Figure 11-25.—Salinity cell and valve assembly.
Because the light is intermittent, the eye receives a
series of views rather than one continuous view. To
measure the speed of a machine, find the rate of
intermittent light at which the machinery appears to be
stopped. Then, you either read the speed of rotation
directly from the stroboscope’s indicator or convert the
strobe’s flash rate to rpm.
SALINITY INDICATORS
Electrical salinity indicating cells (fig. 11-25) are
installed throughout distilling plants to maintain a
constant check on the distilled water. An electrical
salinity indicator consists of a number of salinity cells
in various locations in the plant. For example, an
electrical salinity indicator might consist of salinity cells
placed in the evaporators, the condensate pump
discharge, and the air-ejector condenser drain. These
salinity cells are all connected to a salinity indicator
panel.
Since the electrical resistance of a solution varies
according to the amount of ionized salts in the solution,
it is possible to measure salinity by measuring the
electrical resistance. The salinity indicator panel is
equipped with a meter calibrated to read directly, either
in equivalents per million (epm) or grains per gallon
(gpg).
NOTE: Other dissolved solids, in addition to
ionized salt, may change the electrical resistance of
water. To be safe, always assume that any resistance
change is caused by ionized salt.
TORQUE WRENCHES
At times, you will need to apply a specific force to
a nut or bolt head. At these times, you will use a torque
wrench. For example, equal force must be applied to all
the head bolts of an engine. Otherwise, only one bolt
may bear the brunt of the force of internal combustion,
ullimately causing engine failure. A torque wrench will
allow you to apply the specifically required force.
The three most commonly used torque wrenches are
the deflecting beam, the dial-indicating, and the
micrometer-setting types (fig. 11-26). When using a
deflecting-beam or dial-indicating torque wrench, you
visually read the torque on a dial or scale mounted on
the handle of the wrench. The micrometer-setting torque
wrench, however, indicates the torque value by sound.
To use the micrometer-setting torque wrench, you
unlock the grip and adjust the handle to the desired
setting on the scale; then, relock the grip. Next, install
the required socket or adapter to the square drive of the
handle. Place the wrench assembly on the nut or bolt and
pull in a clockwise direction, using a steady, smooth
motion. (A fast or jerky motion results in an improperly
torqued unit.) When the torque applied reaches the
required torque value, a signal mechanism
automatically issues an audible click; and the handle
will release or break, moving freely for a short distance.
The release and free travel are easily felt. his feature
indicates that the torquing process is complete.
You should use a torque wrench that reads about
mid-range for the amount of torque to be applied.
Manufacturers’ and technical manuals generally specify
the amount of torque to be applied. To make sure the
correct amount of torque is applied to the fasteners, you
must use the torque wrench according to the specific
manufacturer’s instructions.
CAUTION
Be sure the torque wrench has been
calibrated before you use it.
Remember, the accuracy of torque measuring
depends on how the threads are cut and the cleanliness
of the threads. Make sure you inspect and clean the
threads. If the manufacturer specifies a thread lubricant,
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