The effect of the gate valve in both directions is the same. There is no requirement for the installation, and the medium can flow in both directions. The shut-off valve needs to be installed in strict accordance with the direction of the arrow mark of the valve body, all from top to bottom.
Viewed from the outside, there are obvious pipes of the globe valve that are not on the same horizontal line. The gate valve flow path is on a horizontal line. The stroke of the gate valve is greater than that of the globe valve.
From the perspective of flow resistance, when the valve is fully opened, the flow resistance of the gate valve is small, and the flow resistance of the globe valve is large. The flow resistance coefficient of the ordinary gate valve is about 0.08 ~ 0.12, the opening and closing force is small, and the medium can flow in both directions. The flow resistance of the ordinary globe valve is 3-5 times that of the gate valve. When opening and closing, it needs to be forced to close to achieve the seal. The spool of the shut-off valve only contacts the sealing surface when it is completely closed, so the wear of the sealing surface is very small. Due to the large flow force, the actuator’s shut-off valve should pay attention to the torque control mechanism.
There are two ways to install the globe valve. One is that the medium can enter from below the valve core. The advantage is that the packing is not under pressure when the valve is closed, which can extend the service life of the packing and can be pressurized before the valve. Under the circumstances, the replacement of the packing is carried out; the disadvantage is that the driving torque of the valve is large, which is about 1 times that of the upper flow, the axial force received by the valve stem is large, and the valve stem is easy to bend.
Therefore, this method is generally only applicable to small-diameter shut-off valves (below DN50). For the shut-off valves above DN200, the medium flows from above(Electric cut-off valve generally adopts the way of medium entering from above.) The disadvantage of medium entering from above is just opposite to the way of entering from below.
Post time: Nov-25-2021