How is leakage between stages prevented?

• A. Mechanical seal
• B. Labyrinth seal
• C. Dry gas seal
• D. Liquid film seal

Answer: (B)

Labyrinth seals prevent leakage between stages by creating a long, winding path with many tight gaps around the rotating part. As gas tries to move from one stage to the next, it must flow through multiple cavities and narrow clearances. Each bend and small gap causes a pressure drop and dissipates energy, so the overall leakage flow is greatly reduced even though there’s no metal-on-metal contact. This non-contact, geometrically complex barrier is especially suited for keeping stages isolated in multistage machinery without wearing seals.

Other approaches rely on different principles but aren’t as effective for this specific purpose. Mechanical seals depend on mating surfaces that can wear and require lubrication or cooling; dry gas seals use a thin film of pressurized gas for shaft sealing but aren’t designed primarily to isolate stages; liquid film seals rely on a liquid layer, which isn’t ideal for preventing cross-stage leakage in gas systems.