Which of the following is NOT listed as a type of bearing seal?

• A. Labyrinth Seals
• B. Carbon Seals
• C. Seal Land
• D. Copper Seals

Answer: (D)

The concept here is recognizing which items are actually categorized as bearing seal types rather than design features or unconventional materials. Labyrinth seals are a recognized bearing-seal type that uses a complex channel to impede leakage without contact, making them well-suited for high-speed shafts. Carbon seals are another established type, using carbon-based faces that tolerate high temperatures and provide good wear resistance in rotating assemblies. Seal land refers to the machined seating surface around a seal—a design feature important for proper sealing, not a separate type of seal. Copper seals aren’t part of the standard bearing-seal taxonomy in turbine engines; copper isn’t used for the sealing interface in these applications because it doesn’t offer the necessary wear resistance, high-temperature stability, or long-term reliability under the engine’s demanding conditions. Therefore, copper seals are not listed as a bearing-seal type.