Positive-Displacement Compressors

Table of Contents

Chapter 1: Reciprocating Compressors

Topics: Features of industrial ammonia reciprocating compressors; Capacity control; Lubrication; Efficiency; Application data; Compound compressors

Learning Objectives:

• Briefly describe the evolution of ammonia reciprocating compressors.
• Describe typical design features of today's reciprocating compressors.
• Explain how capacity control and proper lubrication are achieved in ammonia reciprocating compressors.
• Explain how to use volumetric and adiabatic efficiency data and the performance factor in sizing or selecting compressors for an application.
• Describe the function and basic design requirements of internally compounded reciprocating compressors.

Chapter 2: Sliding-Vane Rotary Booster Compressors

Topics: Rotary vane compressor design and operation; Fixed volume ratio; Applicability; Limitations; Capacity control

Learning Objectives:

• Describe the basic operation of sliding-vane rotary booster compressors.
• Explain the principle of fixed volume ratio compressors.
• Describe typical rotary compressor design features.
• Explain why sliding-vane rotary compressors have been replaced by screw compressors.
• Discuss the reasons for rotary vane compressor speed limitations and the causes and effects of blade wear.
• Describe how capacity control is achieved in rotary compressors.

Chapter 3: Oil-Flooded Screw Compressors

Topics: Oil-flooded screw compressor operation; Fixed volume ratio; Capacity control in fixed, variable compressors; Efficiency; Compound compressors; Application criteria

Learning Objectives:

• Discuss the developments that led to the use and acceptance of the oil-flooded screw compressor in industrial refrigeration.
• Describe typical design features of single-screw and twin helical screw compressors.
• Explain how the compression system works within screw compressors.
• Compare fixed and variable volume machines and their applications.
• Explain how the capacity-control slide valve and variable Vi slide stop function.
• Describe the general range of application for screw compressors.

Chapter 4: Screw Compressor Units

Topics: Screw compressor systems; Drive systems; Lubrication, refrigerant/oil separation, oil cooling, economizer/side load, capacity control, microprocessor control, and safety systems

Learning Objectives:

• Explain why screw compressors are provided as units and describe the main systems that make up the screw compressor unit.
• Explain why a vertical or horizontal oil separator may be preferred and explain why check valves are used on the unit inlet and outlet connections.
• Discuss drive methods and oil distribution methods used on screw compressors and describe tasks provided by the lubricant within the compressor.
• Explain how the refrigerant vapor/oil separation system operates and list the methods and benefits of oil cooling in screw compressor units.
• Discuss the beneficial uses of the side port and the operation of the screw compressor capacity reduction slide valve control system.
• Name the codes and other criteria with which ammonia refrigeration systems must comply to establish and maintain a safe work environment.

Chapter 5: Ammonia Systems Lubrication/Oil Management

Topics: Need for lubrication; Miscibility; Viscosity; Lubricants and oils; Lubricant selection, handling and management; Separators; Low-side oil recovery

Learning Objectives:

• Discuss the purposes of lubricants in ammonia systems.
• Define the terms used to describe and specify lubricants and oils and discuss the importance of the miscibility and viscosity relationships between lubricants and ammonia.
• Describe the proper methods for handling lubricants.
• Explain how oil is separated from the refrigerant vapor within the screw compressor system.
• Describe the IIAR-approved method for removing oil from the system low-side oil pots.
• Name lubricants recommended for use with ammonia systems and explain the importance of using only specified lubrication products.

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