To determine how much cargo remains, ullage measurement assesses which of the following?

To determine how much cargo remains, ullage measurement assesses which of the following?

• A. The volume of cargo remaining
• B. The cargo weight
• C. The distance from liquid surface to top of tank
• D. The pressure inside the tank

Answer: (C)

Ullage measurement focuses on the air space inside the tank—the distance from the surface of the liquid up to the top of the tank. This empty gap is measured because, with the tank’s known shape and size, that distance can be translated into the amount of liquid still in the tank using calibration tables or software. In other words, you’re measuring how far the liquid has dropped from the top, and then you convert that distance into volume to know how much cargo remains. This method doesn’t directly measure cargo weight, which would require knowing the liquid’s density in addition to the volume. It also doesn’t measure the pressure inside the tank, which is not used to determine remaining cargo. While you can combine ullage with temperature to adjust density and thus weight calculations, the ullage itself is the distance from liquid surface to the tank top.

Ullage measurement focuses on the air space inside the tank—the distance from the surface of the liquid up to the top of the tank. This empty gap is measured because, with the tank’s known shape and size, that distance can be translated into the amount of liquid still in the tank using calibration tables or software. In other words, you’re measuring how far the liquid has dropped from the top, and then you convert that distance into volume to know how much cargo remains.

This method doesn’t directly measure cargo weight, which would require knowing the liquid’s density in addition to the volume. It also doesn’t measure the pressure inside the tank, which is not used to determine remaining cargo. While you can combine ullage with temperature to adjust density and thus weight calculations, the ullage itself is the distance from liquid surface to the tank top.