TABLE OF CONTENTS All devices considered in this chapter, even those called controls, are valves in that they are placed in refrigerant lines and can restrict or even completley block the flow of refrigerant. Two-position shutoff valyes are expected to operate either in a completely open or a completely closed position. Other valves modulate the flow rate of refrigerant in response to some variables, such as temperature, pressure, or liquid level.
The specific types of valves explored in this chapter are:
manual shutoff valves
manual expansion valves
check valves
solenoid valves
level controls
pressure-regulating valves
superheat controlling expansion valves
A discussion of safety relief valves appears in Chapter 13, Safety.
A basic valve type distributed liberally throughout an industrial refrigeration system is a manual shutoff valve. In the completely open position, this valve should allow a free flow of refrigerant and when closed completely block the flow. The usual function of the shutoff valve is to isolate a component or a section of the system. Some major categories of manual shutoff valves are globe, angle, inline, and ball valves, as shown schematically in Fig. 11.1. Three desirable characteristics of manual shutoff valves are:
that they permit no passage of refrigerant when closed
that they cause only a low-pressure drop of refrigerant flowing through them when they are open
that they do not leak to atmosphere
Several other...
