A globe valve is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally spherical body.
Globe Valves are named for their spherical body shape with the two halves of the body being separated by an internal baffle. This has an opening that forms a seat onto which a movable plug can be screwed in to close (or shut) the valve. The plug is also called a disc. In globe valves, the plug is connected to a stem which is operated by screw action in manual valves. Typically, automated valves use sliding stems. Automated globe valves have a smooth stem rather than threaded and are opened and closed by an actuator assembly. When a globe valve is manually operated, the stem is turned by a hand wheel.
Globe valves are used for applications requiring throttling and frequent operation. For example, globe valves or valves with a similar mechanism may be used as sampling valves, which are normally shut except when liquid samples are being taken. Since the baffle restricts flow, they're not recommended where full, unobstructed flow is required.
The body and bonnet of Class 150 to Class 900 valves are usually connected with studs and nuts. And the body and bonnet of Class 1500 to Class 2500 valve design usually utilizes a pressure seal bonnet.
Stainless steel + flexible graphite wounded gasket is used for Class150 and Class 300 globe valve. Stainless steel + flexible graphite wounded gasket is used for Class 600, and ring type joint gasket is optional. Ring joint gasket is used for Class 900 globe valve. Pressure seal design is used for Class 1500 to Class 2500 globe valve.
Hand wheel and gearbox operation are applied for globe valve. Chain wheel and electric is available if required.
Molded flexible graphite is used for packing material. PTFE or combined packing material can be applied if required.
The internal surface of the stuffing box, of which area is contacted with the packing, is highly finished (Ra 3.2μm). The stem surface, contacting with the packing, is rolled and pressed after being precisely machined, so as to reach a high finish and compactness (Ra 0.8μm) and ensures a reliable tightness of the stem area.
Belleville Spring Loaded Packing
All our globe valves have a back seating design. In most cases, the carbon steel globe valve is fitted with a renewable back seat.
For stainless steel globe valve, the back seat is machined directly in the bonnet or machined after welding. When the globe valve is in fully open position, the sealing of the back seat can be very reliable. However, as per the requirement of design standards, it is not advisable to add or change packing by means of back seating when the valve is under line pressure.
For carbon steel globe valves, the seat material is usually forged steel. The sealing surface of the seat is overlay welded with hard alloy specified by customer. Renewable threaded-in seats are used for globe valves NPS≤10, and welded-on seats are optional.
Welded-on seats are used for NPS ≥ 12 carbon steel globe valves. For stainless steel globe valves, integral seat are usually adopted or hard alloy welded integrally. Threaded-in or welded on seats are optional for stainless steel globe valves.
The stem is one-piece forged steel. The minimum diameter of the stem shall be as per the standard requirements.
Usually, the stem nut is made of copper alloy. It can be made of ASTM A439 D2 if required. For large sized globe valves, a roller bearing is fitted on both sides of the stem nut in order to minimize the opening and closing torque of the globe valve.