Manitowoc National Crane NBT50 Series, Operator'S Manual

Page: 28 / 158

2-14
Published 03-23-2018 Control # 243-14
SAFETY PRECAUTIONS NBT50 OPERATOR MANUAL
Table 2-5 Awr Ratio and Permissible Wind Speed V(z) - Metric
Example and Sample Calculations (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 1: Crane Configuration:
• boom length = 27.4 m,
• load radius = 9 m,
• wind speed is measured at V(z) ≤ 20.1 m/s.
F r o m t h e R a t e d L o a d C h a r t E x a m p l e - M e t r i c
(Figure 2-3), at maximum permissible wind speed, V(z) =
13.4 m/s, the rated lifting capacity m
( a l l o w )
for this
configuration is 15,050 kg.
The maximum allowable wind resistance area of load is
Awr
(allow)
= 0.0012 x m
(load)
(2.4)
Awr
(allow)
= 0.0012 x 15,050 = 18.06 m
2
For the allowable wind speed > 13.4 m/s and ≤ 20.1 m/s,
reduce the allowable load. Per Table 2-4, the Factor for main
boom length of 27.4 m is 0.8, the allowable load is:
m
(allow)
= 0.8 x 15,050 = 12,040 kg
This reduced capacity load has an allowable wind resistance
area of:
Awr
(allow)
= 0.0012 x 12,040 = 14.45 m
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 (m/s)
For Rated Capacity at 13.4 m/s 12.2 11.4 10.6 10.0 9.5
For Allowable Capacity at 20.1 m/s 18.3 17.0 15.9 15.0 14.2
Table 2-4 Example-Capacity Reduction Factors for Wind Speed V(z) Greater than 13.4 m/s - Metric
(Only for lifting with main boom on fully extended outriggers, with or without stowed extension)
For wind speed V(z) (3-second gust speed at boom tip height) V(z) > 13.4 m/s ≤ 20.1 m/s, the Reduced Capacity
shall be calculated by multiplying the Published Rated Capacity by the following factors:
Main Boom Length in Meters
Wind Speed
V(z) > 13.4 m/s
< 20.1 m/s
10.9 12.2 15.2 18.4 21.3 24.4 27.4 30.5 33.5
Factor 0.9 0.9 0.8 0.8 0.8 0.8 0.8 0.7 0.6
Wind resistance area of load, Awr
(load)
shall not exceed maximum allowable wind resistance area Awr
(allow).
Maximum allowable wind resistance area, [
m
2
] Awr
(allow)
= 0.0012 x calculated reduced capacity in kg.
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 area, Awr
(allow)
refer to crane
Operator Manual.
Lifting Limits at wind speed V(z) ≤ 13.4 m/s at this
configuration:
• Maximum load 15,050 kg
• Maximum wind resistance area of load 18.06 m
2
Lifting Limits at wind speed V(z) > 13.4 m/s and
≤ 20.1 m/s, at this configuration:
• Maximum load 12,040 kg
• Maximum wind resistance area of load 14.45 m
2