of the tank, the tank certified gas free by a gas free
MAINTENANCE
engineer, and specific safety precautions observed.
Routine maintenance performed on most liquid
When replacing a liquid control device, take care in
control devices is accomplished by PMS. Routine
tagging the leads to assure proper replacement.
maintenance includes inspecting the devices for damage
After you enter the tank, you may find the problem
and proper operation. To check for proper operation, you
is a stuck float. To correct this problem, carefully clean
must lift some liquid control devices manually. You will
and scrape the tube so it offers a smooth surface for the
check others, such as tank level sensors, through
float. If you have to disassemble a liquid control device,
calibration circuits. Some difficulties that you may face
be sure to clean all metal parts with a solvent.
in working with liquid control devices are inaccurate
r e a d i n g s , units that are out of calibration, and
Most liquid control devices are constantly energized
malfunctioning floats. For specific maintenance and
even when the tank is empty or the system is secured.
calibration procedures, refer to the applicable system
You must make sure that electrical power to the control
technical manual.
device is secured before replacing it. Follow the basic
troubleshooting techniques and all applicable electrical
The moving parts of liquid control devices should
safety precautions when troubleshooting, repairing, or
be inspected for smooth operation. They should also be
replacing liquid control devices.
lubricated at definite intervals. When spare parts are
available, repairs and replacements should be made only
by experienced GSEs. In several cases, it is best to
SUMMARY
replace the entire liquid control device and return the
In this chapter, we have discussed your responsi-
faulty one to the manufacturer (if required).
bility for the maintenance of pressure, temperature, and
l e v e l control devices. We have discussed the
TROUBLESHOOTING
troubleshooting, maintenance, and repair of pressure
s w i t c h e s , pressure transducers, and temperature
Most problems with liquid control devices are
switches. We also described the different types of level
discovered during PMS. You may find that during
control devices used aboard gas turbine-powered ships
calibration a meter might not indicate the level it is
and the maintenance procedures you must use for them.
supposed to. You must find the problem by starting
We also talked about the safety precautions associated
proper troubleshooting procedures. Troubleshooting
with the troubleshooting and maintenance of pressure,
procedures include reading voltages, resistances, and
temperature, and level control devices.
currents as well as performing calibration.
These simple devices are vital to the operation of
the engineering plant on a gas turbine-powered ship. As
If you find a faulty liquid control device, you must
replace it as soon as possible. Sometimes this is a simple
a GSE, the attention you give these devices will prevent
process, while other times it will take the participation
several equipment malfunctions associated with your
rating. The information presented in this chapter covers
of many personnel. If the control device is a bilge level
the basic operation and maintenance of control devices.
sensor, the replacement procedure is simple. Just tag out
If you have any questions about the pressure,
the circuit and replace it. However, if the control device
is a fuel tank level sensor, the replacement procedures
temperature, and level control devices just discussed, we
recommend you refer to the proper technical manual.
get a bit more complex. The fuel has to be pumped out
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