Compressor Foundation Analysis Tool (COFANTO)

Reciprocating compressors are generally supported on a heavy concrete foundation. In spite of the large inertia and stiffness of the foundation, problems can occur due to interaction between the mechanical installation and the foundation. Two types of problems may occur. In the first type, the interaction is such that excessive vibration levels occur in the entire concrete structure including compressor frame, cylinders, dampers and piping that can lead to alignment problems and unallowable crankcase deformations. In the second type, failure of the connections between compressor and foundation may occur due to poor design. These problems have often been identified after construction of the plant. Foundations for reciprocating compressors are different than for rotating compressors (high speed, small rotating unbalance) and it appeared that the design of foundations for reciprocating compressors was at a poor level the last 20 years. The new generation of designers exhibits limited experience in the dynamic design of foundations, especially for reciprocating compressors. In most of the designs the soil-structure interaction is not included, even though it can have a large effect on the dynamic design. It is also known that existing foundations are used for new larger compressors without adjusting the foundation and has often led to vibration problems and failures of foundation and compressor system components. Within the R&D group of the EFRC a simple tool has been developed to check the preliminary or existing design of a reciprocating compressor foundation with respect to dynamic loads in an early stage of the project. This tool enables the plant commissioner to perform a check without repeating the detailed analyses already carried out by the design engineers. The paper focuses on the theoretical background of the program, especially the soil foundation interaction and comparison with field measurements is presented.