What is the purpose of a seal oil tank?

• A. To provide head pressure to overcome gas pressure at the compressor height
• B. To store seal oil
• C. To cool the seal oil
• D. To drain condensate from the system

Answer: (A)

The seal oil tank is used to create a hydrostatic head that keeps seal oil at a pressure higher than the process gas at the compressor height. That pressure difference drives a controlled flow of oil to the mechanical seal, forming a protective barrier that prevents gas from leaking along the shaft into the seal oil system. The tank also serves as a reservoir, but the essential purpose is to provide that head pressure so the seal operates with a stable, protective oil film. Cooling the oil or draining condensate are not the primary roles of the tank, though those functions may exist in other parts of the system.