Butterfly valves are versatile industrial valves used for isolation and flow control in various piping systems. Based on their disc design, butterfly valves can be classified as double eccentric, high performance, and double offset high performance types. Each has unique characteristics suited for certain applications.
Double eccentric valves are ideal for tight shutoff duties. High performance valves suit throttling and high temperature media. Double offset valves provide the best of both capabilities. Partnering with a manufacturer experienced in all three technologies ensures access to the ideal butterfly valve for the service conditions. This article will outline the key differences between these butterfly valve varieties in terms of their construction, performance attributes, and suitable applications.
Double Eccentric Butterfly Valves
Double eccentric butterfly valve China has the disc center offset on both sides of the shaft centerline. This allows the use of resilient seating material which conforms to seal against the disc edge despite misalignment from pressure or temperature effects. The offset also reduces disc rubbing and wear. Double eccentric valves provide reliable bi-directional shutoff even after thousands of operation cycles. They handle moderate temperature applications.
High Performance Eccentric Butterfly Valves
High performance eccentric butterfly valve has the disc and shaft centers aligned. The disc edges press against metal seats on both sides to achieve bubble-tight shutoff through metal-to-metal contact. They use disc materials like stainless steel to provide low leakage across a wide temperature range. Their metal seats allow operation up to 800°F. High performance valves provide precise flow control and can be used for throttling applications.
Double Offset High Performance Butterfly Valve
Double offset high performance butterfly valve combines the benefits of both double eccentric and high performance designs. They have the eccentric offset disc for soft sealing as well as metal seats for temperature resistance. The metal-to-resilient dual seating enables zero-leakage shutoff as well as extended service life. They offer high precision flow control capabilities spanning cryogenic to elevated temperature applications.
Performance Comparison
- Shutoff ability: Double offset high performance valves offer best shutoff. High performance valves can have minor seat leakage.
- Temperature range: High performance handles over 800°F. Double eccentric suits lower temperatures. Double offset is in between.
- Flow control: High performance and double offset types allow excellent throttling control. Double eccentric mainly for on/off use.
- Cycle life: Double eccentric offers longest seat life of up to 100,000 cycles. Double offset gives moderate life.
Typical Applications
- Double eccentric: Water, oil, gas, and chemical lines for tight shutoff against differential pressure.
- High performance: Steam lines, power plants, and high temperature processing where precise flow control is critical.
- Double offset: LNG and cryogenic services along with steam and chemical lines needing temperature resistance and low leakage.