components that are not normally
incorporated in the more common
examples given above.
Case study 1
This first case study involves a 350 ft
long 54 in. wide incline conveyor
travelling at 700 ft/min., which is
loaded from two feeders under a
rotary car dumper at a rate of 2000 tph
of bituminous coal fines at a
midwestern steel mill. To facilitate a
blending requirement, a secondary
load point was installed 130 ft
downstream from the initial loading
point.
First challenge
Due to structural and elevation issues
with the original design of the primary
load zone, 20˚ troughing idlers had to
be installed under the load chute
impact area. The belt was then
immediately transitioned to 35˚
troughing idler in less than 4 ft, while
still in the skirt seal area. The width of
the skirting load area also exceeded the
recommended two thirds of the belt
width. This type of idler transition is
not recommended with such a short
distance in the skirted loading area.
This created a material leakage and
dusting issue, as well as the need to
adjust and replace the skirting seals due
to flexing of the belt in this short
transition. The belt was only supported
with these 20˚ idlers on 24 in. centres
under the loading point. Internal wear
resistant skirt seal liners were not used
in the load zone, which also contributed
to the excessive leakage and the need
for constant vacuum cleaning of the pit
area under the railcar dumpers
(Figure 1).
Second challenge
The secondary load point that was
added to the system in order to blend
product did not have a continuous skirt
seal area from the primary loading
point up stream, which caused the
material on the belt to be ploughed off
onto the ground when surge loading or
belt mistracking occurred. The load
profile on the belt was too wide due to
the 20˚ idlers and loading chute that
exceeded the maximum width at the
first zone. These issues also created the
need for weekly coal spillage clean up
using costly vacuum trucks, as well as
excessive air born dusting (Figure 2).
Solution
In order to correct these problems, it
was necessary to redesign and retrofit
both the primary and secondary load
points, while still being limited with
minimal headroom and structural
obstructions in the primary transfer
point.
The engineered solutions involved
using the 20˚ troughing profile under
the primary load point and then
extending the transition distance over a
longer distance before changing to the
35˚ idlers downstream. An intermediate
27.5˚ modular framed troughing idler
was used in this transition, as well as
modular impact and slider support
beds to allow for a constant seal
between the belt and skirting.
A skirting tunnel section that
incorporated the externally mounted
inner skirting wear liner was installed
the full length between the first and
second load zones. In addition, the
second load point was retrofitted with
modular impact load support beds and
an extended exit skirting tunnel with
several dust curtains throughout the
full length. The externally mounted
Figure 1. Primary load point.
Figure 2. Secondary load point.
Figure 3. Secondary load point and full length skirt tunnel.
38
|
World Coal
|
August 2015
