Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FAILURE REPORT
DATE:
17/08/2021
FROM:
Schenck Process Africa (Pty) Ltd
TO:
Vale Moatize Coal Mine
ATTENTION:
Bruno Rabelo, Jordao Humberto, Hudson Gandra
TOPIC:
SLO4361 and SLO4361-3 Screens' crossbeam cleat failures
DOC. No.:
SPR21-60
Preamble
On the 26th of July 2021, Schenck Process Africa conducted a site visit at the Vale Moatize coal mine.
This visit aimed to evaluate the current state of the failed cleats on the SLO4361 screens and perform
a failure investigation to pinpoint the possible reason/s for these failures. In this report, we will convey
our findings to the investigation. We will also share the potential causes of the failures, either accept
or reject the warranty claim based on the findings and set out recommendations to prevent similar
failures in the future.
1
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
Background
We (Schenck Process Africa) supplied several Crossbeams to the client (Vale Moatize Mine) to
refurbish their screens. We offered to have a contractor on-site to supervise the refurbishment
processes to ensure that the client follows approved refurbishment procedures. However, The client
decided against this and followed their own refurbishment procedures unsupervised by the Original
Equipment Manufacturer (OEM). We also advised the client to remove the screens from situ and place
them on an open field before refurbishing. This advisement to remove the screens from situ ensured
that they could efficiently perform the approved refurbishment procedure. However, the client also
decided against this and refurbished these screens in situ.
After refurbishing their screens, the client started encountering crossbeam cleat failures on some of
their SLO4361 slope screens. Thus far, there is a record of four beams on four different screens that
have experienced cleat failures. These cleat failures occurred on screens 4C-SC-102 (SLO4361), 4C-SC201 (SLO4361), 4C-SC-202 (SLO4361), and 4D-SC-104 (SLO4361-3).
The client performed a failure investigation on the first crossbeam cleat failure they encountered, and
the conclusion they have reached is that it is a cleat weld failure. The client claimed that the vertical
plate welded to its adjacent perpendicular plates, which form part of the cleat assembly, has a clean,
smooth break at the joint section indicates no weld penetration in this region. However, the vertical
plate forms part of an unequal angle bolted and welded to the crossbeam. Adjacent to this angle is a
flat plate welded to it and the crossbeam. Therefore, the vertical plate could not have broken off clean
due to improper weld penetration because it was not welded to the so-called perpendicular plates as
it formed part of a solid angle body. After the failure occurred, the continuous operation of the screen
caused the separated components to hit and rub against each other, which smoothed the break
surfaces. From this, it is clear that other possible factors lead to cleat failures on these screens.
We will conduct additional tests on these crossbeam cleats to evaluate the material properties,
conclude if they contain any weld defects and if any weld defects exist, conclude if they could have
possibly contributed to the failures.
2
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
Findings
The findings raised in the failure investigation are listed below:
•
•
•
•
•
•
•
•
•
•
•
•
3
We have found that four crossbeams have experienced cleat failures on four different screens.
All four cleat failures occurred on the discharge beams.
All four cleat failures are the furthest right-hand cleats.
There is a clear pattern to the position of the cleat failures as the failures positions appear not
to occur randomly over the deck of the screen.
Since the cleat failures positions follow a specific pattern, it is evident that the failures are not
due to welding defects as previously stipulated by Vale. If the failures were because of welding
defects, the failures would have occurred much more randomly as all the cleats followed the
same manufacturing process, and the forces acting on all the cleats are more or less equal.
By visual inspection, we have not found any apparent welding defects. We have not found any
undercuts in the components welded together or visible cracks in the welds.
It also appears that the cracks initiate in the curved section of the cleat's unequal angle and
not in the weld on the opposite end. This further proves that it is not welding defects that lead
to these failures. We know that the crack did not form on the welded section as the failing
cleat on screen 4C-SC102 cracked on the curved side, and the weld on the opposite end was
still intact.
