59685 - Test Bench for Characterization and Design Against Steam Turbine Fouling 

The fouling phenomenon is related to the deposition within the turbines of steam impurities and to the presence of solid debris, coming out from upstream plant sections, that can create solid build-ups in stationary and moving parts inside the turbine. As a consequence, fouling causes unit efficiency decline but, in severe cases, also lead to sticking of moving components, such as valves, that may be critical in machine control and/or safety.
Despite well-studied and well-considered in design and operation of large power utility plants,  where steam quality is of primary importance for boilers, super-heaters,  turbines and condensers, this subject is often overlooked in small power generation or industrial applications, where efficiency may be less critical but turbine availability is of paramount importance for plant operation (e.g. LNG plants).   

The fouling is a subject that has been widely studied in the past, but quite neglected in more recent years.    
This paper, with the aim of underlining the importance of fouling in the operation of turbines for industrial applications, starts with examples of field evidences of severe fouling. Then the design of a test bench for the experimental characterization of fouling rates and validation of turbine components, exposed to fouling conditions is presented.    
The study addresses the main deposition physical principles and their implications in the thermodynamic design of the test bench, on the basis of the specific physical properties of the impurities of interest. To better match plant real cases, the contaminants tested included those which have been usually found within the units during maintenance activities and for which specific limits are prescribed by OEMs.              
In the papers, details relevant to the main deposition mechanisms expected at different locations due to components geometry and flow-field are discussed, along with the use of the test bench for validation of fouling removal procedures (such as water washing).

The results obtained are qualitatively in line with literature and internal practices but, through the test activities, it has been possible to establish a quantitative relationship between the concentrations at inlet section for each contaminant and the different thermodynamic conditions along the test bench capturing also the impact of solubility changes along with the steam expansion.