Which item is a dynamic seal?

Which item is a dynamic seal?

• A. Gasket
• B. V-Ring
• C. O-ring
• D. Packing

Answer: (D)

The main idea is understanding what makes a seal dynamic—one that maintains the barrier while there’s relative motion between the sealing surfaces. Packing is the classic dynamic seal used around a moving rod or stem in a stuffing box. The packing material is packed and then compressed by a gland so it continuously rides with the moving part, closing leaks as wear or movement occurs. This setup is designed specifically for motion, wear compensation, and varying pressure, which is why it’s the best choice for a dynamic seal. Gaskets are typically static seals between two stationary faces, so they don’t handle moving surfaces. An O-ring can serve as a seal, but it’s most common in static joints or simple dynamic applications, not the standard moving-rod scenario. A V-ring is a shaft seal used with rotating shafts, which is a different dynamic seal arrangement and not the general moving-seal type described here. Because packing directly exemplifies a moving-seal arrangement around a rod or stem, it is the correct choice.

The main idea is understanding what makes a seal dynamic—one that maintains the barrier while there’s relative motion between the sealing surfaces. Packing is the classic dynamic seal used around a moving rod or stem in a stuffing box. The packing material is packed and then compressed by a gland so it continuously rides with the moving part, closing leaks as wear or movement occurs. This setup is designed specifically for motion, wear compensation, and varying pressure, which is why it’s the best choice for a dynamic seal.

Gaskets are typically static seals between two stationary faces, so they don’t handle moving surfaces. An O-ring can serve as a seal, but it’s most common in static joints or simple dynamic applications, not the standard moving-rod scenario. A V-ring is a shaft seal used with rotating shafts, which is a different dynamic seal arrangement and not the general moving-seal type described here. Because packing directly exemplifies a moving-seal arrangement around a rod or stem, it is the correct choice.