Structural principle of globe valve:
The main opening and closing components of the globe valve are the valve disc and the valve seat. The movement of the valve disc along the centerline of the valve seat changes the distance between the valve disc and the valve seat, which can change the cross-sectional area of the flow channel, thereby realizing flow control. and truncation.
The globe valve is a forced sealing valve, so when the valve is closed, pressure must be applied to the valve disc to force the sealing surface not to leak. When the medium enters the valve from under the valve disc, the resistance that the operating force needs to overcome is the friction force between the valve stem and the packing and the thrust generated by the pressure of the medium. The force to close the valve is greater than the force to open the valve, so the valve stem The diameter of the valve should be large, otherwise the failure of the top of the valve stem will occur.
In recent years, since the emergence of self-sealing valves, the flow direction of the medium has changed from the top of the valve disc into the valve cavity. At this time, under the action of the medium pressure, the force to close the valve is small, but the force to open the valve is large, and the diameter of the valve stem can be reduce accordingly. At the same time, under the action of the medium, this form of valve is also tighter. my country’s valve “Three Chemicals” once stipulated that the flow direction should be adopted from top to bottom.
When the globe valve is opened, when the opening height of the valve disc is 25% to 30% of the nominal diameter, the flow rate has reached a large value, indicating that the valve has reached the fully open position. Therefore, the fully open position is determined by the stroke of the valve disc.
The reason why the globe valve is popular is that the friction between the sealing surfaces is small during the opening and closing process, it is more durable, the opening height is not large, it is easy to manufacture, and it is convenient to maintain. It is not only suitable for medium and low pressure, but also suitable for high pressure.
This valve only allows one-way flow of the medium, and it is directional during installation. The length of the structure is longer than that of the gate valve, and the fluid resistance is large, and the sealing reliability is not strong during long-term operation.
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