What is a Globe valve – Various Globe Valve Types | Globe Valve Manufacturer

What is a Globe Valve?

Valve refers to a valve whose closure (disc) moves along the center line of the seat. According to the movement of the disc, the change of the seat opening is proportional to the disc travel. Because the stem opening or closing stroke of this kind of valve is relatively short and has a very reliable cut-off function, and because the change of the seat opening is proportional to the disc travel, it is very suitable for flow regulation. Therefore, this type of valve is very flexible for cutting or regulating, and throttling.

The globe valve is used for throttling flow control. Shut off is accomplished by moving the disc against the flow stream rather than across it as in the case with a gate valve. The flow pattern through a globe valve involves changes in direction, resulting in greater resistance to flow, causing a high pressure drop. The globe valve is an excellent valve to use in high pressure operation of steam. Our globe valves are factory-made with quality material for long term use.

Globe valve refers to the valve that the plate moves along the center line of the valve seat. According to this form of valve movement, the change of seat opening is proportional to the valve stroke. Because the opening or closing stroke of the stem is relatively short and has a very reliable cutting function, it is very suitable for flow regulation. Globe valves can be divided into external thread type and internal thread type according to the thread. Globe valves can also be divided into the straight type and angle type with the flow direction. Globe valves can also be divided into the straight-flow type and angle type with the flow direction. Globe valves can be divided into packing sealing type and bellow sealing type according to the sealing form.

A globe valve is a linear motion valve used to stop, start, and regulate fluid flow.

A Z-body globe valve is illustrated the globe valve disk can be totally removed from the flow path or it can completely close the flow path.

The essential principle of globe valve operation is the perpendicular movement of the disk away from the seat.

Conventional Globe valves may be used for isolation and throttling services. Although these valves exhibit slightly higher pressure drops than straight=through valves (e.g., gate, plug, ball, etc.), they may be used where the pressure drop through the valve is not a controlling factor.

Because the entire system pressure exerted on the disc is transferred to the valve stem, the practical size limit for these valves is NPS 12 (DN 300). Globe valves larger than NPS 12 (DN 300) are an exception rather than the rule. Larger valves would require that enormous forces be exerted on the stem to open or close the valve under pressure. Globe valves in sizes up to NPS 48 (DN 1200) have been manufactured and used.

Globe valves are extensively employed to control flow. The range of flow control, pressure drop, and duty must be considered in the design of the valve to avert premature failure and to assure satisfactory service. Valves subjected to high-differential pressure-throttling service require specially designed valve trim.

Generally, the maximum differential pressure across the valve disc should not exceed 20 percent of the maximum upstream pressure or 200 psi (1380 kPa), whichever is less. Valves with special trim may be designed for applications exceeding these differential pressure limits.

According to the position of the stem, the screw has the external screw type globe valve and the internal screw type globe valve. According to the flow direction of the medium, there are straight-through globe valves, straight-flow globe valves, and Angle globe valves. Globe valve according to seal form, packing seal globe valve, and bellows seal globe valve.

Bellow seal DIN Carbonsteel globe valve rising stem OY&S with lever DN80

Globe Valve Types

Body designs of Globe valves

There are three primary body designs for Globe valves, namely. Tee Pattern or Z-body, Angle Pattern and Wye Pattern or Y-body body.

Tee Pattern Globe Valve

Tee Pattern Globe valve(T pattern globe valve) design is the most common body type, with a Z-shaped diaphragm. The horizontal setting of the seat allows the stem and disk to travel perpendicular to the horizontal line. This design has the lowest coefficient of flow and higher pressure drop. They are used in severe throttling services, such as in bypass lines around a control valve. Tee-pattern Globe valves may also be used in applications where pressure drop is not a concern and throttling is required.

Angle Globe Valve

Angle Pattern Globe valves(Angle globe valve) design is a modification of the basic Tee Pattern Globe valve. The ends of this Globe valve are at an angle of 90 degrees, and fluid flow occurs with a single 90 degrees turn. They have a slightly lower coefficient of flow than wye-pattern Globe valves. They are used in applications that have periods of pulsating flow because of their capability to handle the slugging effect of this type of flow.

Wye Pattern Globe Valve (Y Type Globe Valve)

Wye Pattern Globe valves(Y type globe valve) design, is an alternative for the high pressure drop, inherent in Globe valves. Seat and stem are angled at approximately 45 degrees, what gives a straighter flowpath 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. They can be rod through to remove debris when used in drain lines that are normally closed.

Bonnet Design of Globe Valves

There are three primary bonnet designs for Globe valves, namely.. screwed bonnet, bolted bonnet, welded bonnet, or pressure seal bonnet.

Screwed Bonnet Globe Valve

Screwed bonnet: This is the most basic design possible, and it is utilized for low-cost valves.

Bolted Bonnet Globe Valve

Bolted-bonnet: This is the most common design and is seen in the majority of globe valves. A gasket is required to seal the junction between the body and the bonnet.

Welded Bonnet Globe Valve

Welded-Bonnet: This is a common design that does not need disassembly. They weigh less than their bolted-bonnet equivalents.

Pressure Seal Bonnet Globe Valve

Pressure-Seal Bonnet: This kind is commonly employed in high-pressure, high-temperature applications. The greater the pressure in the body cavity, the greater the strain on the gasket of a pressure-seal valve

Construction of a Globe valve

Globe valves usually have rising stems, and the larger sizes are of the outside screw-and-yoke construction. Components of the Globe valve are similar to those of the gate valve. This type of valve has seats in a plane parallel or inclined to the line of flow.

