Air Compressors: Types & Operation

Air Compressors, Blowers, and Fans Overview

• Compressors and air systems are essential in industries, providing compressed air for many uses
• Understanding types, components, and maintenance boosts productivity
• Air compressors convert power to potential energy in compressed air for later use

Air Compressor Classifications

• Air compressors are grouped by operation, principle, pressure range, and application

Based on Operation Principle

• Positive Displacement Compressors:
  • Compress air by trapping and reducing volume
  • Reciprocating Compressors (Piston Compressors):
    • These use a piston and crankshaft to compress air in a cylinder
    • Designs include single-stage (low pressure) and multi-stage (high pressure)
    • Can be used in workshops, automotive, refrigeration, and with industrial tools
    • One example is piston-type air compressors in garages
  • Rotary Compressors:
    • Involve rotating elements or interlocking rotors for continuous compression
    • Better choice for large operations needing constant compressed air flow
    • Rotary Screw Compressors:
      • Utilize two interlocking helical screws
      • Efficient, low maintenance, and continuously operate
      • Suited for manufacturing, HVAC, food processing, and industrial plants
    • Rotary Vane Compressors:
      • Incorporate a rotor with sliding vanes for compression
      • Have moderate efficiency, best for medium-duty applications
      • Used in automotive, printing, and vacuum systems
    • Lobe & Scroll Compressors:
      • Lobe compressors are for only low-pressure scenarios
      • Scroll compressors provide quiet, oil-free compression for medical and clean settings

Dynamic Compressors

• (Non-Positive Displacement): Dynamic compressors increase air pressure by converting velocity energy into pressure
  • Centrifugal Compressors:
    • Compressors use high-speed impellers to increase air velocity
    • Impellers alter velocity into pressure
    • Suited for power plants and chemical processing
    • Kinetic energy converts to pressure via diffuser
    • Used in power, refrigeration, and petrochemical
  • Axial Compressors:
    • Compressors move air parallel to the axis via rotor-stator stages
    • Provide extremely high efficiency and pressure ratio
    • Used in jet engines, gas turbines, and high-power industries

Based on Pressure Range

• Low-Pressure Compressors:
  • Range of 0-150 psi
  • Used in HVAC, with small tools, and for airbrushing
• Medium-Pressure Compressors:
  • Range of 150-1000 psi
  • Used in industrial manufacturing and shipyards
• High-Pressure Compressors:
  • Over 1000 psi
  • Used for breathing air (scuba, fire services) and gas pipelines

Based on Lubrication

• Oil-Lubricated Compressors:
  • Durable, used in heavy-duty applications
• Oil-Free Compressors:
  • Used for clean air: medical or food industry

Air Compressor Use Cases

• Reciprocating (Piston) Compressors are used for small tools or garages
• Rotary Screw Compressors are intended for continuous industrial use
• Centrifugal Compressors are used for large-scale plants
• Oil-Free or Scroll Compressors are used for precision air supply

Air Compressor Operation

• Intake: Air drawn from surrounding area
• Compression: Air pressure increases
• Storage: Compressed air stored
• Discharge: Compressed air applied as needed

Air Compressor Applications

• Power construction such as nail guns, jackhammers, and spray guns
• HVAC
• Automotive airbrushing and tire inflation
• Essential for food and beverage: packaging and conveying
• Medical dental and medical devices

Benefits of Air Compressors

• Use as an energy source
• Non-flammable and safer than other energy
• A compact tool in both industrial and DIY situations

Air Compressor Maintenance

• Regular maintenance including:
  • Changing filters
  • Watching oil levels
  • Inspecting hoses
  • Ensuring tank is free from moisture and debris

Fans and Blowers

• Used for ventilation, cooling, and air circulation
• These operate at relatively low pressure and high volume

Fan Types

• Axial Fans: Move air parallel to the axis
  • Propeller Fans: For ventilation and exhaust
  • Tube Axial Fans: More efficient for ducted systems
  • Vane Axial Fans: Very efficient, used in HVAC and industrial cooling
• Centrifugal Fans: Move air perpendicular to the axis
  • Forward-Curved Fans: High volume, low pressure, like HVAC air handlers
  • Backward-Curved Fans: More efficient, used in industrial ventilation
  • Radial Fans: High-pressure, such as in pneumatic conveying
• Mixed Flow Fans: Combine features, suitable for high-performance applications like tunnel ventilation

Fan and Blower Selection

• Key criteria include airflow, static pressure, power consumption, noise, and corrosion resistance for harshness

Types of Blowers

• Centrifugal Blowers:
  • Increase air velocity via rotating impeller
  • Include forward-curved (low pressure, high volume), backward-curved (higher efficiency, medium pressure), and radial/blade (high pressure, lower volume) types
• Positive Displacement Blowers:
  • Force air into discharge system
  • Include rotary lobe (wastewater treatment) and rotary screw (efficient continuous duty) types

Exhauster

• Mechanical device: removes air, gas, and fumes for ventilation, dust, and vacuum tasks

Types of Exhausters

• Centrifugal Exhausters:
  • Move air outward using a centrifugal fan
  • Efficient in high volume, low to medium pressure tasks
  • Typically used in industrial ventilation, dust extraction, and fume removal
• Axial Exhausters:
  • Move air in a straight line using axial fans
  • Typically used where high air flow with low resistance is needed
  • Often used in HVAC, tunnel ventilation, and cooling towers
• Vacuum Exhausters (Positive Displacement):
  • Make a stronger vacuum with rotating or reciprocating parts
  • Rotary Lobe Exhausters are in pneumatic conveying and wastewater jobs
  • Roots-Type Exhausters handle high-vacuum and air movement
  • Liquid Ring Exhausters process chemicals and recover vapors
• These types of exhausters are used in vacuum systems and material handling

Exhauster Applications

• Industrial Ventilation: Removing harmful substances.
• Dust Collection: Cleaning cement, woodworking, and steel areas.
• Pneumatic Conveying: Moving materials with air.
• Combustion Exhaust: Getting rid of combustion gasses.
• Vacuum Applications: Helping processes that need low pressure.

Exhauster Selection Conditions

• Airflow needed
• System static pressure
• Power usage
• Toughness
• Noise and upkeep

Fans vs Blowers

Fans vs Blowers vs Compressors

Fans and Blowers: Evaluation

• Assessment of performance, efficiency, and applications using:

Fans: - Airflow: Measures amount of air moved - Static Pressure: System resistance - Efficiency: Power output vs input - Fan Laws: Forecasting performance Blowers: - Pressure and airflow measured in CFM - Efficiency rating of fans

Evaluation: - Power Consumed impacts costs - IE3 and VFD reduce energy needs - System losses due to duct leakage

Reliability and Maintainability

• Bearings and lubrication: Prevents major damage.
• Blade wear: Especially needed for harsh conditions.
• Vibration: Indicates misalignment or insufficient systems.
• Operation life: Determined by operating environmental factors.

Applications by Use Case

Economics

• Fans as first investment, cheaper operating costs
• Blowers cost more, but less maintenance

When Selecting

1. Determine use case

   • HVAC ventilation: Use fan
   • Cooling systems: Fan
   • Conveying: Use blower
   • Fuel and air: Use blower
   • Capture dust: Fan

2. Set airflow and pressure standards

   • Rate required air/time
   • Check resistance
   • Use Fan laws to set speeds levels