Check valve refers to the valve that automatically opens and closes the valve flap relying on the flow of the medium itself to prevent the backflow of the medium, also known as check valve, check valve, counterflow valve, back pressure valve or isolation valve. The following is a detailed introduction to the check valve:
1. Function
The main functions of the check valve are:
Prevent media backflow.
Prevent pump and drive motor from reversing.
Prevent leakage of container media.
The check valve can also be used to feed the auxiliary system where the pressure may rise above the system pressure.
Second, the working principle
Check valves belong to automatic valves, and the opening and closing parts are automatically opened or closed by the force of the medium flow. Under the action of fluid pressure flowing in one direction, the valve disc opens; When the fluid flows in the opposite direction, the pressure of the fluid is combined with the body weight of the valve disc, which acts on the seat to cut off the flow.
Iii. Classification
Check valves can be classified according to different criteria, the following are several main classification methods:
Divided by structure:
Lift check valve: The disc slides along the vertical center line of the body and can only be installed on horizontal pipes. When the medium is along the flow, the valve disc is opened by the thrust of the medium. When the medium stops flowing, the valve disc falls on the seat by its own weight to prevent the counterflow of the medium.
Swing check valve: the disc is disc-shaped and rotates around the rotating shaft of the seat channel. The inner channel is streamlined, and the flow resistance is smaller than that of the lift check valve, which is suitable for large diameter occasions with low flow rate and no constant change of flow.
Butterfly check valve: the disc rotates around the pin in the seat, the structure is simple, the sealing is poor, and it can only be installed on the horizontal pipeline.
Pipe type check valve: the valve disc slides along the center line of the valve body, small size, light weight, good processing ability, but the fluid resistance coefficient is slightly larger than the swing type check valve.
Pressure type check valve: with a lift type check valve and globe valve or Angle valve combined function, usually used as boiler feed water and steam cut-off valve.
According to the medium: through the selection of different materials, the check valve can be applied to water, steam, oil, nitric acid, acetic acid, strong oxidizing media and uric acid and other media.
Iv. Application scenarios
Check valves are mainly used on pipelines with one-way flow of media to prevent accidents. For example:
In the pump water supply system, the function of the check valve is to prevent the impact of high pressure water backflow on the pump impeller.
In hot water systems, check valves are used to prevent hot water from flowing back into the pipe to avoid burning the pipe or injuring people.
5. Installation and maintenance
Installation:
When installing, pay attention to the direction of the medium flow should be consistent with the direction of the arrow marked on the valve body.
The lifting vertical flap check valve should be installed on the vertical pipe, and the lifting horizontal flap check valve should be installed on the horizontal pipe.
Large check valves should be supported independently so that they are not affected by the pressure generated by the piping system.
Maintenance:
Check check valve seal performance and working status regularly.
Clean up the impurities and dirt inside the valve to keep the valve clean and smooth.
If the valve is found to be damaged or invalid, it should be replaced or repaired in time.
To sum up, the check valve is an important pipeline equipment, with a variety of functions to prevent media backflow, protect the pump and drive the motor reversal. When selecting, installing, and maintaining check valves, select and operate them based on specific application scenarios and requirements.