Field adjustments to solve vibration problems in a modified reciprocating compressor system

Due to constantly tightening laws for the minimization of CO2 and the changes in process parameters, an existing reciprocating compressor of 160 kW had to be replaced by a larger one. The compressor system is installed at the TOTAL Refinery in the eastern part of Germany. For this purpose the customer has chosen a 2-stage Borsig ZM reciprocating compressor with a fixed speed with a power of 630 kW. Not only the compressor had to be changed but also a large part of the pipe system. One of the disadvantages of a reciprocating compressor is that it generates pulsations and vibrations. For that purpose an extensive pulsation and vibration analysis of the piping according to the API Standard 618 has been carried out in an early stage of the project. The compressor had to be installed on an existing concrete block which one didn't need to be changed after calculation of the foundation designer and special attention was given for the correct mounting of the compressor. After start-up of the system unallowable vibrations occurred in several parts of the piping and the concrete block. Vibration measurements have been carried out to investigate the cause of the vibration problems. It appeared that the unallowable pipe vibrations were caused by the fact that some orifice plates and pipe supports were not installed as advised. Further on it appeared that the unallowable vibrations of the concrete block, which on its turn increased the pipe vibrations, were caused by the fact that a mechanical natural frequency of the block was excited by the 2nd harmonic compressor loads. The first part of the paper will discuss the results of the API 618 analysis. The second part of the paper will discuss the results of the vibration measurements together with the field adjustments of the pipe supports layout and concrete foundation to decrease the vibrations to acceptable levels.