Print this page Introduction to Hydraulic Systems
A. Bhatia, B.E.
Course Outline
Hydraulic equipment
and technology is something that we are all at least passingly familiar with.
The shovel on the front of a bulldozer is moved by hydraulics. The long arm
and bucket of a digger is powered using a hydraulic system. The brakes on a
train and the jack a mechanic would use to lift up a car both use hydraulics
too. If we think about it, we know that the principles of hydraulics are applied
to make many common machines work with amazing strength and agility.
This 4-hour course provides the basic principles of hydraulics and describes
the relationship of these principles to the components and systems that power
today's industrial machinery.
This course includes
a multiple-choice quiz at the end, which is designed to enhance the understanding
of course materials.
Learning Objective
At the conclusion of this course, the student will:
- Learn what is hydraulics? Where are hydraulics used;
- Learn the hydraulic principles - calculation of required pressure, required flow and required power;
- Understand hydraulic system options, including open center, closed center, and load compensated hydraulic systems found on today's modern equipment;
- Analyze hydraulic circuits from a schematic drawing;
- Explain the operation and applications of actuators, valves, cylinders, pumps and motors;
- Learn the function and use of relief valves, pressure reducing valves and directional control valves commonly used in hydraulic systems;
- Understand how to interpret pump technical data sheets to understand pump characteristics and pump control operation;
- Describe, how various hydraulic components operate and work together in a circuit;
- Utilize continuity and power balance equations;
- Evaluate filter effectiveness and determine its proper location in the system;
- Understand the basic configuration and operation of hydraulic transmissions; and
- Learn the preventative
maintenance procedures and understand the troubleshooting of hydraulic systems.
Intended Audience
This course is intended for individuals with limited exposure to fluid power - engineers, maintenance personnel, equipment operators, purchasing personnel, plant supervisors and anyone involved with the adjustment, maintenance, specification, or operation of hydraulic systems.
Course Introduction
Hydraulics is a branch of science concerned with the practical applications of fluids, primarily liquids in motion. It is related to fluid mechanics, which in large part provides its theoretical foundation. The basic idea behind any hydraulic system is very simple: - you cannot compress a liquid. The force or pressure that is applied at one point in a sealed system is transmitted to another point. The force is almost always multiplied in the process.
Fluid systems involve the use of fluids to transmit and multiply force. When the fluid is a liquid, the system is called a hydraulic system. When the fluid is gaseous, the system is called a pneumatic system. Hydraulic fluids such as hydraulic oil are incompressible whereas pneumatic fluids such as air are compressible.
Totally understanding hydraulics is very complicated, but a basic understanding of the principle of how it works is actually very straightforward. Hydraulics deals with such matters as the flow of liquids in pipes, rivers, and channels and their confinement by dams and tanks. The scope of this course however extends to mechanical systems and devices as actuators and control systems that power today's industrial machinery.
In this course,
you are required to study the U.S. Army Field Manual No. 5-499. This manual
provides general information on the several types hydraulic systems and its
components such as pumps, valves, and controls. This manual also deals with
piping, tubing, and hoses used to convey fluid under pressure. It describes
the functions and types of reservoirs, strainers, filters, and accumulators.
It discusses the purposes and types of seals and packing used in fluid power
systems.
Course Content
U.S. Army Field Manual No. 5-499 Hydraulics
You need to open or download above document to study this course.
The hydraulic systems work on a simple principle that you cannot compress a liquid, and a force that is applied at one point is transmitted to another point by that incompressible fluid. Because of its liquid nature, hydraulic systems can transmit force through pipes of any shape and length, so the force can be applied at one central point and transmitted efficiently to another point or to multiple points far away.
Most hydraulic systems consist of a pump, hoses and lines, cylinders and motors, valves, a cooling unit, a reservoir, filters and hydraulic fluid (oil). At the heart of the system is the pump which circulates the same fluid repeatedly from a fixed reservoir that is part of the prime mover. The fluid is an almost non-compressible liquid, so the actuators it drives can be controlled to very accurate positions, speeds, or forces. Most hydraulic systems use mineral oil for the operating media but other fluids such as ethylene glycol, or synthetic types are not uncommon. Hydraulic systems usually have a dedicated power unit for each machine. A few other manufacturers are setting up central power units with pipes running to and from the presses out in the plant. These hydraulic systems operate more like a compressed-air installation because the power source is in one location. The central arrangement is ideal when the plant has numerous machines that use hydraulics. Some advantages of this arrangement are: greatly reduced noise levels at the machine, the availability of backup pumps to take over if a working pump fails; less total horsepower and flow, and increased uptime of all machines. Another advantage hydraulic-powered machine is that they can operate at higher pressure -- typically 1500 to 2500 psi. Higher pressures generate high force from smaller actuators, which means less clutter at the work area.
The extensive use of hydraulics to transmit power is due to the fact that a properly constructed hydraulic system possesses a number of favorable characteristics. These are as follows: Eliminates the need for complicated systems using gears, cams, and levers. Motion can be transmitted without the slack inherent in the use of solid machine parts. The fluids used are not subject to breakage as are mechanical parts. Hydraulic system mechanisms are not subjected to great wear.
The main disadvantage
of hydraulics is increased first cost because a power unit is part of the machine.
If the machine life is longer than two years, the higher initial cost is often
offset by lower operating cost due to the much higher efficiency of hydraulics.
Another problem area often cited for hydraulics is housekeeping. Leaks caused
by poor plumbing practices and lack of pipe supports can be profuse. This can
be exaggerated by overheated low-viscosity fluid that results from poor circuit
design. With proper plumbing procedures, correct materials, and preventive maintenance,
hydraulic leaks can be virtually eliminated. In general, hydraulic systems are
usually more complex and require skilled personnel to handle hydraulic problems.
Quiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
