Marine Check Valve
Marine check valves—also known as non-return valves or one-way valves—are critical components in shipboard piping systems. Their primary function is simple yet vital: allow fluid or gas to flow in only one direction while preventing dangerous backflow. In the demanding marine environment, where saltwater corrosion, vibration, and extreme conditions are constant challenges, choosing the right check valve is essential for system reliability and safety.
Overview
Key Types of Marine Check Valves
Marine check valves come in several structural configurations, each suited to specific applications. The two fundamental movement modes are lift type and swing type.
Lift Check Valves
Lift check valves feature a disc that moves vertically along the valve centerline. The structure resembles a globe valve but without the valve stem. Key characteristics include:
Installation requirement: Must be installed on horizontal pipes only, following the "low inlet, high outlet" principle
Flow direction: Medium flows in from the lower (inlet) side and exits from the upper (outlet) side
Best for: Small to medium pipe diameters with clean media
The flow path in lift check valves is somewhat tortuous, creating higher flow resistance than swing types, but they offer excellent sealing performance.
Swing Check Valves
Swing check valves have a disc that pivots around a hinge or shaft, opening and closing like a door. This design offers several advantages:
Flexible installation: Can be installed on both horizontal and vertical pipes
Lower flow resistance: Smoother flow path than lift types
Reduced water hammer: Slower closing action minimizes pressure surges
Swing check valves are widely used in bilge and ballast systems, water treatment, and ventilation/overboard discharge lines.
Wafer/Plate Check Valves
Wafer-type check valves (also called thin plate check valves) are characterized by their ultra-compact face-to-face dimensions. They fit snugly between pipe flanges, making them ideal for space-constrained installations. Standard CB/T 3819-2013 governs this type in China, covering applications in freshwater, seawater, and inert gas systems.
Dual Plate Check Valves
Dual plate (double disc) check valves feature two semi-circular discs that rotate around a common pivot. Benefits include:
Fast closing speed with spring-assisted action
Minimal flow resistance
Excellent water hammer prevention
These are commonly specified for large-diameter, high-flow systems where quick response is critical.
Suction Check Valves
CB/T 3478-2025 covers flanged suction check valves, used at pump inlets. The 2025 revision introduces:
Stainless steel (CF3M) as a new material option for improved corrosion resistance-
Dual flange standards for better international compatibility
Both soft-seal (NBR) and hard-seal (metal) options, depending on media and service frequency
