News
Globe valves are higher than that of low into?
2018-05-26
Globe valves are designed to be low in and high in order to reduce flow resistance and save effort when opening the valve. At the same time, when the valve is closed, the gasket between the valve shell and cover and the packing around the valve stem will not be stressed, and the effect of medium pressure and temperature for a long time will prolong the service life and reduce the probability of leakage. In addition, the valve can be closed to replace or add filler for easy maintenance.
Many people think that the cut-off valve is low in and high in, but it is not. Generally, the globe valve is low in and high in, but there are some special cases where the globe valve is high in and low out:
1. High pressure globe valve with a diameter greater than 100mm
Due to poor sealing performance of large diameter valve, this method is adopted to stop the valve in the closed state, the medium pressure ACTS on the upper valve disc to increase the sealing performance of the valve.
2. Two globe valves in series on the bypass pipeline, and the second one requires "high inlet and low outlet".
In order to ensure the valve's tightness during an overhaul period, the valve with frequent opening and closing operation is required to install two series stop valves. As for the bypass system, the installation function of this bypass is: the inlet balances the front and rear pressure of the main pipe valve, making it easy to open, saving energy and reducing the wear of the main pipe valve; The heating tube with medium and small flow during starting process; The water pressure test of the boiler is carried out by controlling the feed water flow in the main feed water pipeline to control the boiler's lifting pressure speed. The bypass stop valves are primary and secondary valves respectively according to the direction of medium flow. The primary and secondary valves are closed during normal operation of the unit, both of which are in direct contact with the medium. To prevent the packing material between the secondary valve shell and cover and the packing around the stem from being affected by the medium and temperature for a long time, and the packing of the valve can be replaced during operation, the installation direction required by the secondary valve is "high in and low out".
3. Boiler exhaust and vent stop valves
The boiler exhaust and vent shutoff valves are only used in the process of boiler start up and up water, and have a small opening and closing frequency. However, due to poor sealing, they often result in loss of quality.
4. Electromagnetic quick break valve
The function of the solenoid quick break valve is to close quickly and cut off the fuel supply quickly. The structure of the solenoid quick break valve is similar to that of the cut-off valve. If the solenoid quick break valve is also a working material that enters from the lower part and flows from the upper part, the force exerted by the fuel on the lower part of the solenoid quick break valve disc is very large, and the weight of the solenoid quick break valve is much smaller than it. Therefore, if the working material enters the quick-break valve from the lower part, the torque caused by the heavy hammer is less than the torque caused by the fuel pressure. When the quick-break valve ACTS, the fuel cannot be cut off, so it cannot achieve the expected purpose. If the working material enters from the upper part of the quick break valve, the pressure after the quick break valve decreases rapidly once it is operated, the force exerted by the fuel on the lower part of the valve disc drops to zero quickly, and the force exerted by the fuel on the disc and the force generated by the gravity of the weight hammer and lever
Generally speaking, it is difficult to close the valve with low inlet and height under large bore and high pressure. If low inlet and height are adopted under high pressure and large bore, the valve stem is easy to deform and bend under water pressure for a long time, which affects the safety and sealing performance of the valve. Select high inlet and low point for stem diameter can be smaller, for manufacturers and users will also save a little cost.
Many people think that the cut-off valve is low in and high in, but it is not. Generally, the globe valve is low in and high in, but there are some special cases where the globe valve is high in and low out:
1. High pressure globe valve with a diameter greater than 100mm
Due to poor sealing performance of large diameter valve, this method is adopted to stop the valve in the closed state, the medium pressure ACTS on the upper valve disc to increase the sealing performance of the valve.
2. Two globe valves in series on the bypass pipeline, and the second one requires "high inlet and low outlet".
In order to ensure the valve's tightness during an overhaul period, the valve with frequent opening and closing operation is required to install two series stop valves. As for the bypass system, the installation function of this bypass is: the inlet balances the front and rear pressure of the main pipe valve, making it easy to open, saving energy and reducing the wear of the main pipe valve; The heating tube with medium and small flow during starting process; The water pressure test of the boiler is carried out by controlling the feed water flow in the main feed water pipeline to control the boiler's lifting pressure speed. The bypass stop valves are primary and secondary valves respectively according to the direction of medium flow. The primary and secondary valves are closed during normal operation of the unit, both of which are in direct contact with the medium. To prevent the packing material between the secondary valve shell and cover and the packing around the stem from being affected by the medium and temperature for a long time, and the packing of the valve can be replaced during operation, the installation direction required by the secondary valve is "high in and low out".
3. Boiler exhaust and vent stop valves
The boiler exhaust and vent shutoff valves are only used in the process of boiler start up and up water, and have a small opening and closing frequency. However, due to poor sealing, they often result in loss of quality.
4. Electromagnetic quick break valve
The function of the solenoid quick break valve is to close quickly and cut off the fuel supply quickly. The structure of the solenoid quick break valve is similar to that of the cut-off valve. If the solenoid quick break valve is also a working material that enters from the lower part and flows from the upper part, the force exerted by the fuel on the lower part of the solenoid quick break valve disc is very large, and the weight of the solenoid quick break valve is much smaller than it. Therefore, if the working material enters the quick-break valve from the lower part, the torque caused by the heavy hammer is less than the torque caused by the fuel pressure. When the quick-break valve ACTS, the fuel cannot be cut off, so it cannot achieve the expected purpose. If the working material enters from the upper part of the quick break valve, the pressure after the quick break valve decreases rapidly once it is operated, the force exerted by the fuel on the lower part of the valve disc drops to zero quickly, and the force exerted by the fuel on the disc and the force generated by the gravity of the weight hammer and lever
Generally speaking, it is difficult to close the valve with low inlet and height under large bore and high pressure. If low inlet and height are adopted under high pressure and large bore, the valve stem is easy to deform and bend under water pressure for a long time, which affects the safety and sealing performance of the valve. Select high inlet and low point for stem diameter can be smaller, for manufacturers and users will also save a little cost.
|
WeChat
OnlineQQ