Harmonised reference values Natural gas has been a dominant energy source in Europe since the seventies. With the high financial stakes involved, there has been an increasing demand for reliable and stable reference values for high pressure gas flow measurements. As flow calibration facilities in different countries follow separate traceability chains to their own national standards, there is a need to harmonise their values.

In 1999, the German, French and Dutch National Metrology institutes (NMI’s) agreed on a harmonised cubic metre based on the uncertainty-weighted average of the national cubic metres: the so-called Harmonised Reference Value (HRV). Denmark later joined the group. Although NMI’s are directly responsible for harmonisation, Euroloop plays a vital supporting role in the process. Each Euroloop certificate is directly linked to the Dutch and European standards for high pressure gas measurement via VSL and their European partners, FORCE, PTB and LNE


Although being harmonised provides a stable reference with respect to our colleagues throughout Europe, Euroloop continually assures proper measurement by performing inter-laboratory comparisons (round robins).

Euroloop’s liquid facility has recently acquired a 10” travelling reference standard consisting of a 10-path ultrasonic meter and a helical turbine meter. The gas facility has 3 travelling standards using 4”, 10” and 16” SMRI turbines. All travelling standards include dedicated flow conditioners and pipe spools. Travelling standards are calibrated at planned intervals in other laboratories and reports of these round robins are placed on our website.

Internal checking

Euroloop uses pairs of meters in series to provide continuous cross-checking. The liquid facility uses paired ultrasonic meters of different construction, and the gas facility uses turbine meters paired with ultrasonic meters.

Master meters in the liquid facility are checked at intervals against the meter provers, which are also available for direct calibration of client meters. As it is impractical to have a permanently installed gas prover, the gas facility holds 20” and 24” SMRI turbines as sleeping standards to verify consistency internally at defined intervals. It also has a “watchdog” meter in each large test line to provide continuous checking of the flow profile and the total flow delivered to the meter under test.


Euroloop has an ISO 17025 accreditation for calibration laboratories issued by the Dutch Council for Accreditation (RvA) pertaining to flow rate and volume calibrations for the majority of its operating range. The actual scope of accreditation is published on under certificate number K161. RvA accreditation is internationally accepted in over 80 countries.


If meters are required to comply with legal regulations such as the European Measuring Instrument Directive (MID), Euroloop is able organise conformity assessment in co-operation with an appointed national metrology institute.