A globe valve is a kind of valve that is used for controlling the flow in a pipeline as found in many industries like the Oil refining, Petroleum, Natural gas production and Refining industries. It is commonly used in an oil pipeline. It is made of a movable disk-like component and a motionless ring seat in a normally sphere-shaped body.

Globe valves used to mostly have globular bodies hence their name but nowadays globe valves do not now have much of a sphere-shape. The body of globe valves has two halves divided by an internal baffle which has an aperture that forms a seat onto which the plug or disc (disk) can be screwed in to shut the valve.

In globe valves, the disc is linked to a stem which is in manual valves operated by a screw action and in automated valves through smooth sliding stems. An Actuator assembly is used to both open and close automated globe valves. During manual operation the stem of the globe valve is turned by a hand wheel.

Globe valves are used in applications that require throttling and frequent control of the flow and since the internal baffle limits flow, they are not used when full and clear flow is required.

Globe valves usually have two or three ports. The ports in the valve facilitate the flow of fluid in and out of the valve. Two port valves may be fixed parallel to each other on the body, or fixed at other angles such as a right angles. Globe valves with ports at 90o are referred to as angle globe valves. Globe valve can also have a body which is ‘Y’ shaped.

Bonnet valve closures offer a leak-proof closure for the valve body. Globe valves may have a union, a bolted or a screw-in bonnet. The Union bonnet while giving the body additional strength is suitable for applications that require regular cleaning, maintenance or inspections. The screw-in bonnet is the simplest design and offers a long lasting, pressure-tight seal. The bolted bonnet is used higher pressure applications such oil refining, petroleum, natural gas and refining industries. Bonnets also contain the packing, which is made from non-durable substance that preserves the seal between the stem and the bonnet during the action of the valve.

The closure part of the valve, which is known as plug or disc (disk) is connected to the valve stem which is guided up or down to choke the flow. In the same manner the plug can also be screwed down for the same action. Plugs are typically either balanced or unbalanced. Unbalanced plugs are hard and are used with smaller valves or when there is a pressure differential across the valve. They are of a simple design which is an advantage. There is some slight drawbacks however, in that this design has possible leakage at the seat and size is restricted as for larger unbalanced plugs, the force required to seat and restrain the flow can become unreasonable. On the other hand, in balanced plugs, which have holes through the plug, it is easier to shut off the flow because the plug does not succumb to inert forces.

The valve stem is connected to the actuator within the valve and transmits the actuation force. Stems can be either smooth for actuator controlled valves or they can have a thread for manual valves. The smooth stems have packing material around them to prevent substances leaking from the valve. The packing is made of a durable substance, but will have to be replaced when repairs or maintenance is carried out. On smooth stems the ends are threaded to facilitate connection to the plug and the actuator. The stem has to endure a significant amount of pressure from the flow of the fluid during the closure of the valve. They must also have high tolerance when the valve is opened. It is important that the stem remains straight to ensure satisfactory closure of the valve. This also reduces stress on the packing within the bonnet, which provides a seal against leakage. The stem can have a cowling which restricts any matter from getting in to the packing material reducing the risk of wear.

The seat ring offers a steady, unvarying and expendable shut off surface. Seat rings are more often than not held in place by pressure from the attachment of the bonnet to the body. This forces the cage down on to the rim of the seat ring and grips it securely to the body of the valve. Seat rings are also usually given a sloping edge at the surface to facilitate the closing the valve.

Corrosive substances or substances that cause erosion like those of the Oil refining, Petroleum, Natural gas and Refining industries may need materials that are made of metallic alloys such as Hastelloy, Monel, Inconel. Materials are selected based on pressure, temperature and the requirements of the valve to perform its role.

Control valves are used first and foremost to control the force in systems that are used in several industries like the Oil refining, Petroleum, Natural gas and Refining industries. They must endure high speed and vibration for excessive periods without the need for repairs.