Fluid Power Systems: Hydraulics and Pneumatics Components

Posted on Nov 19, 2025 in Technology

Fluid Definition and Application

A Fluid is a substance that flows, deforms, and changes shape when subject to a force or stress. It has no fixed shape but adapts its surface to the shape of its container.

Hydraulic Systems

Hydraulic systems are utilized where large, precise forces are required. Some common applications include:

  • Tablet compression machines
  • Bioreactor mixing and agitation
  • Autoclave door actuation in sterilization units
  • Aseptic packaging
  • Hydraulic presses for sample preparation

All hydraulic systems operate following a defined relationship between area, force, and pressure.

The Hydraulic Power Unit (HPU)

The hydraulic power unit pressurizes, distributes, and conditions the working fluid of the system. Key components include:

  • Positive displacement pump
  • Primary Motor
  • Fluid reserve tank
  • Filters
  • Multiple connections (Manifolds)
  • Relief valve
  • Directional control valve

1. Hydraulic Pumps

Hydraulic pumps operate by creating a vacuum at the pump inlet, forcing liquid from a reservoir into an inlet line, and then to the pump. Mechanical action sends the liquid to the pump outlet, forcing it into the hydraulic system.

Types of Hydraulic Pumps
  • Reciprocating Pumps: As the piston extends, the partial vacuum created in the pump chamber draws liquid from the reservoir through the inlet check valve into the chamber.
  • Rotary Pumps: Rotary motion carries the liquid from the pump inlet to the pump outlet.
    • Screw Pumps: Consist of two Archimedes’ screws that intermesh and are enclosed within the same chamber.
    • Gear Pumps
    • Piston Pumps
    • Vane Pumps: Use a series of rigid vanes mounted in an eccentric rotor, which sweep along the inside wall of a housing cavity to create smaller volumes, forcing the fluid out through the discharge port.

2. Valves

Valves are the elements that govern a hydraulic system, as they are responsible for regulating pressure, blocking the passage of fluid, and governing the operation of the working elements.

Types of Hydraulic Valves
  • Hydraulic Flow Control Valves: Used to regulate the flow volume of passing fluid. These valves have a movable gate that changes the flow domain to modify the flow rate.
  • Hydraulic Pressure Control Valves: Used to regulate the fluid pressure passing through hydraulic arrangements to keep that pressure at the desired amount as restricted by the system operator. They are typically produced for operation at a fixed range of pressures.
  • Hydraulic Directional Control Valves: Used to direct fluid in a system or circuit to several devices as demanded. They shift between discrete positions (such as extend, retract, or neutral locations) for controlling a hydraulic cylinder.

3. Power Output Devices (Actuators)

Actuators convert hydraulic energy into mechanical motion.

  • Linear Actuators (Cylinders): Produce linear movement.
  • Rotary Actuators (Hydraulic Motors): Convert hydraulic energy into rotary mechanical energy.

Pneumatic Systems

Pneumatics is the transmission and control of forces and movements by means of compressed air.

Industrial Applications of Pneumatics

  • Material handling
  • Packaging
  • Filling

Pneumatic Principles

  1. Compressibility
  2. Energy storage
  3. Temperature effects
  4. Flow losses
  5. Pressure and force generation

Pneumatic Components

Control elements govern the actuating elements in accordance with the signals received from the processing elements.

1. Air Compressor

Used to produce the compressed air for the system at the required volume and pressure.

2. Air Tank (Reservoir)

Stores and stabilizes the compressed air, and helps cool the air.

3. Cooling and Drying Unit

These units perform two main functions:

  • Condensate the water vapor from the compressed air.
  • Reduce the compressed air temperature.

4. Piping (Air Distribution System)

The diameter of the air distribution system should be selected in such a way that the pressure loss from the pressurized reservoir to the consuming device ideally does not exceed approximately 10 kPa (0.1 bar).

Air Service Unit

The air service unit provides the pneumatic system with clean, lubricated, and regulated compressed air. Its parts include:

  1. Compressed air filter
  2. Compressed air regulator
  3. Compressed air lubricator

Pneumatic Accessories

  • Manifold (distributor)
  • Shut-off valves
  • Tubes and fittings
  • Pressure gauge

Safety Regulations and Environmental Impact

Hydraulic Machinery Safety

  1. High Pressure Risks: Hazards associated with high operating pressures.
  2. Handling of Fluids: Hydraulic fluids can be flammable, toxic, or environmentally hazardous, requiring careful handling.
  3. Structural Integrity: Ensuring the system structure can withstand operational forces.

Pneumatic Machinery Safety

  1. Compressed Air Hazards: Risks associated with the use of highly pressurized air.
  2. Air Quality: Air must be free of contaminants to prevent system damage and health risks.
  3. Explosion Risk: Potential for rupture or explosion if components fail under pressure.
  4. Emergency Protocols: Necessity of defined procedures for system shutdown and failure.