A seal ring located in a seal ring groove of {HEAD ~ a valve member} of {TAIL ~ a rotary valve assembly} has an outer seal surface in sealing engagement with a surrounding valve housing and is adapted to isolate pressure passages communicating with the valve assembly regardless of the direction of the pressure differential across the seal ring, the seal ring being maintained in sealing engagement with one wall of the seal ring groove and with a surrounding wall of the valve housing by an underseal expander ring that assures continuous sealing action of the seal ring 
A seal ring located in a seal ring groove of { HEAD ~ a valve member } of { TAIL ~ a rotary valve assembly } has an outer seal surface in sealing engagement with a surrounding valve housing and is adapted to isolate pressure passages communicating with the valve assembly regardless of the direction of the pressure differential across the seal ring , the seal ring being maintained in sealing engagement with one wall of the seal ring groove and with a surrounding wall of the valve housing by an underseal expander ring that assures continuous sealing action of the seal ring
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH