Gate valves and globe valves are shut-off valves and are the two most common types of valves. From the appearance, the gate valve is shorter and taller than the stop valve, especially the rising stem valve requires a higher height space. Moreover, the sealing surface of the gate valve has a certain self-sealing ability, and the valve core of the gate valve is in tight contact with the sealing surface of the valve seat by the medium pressure to achieve tightness and leak-proofness. When the forced closing is excessive or the spool with a large temperature change is easy to be stuck. Therefore, high temperature and high pressure wedge 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 valve seat sealing surface are always in 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 rear of the valve core is large, and the sealing surface wear is more serious . Compared with the globe valve, the main advantage of the gate valve is that the fluid flow resistance is small, 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 dimension 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 sealing surfaces of the shut-off valve only touch each other when they are completely closed, and the relative sliding amount of the forcibly closed valve core and the sealing surface is very small, so the wear of the sealing surface is also very small. And the shut-off valve
The abrasion of the cover is mostly caused by debris in front of the valve core and the sealing surface, or due to the improper closed state, which causes high-speed scouring of the medium.
When the shut-off valve is installed, the medium can enter from below the valve core and enter from above in two ways. The advantage of the medium entering from below the valve core is that the packing is not stressed when the valve is closed, and it can be
In order to prolong the service life of the packing, the packing can be replaced when the pipeline in front of the valve is under pressure. The disadvantage of the medium entering from below the valve core is that the drive torque of the valve is large, the axial force on the valve stem is large, and the valve stem is easy to bend. For this reason, the way that the medium enters from below is generally only suitable for manual shut-off valves with small diameters. The electric shut-off valve generally adopts the way that the medium enters from above, and the shortcoming of the medium enters from above is just the opposite of the way to enter from below.
Compared with the gate valve, the shut-off 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 force is large. Gate valves and globe valves are fully open and fully open
The closed valve is used to cut off or connect the medium, and is not suitable for use as a regulating valve.
The application range of globe valves and gate valves is determined according to their characteristics. In smaller passages, when better shut-off tightness is required, stop valves are often used; in steam pipes and large diameters
In the water supply pipeline, because the fluid resistance is generally required to be small, a gate valve is used.
The gate valve is used in a relatively large system to close the gate-off system, while the stop valve is used in a relatively small system and plays a role in adjusting the flow rate of the system. It cannot close the gate according to the specification.
Valves and stop valves are used in different situations.
The shut-off valve can intercept and adjust the flow. It has a small footprint and a small volume. Both can be closed. In the occasions where the linearity of the flow is not required, the flow can be adjusted. However, the stop valve has a large flow resistance due to its structural characteristics, so more gate valves are used where throttling is required. In addition, whether the stop valve is installed in the front or in the reverse installation, there is always a lot of effort in the opening and closing process, so it cannot be made very large, or it is not easy to open and close. In addition, the shut-off valve has the characteristics of good one-way sealing effect, so it is also useful in preventing the backflow of working fluid.
The structure difference between gate valve and globe valve:
The length of the gate valve is shorter than that of the stop valve, and the height is higher than that of the stop valve. The installation of the rising stem gate valve should pay attention to the height. This should be paid attention to when the installation space is limited. The gate valve can rely on the pressure of the medium to be tight
Tightly close with the sealing surface, so as to achieve the effect of no leakage. When opening and closing, the valve core and the valve seat sealing surface always contact and rub each other, so the sealing surface is easy to wear, and the gate valve is close to closed.
When the pressure difference between the front and rear of the pipeline is large, the sealing surface wears more seriously.
The principle difference between gate valve and globe valve
The working principle of the gate valve is different from that of the globe valve. The globe valve is of an ascending stem type, and the hand wheel rotates and rises together with the stem. In the gate valve, the hand wheel rotates and the valve stem moves upward. flow
The amount is not the same, the gate valve is required to be fully opened, but the stop valve is not. The gate valve has no requirements for the direction of the inlet and outlet, and the globe valve has a specified inlet and outlet.
The flow direction difference between gate valve and globe valve:
The shut-off valve is low in and high out. From the outside, it is obvious that the pipeline is not on the horizontal line of one phase.
The gate valve flow path is on a horizontal line. The stroke of the gate valve is larger than that of the stop valve. The flow direction of the gate valve is the same when entering from both sides.
From the perspective of flow resistance, the flow resistance of the gate valve is small when fully opened, and the flow resistance of the load stop valve is large. The opening and closing force of the ordinary gate valve is small, and the medium can flow in two directions.
The flow resistance of ordinary shut-off valves is 3-5 times that of gate valves. When opening and closing, it needs to be forced to close to achieve the seal. The valve core of the globe valve only contacts the sealing surface when it is completely closed, so the sealing surface is worn
It is very small, because the main force of the flow needs to be added to the shut-off valve of the actuator, attention should be paid to the adjustment of the torque control mechanism.
The difference between the sealing surface of gate valve and globe valve:
The sealing surface of the globe valve is a small trapezoidal side of the valve core (see the shape of the valve core in detail). Once the valve core falls off, it is equivalent to closing the valve (if the pressure difference is large, of course it is not tightly closed, but only
The inverse effect is not bad),
The gate valve is sealed by the side of the valve core gate plate, and the sealing effect is not as good as the stop valve, and the valve core will not be closed like the stop valve when the valve core falls off.
