Industry Terminology 

FLO-CORP has compiled and written definitions for several industry terms. This list is designed to be a glossary that helps you better understand the elements of our industries. Process instrumentation is used in an extremely wide range of applications anywhere measurements are needed for media that flows or is stored in a container or tank. Many of these terms will help you understand the technologies used in such measurements.

Accuracy – The accuracy of a flow meter gives the maximum plus or minus deviation between the meter’s indication and the true value of the flow rate, or in the flow total. It is the interval within which the true value of a measured quantity can be expected to be in with a stated probability. Accuracy may also be referred to as uncertainty. Accuracy include the combined errors due to linearity, hysteresis, and repeatability. Accuracy can be stated as a percent of span or full scale, as a percent of rate, or as a percent of upper range value or upper limit value. it is important to understand the differences between the stated value. 

Back Pressure – A reference to pressure as opposed to the desired flow of gases in a given pipe diameter. It is any condition where the pressure in a system becomes greater than the supply pressure. Back pressure is caused by obstructions in the pipe, pipe direction or orientation, pipe surfaces and pipe types as well as tight bends. Because of air resistance, friction between molecules, the term Back Pressure is misleading as the pressure remains and causes flow in the same direction, but the flow is reduced due to resistance. Back Pressure is often confused with Pressure Drop. Back Pressure can contributes to the release of vapor from liquid and are a function of head loss in liquid flow piping systems. This condition is often referred to as Cavitation.

Cavitation – If a liquid enters a flow meter at a pressure near its vapor pressure, the pressure reduction in the meter can cause the liquid to flash partly to a gas. If, with pressure recovery, the gas pressure rises back above the vapor pressure, the bas bubbles will implode, causing cavitation to occur. Plashing and vaccination can destroy many piping systems and many types of flow meters.

Density – The property of a fluid expressed as weight or mass per unit volume. Liquid density is generally a function of temperature. Gas and vapor density varies with changes in temperature and pressure. As an example, water has a density of 62.34 lbs. per cubic foot at 60º F. And a density of 60.13 lbs. per cubic foot at 200º F. 

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