafer design installs between flanges (sandwich type).

Advantages: Very fast closure (spring-loaded). Compact and lightweight. Low cost (sandwich design). Suitable for horizontal or vertical installation. Sizes 2 to 48 inch.

Disadvantages: Higher pressure drop than swing check. Spring fatigue in high-cycle service. Not suitable for abrasive slurries (plate erosion). Pressure limited to Class 600.

Nozzle check valves use a streamlined nozzle and spring-loaded poppet. The nozzle-shaped inlet reduces pressure drop and turbulence. The spring provides consistent closure force.

Advantages: Lowest pressure drop of all check valve types. Very fast closure. No water hammer. Suitable for high-velocity and pulsating flow. Compact design.

Disadvantages: Highest cost. Limited to smaller sizes (typically 12 inch and below). Spring selection critical for proper operation. Not suitable for solids-laden fluids.

1. Closure speed: For rapid flow reversal (pump stoppage), use dual-plate or nozzle check. Swing check is too slow for most pump applications.

2. Pressure drop: For low-pressure systems, swing check or nozzle check. For high-pressure systems, lift check or dual-plate.

3. Fluid type: For clean fluids, any type. For slurries or wastewater, swing check (no small passages to clog). For viscous fluids, swing check (no close tolerances).

4. Installation orientation: Horizontal only: swing check. Horizontal or vertical: lift check, dual-plate, nozzle check.

No. Check valves are designed to prevent reverse flow only. They cannot be manually closed and do not provide reliable shutoff. For isolation, use a gate, ball, or butterfly valve in series with the check valve.

Slamming occurs when flow reverses before the valve closes. The disc slams against the seat, causing noise, vibration, and potential damage. To prevent slamming: use spring-loaded check valves (dual-plate or nozzle) for fast closure. Add a surge suppressor or air chamber to absorb pressure transients.

Ted Wang

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