The slow closing check valve effectively prevents water hammer phenomenon and ensures system safety by optimizing the opening and closing process, controlling the flow velocity of the medium. Its working solution needs to be comprehensively implemented from the aspects of principle design, fault handling, maintenance, installation and commissioning, as follows:
1、 Working principle and design optimization
Slow closing mechanism design: By adjusting the flow velocity of the medium through components such as needle valves, ball valves, and one-way valves, a buffering process is formed when the valve disc is closed. For example, when the water pump is turned off, the medium behind the valve enters the upper chamber of the diaphragm through the ball valve. Due to the check action of the one-way valve, the medium cannot enter the inlet end. At the same time, the medium in the lower chamber of the diaphragm is slowly discharged under the throttling effect, thereby slowing down the closing speed of the valve disc and preventing water hammer phenomenon.
Multi stage speed regulation: Some slow closing check valves have variable frequency speed regulation function, which can be divided into multiple stages to set the opening and closing speed, adapting to different working conditions. For example, during the fast start phase, the water pump responds quickly to start, while during the slow stop phase, the shutdown time is extended to eliminate water hammer.
Intelligent hydraulic control system: The hydraulic control slow closing check butterfly valve achieves automatic slow opening and closing through the intelligent hydraulic control system, combined with fast and slow closing functions (such as fast closing time of 0.5-2 seconds and slow closing time of 3-10 seconds), effectively eliminating water hammer impact and protecting the pump station pipeline and water pump unit.
2、 Common faults and solutions
Valve disc cannot be fully closed:
Reason: blockage of needle valve pipeline system, excessive insertion of piston rod, wear of valve disc and seat sealing surface, etc.
Solution: Clean the needle valve pipeline or adjust the needle valve opening; Adjust the adjusting rod on the cylinder to shorten the insertion length of the piston rod; Repair or replace the sealing surface.
Poor sealing:
Reason: Wear of sealing surface, spring failure, impurities jamming valve disc, etc.
Solution: Repair or replace the sealing surface; Replace the failed spring; Clean the impurities between the valve disc and the valve seat.
Water hammer phenomenon:
Reason: The valve disc closes too quickly, causing a sudden increase in medium pressure.
Solution: Control the closing speed of the valve disc by adjusting the opening of the ball valve or needle valve; Adopt check valves with slow closing function, such as hydraulic control slow closing check butterfly valves.
3、 Maintenance suggestions
Regular inspection: Regularly check the sealing performance, opening and closing flexibility, and wear of various components of the valve.
Cleaning and maintenance: Clean the oil stains and impurities on the valve cavity and sealing surface to prevent blockage and wear.
Lubrication treatment: Lubricate moving parts such as valve stems to reduce friction and wear.
Replace vulnerable parts: Timely replace worn seals, springs, and other vulnerable parts to ensure the normal operation of the valve.
4、 Key points for installation and debugging
Horizontal installation: Slow closing check valves should generally be installed horizontally to ensure smooth medium flow and flexible valve opening and closing.
Flow restriction: During installation, it is necessary to ensure that the flow direction of the medium is consistent with the direction indicated by the valve arrow to prevent damage to the valve caused by reverse flow.
Debugging opening: By adjusting the opening of components such as needle valves and ball valves, the opening and closing speed of the valve disc can be controlled to adapt to different working conditions.
Pressure test: Conduct a pressure test after installation to ensure that the valve is working properly at rated pressure and there is no leakage.