In the field of industrial valves, butterfly valves are widely used in various industries such as oil and gas, water treatment, chemical processing, etc. Among the different types of butterfly valves, two variants take the lead: double eccentric butterfly valve and triple eccentric butterfly valve. In this comprehensive comparison, we will take a deep look at the design, advantages, disadvantages and applications of these two valves.
Double Offset butterfly valve
As the name suggests, double offset butterfly valves have two offsets: the first offset is the shaft eccentricity, that is, the offset of the shaft axis from the centerline of the pipeline, and the second offset is the seal eccentricity, that is, the geometry of the valve disc seal. This design has significant advantages and disadvantages.
Advantages of double eccentric butterfly valve
1. Reduced wear
The purpose of the shaft eccentricity design is to reduce the friction between the valve plate and the valve seat during the opening and closing process, thereby reducing wear and reducing the risk of leakage. It can also extend the life of the butterfly valve and reduce maintenance costs.
2. Enhanced sealing
The second eccentricity makes the sealing surface contact the valve seat only in the final stage of closing, which not only ensures a tight seal, but also effectively controls the medium.
3. Reduced torque
The double offset design reduces the friction coefficient, which reduces the force required to open and close the butterfly valve.
4. Bidirectional sealing
Double eccentric butterfly valves can provide bidirectional sealing, allowing bidirectional flow, and are more convenient to install and use.
Disadvantages of double eccentric butterfly valves:
1. Higher cost
The advanced design and materials of double eccentric butterfly valves generally result in higher manufacturing costs compared to centerline butterfly valves.
2. More water pressure lose
Due to the thicker double eccentric valve plate, protruding valve seat, and narrower passages, the water pressure lose through the butterfly valve may increase.
3. Limited temperature range
Double eccentric butterfly valves may be limited when handling ultra-low temperature or high temperature media because the materials used may not withstand extreme temperatures.
Triple Offset butterfly valve
The triple offset butterfly valve represents a further development of the butterfly valve design with three offsets. On the basis of the double eccentric, the third eccentricity is the offset of the axis compared to the center of the valve body. This innovative design is a unique advantage over the traditional centerline butterfly valve.
Advantages of triple eccentric butterfly valves
1. Zero leakage
The unique shape of the sealing element of the triple eccentric butterfly valve eliminates friction and wear, resulting in a tight seal throughout the life of the valve.
2. High temperature and high pressure resistance
Both the all-metal triple eccentric butterfly valve and the multi-layer triple eccentric butterfly valve can handle high temperature and high pressure fluids.
3. Fireproof design
All materials of the triple eccentric butterfly valve can meet strict fireproof standards, making it outstanding in fireproof applications.
4. Low torque and friction
The triple eccentric butterfly valve can further reduce operating torque and friction, thereby achieving smooth operation, reducing torque and extending service life.
5. Wide range of applications
The triple eccentric butterfly valve is suitable for a variety of applications, including oil and gas, petrochemical, power generation and refining industries.
Disadvantages of triple eccentric butterfly valves
1. Higher cost
The triple eccentric butterfly valve tends to have a higher initial manufacturing cost due to its advanced design and structure.
2. Slightly higher head loss
The additional offset in the triple eccentric design may result in slightly higher head loss than the double eccentric valve.
Double eccentric butterfly valve VS triple eccentric butterfly valve
1. Valve seat
The valve seat of a double eccentric butterfly valve is generally embedded in a groove on the valve plate and is made of rubber such as EPDM, so it can achieve an airtight seal, but it is not suitable for ultra-high temperature applications. The valve seat of a triple eccentric butterfly valve is all-metal or multi-layered, so it is more suitable for high temperature or corrosive fluids.
2. Cost
Whether it is design cost or manufacturing process complexity, triple eccentric butterfly valves are higher than double eccentric butterfly valves. However, the frequency of post-maintenance of triple eccentric valves is lower than that of double eccentric valves.
3. Torque
The original intention of the triple eccentric butterfly valve design is to further reduce wear and friction. Therefore, the torque of the triple eccentric butterfly valve is smaller than that of the double eccentric butterfly valve.