No matter how the valve is installed, the back of the upstream seat protects the face of the downstream seat.
无论阀门如何安装，上游阀座的后背都能够保护下游阀座的表面。
2
Many studies were carried on the technologies and properties of laser cladding on the seal face of valve, but lack of contrast data with plasma spraying Alloy applied at present.
Raised-face seat. A groove around the seat collects particles pushed aside by the knife and prevents clogging. When the valve opens, media pressure cleans the groove.