Pneumatic Drive Compared to Hydraulic Systems

Pneumatics functions similarly to hydraulics. However, there are some significant differences in a pneumatic drive. Therefore, hydraulics and pneumatics operate in different application areas and fulfill different tasks.

Fundamentals of Pneumatics

Pneumatics involves the transmission of forces through compressed gases. Most often, air is used for this purpose. However, there are special cases where nitrogen or inert gases are employed as the transmission medium. Like hydraulics, pneumatics works with force amplification through the enlargement of the cross-section of master and slave cylinders. The essential difference from hydraulics is the medium. Hydraulics fundamentally operates with incompressible liquids. The ratio of pressure to volume flow is therefore always constant in a hydraulic system. Pneumatics works with compressible gases. This makes the operating pressures throughout the entire system highly variable, even with a constant pipe cross-section.

Components in Interaction with a Pneumatic Drive

The components of pneumatic systems are very similar to those in hydraulics.
Typical components for pneumatic systems:

• Pneumatic Drive (Pressure Generator)
• Linear Motors
• Radial Motors
• Lines
• Valves

The essential design difference from closed hydraulic systems is that pneumatic systems using air as a medium are designed as open systems. The pressure-transmitting air is not continuously reused in a circuit. Instead, it is drawn from the environment and released back into the ambient air at the various actuators and valves. This eliminates numerous components required in a hydraulic system. The tank, along with complex cooling and multi-stage filter systems, is therefore omitted in pneumatic systems or is significantly simpler.

Pressure Generation in Pneumatic Drives

The pneumatic drive (pressure generator) is designed as an electric compressor.
The following designs have become established for this function:

• Piston Compressors
• Compressors
• Fans
• Screw Compressors
  

The Piston Compressor

The piston compressor is the standard device used for pressure generation in pneumatic systems. It consists of an electric motor that drives a piston in a cylinder. Ambient air is drawn in, compressed, and directed into a tank. From there, the air pressure is distributed to all consumers via lines.

Compressors

Compressors work with a specially shaped impeller. This draws air in from the front and discharges it laterally. Compressors are less commonly used for classic pneumatics. Their main function is to provide constant operating pressure.

Fans

Fans have the same task as compressors. Instead of a specially shaped impeller, they work with a bladed wheel.

Screw Compressors

Screw compressors are currently the only real alternative to piston compressors. Instead of a cylinder with a piston, this type of compressor works with two side-by-side compressor spindles. Screw compressors are more expensive but significantly quieter, more durable, and smoother running than classic piston compressors.

Advantages and Disadvantages of a Pneumatic Drive Compared to Hydraulics

Pneumatic systems are simpler in design and have a significantly faster response time than hydraulic systems. However, the achievable pressure forces are limited, and their efficiency is lower.