TM 5-810-15
(1) The angle of repose of a material can
The designer will provide adequate access
indicate to the designer how a material reacts while
walkways for all conveyors and equipment. Provide
being conveyed on a running conveyor belt. This
adequate width stairways to and from platforms
angle will affect both the capacity and incline
and walkways.
limitations of the conveyor. The inclined angle of a
(2) The distance from the conveyor belt line to
belt conveyor should be limited to 15 degrees, with
the top of the conveyor walkway should be be-
18 degrees used as an absolute maximum for coal.
tween 36 and 42 inches.
d. Weather covers. For open truss conveyors, the
High angle conveyors are currently being used by
various companies, and the designer should inves-
belts must be protected from rain and freezing and
tigate these before a final design is accepted. High
dust must be prevented from escaping to the
angle conveyors use another belt to "sandwich" the
atmosphere.
material for higher conveying angles. Belt
(1) Full or three-quarter cover type, hinged
replacement on high angle, flexible sidewall and
weather covers will be used to protect the belts, yet
pocket conveyors is more expensive than conven-
allow maintenance of the conveyor belt and idlers
tional belts. High angle type conveyors have more
from the walkway.
carryback. Conveyor design must consider dirty
(2) The truss will be covered with a continu-
conditions. Pocket conveyor life is approximately
ous deck plate. A typical open truss conveyor is
10 years, while smooth conveyor expected life is 15
shown in figure 5-2.
years.
(3) For more extreme climates where
(2) The width of the conveyor belt is deter-
freezing conditions are a hazard or when airborne
mined by several factors: the type of material being
dust must be totally eliminated, a totally enclosed
conveyed, size of lumps, percentage of lumps to
type gallery as shown in figure 5-3, should be
fines, the angle of repose of the material and the
considered. This type of gallery is far more
required belt capacity or conveying rate.
expensive than the open truss conveyor. Enough
c. Walkways. All conveyors will be provided with
room must be allowed around each conveyor in the
a walkway of at least 30 inches in width, including
gallery for maintenance. Tube type galleries are
a handrail. Conveyors that are larger than 36 inches
more easily built, insulated and lagged, and washed.
e. Safety escapes. Conveyors will include means
wide will also have an additional 18 inch minimum
width maintenance walkway on the opposite side.
of egress that comply with all applicable codes. In
(1) Walkway construction may be welded
no case will the distance from any location on the
bar grating or serrated type expanded metal
conveyor to a safety escape to grade level exceed
grating, but wooden walkways will not be used.
200 feet.
5-5
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