Units and Symbols.1. Introduction.2. Some Reminders about Cryogenics and Others.3. Heat Exchangers for Cryogenic use, Reminders.4. Basic Cycles for Helium Refrigeration and Liquefaction.5. Special Cycles for Helium Refrigeration and Liquefaction.6. Technology of the helium Refrigeration Components.7. Helium.8. Introduction to off-design Operation.9. Process control.10. Operating Modes of a Helium Refrigeration Plant.11. Operation and Maintenance of a Helium Plant.12. A Few Examples of Existing Plants.13. A Helium Plant Specification.14. Commissioning Tests.15. The Cryo Tool Box.16. Annex 1 Starting procedures for screw compressors.17. Annex 2 More on ORS.18. Annex 3 Heat exchangers operating in a horizontal position.19. Annex 4 Introduction to the Grafcet language for the description of an automation procedure.20. Terminology.