What is a Check Valve?
Check Valve Basics
Check valve refers to the opening and closing parts for the round valve and rely on their own weight and media pressure to produce action to block the medium backflow of a valve. Belong to the automatic valve category, also known as check valve, check valve, backflow valve or isolation valve. Flap movement is divided into lift and rotary type. Lift check valve and globe valve structure is similar, only the lack of valve stem to drive the valve flap. The medium from the inlet side (lower side) inflow, from the outlet side (upper side) outflow. When the inlet pressure is greater than the weight of the valve and its flow resistance and when the valve is open. Conversely, the medium backflow valve is closed.
Check Valve Function
- The check valve can prevent the medium backflow. Check valve only has one flow direction, that is, only along the direction of the inlet flow, to prevent water flow in the opposite direction. Flowing medium from the inlet side (lower side) into, from the outlet side (upper side) out. When the inlet pressure is greater than the weight of the valve flap and the sum of its resistance to flow, the valve is open. Conversely, the valve is closed when the medium backflow.
- Check valve can prevent the pump and drive motor reversal. Check valve is automatic, in a direction of flow of fluid pressure, valve open; fluid flow in the opposite direction, by the fluid pressure and the self-weight of the valve flap on the valve seat, thus cutting off the flow.
- Check valve can also be used for which the pressure may rise to more than the system pressure of the auxiliary system to provide supply pipeline. Pressure of the auxiliary system to provide supply pipeline.
Check valve can be divided into rotary check valve (according to the center of gravity rotation) and lift check valve (along the axis of movement). They are used in pipelines where the medium flows in one direction, allowing the medium to flow in only one direction to prevent accidents.
Check Valve Applications
Medium flows in the specified direction, when the flow pressure exceeds the opening pressure of the check valve, the valve flap is opened under the action of fluid pressure, thus connecting the pipeline medium circulation. On the contrary, when the pipeline medium backflow backward, under the impetus of fluid pressure, the valve flap is pressed on the check valve body and then the valve is closed, thus cutting off the pipeline medium circulation. In addition, the greater the pressure of the backflow medium, the valve flap closes the tighter and better sealing effect, thus completely eliminating the possibility of media reflux.
Check Valve Types
Lift check valve
The valve body style of a lift check valve is the same as that of a globe valve, so the fluid resistance is high and can be divided into two types: vertical and horizontal. The vertical medium outlet pipeline is the same as the valve seat pipeline, and the flow resistance is much smaller than that of a horizontal one, usually installed on a vertical pipeline;Horizontal check valves are generally installed on horizontal pipelines and are limited in installation, and can only be used in situations with a diameter of DN less than 50.
Swing check valve
The internal channel of this type of check valve is streamlined, with lower resistance and relatively poor sealing performance compared to lift check valves. It is usually used in small and medium-sized diameter and low-pressure large diameter pipelines, mainly to reduce water flow impact when stopping or reversing flow. Swing check valves are divided into three types based on the valve diameter: single valve, double valve, and multi valve. Single valve is normally installed in medium diameter pipelines, double valve is used in large and medium diameter pipelines, and multi valve is used in large diameter pipelines.
Butterfly check valve
The butterfly check valve is a straight through type with a structure similar to that of a butterfly valve, which is relatively simple, has low flow resistance, and low water hammer pressure. It is usually installed in horizontal pipelines, but its sealing performance is not good enough.
Diaphragm check valve
There are many structural categories of this type of check valve, but they all use a diaphragm as the opening and closing part, with excellent waterproof hammer performance, simple structure, and low cost. However, the temperature and pressure used are limited by the diaphragm material, and are usually installed on pipelines prone to water hammer.
