This document specifies the method for in situ calibration of liquid flow metering installations using the radioactive tracer transit time method. The method specified is an application of the flow measurement method described in ISO 2975/Vll for the calibration of permanent flow meter installations.
The aim of the method differs clearly in principle from that of the calibration of flow meters in calibration laboratories, where the flow meters are calibrated under ideal flow conditions. The in situ calibration result obtained by the method specified here involves the total error of the installation position, i.e. both the error component due to the flow meter itself and those caused by a nonideal installation position. The latter components are due to a distorted flow velocity profile, fluid properties, environmental effects etc. They are in practice always present in permanent flow measuring installations and are generally responsible for the major part of the total error.