Orbit Plug Valve (Double block & bleed valve), Class 150-1500 LB

Double block & bleed valve (DBBV) is a non-lubricated, resilient seal, plug-type valve which has a mechanical means of freeing the plug before it is rotated from the closed to the open position.
In opening the valve, the plug is raised, thus retracting the seating segments or slips through their tapered dovetail connections. Only after the slips are fully retracted from the body seat is the plug rotated to the open position.
Conversely, in closing the valve, the plug and slips are rotated freely, with no seal-to-body contact until the slips are positioned over the ports.
Then the plug is driven down between the slips and the tapered surfaces wedge out the slips for a positive upstream as well as downstream shut-off.