v What is a globe valve ?
v Where can I find globe valve suppliers & globe valve manufacturers?
v Globe valve videos
v International standards related to globe valves
What is a globe valve ?
The basic design of a globe valve, which is called globe due to the originally round body shape, hasn’t changed much over the last 200 years. A globe valve is a valve primarily designed to stop or regulate a flow by lifting a disc in a perpendicular motion away from the seat, out of the path of the fluid. Inside the valve, the upstream and downstream side of the valve are separated by an internal baffle. This baffle has an circular opening that forms a seat onto which a movable plug can be pushed to close the valve. The plug is also called a disc or disk. The disc is connected to a stem which is operated by screw action using a handwheel. Typically, automated globe valves use smooth stems rather than threaded and are operated by an actuator assembly.
Due to this construction, and contrary to the gate valve, it does not offer a straight flow path. The change in direction of fluid flow increases resistance, resulting in a higher pressure drop. Therefore typical globe valves are excellent to be used as a regulating valve. A handwheel must be turned many times 360° to go from fully closed to fully open position, which explains why globe valves, just like gate valves are referred to as multi-turn valves. Due to the linear motion of the closure element, it is also called a linear motion valve.
The body can be straight (also referred to as Z-type), Y-shaped or angle-shaped and have flanged, screwed or welded connections. The Y-shaped and angle-shaped body have a more fluent flow (less turns) resulting in a lower pressure drop. The Y-body design has a construction where the seat/stem assembly are angled at around 45°. The angle-body design serves both as a valve and as a piping elbow.
There are different bonnet types depending on the application. Screwed or union-type bonnets are the simplest design, often used for brass gate valves. Bolted bonnet is used for higher pressure and larger valves. A pressure seal bonnet is a special construction where the sealing is actually improved when the internal pressure increases, unlike the other bonnet types where a higher pressure tends to cause more leakage.
The stem of a globe valve must be of a high finish and is typically sealed with graphite (or PTFE) packing material in the stuffing box. Belleville washers or equivalent systems are often used to apply a constant compression force on the packing rings, compensating for fluctuations in operating conditions or wear and ensuring a better reliability and reducing fugitive emissions.
The seat rings are screwed or pressed and welded into the body. They can have hard facing or Stellite overlay for more demanding applications. API 600 defines different materials of seats, stem and wedge for different so called trim numbers. To obtain bubbletight shut-off, the seat ring can also be in PTFE material, but the slightest damage of the PTFE can cause leakage.
The disc can have different shapes to obtain a specific flow control characteristic and better resistance against wear and erosion under certain throttling conditions. While a standard globe valve has a flat disc bottom, the control disc often has a parabolic or conical shape.
Some globe valves have a special feature called backseat. This is an arrangement that provides a seal between the disc/stem and the valve bonnet (inner side). When the valve is at its fully open position and the valve/stem is at its highest position, it seals against the backseat which isolates the stem packing.
For applications with low temperature, globe valves are normally installed so that the (inlet) pressure is under the disc. This way, pressure will assist opening the valve and helps protect the packing.
For applications with high temperature steam service, globe valves are installed so that the (inlet) pressure is above the disc. Otherwise, the stem will contract upon cooling and tend to lift the disk off the seat.
In general, globe valves are limited to DN250 or about because the high forces exerted by the fluid pressure on the disc surface area make it very difficult to operate the valve for larger sizes.
A needle valve and a bellows sealed globe valve are special designs of the globe valve. The needle valve has a disc in the form of a needle to regulate small flow very precisely and/or at high pressure. Needle valves usually are limited to 2” size. The bellows sealed globe valve has a bellow that is welded on one side at the back of the disc/stem, around the stem, and on the other side against the valve body. This means the stem and stem packing is totally isolated from the fluid, giving no leak path through the stem packing. It is therefore often used for applications where leakage (fugitive emissions) to the environment has to be avoided due to the dangerous or toxic nature of the fluid, like heating oil or Chlorine. For more information on the bellows sealed globe valve, please refer to the relevant Valve Basics article.
Advantages of globe valves
·good regulating capability as well as positive shutoff
·faster operation than gate valve (but still slower than quarter turn valves)
·solid build, available in high pressure classes (but limited in size)
Disadvantages of globe valves
·size & weight (compared to ball and butterfly valves)
·not suitable for quick opening/closing
·low capacity (Cv value), high pressure drop
·not suitable for viscous fluids
Where can I find globe valve suppliers & manufacturers?
In our buyers’ Guide/Valve directory you will find many manufacturers and distributors of globe valve, both worldwide and locally. Search our list of gate valve suppliers
Globe valve videos
(Courtesy FBV, Inc.)
International standards related to globe valves
(This list does not pretend to be complete. Only standards where globe valves are mentioned in the title have been listed here. Other - general - standards may be applicable as well)
API RP-621 : Reconditioning of metallic gate, globe and check valves
ASME F885 : Standard Specification for Envelope Dimensions for Bronze Globe Valves NPS 1/4 to 2 El-1996 R(1996)
ASME F1794 : Standard Specification for Hand operated, Globe-Style Valves for Gas (Except Oxygen Gas), and Hydraulic Systems
BS 1873 : Specification for steel globe valves
BS 5154 : Copper alloy globe, globe stop, check and gate valves for general purposes
BS 5352 : Cast and forged steel wedge gate, globe, check and plug valves, screwed and socket welding, £DN50, for petroleum, petrochemical and allied industries (replaced by ISO 15761)
DIN 3356-1 : Globe valves – general data
DIN 3356-2 : Globe valves – cast iron stop valves
DIN 3356-3 : Globe valves – unalloyed steel stop valves
DIN 3356-4 : Globe valves – high temperature steel stop valves
DIN 3356-5 : Globe valves – stainless steel stop valves
DIN 3502 : Stop valves for drinking water supplies on and in private property – straight pattern globe valves with oblique bonnet, rated for nominal pressure PN10
DIN 3512 : Stop valves for domestic water supply – two-way valves – vertical bonnet type PN10 – straight pattern globe valve – Technical rule of the DVGW
ISO 12149 : Bolted bonnet steel globe valves for general-purpose applications
ISO 15761 : Steel gate, globe and check valves for sizes DN100 and smaller, for the petroleum an natural gas industries
MSS SP42 : Class 150 corrosion resistant gate, globe, angle and check valves with flanged and butt weld ends
MSS SP80 : Bronze gate, globe, angle and check valves
MSS SP85 : Cast iron globe & angle valves
MSS SP117 :Bellows seals for globe and gate valves
For more standards, see our overview of valve standards
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