11.3.5 Valve fail safeAn important

11.3.5 Valve fail safe
An important consideration in many systems is the position of the actuators
when there is a loss of power, i.e., will chemicals or the fuel to the heaters continue
to flow or will a total system shut down occur? Figure 11.9 shows an
example of a pneumatically or hydraulically operated globe valve design that
can be configured to go to the open or closed position during a system failure.
The modes of failure are determined by simply changing the spring position and
the pressure port.