Vacuum Valves
The most important factor in the selection of vacuum valves is avoiding an O-ring on a sliding shaft, choosing instead a bellows seal. The bonnet of the valve is usually O-ring sealed, except where bakeability is necessary, in which case a metal seal such as the Conflat is substituted. The nose of the valve is usually an O-ring or
molded gasket of Viton, polyimide for higher temperature, or metal for the most stringent UHV applications. Sealing techniques for the a UHV valve include a knife edge nose/ copper seat and a capture geometry such as silver nose/stainless steel seat (Bills and Allen, 1955).When a valve is used between a high-vacuum pump and
a vacuum chamber, high conductance is essential. This normally mandates some form of gate valve. The shaft
seal is again crucial for reliable, leak-tight operation.Because of the long travel of the actuating rod, a greasefilled double O-ring has frequently been used, but evacuation would be preferable. A lever-operated drive requiring only simple rotation using an O-ring seal, or a bellowssealed drive, provides superior performance.
The most important factor in the selection of vacuum valves is avoiding an O-ring on a sliding shaft, choosing instead a bellows seal. The bonnet of the valve is usually O-ring sealed, except where bakeability is necessary, in which case a metal seal such as the Conflat is substituted. The nose of the valve is usually an O-ring or
molded gasket of Viton, polyimide for higher temperature, or metal for the most stringent UHV applications. Sealing techniques for the a UHV valve include a knife edge nose/ copper seat and a capture geometry such as silver nose/stainless steel seat (Bills and Allen, 1955).When a valve is used between a high-vacuum pump and
a vacuum chamber, high conductance is essential. This normally mandates some form of gate valve. The shaft
seal is again crucial for reliable, leak-tight operation.Because of the long travel of the actuating rod, a greasefilled double O-ring has frequently been used, but evacuation would be preferable. A lever-operated drive requiring only simple rotation using an O-ring seal, or a bellowssealed drive, provides superior performance.
Posts
No comments:
Post a Comment