The objective of this thesis was to examine how the highly customized Shell and Tube Heat Exchangers, which are currently manufactured by the case company could be standardized to enable correct resource allocation, thereby improving the company's financial performance. In course of the research, the economical degree of standardization became the dominant factor affecting the outcome. Standardized design rules were chosen as the basis for the standardization degree of the case company's Shell and Tube Heat Exchangers. In addition to the design rules, a suggestion for automating the modes of operation by using a parametric option table and an electronic manual is included in the product standard. In this thesis,product standardization is considered a rationalization investment and its profitability is evaluated with the help of investment calculations and sensitivity analysis. The initial values in the investment calculations are based on the assumption that the same product standardization method conducted for one Shell andTube Heat Exchanger could be used later for all Shell and Tube Heat Exchangers of that unit of the case company.