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Are the globe valves low in and high out?
- May 22, 2018 -

The globe valve is designed for low inlet and high flow. The purpose is to make the flow resistance small and save effort when opening the valve. At the same time, when the valve is closed, the gasket between the valve housing and the valve cover and the packing around the valve stem are not subjected to force, and will not prolong the service life due to the effects of the medium pressure and temperature, thereby reducing the probability of leakage. In addition, it is also possible to replace or add fillers when the valve is closed to facilitate maintenance. Many people think that the globe valves are low inlet and high flow, but it is not. In general, the globe valves are low-inlet, but there are also some special cases where the shut-off valves are high inlet and low flow:

1. High pressure globe valve with diameter greater than 100mm

Due to the poor sealing performance of large-diameter valves, the use of this method shuts the valve in the closed state, the media pressure acts on the valve flap to increase the sealing of the valve.

2. Two globe valves in series on the bypass pipe, and the second globe valve requires high-in and low-out

In order to ensure the tightness of the valve during a maintenance cycle, valves that are frequently opened and closed require the installation of two series-connected shut-off valves. For the bypass system, the installation of this bypass has: 1 balancing the pressure of the main pipeline before and after the valve, so that the opening is convenient and effortless, reducing the wear of the main pipeline valve; 2 small flow warming pipe during the start-up process; 3 main water supply pipeline Control the supply water flow to control boiler boost pressure for boiler hydro-static test. According to the flow direction of the medium, the bypass stop valves are a primary valve and a secondary valve. When the unit is running normally, the primary valve and the secondary valve are closed, and both are in direct contact with the medium. In order to prevent the dull material between the valve housing and the valve cover and the packing around the valve stem from being affected by the medium and temperature for a long time, and to replace the packing of the valve during operation, the installation direction of the secondary valve requires high and low ".
3, boiler exhaust, venting valve

Boiler exhaust and venting globe valves are used only during the start-up of the boiler, and the frequency of opening and closing is small, but the loss of working medium is often caused by loose seals. For this reason, some power plants will install such stop valves in order to improve the tightness. "High in and low out."

4, electromagnetic speed off valve

The function of the electromagnetic quick-acting valve is to close quickly and quickly cut off the fuel supply. The structure of the electromagnetic quick-acting valve is similar to the structure of the shut-off valve. If the electromagnetic speed globe valve is also the working fluid enters from the lower part and the upper part flows out, the force of the fuel acting on the lower part of the electromagnetic speed-breaking valve disc is large, and the weight of the electromagnetic speed-cutting valve is much smaller than it. Therefore, if the working medium enters the quick-acting valve from the lower part, the torque generated by the weight is smaller than the torque generated by the fuel pressure. When the quick-acting valve is actuated, the fuel cannot be cut off and the intended purpose cannot be achieved. If the working medium enters from the upper part of the quick-disconnect valve, the force behind the valve flap will quickly drop to zero after the quick-acting valve is actuated, and the pressure behind the valve will rapidly decrease, and the force and weight of the fuel acting on the valve flap will be reduced. The force of the lever's gravity.

In general large-caliber and high-pressure state, it is difficult to close the valve when using low in and high out. If the high-pressure and large-diameter state adopts low-in and high-out, the stem will be easily deformed and bent by the water pressure for a long time, which will affect the safety and sealability of the valve. If the high and low positions are selected, the diameter of the valve stem can be small, which will save some costs for manufacturers and users.


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