Accurate Measurement of Bunker Delivery Quantities

Emerson’s Steve Jones, part of the Micro Motion Coriolis flow and density measurement business, recently wrote an article on bunker metering for Bunkerspot magazine. Entitled, Critical Mass in the Bunker Industry, it describes the importance of accurate measurement of bunker fuel–also known as heavy fuel oil (HFO).

For those not familiar with bunker fuel, I found this definition:

Bunker fuel is also known by other names: heavy oil, #6 oil, resid, Bunker C, blended fuel oil, furnace oil and other often locally used names. No matter the origin of bunker fuel it has common properties where ever found: color, viscosity, contaminants, and operator problems.

In the article, Steve pointed to the challenges associated with trying to measure volumetrically the flow of bunker fuel used in the marine industry. Measurement errors are typically 1-3% and can be as high as 5%, which can lead to large discrepancies between fuel supplier and fuel consumer. Imagine if your car’s gas gauge and the gas station refueling pumps were accurate to plus or minus 3%. You’d be wondering if you’d be getting all the fuel you purchased and wondering if you had fuel left in your tank as it runs low.

A better approach is to use mass-based measurement with Coriolis flow meters. Mass measurement can accurately measure the different bunker fuel grades, and impurities that have not been filtered out. Steve also noted:

Coriolis meters are non-intrusive, meaning that there are no moving parts or obstructions in contact with the fluid being measured. In addition to mass measurement, a single device provides an independent and very accurate density measurement of the fluid and a temperature measurement – three measurements from one device.

Bunker delivery operations have tank-stripping processes, which clear the tanks of sludge and water. This process means air can become entrained with the bunker fuel. Coriolis measurement provides accurate measurement even in these conditions, as I’ve discussed in an earlier entrained gas post.

Steve raised one other important requirement for bunker applications–in-situ meter verifications. He wrote:

Meter verification technology on Micro Motion meters measures the actual mechanical characteristics to a very high accuracy — in line and without removing the meter. When a change in the meter’s tube performance is detected, the results determine whether measurement performance remains within the original factory specifications.

Steve described bunker measurement mass flow meter trials with A.P.Moller-Maersk and ExxonMobil Marine Fuels. These trials are entering their second phase with a view to gain custody transfer certification. Steve concludes:

While Emerson continues to work with A.P.Moller-Maersk, ExxonMobil and others to provide international metrology certification of Coriolis measurement in fuel oil bunkering applications, initial test results illustrate the great potential this technology offers to the advantage of the marine industry as a whole.

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