An Italian Refinery Uses Emerson’s Micro Motion Coriolis Flowmeters for Fiscal Measurement
Coriolis for Accuracy
The measurement system skid includes both a duty and a master meter. The master meter has a greater accuracy than the duty meter and is used as a reference point to calibrate and check the performance of the other measurements being taken. The master meter is a Micro Motion ELITE, which offers ±0.05 percent accuracy over a range of 20:1. An advantage of using Micro Motion meters is that they were certified by the Metric Office in 2001 and have subsequently been approved without reserve by the Customs and Excise department. The full range of Micro Motion ELITE meters are also certified under the EU’s new MID (Measurement Instrument Directive).
There are several advantages in using Coriolis flowmeters on a fiscal application. First, since they measure mass and not volume, the accuracy of the results is not affected by environmental influences such as temperature.
Using temperature measured by an external RTD, the Coriolis flowmeter can also convert the mass reading into a standardized volume. This is important when measuring gasoline, kerosene and other light products, which are often sold by volume.
Other advantages include the fact the meters perform better with entrained gas, which can reduce the apparent density of the liquid. The meter can also measure flow in both directions. Together, these characteristics eliminate the need for bidirectional manifolds, motor-operated valves, strainers, and air eliminators. Lastly, Coriolis flowmeters do not need any straight pipe runs to condition the flow before and after the meter. All these factors mean that the skid can be more compact.