Multiport valve including leakage control system, particularly for a

Abstract

A multiport fluid flow control valve, particularly for use in a regenerative incinerator system for treating process emissions to remove volatile organic combustibles (VOCs). A valve housing has at least three main conduit connection openings. A butterfly valve element rotatable within the housing on a valve element axis has at least two radially-extending rectangular wings such that different pairs of the main conduit connection openings are in deliberate fluid communication depending on the position of the valve element. To accommodate thermal expansion, there is a gap between the peripheries of the valve element wings and an inner surface of the valve housing. Leakage across this gap is prevented by a valve element structure which cooperates with a portion of the valve housing inner surface to define a plenum. The plenum is either pressurized or forcibly vented. In one form, the structure which cooperates to define a plenum comprises a U-shaped channel element on the peripheries of the wings. In another form, the structure which cooperates to define a plenum includes a pair of spaced parallel plates fastened to a shaft extending along the valve element axis. For pressurizing or venting the plenum there is a minor conduit, which may take the form of either ports on the valve conduit or a hollow shaft extending along the valve element axis, as examples.