The closure member of a globe valve is a plug‑type disc with flat or conical sealing surfaces. The disc moves linearly along the centerline of the fluid flow. There are two types of valve‑stem movement: the rising‑stem type (the stem moves up and down while the handwheel remains stationary), and the rising‑rotating‑stem type (the handwheel rotates and lifts together with the stem, and the nut is mounted on the valve body). Globe valves are only suitable for full‑open and full‑close operation; throttling or flow regulation is not permitted.
A globe valve is a forced‑sealing valve. When the valve is closed, pressure must be applied to the disc to ensure tight sealing of the sealing surfaces against leakage. When the medium enters the valve from below the disc, the operating force has to overcome two resistances: friction between the valve stem and packing, and thrust generated by medium pressure. The force required to close the valve is greater than that required to open it. Therefore, the valve stem must have a sufficiently large diameter; otherwise, stem bending failure may occur.
In recent years, with the advent of self‑sealing valves, the medium flow direction of globe valves has been changed to enter the valve chamber from above the disc. Under medium pressure, the closing force becomes small while the opening force increases, so the stem diameter can be reduced correspondingly. Meanwhile, this valve type achieves reliable tightness under medium pressure. According to China’s former valve standardization specification, globe valves shall adopt the top‑to‑bottom flow direction.
Also known as stop valves, globe valves are among the most widely used valves. Their popularity stems from low friction between sealing surfaces during opening and closing, good durability, small opening height, easy manufacturing and convenient maintenance. They are applicable not only for medium‑low pressure conditions but also for high‑pressure services.
The closing principle of a globe valve relies on stem‑applied force to press the disc sealing surface tightly against the valve‑seat sealing surface so as to block medium flow. Globe valves allow medium flow in only one direction and shall be installed with correct flow orientation. They have a longer face‑to‑face dimension than gate valves and feature high fluid resistance; their sealing reliability may degrade after long‑term operation.
Advantages
Simple structure, easy‑to‑implement manufacturing and maintenance.
Short working stroke and short opening‑closing time.
Reliable sealing performance, low friction between sealing surfaces and long service life.
Globe valve bodies are available in straight‑way, Y‑pattern and angle‑pattern configurations. The straight‑way type is the most common but delivers the highest fluid resistance. The Y‑pattern type features lower fluid resistance and is often used for fluids with solid particles or high viscosity. Angle‑pattern valve bodies are mostly forged and applied for globe valves with small nominal diameters and high pressure ratings.
Disadvantages
High fluid resistance; large force is required for opening and closing.
Not suitable for media containing solid particles, high‑viscosity fluids or coking‑prone media.
Poor flow‑regulation performance.
By stem thread position, globe valves are classified into outside‑screw type and inside‑screw type. By medium flow direction, they are divided into straight‑way, Y‑pattern and angle‑pattern types. According to sealing form, globe valves include packing‑sealed globe valves and bellows‑sealed globe valves.
Bellows‑sealed globe valves adopt bellows‑sealing design, which completely eliminates the drawbacks of ordinary packing‑sealed valves such as rapid aging and easy leakage at the stem packing. They improve energy efficiency, enhance safety of production equipment, reduce maintenance costs and frequent servicing, and deliver a clean and safe working environment.
Installation and Maintenance
Globe valves operated by handwheel or handle can be installed at any position on the pipeline.
Handwheels, handles and actuators shall never be used for hoisting purposes.
Medium flow direction shall conform to the arrow marked on the valve body.
Globe valves are forced‑sealing valves. When closing, pressure must be applied to the disc to prevent leakage across sealing surfaces. When medium enters from below the disc, the operating force needs to overcome friction between stem and packing as well as thrust from medium pressure. Closing force is larger than opening force, so the stem diameter shall be adequate to avoid stem bending failure. Since self‑sealing valves appeared, globe valves have adopted flow entering the valve chamber from above the disc. Under medium pressure, closing force decreases while opening force increases, allowing a smaller stem diameter. This configuration also provides good tightness assisted by medium pressure. China’s former valve standardization specification stipulated that globe valves shall use top‑to‑bottom flow direction.
Globe valves feature a simple structure. They realize opening or shut‑off by the combined rotating‑and‑lifting motion of the valve stem, ensuring both main sealing and back‑sealing functions. However, this special motion principle imposes unfavorable stress conditions on the back‑sealing pair: it generates both necessary vertical contact pressure and relative sliding friction between sealing surfaces. Practical experience shows that back‑seals often leak after only a few open‑close cycles due to scoring of sealing surfaces. Slightly scored sealing pairs require disassembly and repair; heavily damaged ones must be scrapped. This increases manufacturing costs and impairs valve performance. Tests and improvements have been carried out on back‑seal structures and materials to solve such problems.