Rotary-Screw and Piston Compressors

Rotary-Screw Compressors

• A rotary screw compressor uses two helical-shaped screws to compress air.
• The screws rotate in opposite directions, squeezing air between them.
• Compared to piston compressors, they are quieter and require less maintenance.
• Rotary screw compressors are ideal for heavy-duty applications needing high power for extended periods.
• Key features:
  • Oil-sealed
  • Fewer moving parts
  • Quieter operation
  • Reduced maintenance

The Mechanics of an Air Compressor

• Air compressors use a motor to power a pump that compresses air.
• Air is drawn into the compressor and compressed by reducing its volume.
• Compressed air is stored in a holding tank.
• When the tank pressure reaches a set maximum, the compressor shuts off.
• The compressor turns on again when the tank pressure falls below a set threshold.

Reciprocating Piston Compressors

• Belt-driven systems:
  • The motor turns the belt, activating the pump.
  • Economical option, widely used across all compressor types.
  • Belts are adjustable to change with air demands.
• Direct-drive systems:
  • The motor attaches directly to the compressor's crankshaft.
  • Smaller design and fewer maintenance requirements than belt-driven systems.
  • More efficient because less power is lost in the transfer of power to the crankshaft
  • Compressed air can be used directly without needing to fill a storage tank.

Air Displacement

• Air compressors compress air using two main methods: positive displacement and dynamic (non-positive) displacement.
• Positive Displacement:
  • Most common method.
  • Air is compressed in a chamber that repeatedly opens and closes.
  • Internal components reduce the chamber's volume to compress air.
  • Examples include piston, rotary-screw, and scroll-type compressors.
• ** Dynamic (Non-positive) Displacement:**
  • Uses rotating blades on an impeller to draw air into a chamber.
  • The impeller's motion builds air pressure.
  • Used with turbocompressors to produce large volumes of compressed air quickly.

Reciprocating Piston Compressors

• Operates similarly to a combustion engine.
• The piston moves inside the cylinder, compressing air as it is forced into a storage tank.
• Compression cycles can be single-stage or two-stage.
• Single-stage:
  • Piston completes one cycle of compression.
  • The incoming air is drawn into the cylinder and compressed, then expelled into the storage tank.

Single-Stage Reciprocating Piston Compressor

• Image description:
  • A piston compressor with clear labels for each component.
  • The image shows a clear cut-away so the internal working mechanics can be visualized.

This quiz explores the mechanics and features of rotary-screw and reciprocating piston air compressors. Learn about the operational principles, key characteristics, and advantages of these essential machines in various applications. Test your knowledge on air compression technology and its effectiveness in different scenarios.