The Condition Monitoring of an Upstream Oil and Gas Dry Screw Compressor Drive Train and its Impact on the Control System

Variable speed oil free screw compressors can be used in upstream oil and gas applications such as gas collection and flare gas recovery. The critical nature of these applications is such that the owners closely monitor the drive train of the package as long un-planned stoppages are extremely expensive. If any of the monitored parameters start to deviate from the norm then shut-downs and services can be scheduled in a timely manner preventing costly stoppages. This paper first describes the parameters monitored on the drive train as required by the international standards used by the oil and gas companies. The paper then leads onto an in-depth description of the instrumentation mounted on and even within the drive train, incorporating the main drive motor, gearbox and compressor, and how the instrumentation is monitored by a package machine condition monitoring system that interfaces with the package control system. As the final location of the instruments is often in extremely hazardous environments such as highly corrosive offshore marine environments or abrasive hot desert environments, and the compressors themselves are often compressing highly combustible gas such as methane or even hydrogen, the protection methods employed by the instruments to prevent explosion is then discussed. The multiple communications networks that allow the condition monitoring system to send its values to the package control system and the client’s distributed control system are also discussed. This discussion includes how the measured values make their way from the stand alone machine condition monitoring system to the compressor control system and how the two systems integrate with each other to protect the package before annunciating the system status to the client's distributed control system. Finally a full description is given on how these measured values impact on the running of the package with respect to the compressors service life and the control systems ability to maintain the process setpoints. A solution to the presented problem is then offered.