09-08-2012, 12:54 PM
Hydraulic and Pneumatic Basics
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Objectives
Upon completion of this Section you will be able to understand hydraulic / pneumatic fundamentals and the basic physics involved. You will be able to identify and describe how hydraulic / pneumatic force and energy is transmitted and what types of mediums are used to accomplish that.
What you will learn
¾ What is Hydraulic - Pneumatic
¾ Force - Pressure - Work and Power
¾ Transmission of Hydraulic - Pneumatic Force and Energy
¾ Mediums Used to Transmit Hydraulic - Pneumatic Force and Energy
Hydraulic and Pneumatic Basics - 1
Student Manual
What is Hydraulic - Pneumatic
The following unit will provide you with a brief introduction to hydraulics and pneumatics.
Objectives
Upon completion of this unit you will be able to identify the purpose of and difference between hydraulic and pneumatic systems.
What you will learn
¾ Hydraulics
¾ Pneumatics
Hydraulics
Hydraulics has been defined as a study of the physical behavior of water at rest and in motion. This term has broadened in meaning to include the physical behavior of all liquids. This includes the oils used in present day hydraulic systems.
Hydraulics is also referred to as "Power Hydraulics" or "Fluid Power".
Fluid power is used in practically every industrial sector. It is also found in everyday uses such as machine tools, cars, airplanes, satellites, or a bread making machine. The reason for this widespread use is that a fluid is one of the most versatile means of transmitting power and modifying motions.
The definition of a fluid is a substance that will flow and will take the shape of its container. Liquids and gases are both considered fluids. Gases will be discussed in the next lesson, however liquid fluids can:
• Readily change shape
• be divided into parts to do work in different locations
• move rapidly in one place and slow in another
• transmit a force equally in any or all directions
A liquid fluid is infinitely flexible, yet as unyielding as steel. A liquid is virtually non-compressible. No other medium combines the same degree of positive, accurate, flexible control with the ability to transmit a maximum of power in a minimum of bulk and weight. Unlike mechanical power, fluid power eliminates cams, levers, gears and other drive mechanisms that lose energy through friction.
A 25 mm line of fluid will transmit energy as easily as a 300 mm pipeline of fluid.
Hydraulic and Pneumatic Basics - 1
Student Manual
Pneumatics
Pneumatics is similar to hydraulics. The difference is that pneumatics refers to pressurized air (compressed air) or other gases, instead of liquids, as in hydraulics. The main difference between a fluid and a gas is the fact that a gas is compressible and a liquid is considered to be virtually non-compressible.
By definition a fluid is a substance that will flow and conform to the shape of its container. This means that liquids and gases are considered fluids. Any reference in this curriculum to fluids could include hydraulic liquid media or compressed air or gas.
Hydraulic and Pneumatic Basics - 1
Student Manual
Force - Pressure - Work and Power
The following unit will provide you with a quick snapshot of basic physics involved in hydraulic / pneumatic systems.
Objectives
Upon completion of this unit you will be able to identify basic laws of physics as they apply
to hydraulic / pneumatic systems. You will be able to describe the physical characteristics
of fluids.
What you will learn
¾ Some Basic Physics
¾ Physical Characteristics of Fluids
Some Basic Physics
Force is defined as any cause which tends to produce or modify motion. To move an object,
force must be applied to the object. The amount of force required depends on the objects
inertia.
[Inertia: a property of matter by which it remains at rest or in uniform motion in the same straight line unless acted upon by some external force.]
Force is expressed in any unit of weight measure. Kilograms (Kg) or Pounds (lbs.) are the most common measurements.
Pressure is force per unit of area and is usually expressed in terms of kilograms per square centimeter (Kg/cm2), pounds per square inch (psi) or "Bar" which is equal to 14.7 psi, the atmospheric pressure at sea level.
The relationship between Force, Pressure and Area is expressed mathematically by the following equation: