What is the temperature limit on a fixed roof tank?

• A. 15° or more
• B. 5° or less
• C. 25° or more
• D. 0° to 5°

Answer: (A)

In fixed roof tanks, how much the liquid temperature can rise before safety actions are needed is what this question tests. When a liquid stored in a fixed roof tank is heated, vapors are generated and pressure builds up inside the tank. Because the roof isn’t floated or fully sealed like other designs, you rely on vents to relieve that pressure. A temperature rise of 15 degrees or more is considered a practical threshold where vapor generation becomes significant enough to require closer monitoring and possibly venting or other safety actions. Smaller increases, like 5 degrees or less, don’t typically push vapor pressure into a dangerous range, while much larger rises imply a more extreme condition than the standard procedure intends to cover. So, 15° or more is the safety-relevant limit for this context.