What is a concentric globe valve?
The concentric globe valve is a flow control mechanism that uses a rotating disc to control the flow of medium in the system. The disc remains in the passage, but due to its thinness it offers very little resistance to the flow.
Butterfly valves have many advantages over other types of valves, such as: B. an economical design made up of fewer components, making operation and maintenance easier. The packaging's wafer design and relatively light weight reduce installation, equipment, tube support, labor and setup time costs.
The most common type of butterfly valve is a centric or concentric butterfly valve. This type of butterfly valve consists of a stem that runs along the centerline of the disc in the center of the tube bore and a seat in the inner diameter of the valve body. This non-offset valve configuration is also called a resilient seat valve because the reliability of the seal depends on the flexibility of the seat rubber when the flow is closed. With this type of valve, the disc initially interacts with the seat at approximately 85° during a 90° rotation. Concentric butterfly valves are often used in low pressure applications.
Classification by connection type
Depending on the type of connection, there are different types of concentric butterfly valves.
- Wafer type ends.
- Ends with eyelets.
- Both end with a flange.
- End of butt welded types.
Type of wafer:
Wafer-type butterfly valves are designed to provide a tight seal and protect against bidirectional pressure differentials to prevent backflow in devices built for unidirectional flow. This is achieved by using a tight-fitting cap such as an O-ring, a precision-machined seal, and a smooth valve surface on both the downstream and upstream portions of the valve.
CONCENTRIC WAFER VALVES
Eyelet Type:
The eyelet body type of butterfly valve design is identical to that of the three-piece ball valve, where one end of the piping can be replaced without affecting the other side of the valve. This can be achieved with threaded inserts, flanges and two sets of handles (screws) that do not use nuts, so that each flange has its own screws. It's also important to remember that you don't need to shut down the entire unit to inspect, clean, repair, or replace the butterfly valve.
CONCENTRIC BUTTERFLY VALVE WITH CONNECTION
Flange End Type:
The flanged connection butterfly valve has a flange at both ends, which can be fixed with pipe flanges. This type of end connection is used for very large butterfly valves.
CONCENTRIC BUTTERFLY VALVE WITH FLANGE
Welded End Type:
The welded ends shut-off valve is used where the system is under very high pressure. These types are generally used for small size shut-off valves.
CONCENTRIC WELDING TAB
How does a concentric shutoff valve work?
Concentric butterfly valves have a relatively simple design. Body, gasket, disc and stem are the main parts of the concentric butterfly valve. In traditional butterfly valves, a disc is located in the center of the connected tube and a stem is connected to the actuator or handle on the outside of the valve. When the valve is in the closed position, the disc is perpendicular to the flow and the valve seat is closed. The shaft is sealed with an O-ring. When the valve rotates 90 degrees using the actuator or handle, the disc moves away from the valve seat and becomes parallel to the flow. Rotation through an angle of less than 90 degrees allows the flow to be throttled or proportioned.
When should a concentric globe valve be used?
Concentric butterfly valves use soft sealing material, so they can only be used in basic fluids (water and sewage treatment plants), specialty fluids (chemicals, abrasive fluids, etc.) and gases up to 200 psi and 400° F.
- Water supply.
- Water distribution.
- Water transfer.
- Ventilation system.
- fire protection etc.
Concentric vs. Concentric Butterfly Valve eccentric butterfly valve
- The concentric butterfly valve disc is simple, while the eccentric butterfly valve disc consists of a disc seal, a seal retaining ring and a retaining screw.
- The sealing structure of the concentric valve is very simple: the disc comes into direct contact with the rubber seat, while an eccentric globe valve has a laminated disc seal in contact with the metal seat of the body.
- The concentric globe valve has a soft seal, while the eccentric globe valve seat is made of metal. It can be an assembled seat or a welded seat that can be replaced.
- A concentric globe valve has a pressure limitation and can only withstand a pressure of up to 150 lb/PN25, while an offset/eccentric globe valve can withstand a pressure of up to 600 lb/PN100.
- Due to the different design of the seal structure, the concentric rubber seat cannot withstand high temperatures, but an eccentric/offset globe valve could work as it has a metal/hard seal construction.
- The advantages and disadvantages are obvious and it is very easy to decide which valve to use in a real situation. If there is high pressure or high temperature in the system, an eccentric valve is used.
