Selecting the wrong type of valve always proves to be detrimental to the operation. Therefore, it is necessary to understand the difference between the valves.
A double offset butterfly valve is popularly known as the high-performance butterfly valve. These valves have got two stems offset from the center region. This helps in creating a cam action during the application procedure. In the first offset, the shaft axis is present behind the center line of the disc sealing point to the seat. The axis of the shaft is eccentric to the valve or pipeline center in the second offset. They double offset butterfly valves are being used up for the power generation, pulp and paper, HVAC, Chemical, Oil and Gas, Water and wastewater treatment, Shipbuilding, etc. They are available in the higher pressures when compared to the zero offset style.
In the triple offset valve, there are basically three offsets. Two of them are placed in a similar position as the double offset butterfly valve. However, the third offset is the seating surface geometry, which creates a sort of cone shape with the disc and seat. This cone-shaped angle, along with the eccentric shaft offsets, helps the disc to seal up against the seat with no more friction.
This seat design helps in a uniform sealing mechanism which has a tight shutoff in the metallic seat design framework. This design has its own advantages: easier automatic property, lower cost, and lower torque options than the other alternative styles metallic seated values. The triple offsets are generally used up in the applications which are similar to the gate valve. In the gate valves, the meat seat, tight shutoff, and quarter-turn actuation are required. Some of the applications, such as high-pressure steam, superheated steam, and high-temperature gases, are good for this variety of valves because of the presence of a metallic seat over the soft seat. This three piece ball valve is being used up in the same industries as the double offset butterfly valves. However, it has comparatively got more demand in the applications than the double offset butterfly.