How do check valves work?-Yantai Valtone Valve Co., Ltd.

How do check valves work?

Jul 15,2022

Check valve is a kind of relying on the direction of media flow automatically open and close the valve to stop the medium backflow valve, its working principle is mainly based on the fluid pressure difference and the valve's own gravity (or spring force) of the interaction of the specific principles and different types of check valve operating characteristics are as follows:
First, the core working principle: fluid pressure drive and automatic opening and closing
Positive flow when open
When the medium in the specified direction (positive) flow, fluid pressure will push the valve flap up (or open), the medium through the valve. At this time, the fluid pressure to overcome the gravity of the valve (or spring resistance), so that the valve flap and valve seat separation, the formation of the flow channel.
Reverse flow closed
When the medium tries to reverse flow, the fluid pressure will valve flap pressure on the valve seat, while the valve flap itself gravity (or spring force) to further assist in sealing, to prevent the medium backflow. At this time, the valve flap and the valve seat close to form a sealing surface, cut off the reverse flow path.
Second, the working principle of different types of check valve difference
According to the structure of the form, check valve can be divided into a variety of types, its working principle in the details of the difference:
1. swing check valve
Structural features: the valve flap rotates around the pin outside the valve seat, similar to the ‘swing gate’.
Working principle:
When flowing in the forward direction, the medium pushes the valve flap to rotate upward around the pin, detaching from the valve seat, and the channel opens.
Reverse flow, the valve flap in the fluid pressure and its own gravity, downward rotation and compression of the valve seat, to achieve sealing.
Applicable scene: large diameter pipeline, water flow speed change is not occasions (such as water supply and drainage, municipal pipelines).
2. lift check valve
Structural features: valve flap along the centre axis of the valve seat to do lifting movement, similar to the ‘piston’.
Working principle:
Forward flow, the medium pushes the valve flap to move upward, leaving the valve seat, the medium through.
Reverse flow, the valve flap in the fluid pressure and gravity, back down and press the valve seat to prevent reverse flow.
Variant type:
Vertical lift check valve: valve flap vertical lift, vertical flow of media (such as pump outlet).
Horizontal lift check valve: valve flap horizontal lift, the medium flows horizontally (such as pipeline in the middle).
Applicable scenes: small and medium-sized pipe diameter, the higher requirements for sealing occasions (such as chemical pipelines, hydraulic systems).
3. butterfly check valve
Structural features: the valve flap is disc-shaped, rotating around the axis of the valve body (similar to the butterfly valve).
Working principle:
Forward flow, the medium pushes the valve flap to rotate to the full open position, the channel is open.
Reverse flow, the valve flap in the fluid pressure under the action of rapid rotation closed, fit the valve seat seal.
Advantages: simple structure, small size, low flow resistance.
Applicable scenes: large diameter pipeline, low pressure fluid system (such as sewage treatment, heating pipe network).
4. Diaphragm check valve
Structural features: using the elastic diaphragm as the valve flap, the diaphragm and the valve seat fit to achieve the seal.
Working principle:
Forward flow, the medium top up the diaphragm, diaphragm deformation to open the channel.
Reverse flow, the diaphragm in the fluid pressure against the valve seat, to prevent the media backflow.
Advantages: good sealing, no wear and tear, suitable for corrosive media.
Applicable scene: food, medicine, chemical and other industries with high requirements for hygiene or anti-corrosion.
5. spring loaded check valve
Structural features: valve flap is loaded by spring to enhance the sealing when closing.
Working principle:
Forward flow, the medium pressure to overcome the spring force, pushing the valve open.
Reverse flow, the spring force and fluid pressure together, so that the valve flap quickly compressed valve seat, sealing more reliable.
Advantages: fast closing speed, can prevent the medium backflow caused by water hammer impact.
Applicable scenes: high-pressure pipelines, steam systems, pump outlets and other occasions requiring rapid sealing.