Project summary

A new research project has been granted under the European Metrology Research Program (EMRP). The project has started in May 2010 and lasts for 3 years.

The overall objective of the project is to contribute to a significant reduction of uncertainty in the determination of transferred energy in LNG custody transfer processes. The project is supporting traditional and innovative measurement methods by providing a metrological framework consisting of test & calibration standards together with the written standards and guidelines.

The more specific objectives of this JRP can be summarized as following:

  1. Developing traceability for LNG flow meters
  2. Testing and evaluating LNG quantity metering systems
  3. Improving LNG composition measurement systems
  4. Reducing uncertainties in LNG density and calorific value calculations
  5. Contributing to measurement guidelines, written standards and legal metrology
Currently there exists no LNG flow calibration facility working at -163 oC anywhere in the world. The approach for achieving the first objective starts with completing the development of a primary calibration standard (to provide a direct link to SI units) with top-class accuracy (0,05%) up to 25 m3/h and operational with real LNG at 163 oC. The science and technology needed to realize an industrial scale (5,000 m3/h and higher) calibration facility will be developed by completing a research into up-scaling effects and the propagation of uncertainty. The research includes theoretical, computational and experimental studies. A test-rig that will be set-up for the up-scaling experiments will also become useful as a calibration standard for LNG flow meters up to 200 m3/h. The measurement systems will furthermore be used to validate an economic calibration concept using water instead of LNG. The validation will be supported by computational fluid dynamics (CFD) studies.

The second objective includes the establishment of the real uncertainty for (state of the art) ship-based tank-gauging methods by performing a comprehensive metrological study (desktop based and using real data and experience from industry) based on ISO-GUM principles. The measurement performance of tank gauging and flow metering systems will be compared by designing and performing in-field testing and reviewing test results from other pilot studies. Two newly developed cryogenic testing systems will be available to study cryogenic and installation effects on LNG sensors and flow meter performance. This will provide important information to assess the real uncertainty of LNG flow meters.

In order to achieve the third objective the performance of different sampling systems will be assessed by reviewing design principles and by analyzing real data provided by industry. This will lead to recommendations for sampling system improvements. An alternative optical method (Raman spectroscopy) for determining the LNG composition directly in the LNG pipeline will be compared with sampling based methods.

The fourth objective is to develop laboratory based systems to measure the density of LNG with improved accuracy. An advanced primary LNG densitometer system will be designed and realized to produce new reference data with very low uncertainty (0,02%). The reference data will be used to validate and recommend or improve equations of state that are used to calculate the density. The new reference data will be confirmed by comparing the LNG densitometer results with results obtained by a pycnometer based density metering system that will be redesigned to operate at cryogenic conditions with a target uncertainty between 0,01 – 0,1%.

The fifth objective is to contribute to improvements and extensions of measurement guidelines and international standards. In existing documents the uncertainties are sometimes not well characterized, some technologies (LNG flow metering) are not yet described and in some cases insufficient guidance is provided to industry. Input to the legal metrology framework will also be provided. All this will ensure that the newly created knowledge in this project concerning LNG measurement systems finds its way to the user community.