A check valve prevents backflow by automatically closing when the pressure downstream exceeds the pressure upstream.
Here's a breakdown of how it works:
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Normal Flow: When fluid flows in the intended direction (upstream to downstream), the pressure of the fluid opens the valve. This could be by pushing a hinged clapper, lifting a poppet, or deforming a flexible membrane, depending on the specific check valve design.
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Backflow Attempt: If the pressure downstream becomes higher than the pressure upstream (indicating a potential backflow situation), the check valve mechanism is forced closed.
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Sealing Mechanism:
- Clapper Type: Many check valves use a hinged clapper, often spring-loaded. If backflow occurs, the downstream pressure, assisted by the spring, presses the clapper firmly against a valve seat (often made of rubber or another sealing material). This creates a watertight seal, blocking the reverse flow.
- Poppet Type: In poppet check valves, reverse pressure forces the poppet back against its seat, creating a seal.
- Other Types: Other designs, such as swing check valves or ball check valves, similarly rely on reverse pressure to force a sealing element against an orifice, preventing backflow.
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Automatic Operation: The entire process is automatic and relies solely on pressure differentials. No external control or human intervention is required.
In essence, a check valve acts as a one-way door for fluids. It allows flow in one direction but slams shut to prevent flow in the opposite direction whenever back pressure is detected. This protects equipment and prevents contamination in piping systems.
