Sealing arrangement for knife gate valves

Claim 1

In a knife gate valve for controlling the flow of a pressurized medium along a path, a sealing arrangement comprising: (a) a valve body having an internal flow-through passage which extends along an axis; (b) a liner having upstream and downstream annular flange portions and an annular liner portion located between the flange portions, all of the liner portions engaging and being mounted on the valve body, said liner portion circumferentially bounding, at least in part, the passage and having an annular stop extending radially inwardly into the passage; (c) an annular seat of sealing material and having a generally L-shaped cross-section, said seat having an outer stepped surface mounted on and sealingly engaging the stop and the liner portion, an inner surface located radially inwardly of the outer stepped surface, an upstream surface located upstream of the stop, and a downstream sealing surface located downstream of the stop; (d) a retainer ring having an annular upstream flange engaging the upstream flange portion of the liner, and a retaining portion having an axially-extending surface sealingly engaging the inner surface of the seat and a radially-extending surface sealingly engaging the upstream surface of the seat, said retaining portion and said liner bounding a cavity in which the seat is securely retained against removal during the flow of the medium, said retaining portion bounding an internal flow-through section extending along the axis; and (e) a knife gate mounted on the body intermediate the flow-through passage and the flow-through section for movement between a fully-open position in which the gate is remote from the seat, and a fully-closed position in which the gate sealingly engages the sealing surface of the seat.