Dust collectors require airlocks to prevent air from entering/leaving the dust discharge flange of the dust collector. This provides the isolation between the process environment and the outside.
Airlocks, such as rotary valves, are high maintenance pieces of equipment. The bearings will fail, the rotor will need replacement, etc. When this happens, the system must be shut down so the valve can be removed and repaired. This causes extra process down time unless the valve is able to run until the next scheduled shutdown.
However, installing an isolation valve such as the Aerodyne Stoptight Knife Gate allows you to isolate the dust collector while the airlock is removed and repaired. Dust will build up in the hopper until the knife gate is opened, but this allows you to keep operating while the valve is being repaired or replaced without actually shutting down the system.