Which statement is NOT true about seals?

• A. Labyrinth Seals Are Non-Contacting And Use Geometry To Impede Flow
• B. Carbon Seals Rely On Carbon Faces To Form A Seal
• C. Seal Land Is A Recognized Bearing Seal Type
• D. Labyrinth Seals Require Direct Gas-Tight Contact

Answer: (D)

The key idea here is how labyrinth seals work. They are designed to be non-contacting; their effectiveness comes from a long, winding path that gas must squeeze through, with tight but noncontacting clearances between sealing teeth or lands. That geometry creates resistance and pressure drop, limiting leakage without needing a direct metal-to-metal or gas-tight contact.

Because of that, the statement claiming labyrinth seals require direct gas-tight contact isn’t true. Labyrinth seals intentionally avoid contact to reduce wear and heat, relying on the tortuous path to impede flow rather than forming a perfect seal.

For context, other statements reflect real features: labyrinth seals rely on geometric paths to impede flow; carbon seals use carbon faces to form a sealing interface, often with precise face contact under load; and seal land concepts appear in bearing-seal discussions as recognized seal-feature regions in sealing assemblies. The main takeaway is that non-contacting geometry-driven sealing is what defines labyrinth seals.