Table of Contents
In a double-seated valve (Fig. 29), the controlled agent flows
between the two seats. This placement balances the inlet
pressures between the two discs of the plug assembly and
reduces the actuator force needed to position the plug
assembly. Double-seated valves generally do not provide tight
close-off because one disc may seat before the other and
prevent the other disc from seating tightly.
BRANCH
LINE
INLET
F3
FLOW
NORMALLY OPEN VALVE
Fig. 29. Double-Seated Valve.
Figure 30 shows three-way globe valve assemblies. The mixing
valve has two inlets and a common outlet. The diverting valve
has a common inlet and two outlets.
Three-way valves may be piped to be normally open or
normally closed to the heating or cooling load. If a three-way
valve has linear characteristics and the pressure differentials
are equal, constant total flow is maintained through the
common inlet or outlet port.
F1
F2
OUTLET
FLOW
C2612
Actuators and Final Control Elements
BRANCH
LINE
INLET
FLOW
MIXING VALVE, NORMALLY CLOSED TO
STRAIGHT-THROUGH FLOW
BRANCH
LINE
INLET
FLOW
DIVERTING VALVE, NORMALLY OPEN TO
STRAIGHT-THROUGH FLOW
Fig. 30. Three-Way Valve Assemblies.
70-6925
F1
F2
OUTLET
FLOW
INLET FLOW
F1
F2
OUTLET
FLOW
OUTLET FLOW
C2615
139
- Quick Links:
- Mp953E, F Pneumatic Coil Valve Actuators
Hide quick links:
Table of Contents
