The inclination of the spool of the electric stainless steel globe valve is generally 3 to 6 degrees. When the cylinder is forced to close excessively or the temperature changes greatly, the spool is easily stuck. Therefore, the high-temperature, high-pressure wedge gate valve has taken certain measures to prevent the valve core from being stuck in the structure. When the gate valve is opened and closed, the sealing surface of the valve core and the valve seat always contact and rub against each other, so the sealing surface is easy to wear, especially when the valve is close to the closed state, the pressure difference between the front and the back of the valve core is large, and the sealing surface wear is more serious. .
Compared with the stop valve, the main advantage of the gate valve is that the fluid flow resistance is small, the flow resistance coefficient of the ordinary gate valve is about 0.08~0.12, and the resistance coefficient of the ordinary globe valve is about 3.5~4.5. The opening and closing force is small, and the medium can flow in both directions. The disadvantage is that the structure is complicated, the height is large, and the sealing surface is easy to wear.
The sealing surface of the shut-off valve must be forced to close by the valve to achieve the seal. Under the same caliber, working pressure and the same driving device, the driving torque of the shut-off valve is 2.5~3.5 times of the gate valve. This should be noted when adjusting the torque control mechanism of the electric valve.
The sealing faces of the electric stainless steel globe valves are only in contact with each other when they are completely closed, and the relative slippage of the forcibly closed spool and the sealing surface is small, so that the wear of the sealing faces is also small. The wear of the sealing surface of the shut-off valve is mostly caused by debris before the valve core and the sealing surface, or due to the tightness of the closed state, causing high-speed flushing of the medium.
When the electric stainless steel globe valve is installed, the medium can enter from the bottom of the spool and enter from above. The advantage of the medium entering from below the spool is that the packing is not under pressure when the valve is closed, the service life of the packing can be extended, and the packing can be replaced with the pressure in front of the valve. The disadvantage of the medium entering from the bottom of the valve core is that the driving torque of the valve is relatively large, about 1.05~1.08 times of the upper entry, the axial force of the valve stem is large, and the valve stem is easy to bend. For this reason, the medium enters the mode from below, and is generally only applicable to a small-diameter manual shut-off valve, and the force of the medium acting on the valve core when the valve is closed is not more than 350 kg. Electric shut-off valves generally use a medium to enter from above. The disadvantage of the way the medium enters from above is exactly the opposite of the way it enters below.
Compared with the gate valve, the stop valve has the advantages of simple structure, good sealing performance and convenient manufacturing and maintenance; the disadvantage is that the liquid resistance is large, and the opening and closing forces are large.
Gate valves and stainless steel shut-off valves are fully open and fully closed valves. They are not suitable as regulators for shutting off or turning on the medium. The application range of the globe valve and gate valve is determined according to its characteristics. In smaller passages, shut-off valves are often used when better shut-off sealing is required. In steam pipes and large-diameter water supply pipes, gate valves are used because fluid resistance is generally required to be small.
The check valve is a kind of valve used to prevent the backflow of the medium in the pipeline. When the medium is reversed, the valve flap can be automatically closed to cut off the flow of the medium to avoid accidents. The structure of the check valve is divided into a lift type and a swing type according to the law of the flap motion. The vertical lift check valve shall be installed on the vertical pipe; the horizontal lift check valve shall be installed on the horizontal pipe. When installing the swing-type check valve, it should be noted that the flow direction of the medium is the same as the direction of the arrow shown in the valve body, and it cannot be reversed.
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