Onsite Quality Assurance of Large Flow and Energy Measurements in Paper and Pulp Mills

Systematic measurement errors of 5 to 10% are common in flow and energy measurements in paper and pulp mills. These errors create significant costs to the industry, mainly due to inaccurate process control and misguided investment decisions based on incorrect efficiency calculations. Measurement history data can be used to localise and estimate measurement errors. This can be accomplished by correlating unbalances present in the mass and energy balances with individual measurements. Result error estimates can be calculated for each measurement and corrective actions can be taken in positions where they are really necessary. The metrological base for corrective action is traceable field calibrations. Indmeas has developed a field calibration technology for traceable field calibrations of water, steam, gas, process material used in the paper and pulp mills. The calibration method does not require any process stops or removal of the actual meter. This means that calibrations are carried out during the normal process operation. The field calibrations of Indmeas are accredited with the smallest accredited calibration uncertainty of +-0.5% for liquid, gas and steam flows. The calibration technology has been thoroughly tested and over 10,000 calibrations have been carried out by Indmeas in the Nordic countries to date. One of the key customer groups is paper and pulp mills. The accurate results have been achieved by combining balance analysis and field calibrations. The methodology developed can be used for quality assurance of all process balances. In addition it automatically assures the quality of the individual measurements belonging to the balance. This paper describes how this method is used with pulp and paper mill applications and also shows common application and some results.