• The Structure, Working Principle & Selection of Heavy Hammer Check Valves

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The Structure, Working Principle & Selection of Heavy Hammer Check Valves

  • May 16, 2022
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Check valves are widely used in industrial factories. Lift check valves, swing check valves, butterfly check valves and diaphragm check valves have their advantages and disadvantages, which should be chosen based on the specific conditions. The heavy hammer check valve is one of the main devices in the ventilation system of the nuclear power plant. It mainly protects the fan. It has the characteristics of good sealing, sensitive and reliable opening and closing. In the normal operation of the system, the sensitivity of the valve directly affects the partial energy loss of the medium in the air duct and the flow rate of the air supply system.
 
1.1 Types and structure of heavy hammer check valves
The heavy hammer check valve mainly has three structural forms: the rectangular single-blade check valve, the rectangular double-blade check valve and the circular check valve.

The rectangular single-blade check valve consists of a valve body, a single assembled blade, a heavy hammer component and a shaft. The rectangular multi-blade check valve is divided into ordinary multi-blade check valves and transversely reinforced multi-blade check valves. It is composed of valve bodies, several assemble blades, heavy hammer parts and shafts. Compared with the single blade check valve, when the size of the double blade check valve is greater than 1250mm, a reinforcing plate needs to be set in the middle of the valve body to increase the stability of the valve, which is used to increase the stability of the valve.
 
The circular check valve is mainly composed of valve bodies, heavy hammer components, shafts and gears. In addition, there are bearings, arms, backing plates, connecting pairs, pressing plates, threaded cylindrical pins, positioning screws and nuts. Regardless of the structure of the check valve, a switch pusher and a limit switch can be installed according to the actual requirements of the site. The functions of the main components are as follows:
(1) Valve body: The load-bearing parts are used to support all parts of the valve body such as shafts and vanes, and realize the connection with the air duct.
(2) Blades: The opening and closing parts drive the sealing ring through the rotation and realize the opening and closing of the valve.
(3) Shafts: Connect the vane and the weight assembly, and transmit the torque during the valve action.
(4) Heavy hammer assembly: As the power source in the valve's closing process, the force required to close the valve is applied.
(5) Sealing rings: After the valve is completely closed, the sealing function is realized to ensure that the leakage amount is within the allowable range of the system.
(6) Limit switches: Transmit open and close signals, display the valve's closed or open status, and confirm the valve position.
 
1.2 Working principles
A check valve refers to the valve whose opening and closing parts automatically prevent the reverse flow of the medium by means of the force of the medium. The check valve is also called a one-way valve, which belongs to automatic valves. The hammer check valve is generally installed at the outlet of the fan or air conditioner. When the fan starts running, positive pressure will be formed in front of the valve in the air duct. When the positive pressure is greater than the opening pressure difference of the valve (generally 100 to 200Pa), the valve will be opened against the closing torque. At this time, the opening angle of the blade will change with the change of the wind speed in the pipeline. When the wind speed in the pipeline is fast, the opening angle of the blade will be big and vice versa. The valve is closed under the gravity of the heavy hammer and the blade with or without a reverse pressure difference between the front and rear of the valve of the air duct, cutting off the medium’s circulation path in the air duct, preventing the system from being backflowed, and realizing the function of not flowing back.
 
1.3 The selection of heavy hammer check valves
When selecting a check valve, it is generally based on a qualitative evaluation of the closing speed and its closing speed characteristics required for minimum impact pressure or no impact closing, and then select the required type and size of the check valve. This selection method is not necessarily the most accurate, but the desired results can be obtained in most cases according to work experience.
 
When selecting a heavy hammer check valve, determine the required model for the fan or air conditioner according to the system first, including parameters such as the power of the fan or air conditioner, outlet wind speed, etc., and then the closing speed of the valve should be consistent with the flow rate of the medium at the outlet of the fan or air conditioner. Then, determine the structure and size of the heavy hammer check valve according to these parameters to ensure that the valve can be closed smoothly during the stalling of the fan or air conditioner to prevent great impacts.