Norwegian gas export is a high value business, where small and transient disturbances may cause substantial production losses. Process experience has shown that the compressor system may suffer considerably owing to surge and rotating stall in situations where the compressor is forced to trip. One of the main challenges concerns analysis of the actual trip trajectory to validate whether the compressor has entered the unstable area of the performance characteristics. This type of analysis is paramount with regard to compressor operation and tuning of the compressor safety system. Recent advances in data analytics and digitalization capabilities give promise of new ways to handle and analyse such challenges.
The current work presents data from a real compressor trip. The investigation reveals that plant data alone may not be sufficient for analysis of the trip trajectory. Hence, the trip scenario was analysed in light of experimental data, fan law principles and utilization of a detailed dynamic model. The results reveal that utilization of a dynamic model gives fruitful insight into the compressor system dynamics during a trip. These findings form a basis for future digitalization of the plant.
This idea will be developed into the specification of a concept called a Digital Compressor. The digital compressor may run in off-line or on-line mode with the aim of providing: high resolution estimates (soft sensors) for non-measured or inaccurate process variables; or identification of process parameters and characteristics, such as gas density. Use cases include: off-line “what happened” analysis; identifying the minimal viable instrumentation; on-line advanced condition and performance monitoring.
A digital compressor laboratory setup will be introduced, containing both a dynamic simulation system as well as a complete gas compressor rig — with all necessary computational and communication infrastructure.