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Check valve slow closing structural design
**Abstract:**
To address the issue of water hammer and pressure surges caused by the rapid closure of conventional check valves, this paper proposes an improved design that incorporates a slow-closing auxiliary valve. The enhanced check valve offers smooth opening and closing, significantly reducing the risk of water hammer. Check valves are primarily used to prevent backflow in pipeline systems, ensuring that pumps and motors do not reverse and that media in containers are properly controlled. Common types include swing check valves, where the flap rotates around the valve body, and lift check valves, where the flap moves vertically along the centerline. However, these traditional designs close abruptly when backflow occurs, causing a sudden pressure increase at the inlet side, which can lead to severe water hammer damage. As a result, standard check valves are typically manufactured in sizes ranging from 50 to 500 mm.
To mitigate water hammer effects and extend the application range of check valves, this study introduces a slow-closing auxiliary valve based on existing designs. For the swing check valve, a secondary relief valve is installed on the side or both sides of the main flap using threaded connections. During normal flow, the main valve opens, and the medium pressure pushes open the auxiliary valve, allowing fluid to pass through its orifice and relieve pressure on the inlet side. When backflow occurs, the main flap closes quickly, while the auxiliary valve gradually closes via a buffer cylinder, reducing the impact of pressure surges.
Similarly, for the lift check valve, a slow-closing mechanism is added between the valve flap and the bracket. A pad ring increases the flap’s lift height, and a rubber seal is used between the buffer piston and cylinder. This setup allows for gradual closure during backflow, minimizing pressure fluctuations. Experimental tests were conducted using a calibrated pressure gauge and oscilloscope to record pressure changes. Results showed that a standard check valve without the auxiliary valve experienced a water hammer pressure increase of 0.53 MPa, while the improved version with the slow-closing auxiliary valve only increased by 0.04 MPa.
The proposed design improves performance, enhances reliability, and simplifies maintenance. The auxiliary valve can be repaired or replaced without affecting the main valve’s operation. Overall, the structure is compact, easy to manufacture, and suitable for a wider range of applications.
References:
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