CENTER
OF GRAVITY
The center of gravity of an apparatus is that
point at which the entire weight may be considered
as consolidated. In order to make a level lift,
the crane hook must be directly above this point.
Anytime
dangerous tilting of the load occurs ( a load
tilt of more than 5 degrees), the load should
be landed and re-rigged.
The
center of gravity of an apparatus is that point
at which the entire weight may be considered
as consolidated. In order to make a level lift,
the crane hook must be directly above this point.
Anytime
dangerous tilting of the load occurs ( a load
tilt of more than 5 degrees), the load should
be landed and re-rigged.
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WHAT
IS THE LOAD WEIGHT?
One
of the most important things to know before
you ever lift a load from the ground is how
much it weighs. This can be determined by various
methods.
Refer
to the bill of lading from the manufacturer.
Check
item for a weight tag.
Use
load indicators to make test picks of each end
of the item and then add them together to get
the total weight. This method can also be used
to find the center of gravity of an item.
Refer
to load weights in the back of this catalog.
Calculate the total number of cubic feet of
material in your load and multiply it by its
load factor on chart.
While
not as accurate as the above methods, the following
is one of the fastest and easiest to use. These
procedures should be used only by an experienced
rigger who can accurately estimate the density
factor. You can get this experience by using
this formula and then verifying it with the
above methods.
Load
weight estimate =Volume in cu. Ft. x 500 lbs.
x density factor .02, .03, .035 etc. Contact
your representative for more information.
SLING
ANGLES
When
slings are used at an angle (that is anything
but straight vertical pull) the sling capacity
is reduced.
How
much the sling capacity is reduced depends on
the angle of the legs to the horizontal angle.
It is a good idea to keep the sling leg angle
as close to vertical as possible. As a general
rule the sling length should be longer than
the distance between the load attachment points.
DETERMINE
THE SLING CAPACITY REQUIRED The
amount of tension or load on a sling leg can
be determined by dividing the sling length (a)
by the sling height over the load (b) and then
multiplying this figure by this slings share
of the load. If the sling you are using is a
2 leg bridle its share of the load would be
50% of the total load weight.
Tension
in sling = a/b x share of load Once
you have determined the sling tension you can
refer to the capacity charts in this catalog
to find the correct size sling to properly lift
the load.
