An oil vent line replaced by a fabricated line gets tested to what type of pressure?

• A. Hydrostatic testing
• B. Vacuum test
• C. Low-pressure test
• D. Proof pressure testing

Answer: (D)

When a fabricated oil vent line is installed, the goal is to confirm the line can safely handle the pressure it will encounter in service without leaking or failing. This is done by applying a defined pressure that’s higher than normal operating pressure, which is called a proof pressure test. The idea is to prove the line’s strength and integrity under a realistic, but controlled, load so any weaknesses show up before service.

Hydrostatic testing uses a liquid to check strength and leaks, which is typically used for tanks or piping containing liquids. A vacuum test applies negative pressure to look for leaks under suction, not to verify the line’s ability to withstand positive operating pressure. A low-pressure test doesn’t provide the required margin to ensure reliability in service. Therefore, the standard for verifying a freshly fabricated vent line’s integrity is proof pressure testing.