1, The sealing surface is different
Gate valve in the opening and closing of the valve spool and seat sealing surface is always in contact and mutual friction, so the sealing surface is easy to wear, especially in the valve is close to the closed state, the spool before and after the pressure difference is very large, the sealing surface wear is more serious; and globe valve valve valve flap once in the open condition, it is no longer in contact with the valve seat and flap sealing surface, and thus it is the sealing surface of the mechanical wear is small, but the media if contains Solid particles, easy to damage the sealing surface.
Gate valve sealing surface has a certain degree of self-sealing ability, its spool by the media pressure tightly with the valve seat sealing surface contact, to achieve a tight leakage. Wedge gate valve spool slope is generally 3~6 degrees, when the forced closure of excessive or large temperature changes in the spool is easy to jam. Therefore, high temperature, high pressure wedge gate valve, in the structure of the spool are taken to prevent certain measures.
The sealing surface of the globe valve, must be applied to force the closure of the valve in order to achieve sealing, in the same calibre, working pressure and the same drive device, the driving torque of the globe valve for the gate valve 2.5 ~ 3.5 times. This point in the electric valve torque control mechanism adjustment, should be noted.
Globe valve sealing surface, only in the complete closure of the mutual contact, forced closure of the spool and the sealing surface of the relative slip is very small, and thus the sealing surface of the wear and tear is also very small. And the wear of the sealing surface of the globe valve, most of which is due to the spool and sealing surface before debris, or due to the closure of the state is not tight, caused by the medium of high-speed scouring.
2, Different structure
Gate valve than globe valve structure is complex, the height of the larger size, from the appearance of the gate valve than the globe valve short and high, especially the open stem gate valve requires a higher height space, which is limited in the installation of space in the case of the selection of the type to pay attention to.
3, Different flow resistance
Gate valve in the full open the entire flow path straight through, the medium at this time the operation of the minimum pressure loss, compared with the globe valve, its main advantage is that the fluid flow resistance is small, ordinary gate valve flow resistance coefficient of about 0.08 ~ 0.12, while the ordinary globe valve resistance coefficient is about 3.5 ~ 4.5. open and close the force is small. Gate valve is usually suitable for, do not need to open and close often, and keep the gate fully open or fully closed conditions, is not suitable for regulating, throttling use.
And globe valve in the whole stroke of the flow resistance are very large, the unbalance force is large, the required driving force or torque is also correspondingly much larger. But it is very suitable for fluid regulation, throttling. For high-speed flow of media, the gate in the local open condition, can cause the valve vibration, and vibration, and may damage the sealing surface of the gate and seat, and throttling, the gate will be subjected to media erosion.
4, Different strokes
The stroke of the gate valve is larger than that of the globe valve.
5, Different flow direction
Globe valve in the installation, the medium can enter from the bottom of the spool and enter from above in two ways. Medium from below the spool into the advantage is when the valve is closed when the packing is not under pressure, you can extend the life of the packing, and can be in front of the valve pipeline pressure, the replacement of the packing work. Medium from below the spool into the disadvantage is that the valve’s driving torque is larger, about 1.05 ~ 1.08 times above the entry, the valve stem by the axial force is large, the valve stem is easy to bend. For this reason, the medium from below into the way, generally only applies to small diameter globe valve (DN50 below), DN200 above the globe valve are selected from above the medium into the way. Electric globe valve is generally used in the way the medium enters from above. Medium from above into the way the shortcomings of the way just the opposite of the way below.
And the flow of the gate valve, from both sides into the same effect. Globe valve compared with the gate valve, the advantages are simple structure, good sealing performance, manufacturing and maintenance is convenient; disadvantage is that the liquid resistance is large, open and close the force is large.
6, Maintenance process is different
Gate valve maintenance, not suitable for on-site pipeline, and most of the valve seat and valve flap globe valve, can be replaced online, without the entire valve, from the pipeline down, which is welded to the valve and pipeline into a single occasion, is very suitable.
Of course, the difference between the gate valve and globe valve is not only these kinds of, in the selection and use we have to distinguish their similarities and differences, in order to avoid mistakes. The application range of globe valves and gate valves is determined by their characteristics. In the smaller channel, when the requirements of a good shut-off sealing, more use of globe valves; in the steam pipeline and large-diameter water pipeline, as the fluid resistance is generally required to be smaller, the use of gate valves.