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A globe valve is an instrument used to stop and/or control the flow of fluids in a pipeline. It works by halting the flow of a fluid through a pipe. The name globe comes about due to the valve's cylindrical shape. There are usually two halves of the body within the globe valve that are separated by an internal baffle.
Globe valves are pipe fittings that can be fitted into plumbing systems to control the flow of fluid through them. One pipe is connected to direct the liquid into the valve and another to direct this out.
Otherwise known as globe control valves, they are defined by the following characteristics:
A curved valve body
A gap in the centre of the pipe with a seat that a circular plug can sit in firmly
The circular plug is attached to a handle and stem that is twisted to raise or lower the plug
A bonnet and packing keep the stem in place and prevent fluid from leaking from the system
They can only be used for one-way fluid flow
Good shutoff capability.
Moderate to good valve throttling capability.
Shorter stroke (compared to a gate valve).
Easy to machine or resurface the seats.
Can be used as a stop-check valve.
Can only be used for one-way fluid flow.
Good sealing performance,small friction between sealing face and life long.
To understand the working of a globe valve, one should understand how the disc and seat of the valve are positioned. The disc inside the valve is movable whereas the seat is stationary and is in a spherical body. The seat is parallel to the pipe and perpendicular to the disc.
The disc of the valve will move up and down according to the actuation of the wheel on the top of the valve. The wheel can be moved either manually or through an actuator - when it is moved, the disc rises and falls as it is attached to the valve stem. To stop the flow completely, the disc is fully seated on the seat ring. To resume flow, the disc is lifted up.
Throttling and controlling of flow can be done by adjusting the position of the disc as per need.
If the case is so that the globe valve is operated in low-temperature situations, then the valve is installed in such a way that the pressure falls under the disc. For high-temperature situations, like boilers that work in steam, the valves are positioned to handle pressure above the disc.
No matter what type of globe valve you have, there are several key parts that all globe valves contain: body, seat ring, cage, bonnet, stem, plug (disk), yoke, yoke nut, back seat, packing, and valve Actuator.
Body
The body is the main structure of the valve that keeps everything together. This part contains all internal parts of the globe valve to allow the control of the substance that needs regulation. The opening of the body contains ports (usually two or three ports) to enable the movement of the fluid to the inside or outside of the globe valve.
Seat Ring
The seat is among other globe valve parts that seal the space between the disk/stem and bonnet. The seat ring can be screwed into the valve or torqued. The seat is also known as a seat ring and provides a shutoff surface that's stable and also replaceable. Seat rings can hold the cage firmly to the body of the valve.
Bonnet
The bonnet is one of the outer globe valve parts that's connected to the body to provide a leak-proof closure. There are different bonnet types such as bolted, screw-in, or union bonnet that are used in different globe valves. Each of these bonnet types has its own advantages. For example, the union bonnet not only adds strength to the body but is also great for applications that need regular cleaning or inspection. The screw-in bonnet with its simple design offers a pressure-tight seal. And the last bonnet type, the bolted bonnets that are attached with bolts are great for higher pressures.
Stem
The stem is part of the globe valve that connects the disk to the handwheel or the valve actuator to transmit the actuation force. Since it connects the actuator to the parts inside of the globe valve, it is considered as one of the critical globe valve parts. If the valves are controlled by actuators, the stem is smooth but for the manual valves, they are threaded.
The ends of smooth steam are threaded allowing the connection to the actuator and the plug. A wearable packing surrounds the smooth stem to prevent leaking material from the valve. So, the packing should be replaced regularly in the maintenance period. The stem can withstand a large amount of compression force in the closure state. And when the valve is opening, it has high tensile strength.
Plug (Disk)
The plug or the disk is among the essential globe valve parts. It moves perpendicular to the seat and its movement can block or free the flow since it works as a moveable physical barrier. When the valve is closed, the plug sits against the seat to block the flow and when it sits above the seats. it enables the flow of the material.
Different disk arrangements have been designed for globe valves such as composite type, ball type, and needle type. The composite disk can provide a better shut-off, while the ball type is used for low-temperature and low-pressure systems. The needle disk has the advantage of providing a better throttling compared to the other two.
| DN mm | Flange drilling | L mm | H mm | H3 mm | F mm | F1 mm | F2 mm |
| 40 | PN10/16 | 240 | 200 | 263 | 14 | 16 | 30 |
| 50 | PN10/16 | 250 | 209 | 292 | 14 | 16 | 30 |
| 65 | PN10/16 | 270 | 243 | 336 | 17 | 20 | 34 |
| 80 | PN10/16 | 280 | 282 | 382 | 17 | 20 | 34 |
| 100 | PN10/16 | 300 | 319 | 429 | 19 | 22 | 34 |
| 125 | PN10/16 | 325 | 346 | 471 | 19 | 22 | 34 |
| 150 | PN10/16 | 350 | 403 | 493 | 19 | 22 | 34 |
| 200 | PN10/16 | 400 | 490 | 660 | 24 | 28 | 34 |
| 250 | PN10/16 | 450 | 664 | 864 | 27 | 31 | 47 |
| 300 | PN10/16 | 500 | 740 | 968 | 27 | 31 | 47 |
| 350 | PN10/16 | 550 | 947 | 1207 | 32 | 37 | 55 |
| 400 | PN10/16 | 600 | 959 | 1249 | 32 | 37 | 55 |
| 450 | PN10/16 | 650 | 958 | 1278 | 32 | 37 | 55 |
| 500 | PN10/16 | 700 | 958 | 1316 | 32 | 37 | 55 |
