Overview
Edwards backing/roughing valves with ISO NW roughing and forepump terminations feature manual or pneumatic actuation. They combine the function of separate backing/roughing valves in one integral 3 port unit.
A flexible neoprene connector is supplied for the backing connection. The roughing and forepump ports terminate in the appropriate NW termination.
Technology
The BRV is manually operated by a lever and cam through 180 degree movement.
An important feature is the mid-position, where both ports are isolated from each other, and from the common (or rotary pump) port. Additionally, isolation between the backing and roughing ports is positively maintained during actuation. Both ports are closed under spring pressure and sealed by fluoroelastomer ‘O’ rings.
Each port is leaktight to better than 10-9 mbar l s-1 / 8 x 10-10 Torr l s-1 against 1 bar differential.
Applications
The BRV has been designed for use with the Edwards Diffstak® pumps, but is suitable for use in all applications where backing/roughing changeover is required, with system pressure in the range 2.1 bar to 1 x 10-7 mbar absolute (2.1 x 105 to 1 x 10-5 Pa).