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Globe Valve

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A globe valve, abbreviated as GLV, is a type of valve used for regulating fluid flow, both on/off and throttling, it is a control valve.  The name globe valve comes from the globular shape of the valve body.  This valve is the most common control valve used and can be found in industries such as the oil and gas, chemical, pharmaceutical, shiping, pulp and paper.

Globe Valve Design Classification

Angle Globe Valve  -  The valve is a modified globe valve whose inlet and outlet are at right angles to each other.  The design of this valve is the same as a globe valve, but the ends of this valve is at a 90-degree angle, and fluid flow is at a 90-degree turn.  The angle globe valve’s opening and closing sections are plug shaped valve discs, the sealing surface is flat or conical, and the flap travels linearly down the fluid’s centreline.  Because of their ability to withstand the slugging effect of this form of flow, they are used in applications that include cycles of pulsating flow.  These valves are used in lines where the pipe construction or pressure drop is complex.
Oblique Globe Valve  -  This valve body design is an alternative for the high pressure drop, inherent in globe valves.  Oblique pattern design reduces the flow resistance of the globe valve to a minimum.  Seat and stem are angled at approximately 45 degrees, what gives a straighter flow path at full opening and offer the least resistance to flow.  They can be cracked open for long periods without severe erosion.  They are extensively used for throttling during seasonal or startup operations.
Straight Globe Valve  -  The valve is used to cut off the flow of the medium and is suitable for occasions that need to be throttled frequently, providing large pressure drop across the valve.
Tee Globe Valve  -  Tee globe valves are similar to Y globes but feature three ports instead of two.  As their name implies, these valves form a “tee” shape when viewed from above, which allows them to be used in systems where more precise control over fluid flow is needed than what is possible with standard Y-pattern globes.  Tee pattern globes can also be manual or automated, depending on the application requirements.
Y Globe Valve  -  The wye design mitigates the high pressure drop associated with most global valves by providing a seat and a stem at a 45° angle.  This allows for a straighter flow path when the valve is fully open and reduces friction and turbulence associated with the globe valve design.
Z Globe Valve  -  The Z-shaped partition inside the globe body contains the seat.  The horizontal seating arrangement of the seat allows the stem and disk to travel perpendicular to the pipe axis resulting in a very high-pressure loss.  The valve seat is easily accessible through the bonnet, which is attached to a large opening at the top of the valve body.

 

Globe Valve Advantages and Disadvantages

AdvantagesDisadvantages
  • The working stroke is small and the opening and closing time is short.
  • During the opening and closing process, the friction between the valve flap and the sealing surface of the valve body is smaller than that of the gate valve, so it is wear resistant.
  • The opening height is generally only 1/4 of the valve seat passage, so it is much smaller than the gate valve.
  • Usually there is only one sealing surface on the valve body and the valve flap.
  • The temperature resistance level is higher.
  • Generally used in steam and as a shut-off valve.
  • The adjustment performance is poor.
  • It is not suitable for media with particles, high viscosity and easy coking.
  • The minimum flow resistance of the valve is higher than most other types of valves.
  • Poor regulation performance.

 

Globe Valve Disk Styles

Ball Disk  -  This design is used primarily in relatively low pressure and low temperature systems.  It is capable of throttling flow, but is primarily used to stop and start flow.
Composition Disk  -  Uses a hard, nonmetallic insert ring on the disk which creates a tighter closure.  These disks are primarily used in steam and hot water applications.  They resist erosion and are sufficiently resilient to close on solid particles without damaging the valve.
Needle Disk (Vee Point Disk)  -  This design the flow rate is controlled better than other disk designs and a fine regulation is achieved.  When you need better throttling in different flow velocity.
Parabolic Disk  -  It is similar to the ball type disk, but its parabolic design provides a higher flow regulation, having a better behavior against wear.
Plug Disk  -  Because of its configuration, long and tapered, the plug disk provides better throttling than ball or composition designs.  This disk is available in a variety of specific configurations.

