In fluid power systems, the performance and reliability of the entire operation often hinge on components that are small in size but significant in function. Among these, the check valve stands out as a fundamental, yet frequently overlooked element. Responsible for ensuring unidirectional flow, check valves play a vital role in protecting system integrity, maintaining pressure and preventing costly backflow and downtime. Despite their simplicity, their impact on system performance is profound.
Understanding check valves
A check valve is a mechanical device designed to allow fluid, whether liquid or gas, to flow in only one direction. Internally, the valve contains a spring-loaded poppet or disc that automatically responds to pressure changes, opening to permit forward flow and closing to prevent reverse flow. This passive operation requires no manual intervention, electronic controls or external power, making check valves reliable and maintenance-friendly components. The primary functions of check valves include:
• Preventing contamination and backflow within the system.
• Protecting upstream equipment from pressure surges and spikes.
• Maintaining system pressure during pump shutdowns.
• Avoiding damage to compressors, pumps and filters caused by reverse flow.
Applications across industries
Check valves are integral to a wide array of industries that rely on fluid systems. Their use spans aerospace, agriculture, chemical processing, energy, food and beverage, HVAC and industrial manufacturing. They are specified in numerous applications, including:
• Hydraulic return lines to prevent pressure shocks.
• Cooling systems to ensure coolant flows in the correct direction.
• Fuel and gas lines to eliminate leak paths and ensuring operational safety.
• Compressed air systems to reduce air loss during shutdown.
Design considerations for optimal performance
Selecting the appropriate check valve requires a thorough understanding of the system’s operational parameters and demands. Engineers must consider several critical factors to ensure the valve functions seamlessly within the fluid network.
Seat type
Check valves come with either hard or soft seats, each suited to different operational conditions. Hard seats utilise metal-to-metal sealing surfaces, offering exceptional durability and longevity. Ideal for high-pressure and high-temperature environments, hard seats provide consistent sealing performance over extended periods.
Soft seats feature elastomeric seals that offer tighter shut-off and superior leak resistance. These are preferred in applications requiring minimal leakage, such as fuel systems and medical gas lines. The choice between hard seats and soft seats depends on the fluid type, pressure, temperature and leakage tolerance.
Cracking pressure
Cracking pressure is the minimum upstream pressure needed to overcome the spring force and open the valve. This parameter is crucial for ensuring the valve operates correctly under varying system pressures. A low cracking pressure might permit unwanted backflow or seepage. A high cracking pressure could restrict flow and reduce system efficiency. Parker Hannifin’s quick coupling division offers valves with a range of standard and customisable cracking pressures, allowing engineers to tailor valve responsiveness to specific applications.
Pressure drop
While check valves allow flow in one direction, internal components such as the poppet and spring create resistance, resulting in pressure drop across the valve.
Excessive pressure drop can reduce overall system efficiency. Parker Hannifin designs valves to minimise pressure loss, balancing sealing integrity with flow capacity. Understanding and managing pressure drop is essential for maintaining system performance.
Orifice design
Some check valves incorporate a precision-drilled orifice in the poppet permitting a controlled, limited flow, even when the valve is closed. This feature supports applications requiring minimal circulation to prevent fluid stagnation or allow pressure equalisation. It enhances system flexibility by enabling a small, steady flow during off cycles.
Parker Hannifin’s approach to check valve engineering
At Parker Hannifin’s Quick Coupling Division, check valves are engineered with precision and customisation to meet diverse industry requirements. Their approach includes:
Stringent testing: Each valve undergoes rigorous in-house testing for flow, leakage and durability to ensure reliable performance in demanding conditions, including vibration and thermal cycling.
Custom engineering: Parker Hannifin’s engineers collaborate with clients to modify valve dimensions, adjust cracking pressures and develop bespoke solutions tailored to specific needs.
Integration with couplings: Many valves are designed to integrate seamlessly with Parker Hannifin’s coupling systems, reducing potential leak points, simplifying assembly and enhancing efficiency.
Despite their small size, check valves are indispensable components that quietly ensure system integrity. Properly selected check valves enable other components to function without interruption, directly impacting system uptime and efficiency. Parker Hannifin remains at the forefront of delivering advanced sealing solutions that meet rigorous industry standards and support the transition to cleaner, more efficient technologies.
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| Fax: | +27 11 392 7213 |
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| www: | www.parker.com/za |
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