Cooling water system.

Fuel system.

Feed water or chemical feed system.

Boiler and main steam vents and drains.

Turbine lubricating oil system, etc.

These are the applications of globe valves and the functions, advantages and disadvantages of globe valves will be shared below.

What is a globe valve?

A globe valve is a linear motion valve designed primarily for stopping, starting and regulating flow. The valve plate of a globe valve can be completely removed from the flow path or the flow path can be completely closed.

Conventional globe valves can be used for isolation and throttling services. Although these valves have a slightly higher pressure drop than straight-through valves (e.g., gate, plug, ball, etc.), they can be used in situations where the pressure drop through the valve is not a controlling factor.

Because the entire system pressure applied to the valve flap is transferred to the stem, the actual size of these valves is limited to NPS 12 (DN 300). Shutoff valves larger than NPS 12 (DN 300) are the exception rather than the rule. Larger valves require significant force on the stem to open or close the valve under pressure. Shutoff valves in sizes up to NPS 48 (DN 1200) have been manufactured and used.

Shut-off valves are widely used to control flow. Flow control range, pressure drop and load must be considered in the valve design to avoid premature failure and to ensure satisfactory service. Valves subjected to high differential pressure throttling service require specially designed valve internals.

Typically, the maximum differential pressure across the valve disc should not exceed 20% of the maximum upstream pressure or 200 psi (1380 kPa), whichever is less. Valves with special internals can be designed for applications that exceed these differential pressure limits.

Shutoff Valve Advantages and Disadvantages

Advantages.

Good shutoff capability.

Moderate to good valve throttling

Shorter stroke (compared to gate valves).

Easily machined or resurfaced seats.

Can be used as a shut-off check valve.

Disadvantages.

Higher pressure drop (compared to gate valves).

Requires more force or a larger actuator to seat the valve.

Three basic shutoff body designs exist: Tee, Angle, and Wye. 

Tee Shutoff Valve

This is the most common body type for shutoff valves. The horizontal setting of the seat allows the stem and disc to move perpendicular to the horizontal. This design has the lowest flow coefficient and highest pressure drop. They are used for tight throttling service, such as bypass lines around control valves. This shutoff valve design is a good solution when pressure drop is not an issue and throttling is required.

Angle Shutoff Valves

The Angle globe valve design is a modification of the basic 3-way globe valve. This globe valve ends at a 90-degree angle and fluid flow occurs at a single 90-degree turn. They have a slightly lower flow coefficient than the Y-shaped globe valve. They are used in applications with pulsating flow cycles because they can handle the segment plug effect of this type of flow.

Wye globe valve

This type is an alternative to the high pressure drop common in globe valves and is inherent in globe valves. The seat and stem are at a 45° angle, providing a straighter flow path when fully open and offering minimal resistance to flow. They can be cracked for extended periods of time without severe erosion. This design is typically used for throttling during seasonal or start-up operation. When used on drains that are normally closed, they can be routed through the stem to remove debris.