Manitowoc National Crane NBT50 Series, Operator'S Manual

Page: 29 / 158

NATIONAL CRANE
Published 03-23-2018 Control # 243-14
2-15
NBT50 OPERATOR MANUAL SAFETY PRECAUTIONS
2
At wind speeds greater than 13.4 m/s, it is not permissible to
lift a load greater than 12,040 kg, even if the wind resistance
area of the load is less than 14.45 m
2
.
Refer to the information from the above crane configuration,
examine several load conditions.
Load example 1.1:
With known Wind Drag Coefficient of the load Cd , and
• load to be lifted of 11,200 kg,
• Projected Wind Area Ap = 9.20 m
2
,
• Wind Drag Coefficient Cd = 1.5
wind resistance area of load can be estimated as
Awr
(load)
= Ap x Cd = 9.2 x 1.5 = 13.8 m
2
Refer to the above Lifting Limits at wind speed V(z)
> 13.4 m/s and ≤ to 20.1 m/s . Comparing the load and wind
resistant area to the allowable:
• Is the load to be lifted less than allowable load?
11,200 kg
≤ 12,040 kg YES
• Is Awr
(load)
less than Awr
(allow)
?
13.8 m
2
≤ 14.45 m
2
YES
Conclusion : This load is permissible to lift in wind speed up
to 20.1 m/s.
Load example 1.2:
With unknown Wind Drag Coefficient of the load Cd ,
• Load to be lifted of 10,000 kg,
• Projected Wind Area Ap = 5.45 m
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 = 5.45 x 2.4 = 13.08 m
2
Refer to the above Lifting Limits at V(z) > 13.4 m/s
and ≤ 20.1 m/s . Comparing the load and wind resistant area
to the allowable:
• Is the load to be lifted less than allowable load?
10,000 kg
≤ 12,040 kg YES
• Is Awr
(load)
less than Awr
(allow)
?
13.08 m
2
≤ 14.45 m
2
YES
Conclusion : This load is permissible to lift in wind speed up
to 20.1 m/s.
Load example 1.3a:
With large wind resistance area of the load Awr
(load)
,
• Load to be lifted of 14,000 kg,
• Projected Wind Area Ap = 21.85 m
2
,
• Wind Drag Coefficient Cd = 1.2
the wind resistance area of load can be estimated as:
Awr
(load)
= Ap X Cd = 21.85 x 1.2 = 26.22 m
2
R e f e r t o t h e a b o v e L i f t i n g L i m i t s a t w i n d
speed V(z) > 13.4 m/s and ≤ 20.1 m/s . Comparing the load
to the allowable:
• Is the load to be lifted less than allowable load?
14,000 kg
≤ 12,040 kg NO
Conclusion : This load is NOT permissible to lift in wind
speed up to 20.1 m/s.
R e f e r t o t h e a b o v e L i f t i n g L i m i t s a t w i n d
speed V(z) < 3.4 m/s . Comparing the load to the allowable:
• Is the load to be lifted less than allowable load?
14,000 kg
≤ 15,050 kg YES
The maximum permissible wind speed for this load is
13.4 m/s, depending on the wind resistance area of the load.
• Is Awr
(load)
less than Awr
(allow)
?
26.22 m
2
≤ 18.06 m
2
NO
Conclusion : This load is NOT permissible to lift in wind
speed at 13.4 m/s, but is permitted to lift at a reduced wind
speed calculated as follows:
Ratio = 1.45
From Table 2-5, the maximum permissible wind speed at
ratio of 1.45 (rounded to next higher table value of 1.6) is
10.6 m/s.
Conclusion : This load is permissible to lift in wind speed up
to 10.6 m/s only.
Load example 1.3b:
With large wind resistance area of the load Awr
(load)
,
• Load to be lifted of 8,000 kg,
• Projected Wind Area Ap = 15.25 m
2
,
• Wind Drag Coefficient Cd = 1.3
the wind resistance area of load can be estimated as
Awr
(load)
= Ap x Cd = 15.25 x 1.3 = 19.83 m
2
Refer to the above Lifting Limits at wind speed V(z)
> 13.4 m/s and ≤ 20.1 m/s . Comparing the load and wind
resistant area to the allowable: