An ullage reading measures the distance from which point?

The ullage reading is an important measurement in the context of liquid storage tanks, as it provides insight into the amount of liquid present. Specifically, the ullage refers to the empty space above the liquid in a tank. Therefore, the correct understanding of how ullage is measured is from the top of the sounding tube to the surface of the liquid within the tank. This measurement assists in determining how much space is available for expansion and prevents overfilling.

The sounding tube is designed to provide a reference point for measuring the level of the liquid, and by measuring from this point down to the surface, you can accurately assess the ullage. This is critical for safe operations especially in the context of fuel oil and other liquid storage systems. Understanding this correct measurement is essential for effective tank management, operational safety, and compliance with various regulations regarding liquid storage.