When working with batteries, ensure you wear
proper protective clothing (such as safety glasses,
rubber gloves, rubber apron, and rubber boots).
The battery water contains acids which can ruin
clothes and cause severe burning. Be sure you
follow the safety precautions found in Naval
Ships' Technical Manual, Chapter 313, "Portable
Storage and Dry Batteries," and those found on
the PMS card.
HOISTING AND LIFTING DEVICES
When performing maintenance, you may have
to move or lift some of the heavy equipment or
components. You can use various devices to do
this. The selection of the proper device depends
on many factors, such as the equipment to be
moved and the available work space. A working
knowledge of the following devices will aid you
in selecting the right device.
CHAIN HOISTS
Chain hoists (chain falls) provide an easy and
efficient method for hoisting loads by hand. The
advantages of chain hoists are that one person can
raise a load of several tons, and the load can
remain stationary without being secured. A chain
hoist permits small movements, accurate adjust-
ment of height, and gentle handling of loads.
For these reasons they are particularly useful
in hoisting motors or parts which must be
precisely aligned with other parts. Two of the
most common types used for vertical hoisting
Figure 3-41.--Chain hoists.
operations are the differential chain hoist and the
spur gear hoist (fig. 3-41). The load capacity of
Before using a chain hoist, inspect it to
a chain hoist can range from 1/2 ton to 40 tons
ensure safe operation. Replace a hook that shows
and is stamped on the shell of the upper block.
signs of spreading or excessive wear. If links in
The differential chain hoist is suitable for light
the chain are distorted, the chain hoist has
loads. This hoist is only about 35 percent efficient.
probably been overloaded. Make sure the hoist
In other words, about 35 percent of the energy
is in good repair before attempting to lift a load.
that you exert is converted into useful work for
lifting the load. The remaining 65 percent of the
HAND-OPERATED RATCHET
bearings, and chains.
LEVER HOISTS
The spur gear hoist is used for operations that
require frequent use of a hoist and where few
personnel are available to operate it. The spur gear
more commonly called come-a-longs, are similar
hoist is about 85 percent efficient.
to the chain hoist. The main difference is that you
The lower hook is usually the weakest part in
operate a ratchet handle to move the load vice a
the assembly of a chain hoist. This is intended as
chain. The direction of movement is changed by
a safety measure so the hook will start to spread
a lever on the side of the unit or in the handle.
open if overloaded. Thus, you must closely watch
Compared to the chain hoist, the come-a-long
the hook to detect any sign of overloading in time
is smaller because of the size difference of the top
to prevent damage.
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