Hydraulic System Introduction

18784 Words Apr 25th, 2013 76 Pages
HYDRAULIC THEORY

Introduction

A hydraulic system is defined as a, ‘machinery unit which uses fluid as a pressure medium’. It has a number of advantages over an electrical system of a similar working capacity.

Advantages:

(1) The power to weight ratio is at least 14 times better than an equivalent electrical system. (2) Self-resetting overload protection. (3) Self-lubricating. (4) Infinitely variable speeds. (5) No static electricity. (6) Linear motion. (7) Low speed, high torque with motors.

However, there is a downside!

Disadvantages:

(1) Large pipework is often employed (in contrast to the relatively thin wiring used in electrical systems). (2) Units are often physically
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Hydraulic Circuit Definition

The primary aim of a circuit diagram is to show the operation of the system as clearly as possible. There is no requirement to show the construction of components or where they are sited. In the Equipment Handbook, layout and mechanical drawings will also be provided - in addition to the circuit diagrams - to illustrate these.

Hydraulic Circuit Rules

Ideally a circuit diagram should show an input into the system on the left and the output on the right of the diagram, this is not always possible, but when drawn that way, it should show how the system, or sub-system, works in a smooth flow from left to right with the minimum of doubling back and forth across, or up and down, the diagram. Occasionally, the supply is shown at the bottom of the diagram flowing up through control valves and other hydraulic components shown in functional groups.

Circuit diagrams may be at equipment or sub-assembly level and partial or simplified circuits may be drawn separately from the remainder of the circuit diagram, ie the hydraulic power pack circuit is sometimes drawn separately from the machines it is supplying; this is usually due to the complexity of the circuit or because the power pack is sited away from the remainder of the hydraulic machinery. Hydraulic circuit diagrams should be annotated to indicate the function of groups of components and inputs or

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