Abstract: A valve flushing system supplies a cleaning gas to a relatively large plenum, which in turn communicates with a restricted passage directing the flow along a face of the valve disk. In a main feature of this invention, a flushing gas flow moves through a restricted path along a face of a valve disk away from a valve disk contact area with a valve seat. In this way, the flushing gas prevents a potential leakage gas flow from approaching the valve/valve seat interface. In this way, leakage is reduced. Although the efficiency of the system may be reduced by a small amount, the resulting prevention of leakage more than justifies this potential small decrease in efficiency. The use of the relatively large plenum ensures that there will be complete and adequate coverage of the valve disk preventing any leakage across the valve disk. In an important feature of this invention, supply passages extend into the plenum along a direction which does not include a component moving in the direction of the valve disk.