Difference Between Silent Check Valves and Noise-Reducing (Axial Flow) Check Valves

1. Silent Check Valve

Silent check valves are primarily used in water system pipelines, typically installed at pump outlets. They consist of a valve body, disc, stem, spring, and other components.
 
Design & Operation:
 
● The valve has a short closing stroke, and the reverse flow speed during closure is low.
● The disc uses rubber soft sealing, and spring-assisted return ensures smooth, impact-free operation.
● This reduces noise and water hammer, which is why it is called a “silent check valve.”
● The valve core uses a lift-type design, making it a variant of lift check valves.
 
Installation:
 
● Mainly vertical installation.
● For valves with double-guided discs, horizontal installation is also possible.
● Large-diameter valves should preferably be installed vertically because the weight of the disc can cause uneven wear on the guide sleeve, potentially affecting sealing performance.
 

2. Noise-Reducing (Axial Flow) Check Valve

The standard name for the noise-reducing check valve is the axial flow check valve, as per:
● GB/T 21387-2008: Axial flow check valve (national standard)
● JB/T 13460-2018: LNG axial flow check valve (Ministry of Machinery standard)
 
Applications:
 
● Installed at pump or compressor outlets to prevent backflow.
● Features include high flow capacity, low flow resistance, smooth flow, reliable sealing, and closure without water hammer.
● Widely used in long-distance oil & gas pipelines, nuclear power main water supply, large ethylene plants’ compressors, and large pump systems.
 
Structure & Design:
 
● Composed of valve body, seat, disc, spring, guide rod, guide sleeve, and flow diverter (deflector).
● Flow surfaces (body cavity, diverter, disc) are streamlined, with a rounded front and tapered rear, promoting laminar flow with minimal turbulence.
 
The valve body cavity is of Venturi design, gradually narrowing and expanding the flow path, which:
● Minimizes vortex formation
● Reduces pressure loss
● Maintains stable flow
● Prevents cavitation
● Produces low noise
 

Structural Types & Installation:

● Available as disc type, annular disc type, and sleeve type.
● Can be installed horizontally or vertically.
● For large-diameter horizontal installations, the guide rod should use a double-guided structure to avoid excessive one-sided wear of the guide sleeve and rod caused by the disc weight, which could degrade sealing and increase closure noise.