The sealing surface of multi-level hard sealing butterfly valve is made of superhard material or surface hardening treatment. The surface hardening of hard sealing ball valve can not be processed with ordinary tools. Even if it can be processed, its machining accuracy can not meet the requirements. Therefore, it is very important to select appropriate tools for machining.
The precision grinding of multi-level hard seal butterfly valve generally adopts a special grinder. The structure of hard seal ball valve is mainly composed of the rotating shaft and grinding head of clamping ball. The grinding head is mainly composed of shaft connected centering flange plate (connecting plate), spring floating mechanism, grinding strip clamping plate and grinding strip. According to the surface treatment of the sphere, the grinding strip can be made of oilstone sand strips of various materials or artificial diamond materials.
The base material of multi-level hard sealing butterfly valve seat shall be made of stainless steel with linear expansion close to the shell material. The hardening treatment process of sealing surface can also adopt manual surfacing or plasma spray welding cemented carbide. The final thickness of surfacing layer shall be.
Generally, the sealing surface of the valve seat of the multi-level hard sealing butterfly valve is precisely grinded with the ball by using the planetary grinding principle on the special ball grinding machine, and then manually grinded with the ball one-to-one, and inspected by indentation method.
The multi-level hard sealing butterfly valve adopts the structural design of single inclined elastic sealing ring or V-groove elastic sealing ring. When the medium pressure is too small, the contact area between the sealing ring and the ball is small, so there is a large sealing specific pressure to ensure reliable sealing. When the medium pressure is large, the contact area between the sealing ring and the ball increases, so the sealing ring can be pushed by the medium without damage. Due to the good self lubrication of sealing ring materials such as polytetraethylene and small friction loss with the ball, the service life of the ball valve is long. Due to the spring load, the auxiliary seal of hard sealed ball valve expands to realize the sealing between valve body and valve seat. The spring load is sufficient to provide reliable sealing between valve seat and ball. Under low pressure, a sealing grease injection system can be designed between the sealing surface of valve seat and ball.