maintains power relay K1-1, operated so that its
the size of the tank and its shape, as well as the desired
contacts are closed. (For simplicity, only one
type of level indication.
solenoid-operated valve is shown.)
The electrical signals generated by the level links
and transmitters are converted at the receivers and
TANK LEVEL INDICATOR SYSTEMS
indicated on meters in gallons. Each meter is
calibrated for a specific tank, and each tank is different
Tank level indicator systems provide an accurate
in size and shape. The size and shape of the tank also
measure of the fluid level within a tank, as well as
accounts for the nonlinearity of the meter forces.
sound an alarm, audible and/or visual, to indicate
either a high or low fluid level. The fluid levels can be
c o n t i n u o u s l y indicated or in predetermined
increments, depending on the type of equipment
Preventive maintenance for the ship's order
installed in the tank. This can be accomplished using
indicating and metering systems consists of routine
various types of detection equipment, the most
tests, inspections, cleaning, and lubrication. All
common of which is the magnetically operated reed
preventive maintenance should be accomplished
switch. For the purposes of our discussion, we will talk
according to current applicable MRCs.
about the magnetically operated reed switch.
Corrective maintenance for the systems consists
The system consists of a level detector, which is
mainly of replacing burned out illumination lamps and
installed in the tank, a receiver mounted outside the
z e r o i n g synchros. For detailed information
tank, and an alarm device. The types of alarm devices
concerning the maintenance of synchro systems and
used varies depending on the system; however, they
perform the same function.
Electronics Training Series (NEETS), NAVEDTRA
The level detectors used in a tank level indicating
172-15-00-85, Module 15.
system fall into two categories: level links and
transmitters. Level links indicate the fluid level in
increments. Transmitters provide continuous fluid
level indications and are used in systems requiring
In this chapter, we have described the purpose of
the ship's order indicating and metering systems. We
The method of indication for level links and
have identified and discussed the operation of the
transmitters are the same. A permanent magnet, which
ship's control order and indicating systems and the
moves with the fluid level, is enclosed in the float.
various control consoles used with the systems. We
When the permanent magnet becomes parallel to a
have identified and discussed the operation of some of
switch, the switch closes. As it moves further on the
the various metering and indicating systems installed
stem, it will make the next switch before opening the
on Navy ships. We have briefly discussed some of the
former switch (make-before-break).
preventive and corrective maintenance measures
Transmitters and level links are sometimes used
associated with the ship's order indicating and
together. The actual combinations are determined by