to override a pneumatic or electrical type of actuator
in the case of an actuator or control valve failure. For
example, the steam diverting valve used on the CG-
47 and DD-963 class ships has a valve handwheel.
The handwheel is coupled directly through the
diaphragm to the valve stem to allow for manual
operation of the valve.
MECHANICAL LINKAGES. The purpose of
valve operator mechanical linkages is to connect
remotely positioned valves with an operator
handwheel by a series of rods (linkages) or a flexible
cable. Valve operator mechanical linkages are needed
to control hard-to-inch valves, such as those located
in the bilge area or the overhead. With proper
maintenance and upkeep, these mechanical operators
serve as real time savers.
Now that we have discussed some of the automatic
control valves in terms of their basic operations and
components, let's talk about how you will be required
to test, inspect, and maintain them.
Tests and Inspections
In this section, we will briefly discuss some of the
tests and inspections you may be required to perform
Figure 4-3.-Diaphragm control valve actuator.
on the various types of control valves and other
associated components. Normally, you will conduct
Solenoid Valves. Solenoid valves are used
periodic tests and inspections when the component is
extensively throughout the engineering plant of any
operating or according to approved maintenance
gas turbine-powered ship. The solenoid valve we will
procedures, such as the PMS.
discuss as our typical example is the one that is used
as a level control device in the FO service system on
LEVEL CONTROL VALVES In testing and
DD-963 class ships. These valves do not have any
inspecting level control valves, you will sometimes
specific tests or inspections as per PMS. According to
require the assistance of a GSE. If the test or
the NSTM, Chapter 505, "Piping Systems," however,
inspection pertains only to the valve itself or if the
extensive damage may occur if these valves are not
sensing features of the system are mechanical, such
exercised periodically. This is particularly true if the
as those on the WHBs, then you will be able to
valves are located in areas that are difficult to keep
complete the checks on your own. If the operation of
clean, such as the bilges in main engine room (MER)
the tank level sensing system you must test or
inspect is electrical, however, then you will need the
assistance of a GSE.
Solenoid valves should always be cycled before the
system is placed in operation. For proper operation,
Frequently, you will inspect the operation of a
they should also be cycled at least once per month.
level control valve during normal operation. You will
You can perform an operational test on a solenoid
normally perform tests on this valve during a
valve by using the thumbwheel override built into the
training evolution or a propulsion plant inspection, or
side of the valve. When performing a test or
when you are planning to perform general
inspection, you should be checking for proper
maintenance. Regardless of the circumstances, you
operation of the valve and leaks around the stem or
must perform your inspections and tests of these
associated fittings and flanges.
valves according to the PMS or other authorized
procedures just as you would for any other test or
Pilot Operated Valves. Pilot operated valves
inspection you are required to accomplish.
are normally tested and inspected according to the
PMS. In performing a normal test, you will check the
Basically, the two most popular types of level
full travel range of the valve stem and match it with
control valves you will need to be familiar with are
the scale mounted on the control valve actuator yoke,
the solenoid-operated, needle type and the
pneumatic-operated globe type.