Globe valves are linear motion valves with rounded body structure. Their outlook is similar to other valves hence they can only be differentiated on the basis of their internal structure. Globe valves are best suited for throttling service. Their flow characteristics permit accurate and repeatable flow control. However, caution must be exercised to avoid extremely close throttling when pressure drop exceeds 20%. This creates excessive noise, vibration and possible damage to valves and piping.
A lot of globe valve manufacturers do not recommend applications in excess of this due to possible damage to the valve. Globe valve applications are usually found in systems that require frequent vacuum, stroking or systems with varying temperature ranges.
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Globe valves have a rounded body through which the fluid passes in a circuitous path. This results in more pressure drop through a fully open glove valve than similar sized gate or ball valve.
Globe valves are created with a disk that translates against a seat. The flow fluid is usually directed up through the seat and around the disk. Most large globe valves have direction arrow embossed on the body casting to show direction of flow.
Globe Valve Types
There are three main designs of glove valves
- Tee Pattern is the most common type of globe valve with a z shaped diaphragm. The seat is oriented horizontally allowing the stem and disk to travel perpendicular to the horizontal line. This also results in low flow coefficient and higher pressure drop. Tee pattern globe valve is mostly used in throttling application
- Angle Pattern Globe Valve have ends that are at angle of 90 degree and fluid flow through this 90 degree turn. Their coefficient of flow is lower than WYE pattern globe valves. Angle pattern globe valve are useful in applications with pulsating flow.
- WYE Pattern Globe Valve have seat and stem at a 45 degree angle. WYE pattern allow removal of debris and are useful in drain lines that are normally closed.
Globe Valve Design
- Disk: Disk of globe valve are either ball, composition disk or plug disk. Ball disk is primarily used in low pressure application. Composition disk used non metallic insert ring on the disk which results in a tight closure. Plug disk provides better throttling and can be either long or tapered shape.
- Seat: Globe valve seats are available in integrated or screwed configuration. Many globe valves have back seats inside the bonnet that provides a seal between stem and bonnet, preventing pressure build up against valve packing.
- Stem: There are two types of connecting the disk and stem. The T-Slot or the disk nut construction. In T Slot, the disk slides over the stem whereas in the nut design the disk is screwed into the stem.
Globe Valve Video