Measurement accuracy of heat meters: In situ Calibration of Heat Meters in Operation

TÜV Rheinland, Cologne/Germany, has developed a new optical procedure in cooperation with two companies specializing in Laser optic measurement technology. The process enables the highly precise analysis of measurement accuracy of flow meters in situ without the need to interrupt operation. The method has been further developed in such a way that the access is now closed off with a pressure-tight sight glass, thereby creating an optical access. The results of the measurements carried out with the new procedure emphatically demonstrate the necessity of in situ inspections. Velocity profiles are recorded across the entire cross-section of the pipe. The flow rate is subsequently determined by integrating the velocity distribution. The measurement deviation of the flow meter in the installed state is determined by comparing the flow rate obtained by the LDV method with the value delivered by the device being inspected.