Types of Compressors & Applications

3.1 Introduction to Compressor Types

• Two major categories: Positive Displacement& Dynamic (Centrifugal)
• Selection depends on pressure, flow, duty cycle, and application
• Trainer note: emphasize “no one-type-fits-all” — match compressor to demand

3.2 Positive Displacement Compressors

• Operate by trapping air and reducing volume
• Deliver constant volume regardless of discharge pressure (within limits)
• Common in industrial plants for reliability and pressure stability

3.2.1 Reciprocating (Piston) Compressors

• Work like an internal combustion engine — piston compresses air
• Suitable for small to medium capacities, high pressures
• Single-stage or multi-stage
• Require more maintenance, noisy operation
• Common in workshops, small plants, PET bottle blowing

3.2.2 Rotary Screw Compressors

• Two inter-meshing rotors compress air continuously
• Provide steady, pulse-free air flow
• Efficient for continuous duty and higher volumes
• Available in oil-injected and oil-free designs
• Dominant in manufacturing and general industry

3.2.3 Scroll & Vane Compressors

• Scroll: quiet, compact, ideal for clean applications (labs, dental, electronics)
• Vane: simple design, moderate efficiency, used in light industrial and service sectors

3.3 Dynamic Compressors

• Rely on velocity and centrifugal force to raise air pressure
• Best suited for large flow, constant demand
• Higher initial cost but efficient at scale

3.3.1 Centrifugal Compressors

• High-speed impellers accelerate air → diffuser converts velocity to pressure
• Oil-free, continuous operation
• Used in large plants, refineries, steel, and process industries

3.3.2 Axial Compressors (Specialized)

• Multi-stage rotor and stator blades
• High-volume, low-pressure rise per stage
• Common in gas turbines, jet engines, or specialized processes

3.4 Oil-Injected vs Oil-Free Compressors

• Oil-injected: economical, better cooling & sealing, but air needs treatment
• Oil-free: essential for pharma, food, electronics; higher capital cost
• Trainer cue: stress “quality vs cost” trade-off

3.5 Compressor Selection Criteria

• Required flow rate & pressure
• Duty cycle and operating hours
• Air quality class (ISO 8573-1)
• Noise level, maintenance, energy efficiency
• Environment & installation space

3.6 Typical Applications by Type

• Reciprocating → workshops, garages, bottling, high pressure
• Screw → general manufacturing, packaging, automation
• Scroll → medical, dental, clean industries
• Centrifugal → large-scale industrial, petrochemical, steel

3.7 Summary & Transition

• Each compressor type serves a distinct purpose
• Proper selection = balance between performance, reliability, and cost
• Transition: “Next, we’ll look inside — exploring Compressor Components & Equipmentto understand how these machines actually work.”