Why Are Globe Valves Installed with Low Inlet and High Outlet?

Many people assume all globe valves adopt low-inlet and high-outlet flow direction, which is not correct. While low inlet and high outlet is the common configuration, 

certain special applications require globe valves to be installed with high inlet and low outlet.

Also known as stop valves, globe valves are forced-sealing shut-off valves. They are classified into three connection types: flanged connection, threaded connection and welded connection.
According to the national "Three Standardization" policy for valves in China, the medium flow direction of globe valves shall be from top to bottom, which means they must be installed in the specified orientation.

This type of throttling globe valve is suitable for shut-off, flow regulation and throttling services. The valve stem has a relatively short travel for opening and closing, 

delivering reliable shut-off performance. Furthermore, the variation of the valve seat opening is proportional to the travel of the valve disc, making it ideal for flow adjustment.

Globe valves are designed for low inlet and high outlet to reduce flow resistance and lower the force required to open the valve. Meanwhile, when the valve is closed, 

the gasket between the valve body and bonnet as well as the packing surrounding the valve stem bear no load. They will not be exposed to medium pressure and temperature continuously, 

extending service life and lowering leakage risks. Besides, packing can be replaced or replenished while the valve remains closed, facilitating maintenance work.

Special Conditions Requiring High Inlet and Low Outlet Installation
High-pressure globe valves with nominal diameter over 100 mm

Large-diameter valves feature relatively poor inherent sealing performance. With high inlet and low outlet arrangement, medium pressure acts on the upper side of the valve disc after valve closure, 

improving the tightness of sealing.

The second globe valve of two series-connected globe valves on bypass pipelines
To guarantee valve tightness within one maintenance cycle, two globe valves installed in series are adopted for frequently operated circuits.
The functions of bypass pipelines are as follows:
① Balance the pressure upstream and downstream of the main pipeline valve for easier opening and less wear on the main valve;
② Small-flow warm-up of piping during unit startup;
③ Control feedwater flow rate on main feedwater pipelines to adjust boiler pressure rise speed during boiler hydraulic tests.

Based on medium flow direction, the two bypass globe valves are defined as primary valve and secondary valve. 

Both valves stay closed under normal unit operation and are in direct contact with process medium.

To prevent prolonged exposure of the bonnet gasket and stem packing of the secondary valve to medium pressure and temperature, and allow packing replacement during operation, 

the secondary valve shall be installed in high-inlet and low-outlet orientation.

Boiler vent and blowdown globe valves

Boiler vent and blowdown globe valves are only used during boiler filling and startup with low operation frequency. However, internal leakage often causes working medium loss. 

For this reason, some power plants install such globe valves with high inlet and low outlet to enhance sealing tightness.

Solenoid quick shut-off valves
The function of solenoid quick shut-off valves is rapid closure to cut off fuel supply immediately. Their structure is similar to conventional globe valves.

If the medium enters from the bottom and exits from the top, fuel pressure creates a large upward force on the bottom of the valve disc. This force far exceeds the load from the valve counterweight. 

The torque generated by the counterweight cannot overcome the hydraulic torque from fuel pressure, so the valve will fail to cut off fuel upon actuation.

If the medium enters the quick shut-off valve from the upper side, the downstream pressure drops sharply once the valve trips. The upward hydraulic force acting on the valve disc quickly reduces to zero, 

while the downward force formed by fuel pressure on the disc together with the weight of counterweight and lever ensures reliable shut-off.

Generally speaking, for large-diameter and high-pressure conditions, globe valves with low inlet and high outlet require great force for closing. 

When low-inlet high-outlet arrangement is used under high pressure and large diameter working conditions, the valve stem bears sustained hydraulic pressure and is prone to bending deformation, impairing valve safety and sealing performance.

Adopting high inlet and low outlet allows the use of valve stems with smaller diameter, cutting costs for both manufacturers and end users.