Difference between globe valve and gate valve

Difference between globe valve and gate valve

     The working principle is different. The shut-off valve is a rising stem type, and the hand wheel rotates and rises along with the stem. The gate valve is rotated by the hand wheel, and the valve stem is moved upward. The flow is different, the gate valve requires full opening, and the shut-off valve is not. Gate valves do not have inlet and outlet direction requirements, and stop valves have prescribed inlets and outlets. Gate and globe valves are shut-off valves and are the two most common types of valves.

     From the perspective of the appearance, the gate valve is shorter and taller than the shut-off valve, especially the open stem valve needs a higher height space. The sealing surface of the gate valve has a certain self-sealing ability, and its valve core is tightly contacted with the sealing surface of the valve seat by the pressure of the medium to achieve tightness and leakage. The wedge gate valve generally has an inclination of 3 to 6 degrees. When the valve core is forced to close excessively or the temperature changes greatly, the valve core is liable to seize. Therefore, high-temperature and high-pressure wedge-shaped gate valves have taken certain measures to prevent the valve core from jamming in structure. When the gate valve is opened and closed, the valve core and the seat sealing surface 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 back of the valve core is large, and the sealing surface wear is more serious. . Compared with the gate valve, the main advantage of the gate valve is that the fluid flow resistance is small. The flow resistance coefficient of the common gate valve is about 0.08 ~ 0.12, while the resistance coefficient of the common gate valve is about 3.5 ~ 4.5. The opening and closing force is small, and the medium can flow in two directions. The disadvantage is that the structure is complex, 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 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 to 3.5 times that of the gate valve. This point should be paid attention to when adjusting the torque control mechanism of the electric valve. The sealing surfaces of the shut-off valve contact each other only when they are completely closed. The relative slip between the valve core and the sealing surface that is forced to close is small, so the wear on the sealing surface is also very small. The wear of the sealing surface of the shut-off valve is mostly caused by debris in front of the valve core and the sealing surface, or due to the tightness of the closed state, which causes high-speed flushing of the medium.

     When the shut-off valve is installed, the medium can be entered from below the spool and from above. The advantage of the medium entering from below the valve core is that when the valve is closed, the packing is not under pressure, which can extend the service life of the packing, and can replace the packing under the pressure of the pipeline before the valve. The disadvantage of the medium entering from the lower part of the valve core is that the driving torque of the valve is large, which is about 1.05 ~ 1.08 times of the upper entering. The axial force on the valve stem is large, and the valve stem is easy to bend. For this reason, the medium enters from below. Generally, it is only suitable for small-diameter manual shut-off valves. The limit is that the force of the medium acting on the spool when the valve is closed is not more than 350kg. Electric shut-off valve is generally used to enter the medium from above. The disadvantage of the media entry from above is exactly the opposite of the entry from below.

    Compared with the gate valve, the advantages of the globe valve are simple structure, good sealing performance, convenient manufacturing and maintenance; the disadvantages are large liquid resistance and large opening and closing force. Gate valves and globe valves are fully open and fully closed valves. They are not suitable for regulating valves as they are used to shut off or connect the medium.

    The application range of globe valve and gate valve is decided according to its characteristics. In smaller passages, when better shut-off is required, stop valves are often used; in steam pipes and large-diameter water supply pipes, gate valves are generally used because of the low fluid resistance requirements.