Hydraulic Circuits and Systems

Unit - 3

Hydraulic Circuits and Systems

Chapter 8: Industrial Hydraulic Circuits

Chapter 9: Accumulators and Intensifiers

Chapter: 8

"What is the life we have lost in living?

What is the wisdom we have lost in knowledge? Where is the knowledge we have lost in informa- tion?

Where is the information we have lost in data?"

- T.S. Eliot

"We could never learn to be brave and patient if there were only joy in the world.

- Helen Keller

"You gain strength, cour- age, and confidence by every experience in which you really stop to look fear in the face. You must do the thing which you think you cannot do."

- Eleanor Roosevelt

Learning Objectives

While reading and after studying this chapter, you will be able to:

• Present a basic structure of a hydraulic system.

• Describe and design the variety of hydraulic circuits including regenerative circuit, pump-unloading circuit, sequencing circuits, synchronizing circuits, fail-safe circuits, and speed control circuits.

• Appreciate the advantages of using hydropneumatic circuits.

• Describe the operation of air-over-oil circuit. Explain the open-circuit and closed-circuit hydro- static transmission system.

• Describe the application of hydromechanical servo system.

1. INTRODUCTION

So far, we have discussed about the fundamentals and system components that are related to hydraulic systems. In this chapter, we shall discuss about how basic hydraulic circuits are designed and constructed. Fluid power circuits are drawn by using graphical symbols of components just like in electrical circuit diagrams. In a fluid power circuit, various components such as pumps (compressor in case of pneumatic circuits), actuators and control valves are arranged in a systematic manner to perform useful task. Also it is mandatory for the fluid power engineers or technicians to have a knowledge of fluid power components and how they operate in fluid power circuits.

In this chapter, we shall discuss a variety of hydraulic and pneumo-hydraulic circuits so as to better understand the basic design features of simple fluid power circuits.