2-18
Published 11-01-2020 Control # 710-00
SAFETY PRECAUTIONS
NBT60XL OPERATOR MANUAL
the wind resistance area of load can be estimated as:
Awr
(load)
=
Ap
x
Cd
=
180 x 1.2 = 216 ft
2
Refer to the above
Lifting Limits at wind speed V(z) >
30 mph and
≤
45 mph
. Comparing the load to the allowable:
•
Is the load to be lifted less than allowable load?
22,000 lb
≤
20,160 lb
NO
Conclusion
: This load is NOT permissible to lift in wind
speed up to 45 mph.
Refer to the above
Lifting Limits at wind speed V(z) up to
30 mph
. Comparing the load to the allowable:
Is the load to be lifted less than allowable load?
22,000 lb
≤
25,200 lb . . . . . . . . . . . . . . . . . . . YES
The permissible wind speed for this load is 30 mph,
depending on the wind resistance area of the load.
•
Is
Awr
(load)
less than
Awr
(allow)
,?
216 ft
2
≤
149 ft
2
. . . . . . . . . . . . . . . . . . . . . . . . . NO
Conclusion
: This load is NOT permissible to lift in wind
speed at 30 mph, but permitted to lift at a reduced wind
speed calculated as follows:
Ratio
= 1.45
From Table 2-7, the maximum permissible wind speed at
ratio of 1.45 (rounded to next higher table value of 1.6) is
23.7 mph.
Conclusion
: This load is permissible to lift in wind speed up
to 23.7 mph only.
Conclusion
: This load is permissible to lift
in wind speed up to 38.0 mph only.
Load example 2.3b:
With large wind resistance area of the load
Awr
(load),
•
Load to be lifted of 12,000 lb,
•
Projected Wind Area
Ap
= 125 ft
2
,
•
Wind Drag Coefficient
Cd
= 1.3
the wind resistance area of load can be estimated as:
Awr
(load)
=
Ap
x
Cd
= 125 x 1.3 = 162 ft
2
Refer to the above
Lifting Limits at wind speed V(z)
> 30 mph and
≤
45 mph
. Comparing the load and wind
resistant area to the allowable:
•
Is the load to be lifted less than allowable load?
12,000 lb
≤
20,160 lb
YES
•
Is
Awr
(load)
less than
Awr
(allow)
,?
162 ft
2
≤
119 ft
2
NO
Conclusion
: This load is NOT permissible to lift in wind
speed up to 45 mph, but permitted to lift at a reduced wind
speed calculated as follows:
Ratio
= 1.37
From Table 2-7, the maximum permissible wind speed at
ratio of 1.37 (rounded to next higher table value of 1.4) is
38.0 mph.
Lifting Operations
Before lifting, position the equipment on a firm surface,
properly extend and set the outriggers, and level the
equipment. Depending on the nature of the supporting
surface, adequate cribbing may be required to obtain a
larger bearing surface.
The equipment is equipped with a bubble level that should
be used to determine whether the equipment is level. The
load line can also be used to estimate the levelness of the
equipment by checking to make sure that it is in-line with the
center of the boom at all points on the swing circle.
If the jib, or auxiliary boom nose is to be used, make sure that
the electrical cable and the weight for the Anti-Two-Block
Switch are properly installed and the Rated Capacity Limiter
(RCL) is programmed for the equipment configuration. Refer
to the RCL operator manual supplied with the equipment.
Verify the equipment’s capacity by checking the
Load Chart
against the weight of the load. Then, lift the load slightly at
first to ensure stability before proceeding with the lift.
Make sure that the load is properly rigged and attached.
Always determine the weight of the load before you attempt
to lift it and remember that all rigging (slings, etc.) and lifting
devices (hook block, jib, etc.) must be considered part of the
load.
Measure the load radius before making a lift and stay within
approved lifting areas based on the range diagrams and
working area diagrams on the equipment’s
Load Chart
.
Table 2-7
Awr
Ratio and Permissible Wind Speed
V(z) - Non-Metric
Note: Permissible and rated wind speeds in this table are the 3-second gust wind speeds at boom tip height.
Ratio:
1.2
1.4
1.6
1.8
2
Maximum Permissible Wind Speed (mph)
For Rated Capacity@ 30 mph
27.4
25.4
23.7
22.4
21.2
For Allowable Capacity@ 45 mph
41.1
38.0
35.6
33.5
31.8
Fo
r
Reference
Only
