Control and Operation of Centrifugal Gas Compressors

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COURSE DESCRIPTION

Intensive, three-day, hands-on course using dynamic simulation models to give a practical introduction to centrifugal gas compressors, their performance characteristics and their operation within a process plant. Topics will include compressor performance and selection, control strategies for capacity and surge protection and compressor operations.

PRE-REQUISITE

This course is designed for participants with no prior knowledge of centrifugal gas compressors, and for those with experience who want to learn more.

PARTICIPANT PROFILE

Engineers, operations and maintenance personnel who are either supervisors or who are responsible for the day-to-day operation or maintenance of centrifugal compressors. Other professions which may be interested in this course include process operators, technicians and engineers, including those responsible for the design or modification of a process plant, as well as rotating machinery engineers seeking a deeper understanding of the principles of operation and control of centrifugal compressors.

LEARNING OUTCOMES

At the end of this course, delegates will:

  • Be able to identify the most common types of compressors in use today.
  • Understand the thermodynamic and physical principles of compression systems.
  • Be able to explain the purpose and function of the main compressor components.
  • Appreciate the impact of suction condition variations (molecular weight/ composition, pressure, temperature) on compressor performance.
  • Be familiar with the most commonly used capacity control systems.
  • Appreciate how the design of an overall plant control scheme relates to the compression system.
  • Have a thorough understanding of surge and its consequences for the machine.
  • Understand the principles of more complex anti-surge control systems.
  • Be able to set up simple anti-surge control systems for both fixed and variable speed compressors.
  • Be able to explore typical compressor operating scenarios (including start up) and identify commonly encountered problems.
  • Appreciate how to prevent a compressor surging on trip and how to use hot-gas bypass valves.

COURSE CURRICULUM

This course will cover compressor performance and selection, instrumentation and control, surge protection and compressor operation with the following sessions:

  1. Compression Principles:
  • Explore the differences between positive displacement (PD) and dynamic compressors and how they influence the technical selection process.
  • Understand the principles of the compression process and how they relate to the laws which govern the performance of the machine.
  • Learn how a centrifugal compressor raises pressure.
  1. Compressor Performance:
  • Explore the ways in which compressor performance is mapped and identify the important variables used (head, flow, efficiency and speed).
  • Study the effects on performance of changes to suction and discharge conditions, primarily pressure and gas composition.
  • Study the main differences in performance between fixed and variable speed compressors.
  • Explore compressor efficiencies and how they are defined and mapped.
  • Hands-on: instructor gives a demonstration using a simulator to show how fixed and variable speed compressors move on their curves/maps.
  • Hands-on: using dynamic simulation, participants investigate the performance of compressors (fixed and variable speed) against changing suction and discharge conditions. They are encouraged to identify the suitability of using different variables to define the performance map.
  1. Capacity Control:
  • The common methods of capacity control are explored for both fixed and variable speed compressors.
  • For each method, a summary based on applicability and efficiency is considered:
    • Applications.
    • Energy efficiency.
    • Choice of controlled variable.
    • Choice of manipulated variable.
  • The concept of shared load control for parallel compressor configurations is introduced.
  • Hands-on: short dynamic simulation exercises are used to explore some typical applications of capacity control.
  • Hands-on: three case studies are presented showing typical control strategies and delegates are encouraged to identify the strategies in question, identify potential problem areas and summarise the operational characteristics of each.
  1. Simple Anti-Surge Control:
  • Explore the phenomena of surge:
    • How it occurs.
    • Speed of onset.
    • Consequences.
  • Introduction to the basic principles and the theory of anti-surge control.
  • Explore the significance of the “safety margin” and its magnitude.
  • Explore the principles and design of a flow/deltaP anti-surge control system.
  • Hands-on: dynamic simulation is used to allow delegates to investigate the dynamics of the responses of an anti-surge control loop.
  • Hands-on: dynamic simulation is used to allow delegates to investigate the structure and tuning of typical anti-surge control systems.
  • Hands-on: delegates carry out a surge test on a fixed speed compressor.
  1. Recycle Valve Sizing:
  • Introduction to the theory of sizing valves, demonstrating the ways in which recycle valves are used to protect compressors during run-down and normal operation.
  • Hands-on: participants are given some practical methods to work out the size of a recycle valve.
  1. Complex Anti-Surge Control:
  • Demonstration of the CCC (Compressor Control Corporation) anti-surge control technology is used to explain the principles of complex anti-surge control:
    • Explanation of the mapping technologies used to determine the position of a compressor within its operating envelope.
    • Defining the surge map.
    • Explore the control safety margin.
    • Explore how an anti-surge controller is configured to provide consistent Ω surge protection.
    • Explanation of parallel compressor load share techniques.
  • Hands-on: a dynamic model is linked to real CCC hardware to allow the tuning and configuration of the system to be explained in detail.
  1. Compressor Operations:
  • Developing a start-up strategy for a pipeline compressor.
  • Investigating multi-stage compressor operation.
  • Hands-on: delegates are given the opportunity to conduct a start-up of a compressor using a dynamic simulation model.
  • Hands-on: various exercises are performed on a multi-stage centrifugal compressor.
  1. Compressor Protection:
  • Explore methods of protecting compressors from surge or damage on trip:
    • Parallel recycle valves.
    • Hot-gas bypass valves.
  • Understand the principles to be adopted for the optimum design and layout of equipment around the compressor:
    • Non-return valves.
    • Coolers.
    • Scrubbers.
    • Recycle lines/valves.
  • Appreciate the impact of poor design on the performance of the anti-surge control system:
    • Coolers.
    • Recycle lives/valves.
  1. Performance and Efficiency Monitoring:
  • Introduction to factory testing (PTC10).
  • Methods for monitoring and tracking the performance of a centrifugal compressor on a day to day basis.