Swing Check vs Dual Plate Check Valve

Swing check and dual plate check valves both prevent backflow, but they differ significantly in closure speed, weight, and water hammer risk. Choosing the right type depends on the application, installation space, and how critical fast closure is.

Feature	Swing Check	Dual Plate (Wafer)
Disc configuration	Single full-bore disc	Two semicircular plates
Closure mechanism	Gravity + reverse flow	Spring-assisted + reverse flow
Closure speed	Slow (long arc)	Fast (short arc, spring force)
Water hammer risk	High in large sizes	Low
Weight (typical 10”)	~180 kg	~25 kg
Body standard	BS 1868 (flanged)	API 594 (wafer/lug)

Design Differences

A swing check valve has a full-bore disc that pivots on a hinge pin at the top of the body. The disc swings fully open against a stop and swings shut when flow reverses. The long arc of travel means slower closure.

A dual plate (double-disc) check valve has two D-shaped plates mounted on a central hinge pin with torsion springs. The plates open with forward flow and snap shut when flow stops or reverses. The short travel distance (approximately 35 degrees vs 70+ degrees for swing) enables rapid closure.

Full Comparison

Parameter	Swing Check	Dual Plate (Wafer)
Disc configuration	Single full-bore disc	Two semicircular plates
Closure mechanism	Gravity + reverse flow	Spring-assisted + reverse flow
Closure speed	Slow (long arc)	Fast (short arc, spring force)
Water hammer risk	High in large sizes	Low
Pressure drop	Low	Slightly higher than swing
Face-to-face length	Full body length (flanged)	Wafer (fits between flanges)
Weight (typical 10”)	~180 kg	~25 kg
Installation orientation	Horizontal only	Horizontal or vertical (flow upward)
Body standard	BS 1868 (flanged)	API 594 (wafer/lug)
Pressure rating	ASME B16.34 Class 150-2500	ASME B16.34 Class 150-2500
Max size (common)	60”+	48”
Cost	Higher (more material, heavier)	Lower (compact, less material)
Maintenance	Body must be removed from line	Can be removed without disturbing pipe

Water Hammer Performance

Water hammer is the primary reason dual plate check valves have replaced swing checks in many applications. The pressure surge from a slamming swing check in a 16” pump discharge line can exceed 20 bar. A dual plate valve in the same service typically generates less than 2 bar surge because the spring-loaded plates close before significant reverse velocity develops.

For reciprocating compressor discharge and pump stations with frequent start/stop cycles, dual plate check valves are the standard recommendation.

When Swing Check Is Still Preferred

Swing checks remain the better choice for dirty or viscous services where debris could jam the dual plate springs or hinge mechanism. They are also preferred for low-velocity applications where the dual plate springs may prevent full opening, causing excessive pressure drop.

Large-diameter pipeline applications (36” and above) sometimes use swing checks with external counterweights and dampers for controlled closure.

Common Mistake

Installing a dual plate wafer check valve with the flow arrow reversed. Unlike swing checks (where reverse installation is obvious), a wafer check installed backward may still appear to function but will not seal properly on reverse flow.

Both valve types use common body materials such as ASTM A216 WCB (carbon steel) and A351 CF8M (316 stainless).

Read the full guide to valve types