Globe Valve Parts

Handwheel and Nut  -  Manual operated actuators use a handwheel to open or close the valve.  They offer the user the ability to position the valve as needed.
Yoke  -  It connects the valve body or bonnet with the actuating mechanism and can provides support for the gland pull down bolts.  On many valves, the yoke and bonnet are designed as a one piece construction.  For automated actuated valves, the yoke arms are of a heavier construction to provide adequate support to the actuator.  The yoke usually has openings to allow access to the stuffing box.  A yoke must be sturdy enough to withstand forces, moments, and torque developed by the actuator.
Stem  -  There are two methods for connecting the disk and the stem, the T-slot and the disk nut.  In the T-slot design, the disk slides over the stem, in the disk nut design, the disk is screwed into the stem.

  • Rising Stem  -  The threaded part of the stem is inside the valve body, and the stem packing is along the smooth part that is exposed to the atmosphere outside.  In this case the stem threads are in contact with the flow medium.  When rotated, the stem and the handwheel rise together to open the valve.  This design is commonly used in the smaller sized low to moderate pressure gate, globe, and angle valves.
  • Non-rising Stem  -  The threaded part of the stem is inside the valve and does not rise.  The valve disc travels along the stem like a nut when the stem is rotated.  Stem threads are exposed to the flow medium and, as such, are subjected to its impact.  This design is used where space is limited to allow linear stem movement, and the flow medium does not cause erosion, corrosion, or wear and tear of stem material.
  • Sliding Stem  -  This stem does not rotate or turn.  It slides in and out of the valve to close or open the valve.  This design is used in hand lever operated quick opening valves.  It is also used in control valves that are operated by hydraulic or pneumatic cylinders.
  • Rotary Stem  -  This is a commonly used design in ball, plug, and butterfly valves.  A quarter-turn motion of the stem opens or closes the valve.

Stem Packing  -  Depending on the application, the packing is to prevent leakage of flow medium to the environment and prevent outside air from entering the valve in vacuum applications.  The packing is made of a wearable material and must changed during valve maintenance.
Yoke  -  It connects the valve body or bonnet with the actuating mechanism and can provides support for the gland pull down bolts.  On many valves, the yoke and bonnet are designed as a one-piece construction.  For automated actuated valves, the yoke arms are of a heavier construction to provide adequate support to the actuator. The yoke usually has openings or windows to allow access to the stuffing box.  A yoke must be sturdy enough to withstand forces, moments, and torque developed by the actuator.
Yoke Bushing  -  An internally threaded nut held in the top of a yoke through which the valve stem passes.   In gate and diaphragm valves, the yoke nut is turned and the stem travels up or down depending upon the direction of rotation of the nut.   In the case of globe valves, the nut is held fixed and the stem is rotated through it.   Valves which require greater effort to open or close are provided with antifreeze yoke sleeve bearings that minimize the friction between the hardened stem and the yoke bushing.
Cage  -  The cage includes in the most important parts of the globe valve.  It surrounds the valve disc and is located within the valve body.  When the disc moves, more opening inside the cage is exposed, and the flow rate increases.
Gland Packing  -  A gasket that provides a seal between the valve’s stem and the bonnet.  It is used to prevent liquid leaks in valve stems and stuffing boxes.  The gland should be tightened until the valve is leak proof.  Tight the packing to tight may affect the valve movement and may cause damage to the stem.
Disk/Plug  -  The disc is the part which allows, throttles, or stops flow, depending on its position.  A disc is seated against the stationary valve seat or seats when the valve is in the closed position.  When the valve is closed, the disc performs pressure retaining functions.
Seat  -  Globe valve seats are either integrated or screwed in to the valve body.  Many globe valves have backseats inside the bonnet.  Back seats provides a seal between the stem and bonnet and prevents system pressure from building against the valve packing, when the valve is fully open.
Body  -  The body is the main pressure containing of the valve and can identified as it forms the mass of the valve.  It contains all of the valve’s internal parts that will come in contact with the substance being controlled by the valve.  The bonnet is connected to the body and provides the containment that is being controlled.

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