A dual pendulum valve assembly for connecting a process chamber and a vacuum pump of a semiconductor manufacturing system. The valve assembly includes an isolation valve for sealing an opening to the pump during cleaning of the system and an annular cover for protecting a valve seat of the opening to the pump during use of the system. In particular, the valve assembly includes a housing having an interior space and a pair of openings through which fluid can enter and exit the interior space. A process valve is movable within the interior space between an opened position allowing fluid to pass through a first of the openings from the process chamber and a closed position sealing the first opening. The isolation valve is movable within the interior space between an opened position allowing fluid to pass through a second of the openings into the vacuum pump and a closed position sealing the second opening. The annular cover is movable within the interior space between a first position wherein the cover protects the valve seat of the second opening and a second position wherein the cover is spaced from the valve seat such that the isolation valve can engage the valve seat and seal the second opening.