Hydraulic System Introduction
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 larger. (3) Large diversity of units available which can sometimes mean that spares are difficult to obtain. (4) Hydraulic units, particularly those designed to work under high pressures, can be very expensive. (5) Hydraulic fluids under pressure are dangerous and under certain conditions, flammable.
PRINCIPLES OF HYDRAULIC SYSTEM OPERATION
Introduction
Hydraulic systems employ fluids to transmit energy from the point of application, ie power source to the output actuator. A fluid is defined as, ‘a substance that will readily take up the shape of its container’ and it may be either a liquid or a gas. However, one of the main characteristics of gases is that they are compressible and this means that they are not suitable for use in hydraulic systems. Liquids, on the other hand are incompressible and this means that any movement at one extreme of a column of fluid in a pipe, or other component, is immediately reproduced at the other. This characteristic of, ‘positive displacement hydraulics’, together with ‘Pascal’s Law’ (see below) are the fundamental principles on which hydraulic systems operate.
Pascal’s Law: States that, a force applied to a liquid in an enclosed container, will be transmitted,
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 larger. (3) Large diversity of units available which can sometimes mean that spares are difficult to obtain. (4) Hydraulic units, particularly those designed to work under high pressures, can be very expensive. (5) Hydraulic fluids under pressure are dangerous and under certain conditions, flammable.
PRINCIPLES OF HYDRAULIC SYSTEM OPERATION
Introduction
Hydraulic systems employ fluids to transmit energy from the point of application, ie power source to the output actuator. A fluid is defined as, ‘a substance that will readily take up the shape of its container’ and it may be either a liquid or a gas. However, one of the main characteristics of gases is that they are compressible and this means that they are not suitable for use in hydraulic systems. Liquids, on the other hand are incompressible and this means that any movement at one extreme of a column of fluid in a pipe, or other component, is immediately reproduced at the other. This characteristic of, ‘positive displacement hydraulics’, together with ‘Pascal’s Law’ (see below) are the fundamental principles on which hydraulic systems operate.
Pascal’s Law: States that, a force applied to a liquid in an enclosed container, will be transmitted,