3.1 Objectives

This chapter serves to review the basic types and principle of operation of process control valves and their associated actuator and positioner systems. As a result of studying this chapter, the student should be able to:

• List the common types of process control valves, and briefly describe their design and basic construction

• Explain the meanings of valve characteristics, rangeability and sizing

• Describe the types of actuators commonly found in process control systems, and list their applications.

3.2 An Overview of Eight of the Most Basic Types of Control Valves

In most process control systems the final control element, driven by the output of the process controller, is usually some form of valve. This chapter serves to introduce the student to eight of the most common types of control valves, flow throttling devices and the basic range of actuators used to control them.

Sections 3.2.1 through to 3.2.8 describe the various types of valves in question, starting with an overview and general description, the types and variances within their manufactured ranges, sizes, design pressures and temperature ranges and their rangeability.

Any special attributes or uses a valve may have are also described.

Section 3.2.9 introduces the reader to some of the more unusual types of valves, their design and usages.