Labyrinth seals are designed for applications where

• A. All leakage must be prevented
• B. Some leakage is permitted
• C. They operate only at high speeds
• D. They seal lubricants only

Answer: (B)

Labyrinth seals work by forcing fluid to travel a long, winding path between a rotating and a stationary surface. This non-contact design creates many barriers to flow and greatly reduces leakage, but it cannot create a perfect seal. Because the seal relies on clearances rather than tight contact, a small amount of leakage is inevitable and, in many applications, acceptable. This smaller leakage rate helps avoid excessive friction, wear, and heat, while still keeping contaminants out and lubricant in.

That’s why the best answer is that some leakage is permitted. It’s not practical to expect complete, zero leakage with this type of seal. At the same time, labyrinth seals aren’t limited to high speeds, and they’re not meant to seal lubricants exclusively; they’re used to control leakage and contamination for a range of fluids and operating conditions.