Definition - What does Ullage Rule mean?
Ullage Rule is a strip of rigid material that is attached to a dip tape to facilitate the measurement of ullage. It is one of the measuring scales tied to the portion of the dipstick when it is pulled inside the storage tank in order to know the level of petroleum liquid inside the tank. Ullage rule is also known as ullage ruler as it is very much similar to the measuring ruler, but it is of larger length.
Petropedia explains Ullage Rule
Ullage rule or ullage ruler, is an important piece of measuring the meniscus cut level of petroleum and liquids inside storage tanks. The ullage ruler is tied to the ullage dipstick and ullage paste is applied on the dipstick and ullage ruler. The dipstick is lowered to the bottom of the fuel tank along with the tied ruler. When the dipstick or ruler comes in contact with the liquid fuel, the ullage paste changes color to indicate how high the level of liquid is. This level is noted down as per the scale it matches with on the ullage rule.