Main Steam Line Flow Measurement

Increasing energy costs and environmental pressures encourage steam turbine users to find the most economical and efficient operation points for their plant. Main steam flow to the turbine is one of the key measurements to determine turbine efficiency and performance. Conventional inferred mass flow measurements, using pressure readings from the turbine first stage, have inherent inaccuracies and assumptions that often lead to incorrect steam flow readings. If those reading accuracies can be improved, the turbine operator will see many advantages, including improved fuel intake and heat rate measurements, higher turbine efficiency over varying loads, better steam control, and increased power generation. Since fuel contributes almost 50% of the total variable cost of electricity generation, operators are discovering the cost benefit of adding direction main steam line flow measurement. This paper compares and contrasts various techniques for computing steam mass flows in utility boilers and outlines the operational benefits of using real time main steam line flowmeters over inferential steam flow computations. Also, a case study is presented which highlights the operational improvements of direct steam flow measurement.