Manitowoc Grove GRT8120, Operator'S Manual

Page: 43 / 448

Grove
Published 3-22-2021, Control # 702-02
2-19
GRT8120 OPERATOR MANUAL SAFETY INFORMATION
2
Example, wind speeds greater than 13.4 m/s is NOT
permissible to lift a load greater than 20,160 lb, even if the
wind resistance area of the load is less than 119 ft
2
.
Refer to the above crane configuration for the following load
conditions:
Load example 2.1:
With known Wind Drag Coefficient of the load Cd ,
• load to be lifted of 19,500 lb,
• Projected Wind Area Ap = 70 ft
2
,
• Wind Drag Coefficient Cd = 1.5
then the wind resistance area of load can be estimated as
Awr
(load)
= Ap x Cd = 70 x 1.5 = 105 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?
19,500 lb
≤ 20,160 lb YES
• Is Awr
( load)
less than Awr
(allow)
?
105 ft
2
≤ 119 ft
2
YES
Conclusion : This load is permissible to lift in wind speed up
to 45 mph.
Load example 2.2:
With unknown Wind Drag Coefficient of the load Cd ,
• Load to be lifted of 18,000 lb,
• Projected Wind Area Ap = 45 ft
2
,
• Wind Drag Coefficient Cd = unknown
NOTE: If exact Wind Drag Coefficient is not known, it shall
be assumed as 2.4.
the wind resistance area of load can be estimated as
Awr
(load)
= Ap x Cd = 45 x 2.4 = 108 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?
18,000 lb
≤ 20,160 lb YES
• Is Awr
(load)
less than Awr
(allow)
?
108 ft
2
≤ 119 ft
2
YES
Conclusion : This load is permissible to lift in wind speed up
to 45 mph.
Load example 2.3a:
With large wind resistance area of the load Awr
(load)
,
• Load to be lifted of 22,000 lb,
• Projected Wind Area Ap = 180 ft
2
,
• Wind Drag Coefficient Cd = 1.2
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.
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