NGT - Tandem Dry Gas Seal with intermediate Labyrinth
Where the process gas leakage to the atmosphere as well as buffer gas leakage to the process gas is both inadmissible, the tandem arrangement with an intermediate labyrinth is used.
The labyrinth seal is installed between primary and secondary seal of tandem seals. Except the process gas, the nitrogen gas needs to be used between secondary seal and labyrinth seal. The secondary seal could be a back-up when the primary seal breaks down.