LiBRA: the accredited calibration laboratory conforming UNI EN ISO/IEC 17025

The LiBra calibration laboratory of Hemina Spa - ISOIL Industria

The laboratory, accredited since October 2013, allows the Libra Division to calibrate instruments of measurement in volume, range in volume, mass flow and total mass, both on meters produced by Isoil, and on metering produced by third parties and to issue the relevant Certificate Accredia. The lab is able to calibrate Flow/Volume/Mass meters from DN 3 to DN 3000.

The calibration laboratory consists of plants and devices for the calibration of measuring instruments for the following physical quantities: volume (totalized), volume flow, mass (totalized) and mass flow.

The system consists of eight lines, each calibration line is designed for the hydraulic connection of a group of nominal diameters da dn 3 a dn 3000.

The plant consists of 8 calibration lines running on static weight based, direct comparison with a Master Meter or Master Volume method.

The system consists of a calibration system using the static weighing method complying with the norm UNI EN 24185:1994 “Measurement of fluid flow in closed conduits - Weighing Method”.

This standard is specific for calibration of the flow rate (in volume and in mass).

The same standard is used as a reference for the calibration of the volume and mass totalized.

The method involves direct comparison between the instrument to be calibrated and one or more instruments used as reference. The system is designed in such a way as to allow the installation of the measuring tube of the instrument used as reference sample and measuring instrument to be calibrated in series.

The two instruments are directly connected by means of a hydraulic line made of steel pipes. The metrological performance of the measurement is ensured by the possible choice of each line and one of three Master Meters of different nominal diameters.

The method involves direct comparison between the indication of the instrument to be calibrated and the volume of the reference tank between the initial and final levels determined by the calibration.

The reference volumetric flow rate is determined by the ratio between the volume and the emptying time.

The 8 calibration lines use different calibration methods; static weighing, direct comparison with Master Meter or with a sample volume.

The calibration lines from 1 to 6 are equipped with submersed power pumps regulated by an inverter (the pumps are installed in a common tank with a capacity of 600 m3), a system of steel pipelines making the hydraulic path, valves, devices for air venting, process connections for the

devices under test to be calibrated and an electronic scale with storage tank of adequate measurement volume capacity. A high-precision flow diverter controls the filling of the weighing tank.

A bypass hydraulically connects the flow diverters of the six calibration lines, allowing optimization of the metrological calibration performance using the most appropriate scale for resolution and accuracy. Line 7 consists of a closed loop hydraulic circuit that includes a pumping station and four master meters. Calibration lines 1 to 7 can perform calibrations utilizing the comparison with Master Meter method.

On each line there are several master meters, appropriately sized, so as to guarantee high metrological calibration performances over a wide range of flow rates. The calibration line 8 is equipped with a volumetric tank of 550 m3 capacity, the calibration of the instrument (DUT device under test) foresees the progressive emptying of the tank under controlled conditions.

Calibration processes activities are completely automated and directly interface with system management software that controls all calibration operations and the management of all calibration orders is fully automated and is directly linked with the software system issuing Certificates of Calibration at the end of the tests.