Work is underway to re-instate the Primary Liquid Densitometer at NEL. This will enable NEL to enhance its services and improve the accuracy of the measurements it offers for the calibration of industrial densitometers.
“The work began in December 2017 and a review of current NEL density calibrations systems has been undertaken,” says Principal Consultant, Dr Norman Glen. “We have also started the process of upgrading relevant system control and data-processing software. The project is scheduled to finish in May.”
According to Norman, this nationally important project will re-establish traceability to primary standards for liquid density measurement at elevated temperatures and pressures.
“Our approach uses Archimedes’ principle,” Norman explains. “It measures the apparent mass of a reference body (made from fused silica) in the fluid that we are trying to determine the density of.”
“This work has become a priority due to the demands for enhanced accuracy at elevated pressures that our new era multi-phase test facility will bring,” says Norman. “We are also seeing requests from meter manufacturers for enhanced density calibration services for next-generation industrial density measurement devices.”
At present NEL uses reference fluids to establish density and there is no direct chain of traceability to primary standards. Whilst this is adequate for most purposes (e.g. calibration of industrial densitometers with an uncertainty of the order of 0.5 to 0.8 %), it is not acceptable for use in primary standard applications.
The use of reference fluids adds an additional source of uncertainty. The completion of the Primary Liquid Densitometer project will allow this uncertainty to be removed, resulting in lower overall uncertainties and improved measurements for industry.
“Highly accurate knowledge of the density of a fluid and its variation with temperature and pressure is particularly important in the oil and gas sector,” explains Norman. “This is because volumetric flow measurement devices are used but mass is the quantity required for reporting. Highly accurate density information is needed to convert one to the other.”
For more details, contact Dr. Norman Glen
Updated 15 February 2018
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