NATIONAL CRANE Published 09-06-2019 Control # 691-01 2-11
NBT60L OPERATOR MANUAL SAFETY PRECAUTIONS
Table 2-2 Wind Drag Coefficient
Maximum Permissible Wind Speed
If the wind resistant area of the load Awr
(load)
is greater than
the allowable wind resistant area Awr
(allow)
, the ratio can be
used to determine a permissible wind speed V(z) for the load
using Table 2-3.
Table 2-3 Awr Ratio and Permissible Wind Speed V(z) - Imperial units
8384-2
Shape
Cd
1.1 to 2.0
0.3 to 0.4
0.6 to 1.0
0.8 to 1.2
0.2 to 0.3
0.05 to 0.1
Approximately 1.6
Turbine Blade or
Complete Rotor
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 at 30 mph 27.4 25.4 23.7 22.4 21.2
For Allowable Capacity at 45 mph 41.1 38.0 35.6 33.5 31.8
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