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Chapter 9
Dynamics of Centrifugal Compression Systems

Excerpt

Compression systems employed in gas processing plants and in gas pipeline transmission systems provide vital function to the overall operation of both systems and, therefore, must be vigilantly attended to in order to ensure a high level of operational reliability. The majority of these compression systems employ centrifugal compressors, either single- or multi-staged, driven by either gas turbines or electric motors with∕without gearboxes. These compression systems are required to not only withstand uninterrupted operation for extended periods of time but also be able to cope with flow and pressure transients associated with surge control, startup and emergency shutdown (ESD) [1–8]. During these transients, the centrifugal compressors interact dynamically with system components around them, i.e., piping, fittings and equipment, drivers, as well as the associated control protocols. Fluid inertias and compressor∕driver rotor inertias play an important role in either stabilizing or destabilizing the system dynamics [9]. The compressors' performance characteristics also play an important role in the system dynamics behaviour [10]. Ensuring reliable and safe operation of the various aspects of these compression systems requires a good understanding of their dynamic behavior, which enables sound system design, operation and control.

Several experimental and numerical investigations aimed at analyzing the dynamic interactions that take place between compression system components, particularly during ESD, have been reported, e.g., references [11–13]. In these investigations, the surge model proposed by Greitzer and Moore [14, 15] has been extended to centrifugal compressors. The method of characteristics for the solution of the governing one-dimensional equations of gas flow [16] has been proven to be adequate and correlates well with field measurements [10].

  • 9.1 Introduction
  • 9.2 Fundamentals of Dynamic Instabilities of Compression Systems
  • 9.2.1 Simple Compression Systems
  • 9.2.2 Complex Compression Systems
  • 9.2.3 Control Dynamics
  • 9.2.4 Solution Techniques
  • 9.3 Emergency Shut Down
  • 9.3.1 Effects of Compressor Performance Characteristics
  • 9.3.2 Effects of Rotor Inertia
  • 9.3.3 Example of Dynamic Instabilities in Industrial Compression System
  • 9.3.4 Concept of Inertia Number
  • 9.4 Check Valve Dynamics
  • 9.4.1 Dynamics of Swing Type Check Valves
  • 9.4.2 Slamming Characteristics of Swing Check Valves
  • 9.4.3 Effects of Counterbalance on Maximum Reverse Velocity
  • 9.4.4 Dynamics of Piston Type Check Valves
  • 9.4.5 Dynamics of Water Type Check Valves
  • 9.4.6 Effects of Check Valves of Compression Recycle System
  • 9.5 Relief Valve Dynamics
  • 9.5.1 Dynamics of Pilot-Operated Relief Valves
  • 9.5.2 Solution Technique
  • 9.5.3 Example
  • 9.5.4 Fields Tests
  • 9.6 Station and Gas Pipeline Blowdown
  • 9.6.1 Volume Model
  • 9.6.2 Pipe Model
  • 9.6.3 Comparison Between Models
  • 9.6.4 Non-Isothermal Blow-Down
  • References

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