Check Valves — Swing, Lift & Dual Plate

What is a Check Valve?

A check valve opens under forward flow and closes by gravity, spring force or back-pressure when flow stops, protecting pumps, compressors and systems from reverse flow. Swing check valves hinge a disc off the seat and suit larger lines with steady flow. Lift (piston) check valves move a disc or ball vertically and are common in small forged valves. Dual plate check valves use two spring-loaded half-plates in a short wafer body, saving weight and space and closing fast to reduce water hammer.

Key features

• Swing check: API 594 Type B or ASME B16.34, bolted cover
• Dual plate wafer, lug and double-flanged: API 594 Type A
• Lift / piston and ball check: API 602 forged, NPS ¼–4
• Spring-assisted closure to limit slam and water hammer
• Horizontal or vertical (upward flow) installation per design

Specification

Applications

• Pump and compressor discharge
• Cooling water and firewater systems
• Steam and condensate lines
• Hydrocarbon process and pipeline service
• Seawater and desalination (duplex)

Swing check vs dual plate check valve

A swing check has a single hinged disc in a full-size body; it has low pressure drop but is long and heavy and can slam on sudden flow reversal. A dual plate check (API 594 Type A) uses two spring-loaded half-discs in a short wafer or lug body, so it is lighter, fits between flanges and closes faster, which reduces water hammer. Dual plate is common on pump discharge and large water lines.