How does a high-pressure globe valve work?
A high-pressure globe valve operates using a manual handwheel or an actuator. The valve starts when the handwheel is rotated in a clockwise direction. The working principle is the same whether the valve is manually operated or automated. A component known as a stem transmits the torque applied on the handwheel to the disc. The stem turns as it moves upwards, and thus the valve disc moves upwards. This process leaves the valve interior open, allowing fluid flow to occur. Fluid flow stops when the handwheel rotates in the counterclockwise direction. As such, the stem rotates in the same direction as it moves downwards. The stem’s downward movement causes the disc to move downwards to its seating position. At this position, the valve disc seals the flow path completely, ensuring no fluid flows through the valve. In the case of throttling, slight rotation of the handwheel forces the valve disc to move upwards slightly, leaving the valve partially open.
Figure: Working of a high-pressure globe valve.
Types of high-pressure globe valves
Z-pattern high-pressure globe valve
The z-pattern high-pressure globe valve is one of the most common valve types. This valve is also known as a standard pattern valve. It has a flat seat setting allowing the disc and stem to move normal to the fluid flow direction. The flow resistance in this valve is very high compared to other valves. The increased flow resistance leads to a high-pressure drop. So, it is advisable to purchase this valve for if the area of application will not be severely affected by the low-pressure drop. However, this valve will serve very well when it comes to throttling.
Figure: T-pattern high-pressure globe valve.
Angle pattern high-pressure globe valve
This is a unique valve designed to turn media flow to an angle of 90o degrees without the pipeline utilizing any elbow. Like other valves, the valve disc moves upwards to open media flow and downwards to the seating position when it is closing the valve. One main advantage of this valve is that it can serve as a valve and also serve as a pipe elbow, thus reducing the cost of the piping system.
Figure: Angle-pattern high-pressure globe valve.
Y-pattern high-pressure globe valve
This valve is also known as an oblique pattern high-pressure globe valve. It is designed as an alternative for high-pressure drop common in other globe valves. The valve is designed such that the valve stem and seat meet at an angle of 45o degrees. This design leads to a straight flow path when the valve is fully open, resulting in low fluid flow resistance. It has low flow resistance, which helps to reduce pressure drop. The valve can remain partially open for a long duration without suffering from erosion.
Figure: Y-pattern high-pressure globe valve.
Flanged-end high-pressure globe valves
These are valves that are made with flange ends. The flange ends are meant to contain the holes that help to connect the valve to the pipe. The pipe end to be connected should also have a flanged end of the same size as the valve. High-pressure globe valve manufacturers design these valves with thick flanges to ensure they can withstand the high strength needed to secure the valve and the pipe. This type of valve is easy to assemble and disassemble from the pipe. It is also highly reliable in ensuring zero leakage due to its high strength. However, it is heavy. The increased weight emanates from the flanged ends and the number of bolts and nuts used.
Figure: Flanged end high-pressure globe valve.
Welded-end high-pressure globe valve
These are valves that are connected to the pipe through welding. The welding approach is mainly used where the fluid conveyed through the piping system is highly hazardous. Thus any slight leakage may lead to considerable losses to the environment or to the piping personnel. The valve is designed with a butt end or socket end. The ends are inserted into the pipe, and a welding machine is used to weld the valve and the pipe together. This type of connection is very reliable for high-pressure, high-temperature, flammable, and corrosive products. However, once the valve is connected to the pipe, it is impossible to remove it unless the weld is properly removed.
Figure: Welded end high-pressure globe valve.
Electric high-pressure globe valve
This is a high-pressure globe valve that operates using an electric actuator. An electric actuator operates by using electrical energy. The electrical energy from the mains supply powers a motor in the actuator. The motor then rotates its shaft converting electrical energy to mechanical energy. The mechanical energy provides the torque or rotary motion the valve stem needs to move the disc to open or close fluid flow. This valve can be automated or semi-automated. It is a valve with high levels of hygiene since it does not contribute to dirt. Considering its level of cleanliness, the valve can be used in applications that demand high levels of hygiene. However, this valve relies on electricity; thus, in a power outage, it adversely affects plant operations.
Figure: Electric high-pressure globe valve.
Pneumatic high-pressure globe valve
This is a valve that operates using a pneumatic actuator. The actuator operates by use of compressed air. However, this actuator needs a power source to compress the air, and thus electricity is required. The compressed air acts on a piston within a cylinder creating rotary motion. This motion is transmitted to the valve stem, forcing the disc to open or close fluid flow. This valve can be automated to reduce labor costs and the possibility of injury to the valve operator. The valve is very clean and thus suitable for use if high hygiene levels are demanded.
Figure: Pneumatic high-pressure globe valve.