A non-return valve (NRV), also known as a check valve, is a safety device designed to allow fluid flow in only one direction while preventing reverse flow in the pipeline system. It operates automatically using system pressure and does not require manual operation.
Inside the valve, the check disc moves against spring force when fluid flows in the correct direction. If the flow reverses or pressure drops, the spring pushes the disc back onto its seat, instantly blocking reverse flow and protecting pumps, compressors, boilers, and piping systems from damage.
Non-return valves are widely used in marine engineering systems such as fuel oil lines, cooling water systems, bilge systems, ballast systems, air compressors, fire lines, and pump discharge pipelines. They help maintain system pressure, prevent contamination, avoid backflow damage, and improve operational safety onboard ships.
Proper maintenance includes checking for leakage, spring wear, sticking discs, corrosion, and seat damage. Faulty NRVs can cause pressure loss, reverse rotation of pumps, water hammer effects, and system instability if not maintained correctly.
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