Which statement correctly differentiates static seals from dynamic seals?

Which statement correctly differentiates static seals from dynamic seals?

• A. Static seals seal moving surfaces; dynamic seals seal stationary surfaces.
• B. Static seals seal stationary surfaces; dynamic seals seal moving surfaces.
• C. Dynamic seals seal stationary surfaces; static seals seal moving surfaces.
• D. Static and dynamic seals perform the same function.

Answer: (B)

The key idea is whether the sealing surfaces stay still or move against each other. Static seals are used where the mating surfaces do not move relative to each other, so the seal relies on constant compression of a gasket or O‑ring between fixed parts. Dynamic seals, on the other hand, are designed for situations where one surface slides or rotates against another, so the seal must maintain contact and prevent leakage despite relative motion, often with specialized lips and lubrication considerations. That’s why the correct statement is that static seals seal stationary surfaces while dynamic seals seal moving surfaces. It isn’t correct to say static seals seal moving surfaces, or that both types perform exactly the same function, since their designs and operating conditions center on different relative motions.

The key idea is whether the sealing surfaces stay still or move against each other. Static seals are used where the mating surfaces do not move relative to each other, so the seal relies on constant compression of a gasket or O‑ring between fixed parts. Dynamic seals, on the other hand, are designed for situations where one surface slides or rotates against another, so the seal must maintain contact and prevent leakage despite relative motion, often with specialized lips and lubrication considerations.

That’s why the correct statement is that static seals seal stationary surfaces while dynamic seals seal moving surfaces. It isn’t correct to say static seals seal moving surfaces, or that both types perform exactly the same function, since their designs and operating conditions center on different relative motions.