1. Functions and tasks: - One-way valve is the type of valve only flowing through the directional valve to the opposite direction, the valve closed. In normal state, no effect of flow direction, disk weight or other auxiliary forces will cause the valve to close. - One-way valves are usually installed after the compressor, pump or after a backup system to ensure that they are not subjected to backflow when not in operation. 2. Classification: - The main types of DC valves include: Slipform and rotary type. Or we can understand by the type of movement in the valve: According to the movement of the sealing element to close or open the valve that we can divide: - One-way valve with lift lift (lift checkvalves). - One-way valve with swing check valves. - One-way valve with tilting-disc check valves. - Diaphragm check valves. a) Sliding one-way valve: - Compared with other types of one-way valves, the slider valve has a much simpler structure. Thanks to the simple structure of the slide valve, reliable operation, but also the slide valve can easily clog if the liquid needs not be filtered carefully. - Structurally, the one-way slider valve ensures that the pipe axis is perpendicular to the axis of the support. Often, the slide element is located on the support plate by its mass, but always ensures that the valve is installed horizontally. In order to ensure that the slidable valve can be mounted on a vertical pipe, the spring is used as a support element for clamping. Another alternative that can be used is to change the valve structure: one-way valves. This valve is only used in small pipes.
b) Rotary one-way valves: - The characteristic feature of the rotary valve is that the axis of the support always coincides with the axis of the liquid-gas pipeline. When there is no liquid-gas flow to the valve, the support is closed by the rotating door. When there is a liquid-gas flow to the valve, the rotary valve revolves around the shaft allowing the liquid-air to pass through the valve. When the line break through the revolving door valve returns to its closed position thanks to its own mass. In the horizontal form, the rotary shaft of the rotary door is designed higher than the axis of the pipe, to ensure the shutters return to the closed position when no line (see Figure 3). At the time of line break The valve, which rotates from the open position back to the closed position, with large valves, can produce a hydraulic impact between the rotating door and the support. To overcome this problem people divided two cases: - No need to fix: When the diameter of the shutter is less than 400mm, then the impact does not seriously affect the performance of the valve and the system. - Need to fix: with the one-way valves in specialized equipment need to machining the collision of the door is soft enough and smooth. Attach the shock absorber, the lever on the revolving door. Advantages of this type of valve compared to other one-way valves - It is possible to work with large diameter pipes, raw liquids (many impurities, not thoroughly filtered). c) Flanged one-way valves. - Flanged one-way valve offers high technical efficiency with major advantages of reducing valve length and assembly cost. - Flanged type flanges are of two types: flange spring, double door. - The basic difference of one-way flanges with other one-way valves is that they do not use flanges to connect the valve to the pipeline. As a result, the valve volume decreased 5 times, and the length of the valve assembly reduced 6-8 times than other one-way valve.
The working element of the valve undergoes a liquid-gas flow that moves along the flow direction and creates a clearance that allows fluid flow through the valve. Flanged valves can be installed both horizontally and vertically. 3. Main components: - Sliding element - sliding form (swing door - swing type), support base, support element (spring, key, ...). 4. Principle of operation: - When there is no liquid-gas flow through the valve, the sliding element (valve door) of the lower valve acts on its own weight or spring force is held firmly in the "closed" position. When the flow to the valve occurs, the sliding element under the effect of the flow energy is pushed out of the closed position and allowed to flow through the valve. At the velocity of the flow to zero, the sliding element (rotary door) returns to the closed position, the outlet pressure of the valve acting on the sliding element holds the slider at the closed position and prevents the flowing back. the inlet of the valve. Thus the operation of the one-way valve is fully automatic under the action of liquid-gas.