Globe valves are designed to have a low inlet and high outlet to minimize flow resistance and save effort when opening the valve. At the same time, when the valve is closed, the valve shell and valve cover between the gasket and the packing around the valve stem are not subjected to force, not to be subjected to media pressure and temperature for a long time by the action of the service life can be extended to reduce the chance of leakage. In addition, this can also be replaced in the state of the valve off or add packing, easy maintenance.
Many people think that the globe valve is low into the high out, in fact, not. In general, the shut-off valve is low into the high out, however, there are some special circumstances shut-off valve is high into the low out:
Due to the poor sealing performance of large diameter valves, the use of this method of globe valve in the closed state, the media pressure acts on the valve flap above to increase the sealing of the valve.
2.Bypass pipeline in series with two globe valves, the second globe valve requires a "high in low out"
To ensure the tightness of a maintenance cycle of the valve, often opening and closing the valve requires the installation of two tandem globe valves. For the bypass system, the installation of this bypass role:
① Balancing the pressure before and after the main valve, so that it is convenient to open the effort to reduce the wear and tear of the main valve;
② Start the process of small flow warming pipe;
③ Main water pipeline, control water flow to control the boiler pressure rate for boiler pressure test. According to the direction of media flow bypass globe valves are primary and secondary valves, primary and secondary valves are closed during normal operation of the unit, both of which are in direct contact with the media. To prevent the secondary valve shell valve cover gasket and valve stem around the packing for a long time by the media and temperature, as well as in the process of operation can be replaced valve packing, the secondary valve requires the direction of the installation of the “high into the low out”.
The boiler exhaust and venting globe valve are only used in the boiler start-up water process, opening and closing frequency is small, but often due to poor sealing and causes loss of quality, to improve the tightness of the power plant will be such a globe valve installed in the direction of “high in low out”.
Electromagnetic quick disconnect valve
The electromagnetic quick disconnect valve function is to quickly shut down, and quickly cut off the fuel supply. The electromagnetic globe valve structure and the structure of the globe valve are similar, if the electromagnetic globe valve is also from the lower part of the mass into the upper part of the outflow, then the fuel in the electromagnetic globe valve flaps the lower part of the force is very large, and the electromagnetic globe valve is much smaller than the weight of the valve. Therefore, if the material from the lower part of the quick disconnect valve, because the weight produces a torque less than the moment generated by the fuel pressure, when the quick disconnect valve action can not cut off the fuel, and thus can not achieve the desired purpose. If the mass from the upper part of the quick disconnect valve into, because the quick disconnect valve once the action of the valve, the pressure behind the valve is rapidly reduced, the fuel acting on the lower part of the flap of the force is quickly reduced to zero, while the fuel acting on the flap of the force and the weight of the hammer, the lever’s gravity of the formation of the force.
Generally, in large diameter and high-pressure states using low into high out and then closing the valve is more difficult, if in the state of high pressure and large caliber using low into high out, the valve stem long-term water pressure is easy to deform and bending, affecting the safety of the valve and sealing; selection of the high into the low place, then the diameter of the valve stem can be a little bit smaller, for manufacturers and users will also save a little cost.