Manitowoc Grove GRT880, Operator'S Manual

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SAFETY INFORMATION GRT880 OPERATOR MANUAL
2-18
Published 3-25-2020, Control # 643-04
Table 2-7 Awr Ratio and Permissible Wind Speed V(z) - Non-Metric
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
rated lifting capacity m
(allow)
for this configuration is
25,200 lb.
The maximum allowable wind resistance area of load is:
Awr
(allow)
= 0.0059 x m
(load)
(2.5)
Awr
(allow)
= 0.0059 x 25,200 = 149 ft
2
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
(allow)
= 0.8 x 25,200 = 20,160 lb
This reduced capacity load has an allowable wind resistance
area of:
Awr
(allow)
= 0.0059 x 20,160 = 119 ft
2
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
Table 2-6 Example-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:
Main Boom Length in Feet
Wind Speed
Vz > 30 mph
< 45 mph
36 40 50 60 70 80 90 100 110
Factor 0.9 0.9 0.8 0.8 0.8 0.8 0.8 0.7 0.5
Wind resistance area of load, Awr
(load)
, shall not exceed maximum allowable wind resistance area Awr
(allow) .
Maximum allowable wind resistance area in [ft
2
], Awr
(allow)
= 0.0059 x calculated reduced capacity in lb.
Wind resistance area of load, Awr
(load)
= projected wind area Ap x wind drag coefficient Cd for the load.
For wind resistance area of load, Awr
(load)
> maximum allowable wind resistance, Awr
(allow) ,
refer to crane Operator
Manual.
SA
MP
LE
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
2
L i f t i n g L i m i t s a t w i n d s p e e d V ( z ) > 3 0 m p h
and ≤ 45 mph at this configuration:
• Maximum load 20,160 lb
• Maximum wind resistance area of load 119 ft
2