Manitowoc Grove RT770E Operator's Manual page 36

SAFETY INFORMATION
Table 2-6Example-Capacity Reduction Factors for Wind Speed V(z) Greater than 30 mph - Non-metric
(Only for lifting with main boom on fully extended outriggers, with or without stowed extension)
For wind speed Vz (3-second gust speed at boom tip height) is greater > 30> mph ≤ 45 mph, the Reduced Capacity
shall be calculated by multiplying the Published Rated Capacity by the following factors:
Wind Speed
Vz< 30 mph
< 45 mph
Factor
Wind resistance area of load, Awr
Maximum allowable wind resistance area in [ft
Wind resistance area of load, Awr
For wind resistance area of load, Awr
Manual.
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:
For Rated Capacity@ 30 mph
For Allowable Capacity@ 45 mph
Example and Sample Calculations (Non-metric)
The following example illustrates how to calculate allowable
load while operating in wind speed (3-second wind gust
speed) above 13.4 m/s (30 mph) and maximum permissible
wind speeds with various combinations of lifted load and
wind resistance area.
NOTE: Permissible and calculated wind speeds in this
example are the 3-second wind gust speeds at
boom tip height V(z).
Example 2:
A crane is configured with:
• boom length = 90 ft,
• load radius = 40 ft, and
• wind speed is measured at V(z) ≤ 45 mph.
The Rated Load Chart Example - Non-metric (Figure 2-4),
at maximum permissible wind speed, V(z) = 30 mph, the
2-18
36 40 50
0.9 0.9 0.8
, shall not exceed maximum allowable wind resistance area Awr
(load)
= projected wind area Ap x wind drag coefficient Cd for the load.
(load)
> maximum allowable wind resistance, Awr
(load)
1.2
27.4 mph
41.1 mph
Published 04-04-2017, Control # 446-09
Main Boom Length in Feet
60 70 80
0.8 0.8 0.8
2
],Awr = 0.0059 x calculated reduced capacity in lb.
(allow)
1.4 1.6
Maximum Permissible Wind Speed (mph)
25.4 mph 23.7 mph
38.0 mph 35.6 mph
rated lifting capacity m
25,200 lb.
The maximum allowable wind resistance area of load is:
Awr = 0.0059 x m
(allow)
Awr = 0.0059 x 25,200 = 149 ft
(allow)
Lifting Limits at wind speed V(z) < 30 mph at this
configuration:
• Maximum load 25,200 lb
• Maximum wind resistance area of load 149 ft
For the allowable wind speed > 30 mph and ≤ 45 mph,
reduce the allowable load. , the Factor for a main boom
length of 90 ft is 0.8, thus the allowable load is:
m = 0.8 x 25,200 = 20,160 lb
(allow)
This reduced capacity load has an allowable wind resistance
area of:
Awr = 0.0059 x 20,160 = 119 ft
(allow)
RT770E OPERATOR MANUAL
90 100
0.8 0.7
refer to crane Operator
(allow),
1.8 2
22.4 mph 21.2 mph
33.5 mph 31.8 mph
for this configuration is
(allow)
(load)
2
2
110
0.5
(allow).
(2.5)
2