Accurate measurement of liquids is important for all oil and gas industry production or consumption sites. This is especially true for bulk transfer devices where large volumes of products are being moved and must be monitored, including crude oil depots, gasoline and jet fuel tank farms, refineries, and even cruise line terminals.
In the past, mass transfer was measured in batches with weigh scales or load cells. However installation, calibration, and maintenance of a scale or load cell are costly, difficult to do, time consuming, and don’t work for continuous processes. For these processes, such methods as orifice plates and magnetic flow tubes can measure volumetric flow, but additional instruments are needed to measure temperature and pressure to compensate for fluid density changes. Introducing additional instruments also introduces errors, which can result in an overall measurement error rate as high as three percent.
Now, several measurement standards are moving towards use of Coriolis mass flowmeters, which can measure mass flow directly, at the same time as they measure temperature and density. What’s more, transfer measurement by mass is the most accurate method, since mass is independent of, and unaffected by, changing process fluid characteristics, including pressure, temperature, viscosity, conductivity, and gravity.
Among the Coriolis devices available, the straight tube design is being hailed as the most accurate and easiest to install and maintain. Especially for measurement skids, widely used in the oil and gas industry, the straight tube Coriolis meter can be a factor in minimizing skid size, a definite plus for space-challenged sites.
The Coriolis effect – what is it and why does it help with bulk measurement?
In physics, the Coriolis effect is a deflection of moving objects when they are viewed in a rotating reference frame. In a reference frame with clockwise rotation, the deflection is to the left of the motion of the object; in one with counter-clockwise rotation, the deflection is to the right. The mathematical expression for the Coriolis force appeared in an 1835 paper by the French scientist Gaspard Gustave Coriolis, in connection with the theory of water wheels.