Which gas is used to pressurize accumulators in the seal oil system?

• A. Nitrogen.
• B. Oxygen.
• C. Argon.
• D. Helium.

Answer: (A)

Pressurizing accumulators in a seal oil system requires a gas that is dry, inert, and readily available, to keep oil clean, prevent oxidation, and reduce fire risk. Nitrogen fits this role perfectly: it is inert so it won’t react with oil or metal, it’s dry and non-corrosive, and it’s inexpensive and widely supplied from air separation plants. Using oxygen would risk oil oxidation and potential fire hazards; argon can be inert but is typically more costly and less readily available on-site; helium is expensive and tends to leak away more quickly due to its small molecules. So nitrogen is the practical, safe choice for maintaining accumulator pressure.