Maintenance of Globe valves is relatively easy, as the discs and seats are readily refurbished or replaced. This makes Globe valves particularly suitable for services that require frequent valve maintenance. Where valves are operated manually, the shorter disc travel offers advantages in saving operator time, especially if the valves are adjusted frequently.

The principal variation in Globe-valve design is in the types of discs employed. Plug-type discs have a long, tapered configuration with a wide bearing surface. This type of seat provides maximum resistance to the erosive action of the fluid stream. In the composition disc, the disc has a flat face that is pressed against the seat opening like a cap. This type of seat arrangement is not as suitable for high differential pressure throttling.

In cast-iron Globe valves, discs, and seat rings are usually made of bronze. In steel-Globe valves for temperatures up to 750°F (399°C), the trim is generally made of stainless steel and so provides resistance to seizing and galling. The mating faces are normally heat-treated to obtain differential hardness values. Other trim materials, including cobalt-based alloys, are also used.

The seating surface is ground to ensure full-bearing surface contact when the valve is closed. For lower pressure classes, alignment is maintained by a long disc locknut. For higher pressures, disc guides are cast into the valve body. The disc turns freely on the stem to prevent galling of the disc face and seat ring. The stem bears against a hardened thrust plate, eliminating galling of the stem and disc at the point of contact.

For applications with low temperature, Globe valves are normally installed so that the pressure is under the disc. This contributes to an easy operation and helps protect the packing.

For applications with high temperature steam service, Globe valves are installed so that the pressure is above the disk. Otherwise, the stem will contract upon cooling and tend to lift the disk off the seat.

Typical Applications of Globe valves

The following are some of the typical applications of Globe valves:

  • Cooling water systems where flow needs to be regulated
  • Fuel oil system where flow is regulated and leak tightness is of importance
  • High-point vents and low-point drains when leak tightness and safety are major considerations
  • Feedwater, chemical feed, condenser air extraction, and extraction drain systems
  • Boiler vents and drains, main steam vents and drains, and heater drains
  • Turbine seals and drains
  • Turbine lube oil system and others

Advantages of a Globe Valve:

  • During the opening and closing process, the friction between the disc and the sealing surface of the valve body is smaller than that of the gate valve, so it is wearable.
  • The opening height is generally only 1/4 of the seat passage, so it is much smaller than the gate valve.
  • There is usually only one sealing surface on the valve body and disc, so the manufacturing process is better and easy to maintain.
  • Because its filler is generally a mixture of asbestos and graphite, it has a higher temperature resistance. Generally, steam valves are cut-off valves.
  • Good shutoff capability
  • Moderate to good throttling capability
  • Shorter stroke (compared to a gate valve)
  • Available in tee, wye, and angle patterns, each offering unique capabilities
  • Easy to machine or resurface the seats
  • With disc not attached to the stem, the valve can be used as a stop-check valve
  • Simple structure, convenient manufacture and easy to maintenance
  • Small working stroke, short opening and closing time.
  • Good sealing, low friction between the sealing surfaces, and long service life.
  • The annular space between the disk and seat ring gradually closes as the valve is closed. This characteristic gives the globe valve good throttling ability, which permits its use in regulating flow. Therefore, the globe valve may be used for both stopping and starting fluid flow and for regulating flow.
  • When compared to a gate valve, a globe valve generally yields much less seat leakage. This is because the disk-to-seat ring contact is more at right angles, which permits the force of closing to tightly seat the disk.
  • Globe valves can be arranged so that the disk closes against or in the same direction of fluid flow. When the disk closes against the direction of flow, the kinetic energy of the fluid impedes closing but aids in the opening of the valve. When the disk closes in the same direction of flow, the kinetic energy of the fluid aids closing but impedes opening. This characteristic is preferable to other designs when quick-acting stop valves are necessary.

Disadvantages of a Globe valve:

  • The minimum flow resistance of the globe valve is also higher than that of most other types of valves because the flow direction of the medium through the valve has changed.
  • Because of the long travel, the opening speed is slower than the ball valve.
  • Big flow resistance and large opening and closing power
  • Poor regulation performance
  • The most evident shortcoming of the simple globe valve is the high head loss from two or more right-angle turns of flowing fluid.
  • Obstructions and discontinuities in the flow path leading to head loss. In a large high-pressure line, the fluid dynamic effects from pulsations, impacts, and pressure drops can damage trim, stem packing, and actuators.
  • In addition, large valve sizes require considerable power to operate and are especially noisy in high-pressure applications.
  • Other drawbacks of globe valves are the large openings necessary for disk assembly, heavier weight than other valves of the same flow rating, and the cantilevered mounting of the disk to the stem.
  • Higher pressure drop (compared to a gate valve)
  • Requires greater force or a larger actuator to seat the valve (with pressure under the seat)Throttling flow under the seat and shutoff flow over the seat
  • High fluid resistance, greater force required for opening and closing
  • Globe valve does not apply to medium with particle, high viscosity, and easy coking
What is Globe valve, Advantages and Disadvantages of  Globe Valves
What is Globe valve, Advantages and Disadvantages of  Globe Valves

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ZECO Valve is established in 1991, as a professional industrial valve manufacturer and water valve manufacturer in Shanghai, China.

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