The stainless steel electric globe valve is designed with low inlet and high outlet, 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 shell and the valve cover and the packing around the valve stem are not stressed, so they will not be affected by the medium pressure and temperature for a long time, which can extend the service life and reduce the chance of leakage. In addition, the packing can be replaced or added when the valve is closed, which is convenient for maintenance.
Many people think that globe valves are low inlet and high outlet, but this is not the case. In general, globe valves are low inlet and high outlet, but there are some special cases where the globe valve is high inlet and low outlet:
1. High-pressure globe valve with a diameter greater than 100mm
Due to the poor sealing performance of large-diameter valves, this method is used to make the medium pressure act on the top of the valve disc when the globe valve is closed to increase the sealing of the valve.
2. Two globe valves in series on the bypass pipeline, the second globe valve requires "high inlet and low outlet"
In order to ensure the tightness of the valve within a maintenance cycle, valves that are frequently opened and closed require two globe valves in series. For the bypass system, the installation functions of this bypass are: ① Balance the pressure before and after the valve of the main pipeline, make it convenient and labor-saving to open, and reduce the wear of the valve of the main pipeline; ② Warm the pipe with a small flow rate during the startup process; ③ On the main water supply pipeline, control the water supply flow to control the boiler pressure increase speed for the boiler water pressure test. According to the flow direction of the medium, the bypass globe valve is divided into a primary valve and a secondary valve. When the unit is operating normally, the primary valve and the secondary valve are closed, and both are in direct contact with the medium. In order to prevent the gasket between the valve shell and the valve cover of the secondary valve 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 secondary valve requires the installation direction of "high in and low out".
3. Boiler exhaust and vent globe valve
The boiler exhaust and vent globe valve is only used during the boiler startup and water supply process. The opening and closing frequency is small, but it often causes working fluid loss due to poor sealing. For this reason, some power plants install this type of globe valve in the direction of "high in and low out" to improve the tightness.
4. Electromagnetic quick-break valve
The function of the electromagnetic quick-break valve is to close quickly and quickly cut off the fuel supply. The structure of the electromagnetic quick-break valve is similar to that of the globe valve. If the electromagnetic quick-break valve also has the working fluid entering from the bottom and flowing out from the top, the force exerted by the fuel on the lower part of the electromagnetic quick-break valve disc is very large, while the weight of the electromagnetic quick-break valve is much smaller than it. Therefore, if the working fluid enters the quick-break valve from the bottom, the torque generated by the weight is smaller than the torque generated by the fuel pressure, and the fuel cannot be cut off when the quick-break valve is actuated, thus failing to achieve the desired purpose. If the working fluid enters from the top of the quick-break valve, once the quick-break valve is actuated, the pressure behind the valve drops rapidly, and the force exerted by the fuel on the lower part of the disc quickly drops to zero, while the force exerted by the fuel on the disc and the force formed by the weight of the weight and the lever
Generally, it is difficult to close the valve if low inlet and high outlet are used under large-caliber and high-pressure conditions. If low inlet and high outlet are used under high-pressure and large-caliber conditions, the valve stem is easily deformed and bent by water pressure for a long time, affecting the safety and sealing of the valve; if high inlet and low outlet are used, the valve stem diameter can be smaller, which will also save some costs for manufacturers and users.