Schwing SPB 28, Operation Manual

Page: 52 / 216

GENERAL RULE S
PAGE 22
700+ smgr.fm
S AF ETY M AN U AL
6.23
Tipping hazard! Do not unfold the boom until the outriggers
have been correctly positioned and secured! The outriggers must be completely
extended and opened as described in the operation manual. Do not partially
extend the outriggers because intermediate positions are
not safe! See the infor-
mation regarding shortrigging (paragraph 6.22).
6.24
Tipping hazard! Check ground conditions before jacking the
outriggers. If necessary, use cribbing or suitable pads under the outrigger legs to
increase the area of contact. See the chart in Figure 27 for examples of load bear-
ing capacities of surfaces and for an example of how to calculate how much crib-
bing is needed. If in doubt, the site management may be able to supply the load
bearing capacity of the surface being used.
6.25
Always use at least the outrigger pads supplied by the manufac-
turer, even if setting up on concrete.
6.26
When setting the outriggers, jack the unit to within 3° of level,
or according to the operation manual of your unit. If the unit is not set up within
the specification for level, the boom brakes could fail, causing the boom to rotate
downhill by the force of gravity.
6.27
TIPPING HAZARD! Maintain a safe distance between the unit
and the edge of a cliff or any excavation. The rule of thumb is: for every foot of
drop, stay back from the base edge at least 1 foot (the one-to-one rule). (See Fig-
ure 28.) Note that the forces on the outriggers are transferred to the soil at a 45°
angle. Watch out for the conditions shown in Figure 29 and Figure 30.
WARNING
WARNING
Virgin ground
Asphalt, min. 8" thick
Compressed crushed stone
Clay/silt soil, firm
Mixed granular soil
Firm compacted gravel
more compacted
more compacted (e.g. class 5)
Brittle weathered rock 22 PSI
29 PSI
36 PSI
43 PSI
51 PSI
58 PSI
72 PSI
109 PSI
145 PSI
soilpres2.eps
Approximate Load Bearing Capacity
of Various Surfaces
EXAMPLE: Load bearing capacity of 8 inches of asphalt = 29 PSI
Force on the asphalt by the outrigger leg = 40,000 pounds (from decal)
Area of the outrigger pad = 12” x 12” (144 square inches)
40,000 ÷ 144 = 278 PSI.
In this example, you could expect the outrigger to sink into the asphalt and
possibly cause a tipover. To prevent this, you install additional cribbing:
Additional cribbing = 40” x 40” (1600 square inches)
40,000 ÷ 1600 = 25 PSI. NOW the asphalt should support the outrigger.
To calculate surface pressure, divide the
force imposed on the surface by the
outrigger leg (shown on a decal on the
outrigger) by the number of square inches in
contact with the surface.
PSI = Force ÷ Area
PSI = pressure on the surface
Force = how many pounds the outrigger is
imposing on the surface
Area = square inches of surface contact
Figure 27
Calculating load bearing capacity
WARNING
WARNING
WARNING