Flow direction of a globe valve
Generally, the current medium of the globe valve flows upward from the bottom of the valve seat, which is customarily called "low-in and high-out". When the valve is closed, the sealing packing of the valve stem is not affected by the pressure and temperature of the working medium, and the filling change work can be also operated when the valve is closed. The disadvantage is that the valve has a large closing force, and it is difficult for a globe valve with large diameter to achieve sealing.
Therefore, sometimes the medium is also allowed to flow down from the top of the seat, called "high-in and low-out". In the upper part of the disc, the valve is easy to seal, but such a valve has a large opening torque which is easy to cause leakage of the sealing packing, and the valve packing cannot be replaced.
In general, considering the closing torque, for globe valves ≤ 6 inch, with nominal pressure ≤ PN160, we should mostly use the flow direction of "low-in and high-out", while for globe valves ≥ 8 inch, with nominal pressure ≥PN200, we mostly use "high-in and low-out." In order to reduce the opening or closing torque, the valve is normally set by an internal bypass or an external bypass above an 8 Inch globe valve.
Therefore, sometimes the medium is also allowed to flow down from the top of the seat, called "high-in and low-out". In the upper part of the disc, the valve is easy to seal, but such a valve has a large opening torque which is easy to cause leakage of the sealing packing, and the valve packing cannot be replaced.
In general, considering the closing torque, for globe valves ≤ 6 inch, with nominal pressure ≤ PN160, we should mostly use the flow direction of "low-in and high-out", while for globe valves ≥ 8 inch, with nominal pressure ≥PN200, we mostly use "high-in and low-out." In order to reduce the opening or closing torque, the valve is normally set by an internal bypass or an external bypass above an 8 Inch globe valve.
