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.
Technology
The BRVP models are actuated by an integral pneumatic cylinder, complete with two microswitches for indicating port position.
An important feature of both models 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 valves have been designed particularly for the Diffstak® pumping systems, but have applications where a compact change-over valve is required in the pressure range 10-7 - 2000 mbar / 8 x 10-8 - 1500 Torr.