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HYDRAULICS

 

Hydraulic circuits
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Hydraulic circuits transmit and control power from a mechanical input to a mechanical output by means of liquids, mostly oils. Power is transmitted hydrostatically, where high pressures make static forces dominate over dynamic forces, and energy is transmitted mostly through static pressure at low flow velocities.
 
Circuits are composed of a number of hydrostatic components which are connected to each other by means of piping, manifolds, or directly, to enable transmission and control of power or signals through liquids.
 
Hydraulic circuits can be represented in various ways:
  • Block Diagrams show the components of a hydraulic circuit as blocks joined by lines, which indicate connections and/or interactions.
  • Cutaway Diagrams show the internal construction of hydraulic components and their flow paths. Because these diagrams typically use colours, shades or patterns in the lines and passages, they are very effective at illustrating different flow and pressure conditions.
  • Pictorial Diagrams show a hydraulic circuit's components and piping arrangement. The hydraulic components are seen externally and are usually in a close reproduction of their actual shapes in scaled sizes. This aids in hydraulic component recognition and identification.
  • Graphical Diagrams are the shorthand system of the fluid power hydraulics industry. They comprise simple, geometric symbols, drawn to ANSI or ISO standards that represent the hydraulic components, their controls and connections.
The most common representation of hydraulic circuits is the graphical system.  It is important to know and understand the different symbols.
 
Here is a list of the most common hydraulic symbols and there meaning:
 
COMPONENT SYMBOL

Reservoir

 
Electric motor

 

Hydraulic pump

 
Hydraulic fluid

 
Filter

 
Actuator

Hydraulic motor (rotary actuator)

 
Accumulator

Directional control valve

Flow control valve

Pressure relief valve

Check valve

Pipes and fittings (lines)

Oil cooler
Pressure gauge
 
Example of a typical hydraulic circuit in drawing:
 

 
Same Example of a typical hydraulic circuit in symbols: