In December 2007, the online monitoring system avoided a major and cost-intensive damage at one compressor. The permanent piston rod position monitoring detected a cracked respectively a virtually broken piston rod at the 1st stage. Prior to a complete rod failure, the machine had been automatically stopped and costly consequential damages have been avoided.
The urea plant operates, besides others, two Thomassen reciprocating compressors in carbon dioxide (CO2) service. Both compressors are equipped with PROGNOST®-NT since October 2001. In the last years, several machinery failures have been detected by the system such as rider ring wear, loosened components and valve problems. The machines are 4-throw, double-acting, 4-stage horizontal compressors and in operation since 1997.
The PROGNOST® monitoring system continuously monitors all safety and performance relevant parameters on the compressors. Vibration and displacement sensors, as well as pressure probes produce the signals needed for gapless and meaningful machine protection and condition monitoring. Additionally, all relevant process data from the DCS are integrated, monitored and trended. YARA decided to have an automatic shutdown in case a dangerous machine status occurs. Based on crank angle-related rod-position analyses, PROGNOST® shuts down the machine. The system calculates the peak-to-peak value of the segmented piston rod-position (run out) signal, providing additional information regarding the condition of motion works components.