TO BEGIN WITH:
When it comes to the safety of other components like boilers, reactors, pumps etc., valves play an important role. In many shut-off applications, butterfly valves are the primary selection because of its quarter turn operation, compact design, and simplicity, one of the primary reasons why many valve suppliers prefer these valves to customers with specific industrial needs.
Butterfly valves control fluid flow in a pipe by using a disc attached to a central shaft. This disc controls the amount of fluid passing through the valve by creating a variable opening. These valves can be classified according to the alignment of the disc with respect to the valve body:
1. Zero offset or concentric butterfly valve
2. Double offset butterfly valve
3. Triple offset butterfly valve
Majority of butterfly valves with plastic linings are zero offset. Those that are made of metal and some with rubber lining are either double or triple offset butterfly valves.
DOUBLE OFFSET VALVE:
A double offset butterfly valve is named so because of its double offset, which allows the disc to be displaced from its seat via a cam action. The cam action is created through the offset of the shaft from the disc seat’s centreline and body seal, which is also offset from the bore’s centreline. The cam action results in friction between the disc and the seat only during the first and last 10% of its opening and closing action.
The double offset valve has two offsets. The first offset is a shift of position shaft behind the valve disk, and a second offset is a shift of shaft position behind the valve disk slightly one-sided to pipe centreline. Due to this offset, disk moves as cam action movement, which limits contact of the disk with the seat. This enhances the life of the valve and gives the capability to work at a high-pressure rating than the simple concentric butterfly valve. From the valve manufacturers point of view, of the total cost of the control valve, the cost of an actuator is up to 30 to 40%.
The movement of a double offset butterfly valve follows a conic profile in sealing the valve. The arrangement of the offsets of the disc and the shaft generates a cam action of the disc into the seat, reducing the required torque to close or open the valve.
This offset geometry also allows the 90° rotation of the disc to get into contact with the seat on the first 1° to 3° of rotation only. Moreover, the design of double offset butterfly valves minimizes wearing at the touch points of the seat and disc which happens in conventional butterfly valves.
As pointed out by Butterfly valve supplier, double offset butterfly valves are popular because they can be used in a wide range of applications. They can survive extreme pressures and temperatures and are suitable for handling gas, oil, steam, and water in a light weight and cost-effective design compared to triple offset butterfly valves.
The corrosion resistance and design strength of double offset butterfly valves allow them to be used either as buried valves or as parts of plants.
Double offset butterfly valves are best suited for pressures higher than zero offset butterfly valves can handle. Some of the most common applications and industries that use these kinds of butterfly valves which includes: Seawater, Steam, Toxic and Wastewater in Industries like Chemical, Food and Beverage, Mining, Oil and Gas, Petrochemical, Refining and Water Filtration.
Industrial valves have higher requirements regarding pressure and temperature ranges compared to traditional butterfly valves. This gave to the rise of high-performance butterfly valves that can handle high pressure and high temperature, one of which is a double offset butterfly valve.
As pointed out by a leading valve stockist in Dubai, although there is only one point of design difference between double offset and other butterfly valves, the result of this single difference significantly changes the performance of the valve. The double offset butterfly valve advantages far outweigh those of the other butterfly valve if used in an environment where elements such as temperature, pressure or media are critical to the application.
Fevisa, a leading globe valves supplier, has just what you need. We offer butterfly valves along with other industrial valves in various material body, disc, seat, and end-type connection designs. For more information, you can explore our website or reach out to us.
For more information on which butterfly valve is right for your application, or to discuss whether the double offset butterfly valve advantages are relevant to your needs, why not contact our team of expert’s @ Fevisa.
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