Globe valve is a linear motion valve. It is used to stop, start and regulation of working fluid. Globe valve has the same components as a gate valve with different arrangements. In a globe valve, flow control accomplished through a plug or disc. This plug or disc seat on an orifice that arranged at 900 angles to the axis of the flow path. In other words, the principle of globe valve operation is the vertical movement of the disc away from the seat. Disc or plug totally removes in valve open position and totally close the flow path in the closed position. Globe valve has much less seat leakage due to disc to seat ring contact is more at 900 angle.
Globe valve disc can close in the same direction of fluid flow or against the direction of fluid flow. If the disc closes in the same direction of flow, then the kinetic energy of fluid helps in valve closing. This kinetic energy also obstructs/ blocks the opening of the valve. If the disc closes against the direction of flow, then the kinetic energy of fluid helps in valve opening and obstructs/ blocks valve closing. This characteristic is better to other designs when quick-acting stop valves are necessary.
Pressure drop or head loss through the globe valve is much higher than in the gate valve. This is due to two or more right angle turns of flowing fluid. Obstacles and discontinuities in the flow path leading to head loss. In a large high-pressure line, the fluid effects from impacts, pulsations, and pressure drops. These factors can damage trim, stem packing, and actuators. Also, large valve sizes require huge power to operate. These valves also create noise in high-pressure applications.
These valves heavier in weight than other valves of the same flow rating.
Globe Valve Direction of Flow:
For low temperature or liquid applications, flow directed from under the plug or disc. This promotes easy operation, helps protect the packing, and removes a certain amount of erosive action to the disc and seat faces. An arrow on the valve body gives the correct flow direction.
In case of high-temperature steam applications, flow is in the reverse of the direction of the liquid. Globe valves are fitted so that pressure is above the disc. By directing the steam from above instead of from below, the stem will remain heated and will not contract. Otherwise, the stem will contract during cooling and causes to lift the disc off the seat.