The working principle is different. The globe valve is a rising stem type. The handwheel rotates and rises with the stem. Gate valves are hand wheels rotating and stem rising. Flow rate is different, gate valve should be fully open, cut-off valve is not. Gate valves have no import and export direction requirements, globe valves have specified import and export! Gate valves and globe valves are shutoff valves, and are the two most common types of valves. The gate valve is shorter and higher than the globe valve in appearance, especially the open stem valve needs higher height space. The sealing surface of gate valve has certain self-sealing ability. Its valve core contacts with the sealing surface of valve seat tightly depending on medium pressure, so as to achieve tightness and leakproof. The inclination of the spool of wedge gate valve is generally 3-6 degrees, and it is easy to jam when excessive closure or large temperature change is forced. Therefore, high temperature and high pressure wedge gate valves have taken some measures to prevent the valve core from being stuck. When the gate valve is opened and closed, the sealing surface of the valve core and seat always contacts and rubs 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 very large, and the wear of the sealing surface is more serious. Compared with globe valve, the main advantage of gate valve is that the fluid flow resistance is small. The flow resistance coefficient of common gate valve is about 0.08~0.12, while that of common globe 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 and size are large, and the sealing surface is easy to wear. The sealing surface of globe valve must be closed by force to achieve sealing. Under the same caliber, working pressure and driving device, the driving torque of globe valve is 2.5-3.5 times of that of gate valve. Attention should be paid to this point when adjusting the torque control mechanism of electric valves. The sealing surface of globe valve contacts each other only when it is completely closed. The relative slip between the mandatory closing spool and the sealing surface is very small, so the wear of the sealing surface is also very small. The wear of sealing surface of globe valve is mostly caused by debris before the valve core and sealing surface, or by the high-speed erosion of medium caused by the inadequate closing state. When the globe valve is installed, the medium can enter from the bottom of the spool and from the top. The advantage of medium entering from the bottom of the valve core is that when the valve closes, the packing root is not under pressure, which can prolong the service life of the packing root and replace the packing root under the pressure of the pipe in front of the valve. The disadvantage of medium entering from the lower part of the spool is that the driving torque of the valve is larger, about 1.05-1.08 times that of the upper part, the axial force on the valve stem is large, and the valve stem is easy to bend.
For this reason, the media from the bottom of the way, generally only applicable to small-caliber manual cutoff valve, in the valve closure when the force acting on the valve core is not greater than 350kg limit. Electric Globe valves are generally used to enter the media from the top of the way. The disadvantage of the way the media enters from above is exactly the opposite of the way it enters below. Compared with the gate valve, the advantages of the cut-off valve are simple structure, good sealing performance and convenient manufacturing and maintenance. The disadvantage is that the liquid resistance is large, the opening and closing force is large. Gate valve and globe valve belong to all-open full-off valve, as the use of cutting or connecting media, should not be used as a regulating valve. The application range of globe valves and gate valves is determined according to their characteristics. In smaller channels, when a good shutdown seal is required, the cut-off valve is used, and the gate valve is used in the steam pipe and the large diameter water supply pipe because the fluid resistance is generally less demanding.
