The liquid facility of Euroloop is the world’s most accurate and innovative testing and calibration laboratory for high-flow liquid calibrations. As the first closed-loop liquid facility we are able to calibrate liquid meters all year long. The installation is based on two piston provers with an overall uncertainty of 0.02 %. The nominal viscosities available are 1, 25 and 300 centistokes, adjustable via temperature.


Within the closed-loop installation, six master meters are installed per viscosity. In addition to these master meters, two piston provers are available: one for the small meters (<10”) and one for larger meters (>10”). This principle allows us to test for the lowest possible uncertainties: the uncertainty for measuring against the master meters is 0.06 % and the uncertainty for testing against the piston prover is 0.02 %.


The performance of a liquid flow meter may depend strongly on the velocity profile of the flowing liquid. For this reason, Euroloop’s liquid flow facilities permit calibration over a wide range of Reynolds numbers utilising three different viscosities in the range of 1 -300 mm²/s (centistokes). Each circuit is split between a small- and a large-bore loop. The temperature increase resulting from the energy exerted on the liquid by the pumps is reduced by means of a water cooling system. A back pressure of 9 bar avoids cavitation in the liquid. The primary references for calibration consist of a large piston prover and a small piston prover, which are both operated on all three liquids. The secondary references are master meters, which are a combination of an upstream full bore and a downstream reduced bore ultrasonic meter

The temperature in each circuit is measured by unique fast ultrasonic sensors that detect the average temperature in a cross section of the pipe without disrupting the flow pattern. The temperature stability during the calibration run is better than 0.1 °C. Utilizing the ultrasonic technology together with conventional thermowells at 48 points throughout the different loops allows us to guarantee quality at any given time. Due to the closedloop system, the quality of the liquids remains constant and is monitored regularly by means of a sample analysis by external laboratories

Piston provers

The primary reference for Euroloop’s liquid facilities consists of two of the biggest piston provers in the world. The ‘small’ prover is 36 m in length and 60 cm in diameter and has a metrological volume of 6,7 m3, capable of producing 1.200 m3/h. The large prover is 46m in length and 1.10m in diameter and has a metrological volume of 23m3 , producing flows up to 5.000 m3/h. Their dimensions of the provers are impressive, but so are their mechanical properties. The provers are made entirely of stainless steel, with a variation in diameter of only a few hundredths of a millimeter. They are equipped with a wide range of measuring instruments, including sensors for measuring the diameter of the prover at various points during testing.