Labyrinth seals are used when

• A. No leakage is permitted
• B. They seal completely without leakage
• C. They are used for high speed operation
• D. Some leakage is permitted

Answer: (D)

Labyrinth seals are designed to keep leakage to a very small, controlled amount rather than trying to seal perfectly. They create a long, tortuous path between the rotating and stationary parts, which makes it hard for fluid to pass through. Because they are non-contact seals, there’s no wear from rubbing, which is great for high-speed shafts and in dirty or harsh environments. But because there’s always a gap and a pressure difference, some fluid will leak through the labyrinth path. The purpose is to minimize and control that leakage to an acceptable level, not to eliminate it completely. This approach works well in systems where a tiny amount of leakage is permissible and where durability and speed are more important than achieving zero leakage. If zero leakage were required, a different, more tightly sealing solution would be needed.