View A of figure 1-1 shows the internal components
of the device. The temperature-sensitive element is a
Temperature readings normally are taken once a
single-helix low-mass coil. The coil fits closely inside
day. The exact time may vary, but on most ships the
the thermometer stem. The bimetal element is carefully
readings are taken in the morning (around 0800 for
sized and aged for lifetime stability, and is covered with
example). A special maximum and minimum
a fluid to assure good heat transfer. The fluid also
thermometer is used. (Sometimes it's called a high-low
permits maximum speed of response and reduces
thermometer.) Figure 1-1 illustrates a typical maximum
pointer oscillations caused by outside vibrations. The
and minimum thermometer.
case and stem are made from stainless steel for strength
and anticorrosion purposes.
Every magazine or locker will have at least one
such direct-reading thermometer, located where
View B of figure 1-1 illustrates the dial face of the
maximum space temperature variations normally occur.
thermometer. It is 3 inches in diameter, with a plastic
It will be installed so that it is readily accessible for
window to protect the index pointers. The index reset
taking readings and for resetting the index pointers.
arm is on the outside of the window and is used to reset
the high-low pointers. Temperature graduations on our
example are marked off in 20-degree increments. The
approximate readings on this thermometer are 100F,
high; 78F, present; and 55F, low. If you are assigned
the duty of taking magazine temperature readings, you
should record the high, low, and present temperatures
and then reset the high and low pointers in line with the
present pointer. As temperature rises during the day, the
present pointer will push the high pointer up the scale.
As temperature falls during the night, the present
pointer will reverse direction and push the low pointer
down the scale. As the sun comes up, the present
pointer will move back up the scale. Thus, the inspector
will see three different temperature readings that reflect
the temperature variations throughout a 24-hour period.
The 45-degree spread between the high and low
pointers in our example is a bit large, but is used for
clarity. Check the temperature requirements for the
magazine you are inspecting and have the magazine air-
conditioning (A/C) or ventilating system turned on if
the temperature rises into the high zone. The optimum
temperature should be around 70F. If the A/C system is
not working, artificial cooling (fans, blowers) may have
to be used.
T h e bimetallic maximum and minimum
thermometer in figure 1-1 is becoming the standard
thermometer in shipboard magazines. However, you
may come across a different model with only a
maximum (high) index pointer and a reset knob. This
type of thermometer is acceptable. The older liquid-in-
glass (tube) mercury high-low thermometer is no longer
authorized for shipboard use. If you see one of the
Figure 1-1.--Bimetallic maximum and minimum thermometer:
mercury units in a magazine, notify your supervisor.
A. Internal components; B. Dial face and pointers.