There are many reasons for the poor accuracy of steam measurement data. The most important reasons can be concluded as follows:1. The working conditions of the instrument deviating from the designed conditions Data Processing Approaches for the Measurements of Steam Pipe Networks in Iron and Steel Enterprises 245At present, the mass flow rates are mostly deduced by the volume flow rates and the density. However, the changes of temperature and pressure in the transmission process would lead to the density of steam deviate from the original designed value [3]. The measurement errors would be very large [1]. Any more, some superheated steam would change into a vapor-liquid two-phase medium, which making precision worse. The Complexity of Steam CharacteristicsWith the ambient temperature changing, the total amount of the condensate water in the transmission process will be different. That makes difference between the amount of the production and the consumption of steam. In addition, the steam pipe leakage will add to the difference. Therefore, the accumulated readings are always doubtful.3. The Occurrence of wearing or damage to the Key Components As the orifice differential pressure flow rate meter being in use for long time, the size of aperture would differ from the original size because of the adhered foreign bodies, or erosion by the durative high temperature steam flow. As the parameters can not be adjusted on time, and it is hard to calibrate the instrument, the measurement errors will accumulate.