Language
The eccentric butterfly valve significantly reduces the friction between the valve plate and the valve seat through the design of the valve stem deviating from the center line of the valve body (double eccentric and triple eccentric).
For Double eccentric design: the valve stem deviates from the center of the valve body (first eccentricity) and the center of the valve plate sealing surface (second eccentricity), and the valve plate and the valve seat quickly separate during opening and closing to reduce friction.
For Triple eccentric design (metal hard seal): increase the sealing surface cone angle (third eccentricity) to achieve zero friction opening and closing, and high temperature and high-pressure resistance.
Of course, it has own pros and cons. For advantages including: Long life: there is no sliding friction between the valve plate and the valve seat during opening and closing, and the wear is very small; High sealing level: the three-eccentric butterfly valve can reach ANSI Class VI (zero leakage) and is suitable for harsh working conditions.; Wide temperature range adaptation: the metal sealing type can withstand extreme temperatures from -196℃ to 800℃;Anti-particle erosion: the hard sealing surface (such as stainless steel + STL alloy) is corrosion-resistant and erosion-resistant.
For disadvantages are following: High cost: the price of the three-eccentric butterfly valve can reach 3~5 times that of the centerline valve; High installation accuracy requirements: the eccentric structure needs to be strictly aligned, otherwise it is easy to cause leakage.
Because of its hard seal, it was wide applied in Petroleum and natural gas: oil pipelines, LNG storage and transportation systems.; Power industry: boiler feed water, steam regulation.; Chemical metallurgy: pipelines for strong acid, alkaline media and slurry containing particles.
