The valve is the control device of the fluid pipeline. Its basic function is to connect or cut off the circulation of the pipeline medium, change the flow direction of the medium, adjust the pressure and flow of the medium, and set various valves, large and small, in the system. An important guarantee for the normal operation of the pipe and equipment.
There are several common types of water treatment valves:
1. Gate Valve.
It is the most commonly used opening and closing valve, which uses the gate (the opening and closing part, in the gate valve, the opening and closing part is called the gate， and the valve seat is called the gate seat) to connect (fully open) And cut off (fully close) the medium in the pipeline. It is not allowed to be used as throttling, and the gate should be avoided to be opened slightly during use, because the erosion of the high-speed flowing medium will accelerate the damage of the sealing surface. The gate moves up and down on a plane perpendicular to the centerline of the channel of the gate seat, and cuts off the medium in the pipeline like a gate, so it is called a gate valve.
Features:
1. Small flow resistance. The medium channel inside the valve body is straight through, the medium flows in a straight line, and the flow resistance is small.
2. It is less labor-saving when opening and closing. It is relative to the corresponding valve, because it is open or closed, the direction of the gate movement is perpendicular to the flow direction of the medium.
3. Large height and long opening and closing time. The opening and closing stroke of the gate increases, and the speed reduction is carried out through the screw.
4. The phenomenon of water hammer is not easy to occur. The reason is that the closing time is long.
5. The medium can flow in any direction of the pump, and the installation is convenient. The gate valve channel water pump is extremely.
6. The structural length (the distance between the two connecting end faces of the shell) is small.
7. The sealing surface is easy to wear. When the opening and closing are affected, the two sealing surfaces of the gate plate and the valve seat will rub and slide against each other. Under the action of medium pressure, it is easy to cause abrasion and wear, which affects the sealing performance and the entire service life.
8. The price is more expensive. The contact sealing surface mark is more complicated to process, especially the sealing surface on the gate seat is not easy to process
2.Globe Valve
The globe valve is a closed-circuit valve that uses the disc (the closing part of the globe valve is called the disc) to move along the center line of the channel of the disc seat (valve seat) to control the opening and closing of the pipeline. Globe valves are generally suitable for transporting liquid and gaseous media under various pressures and temperatures within the specified standard range, but are not suitable for transporting liquids containing solid precipitation or crystallization. In the low-pressure pipeline, the stop valve can also be used to adjust the flow of the medium in the pipeline. Due to structural limitations, the nominal diameter of the globe valve is below 250mm. If it is on a pipeline with high medium pressure and high flow velocity, its sealing surface will wear out quickly. Therefore, when the flow rate needs to be adjusted, a throttle valve must be used.
Features:
1. The wear and abrasion of the sealing surface are not serious, so the work is more reliable and the service life is long.
2. The area of the sealing surface is small, the structure is relatively simple, and the man-hours required to manufacture the sealing surface and the precious materials required for the sealing ring are less than those of the gate valve.
3. When opening and closing, the stroke of the disc is small, so the height of the stop valve is small. Easy to operate.
4. Using the thread to move the disc, there will be no sudden opening and closing, and the phenomenon of "water hammer" will not easily occur.
5. The opening and closing torque is large, and the opening and closing is laborious. When closing, the movement direction of the disc is opposite to the direction of the medium movement pressure, and the force of the medium must be overcome, so the opening and closing torque is large, which affects the application of large diameter globe valves.
6. Large flow resistance. Among all kinds of cut-off valves, the flow resistance of the cut-off valve is the largest. (The medium channel is more tortuous)
7. The structure is more complicated.
8. The medium flow direction is one-way. It should be ensured that the medium flows from bottom to top, so the medium must flow in one direction.
In the next article, we will talk about butterfly valves and check valves in water treatment valves, which are already prone to failure and maintenance.