Control Components (Hydraulic Valves)

Chapter : 6

Control Components (Hydraulic Valves)

"Nothing has such power to broaden the mind as the ability to investigate systematically and truly all that comes under thy observation in life."

- Marcus Aurelius

"Science is simply common sense at its best, that is, rigidly accurate in observation, and merciless to fallacy in logic.

- Thomas H. Haxley

"The butterfly counts not months but moments, and has time enough."

- Rabindranath Tagore

Learning Objectives

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

• Identify, understand, and appreciate the various control valves required for proper functioning of the hydraulic systems.

• Describe the purpose, construction, and operation of three types of valve configurations-poppet valves, sliding spool valves, and rotating spool valves. 

• Understand and explain the construction, operation, and application of various directional control valves (such as check valves, position valves, and shuttle valves).

• Distinguish between 2/2, 3/2, 4/2, and 4/3 directional control valves.

• Understand and explain the construction, operation, and application of various pressure control valves (such as pressure relief valves, pressure reducing valves, and sequence valves).

• Understand and explain the construction, operation, and application of various flow control valves (such as globe valves, needle valves, pressure- compensated flow control valves).

• Describe the purpose construction and operation of various types of servo and proportional valves.

1. INTRODUCTION

I. HYDRAULIC VALVES: THE REGULATOR

So far, we have discussed about hydraulic pumps for generating pressure, and about hydraulic cylinders and motors for converting that pressure into useful mechanical work. But to direct and regulate the pressure and the flow of the fluid from the pump to the actuators, all the hydraulic (as well as pneumatic) systems require control valves. In fact, the efficient function of the entire fluid power systems depend to some extent on the control components (i.e., valves) used. Although there are significant practical differences between the hydraulic and pneumatic devices (mainly in terms of operating pressures and types of seals), the operating principles and descriptions of control valves are very similar.

In this chapter, we shall discuss about the various control valves required for proper functioning of the hydraulic systems. Also special control valves viz., servo and proportional control valves are presented in the later sections of the chapter.

1. What are Hydraulic Valves ?

• Hydraulic valves are devices used to control pressure, flow direction, or flow rate in hydraulic circuits.

• These control valves utilize mechanical motion to control the distribution of hydraulic energy within the system.

2. Types of Control Valves

Control valves are classified into three basic types, based on their function in the hydraulic system, as:

1. Directional control valves,

2. Pressure control valves, and

3. Flow control (or volume control) valves.