The structure of the gate valve will be more complex than the globe valve, from the appearance point of view, under the same caliber, the gate valve is higher than the globe valve, the globe valve is longer than the gate valve. In addition, the gate valve has open rod and dark rod. No globe valve.
The gate valve can rely on the medium pressure tightly and the sealing surface tightly, so as to achieve the effect of no leakage. When opening and closing, the spool and the sealing surface of the seat always contact and friction each other, so the sealing surface is easy to wear. When the gate valve is close to closing, the pressure difference between the front and back of the pipeline is very large, making the sealing surface wear more serious.
Working principle:
The flow rate is different, the gate valve is required to be fully open or fully closed, and the globe valve is not required. The globe valve has a specified import and export direction, and the gate valve has no import and export direction requirements.
When the globe valve is opened and closed, it is a rising valve stem type, that is to say, the hand wheel will rotate and lift with the valve stem. Gate valve is to rotate the hand wheel, so that the valve stem to do lifting movement, the hand wheel itself position unchanged.
In addition, the gate valve is only fully open or fully closed two states, the stroke of the gate plate opening and closing is large, and the opening and closing time is long. The motion stroke of the valve plate of the globe valve is much smaller, and the valve plate of the globe valve can be stopped in a certain place during the movement to do flow regulation. The gate valve can only be used for truncation and has no other functions.
Performance difference:
Because the gate valve can only be fully opened and fully closed, when it is fully opened, the medium flow resistance in the valve body channel is almost 0, so the opening and closing of the gate valve will be very labor-saving, but the distance between the gate plate and the sealing surface is far, and the opening and closing time is long.
The globe valve can be used for both truncation and flow regulation. The fluid resistance of the globe valve is relatively large, and it is more laborious to open and close, but because the distance between the valve plate and the sealing surface is short, the opening and closing stroke is short.
Installation and flow:
The effect of gate valve flow in both directions is the same, the installation has no import and export direction requirements, and the medium can flow in both directions. The globe valve needs to be installed in strict accordance with the direction of the arrow marked by the valve body, and there is a clear provision on the import and export direction of the globe valve.
The globe valve is low into high, from the outside view there is an obvious pipeline is not in a phase level line. The gate valve channel is in a horizontal line. The travel of the gate valve is larger than that of the stop valve.
From the point of view of flow resistance, the flow resistance of gate valve is small when it is fully opened, and the flow resistance of load stop 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 two directions. The flow resistance of ordinary globe valves is 3-5 times that of gate valves. When opening and closing, it is necessary to force closure to achieve the seal, and the spool of the globe valve contacts the sealing surface when it is completely closed, so the wear of the sealing surface is very small, and the globe valve of the actuator should pay attention to the adjustment of the torque control mechanism due to the large flow force.
There are two ways to install the globe valve, one is that the medium can enter from below the spool, the advantage is that the disc is not under pressure when the valve is closed, which can extend the service life of the disc, and can replace the disc under the pressure of the pipeline in front of the valve; The disadvantage is that the driving torque of the valve is large, which is about 1 times that of the upper flow, and the axial force on the valve stem is large, and the valve stem is easy to bend.
Therefore, this method is generally only suitable for small diameter globe valves (below DN50), and the globe valves above DN200 use the way that the medium flows from the top. (Electric stop valves generally use the medium to enter from above.) The disadvantage of the medium entering from above is exactly the opposite of the way entering from below.
Both globe valves and gate valves are commonly used in chemical plants, and we recommend valve types and material designs for customers according to their different use scenarios.For example, the Ajaokuta-Kaduna-Kano (AKK) gas pipeline project in Nigeria uses a large number of globe valves.
