SAFETY INFORMATION RT765E-2 OPERATOR MANUAL
2-8 Published 4-09-2021, Control # 364-11
Table 2-1 Beaufort Wind Scale
Wind Speeds
The maximum permissible wind speed referred to in the load
charts is the 3-second wind gust speed measured at the
boom tip height and is designated as V(z). This value is
either recorded at boom tip or calculated based on mean
wind speed recorded at crane operation site. For lift planning
purposes only, the 3-second wind gust speed, V(z), may be
calculated based on mean wind speed reported at http://
www.windfinder.com “Super Forecast”.
This 3-second wind gust is assumed to act on the entire
crane and the load. The wind effect on the load can be
conservatively estimated as:
a) If V(z) is ≤ 13.4 m/s (30 mph), then the allowable
load is the published rated capacity from the Load Chart.
b) If V(z) is > 13.4 m/s (30 mph) and is ≤ 20.1 m/s
(45 mph), the allowable load is the published rated
capacity multiplied by the Capacity Reduction Factor
from Table 2-4 (metric) or (non-metric).
NOTE: This condition is limited to operation with the main
boom on fully extended outriggers only.
c) If V(z) is > 20.1 m/s (45 mph), then lifting is NOT
permitted. Cease lifting operations and lower and retract
the boom.
In both cases a) and b) above, the lift may also be limited by
the projected wind area of the load Ap and by the wind drag
coefficient Cd: This limit can be determined by comparing
the Actual wind resistance area with the Allowable wind
resistance area.
Refer to Figure 2-1 for a simplified calculation method to
determine permissible wind speed.
Maximum Wind Speed
Beaufort
Number
Description m/s km/h mph
Visible Indicator
Effects of wind as observed on land
Zero (0) Calm 0.3 1.1 0.7 Calm; smoke rises vertically
1 Light Air 1.5 5.4 3.4
Smoke drift indicates wind direction. Leaves and wind vanes
are stationary.
2 Light Breeze 3.3 11.9 7.4
Wind felt on exposed skin. Leaves rustle. Wind vanes begin to
move.
3
Gentle
Breeze
5.4 19.4 12.1
Leaves and small twigs constantly moving. Light flags
extended.
4
Moderate
Breeze
7.9 28.4 17.7 Dust and loose paper raised. Small branches begin to move.
5
Fresh
Breeze
10.7 38.5 23.9
Branches of a moderate size move. Small trees in leaf begin to
sway.
6
Strong
Breeze
13.8 49.7 30.9
Large branches in motion. Whistling heard in overhead wires.
Umbrella use becomes difficult. Empty plastic bins tip over.
7 High Wind 17.1 61.6 38.3 Whole trees in motion. Effort needed to walk against the wind.
8 Gale 20.7 74.5 46.3
Some twigs broken from trees. Cars veer on road. Progress on
foot is seriously impeded.
9 Strong Gale 24.4 87.8 54.6
Some branches break off trees, and some small trees blow
over. Construction/temporary signs and barricades blow over.
10 Storm 28.4 102.2 63.5 Trees are broken off or uprooted, structural damage likely.
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