We have found that the cleats follow a similar failure mode. The vertical section of the cleats
breaks loose at its weakest section if it were subjected to a moment force.
Only when subjecting the material of the cleats to sufficient tensile stress will it form cracks.
Therefore, due to the cracks initiating on the curved sections of the cleats, an excessive
moment force must have acted on the cleats that placed these curved sections under
excessive tensile stress. During acceptable operating conditions of these screens, no such
moment force exists that will put the curved section of the cleat under more tensile stress
than the welded area on the opposite end.
We have found that the client has difficulty keeping their discharge side liners in place. We
have noticed that they apply a bonding/sealing agent all around the edges of the discharge
side liners. The application of the bonding/sealing agent could prevent material from flowing
in between the discharge side liners and side plates. When the material flows in between
these components, it builds up and pushes the side liner away from the side plate until it
eventually falls out.
If a discharge side liner were to come out during the normal operation of these screens, the
discharge panels bolted to the deck rails will be loose on the one end as the side liner no
longer retains them. Due to the discharge panel being loose on one side and fixed to the deck
rail on the other side, the panel will entail a pivoting movement relative to the screen deck
during the operation of the screen. This continuous pivoting action of the discharge panels
will induce a cyclic moment force in the outer cleats of the discharge crossbeam as the
discharge panels are connected to the deck rails bolted to these cleats. This induced moment
forces subjects these cleats to additional stress, which reduces their fatigue life.
If the right-hand discharge side liner comes loose, the pivoting panel will induce a bending
moment in the right-hand cleat that will tend to open the cleat angle; this then places the
curved section of the cleat angle under tension. If the left-hand discharge side liner comes
loose, the pivoting panel will induce a bending moment in the left-hand cleat that will tend to
close the cleat angle; this then places the curved section of the cleat angle under compression.
The cleat angles have a higher bending resistance when pushed closed than when pulled open;
therefore, the cleats on the right-hand side will be subject to higher stress than the left-hand
cleats during these pivoting actions of the loose panels. This difference in resistance to
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
•
•
•
•
•
•
4
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
bending could explain why we only see cleats failing on the right-hand side of the screens at
this moment in time.
We have found numerous signs indicating that the side liners come loose, causing the
discharge panels to flop up and down, inducing moment forces in the cleats, as previously
explained. These signs are listed below:
➢ The side liners are bonded and sealed in place.
➢ One of the screens has a broken right-hand discharge ledge.
➢ Indention marks on the ledge angles and along the edges of the discharge panels.
➢ One of the competitor panels has a broken backing plate. It has broken in the region
where it fixes to the deck rail.
➢ Damaged bolting holes on the deck rails.
➢ The drip lips on the discharge ends are damaged.
Further to the discharge side-liners coming loose, we have found that the competitor
discharge panels do not entail the steps in the backing plates like the OEM panels. This causes
the competitor panels to sit skew onto deck rails and ledge angles. If the top surface of the
panels is not in line with the rest of the deck and the bottom surface of the side-liners, it could
cause the side-liners to come loose during operation as the surfaces between the panels and
the side-liners aren't flush. Furthermore, if the competitor panels sit skew on the deck rails,
the bolting faces of the panels backing plate and the deck rail aren't flush; therefore, the
bolting fixture is not secure, and the panels will come loose. When these panels come loose,
they damage the bolting holes on the discharge deck rails.
Further to the discharge side-liners coming loose, we have found that the client uses stepped
wedge brackets to wedge the angled side-liners in place and angled wedge brackets to wedge
stepped side-liners in place. Mis-matching OEM wedge brackets and side-liners with
competitor wedge brackets and side liners do not ensure good fixtures between them if their
designs are different and could cause these side-liners to come loose.
The client threw away the cleat components that came loose in the first crossbeam cleat
failure, and they ground the remaining components off. This obstructs the failure investigation
as we can not analyse the nature of the crack initiations, perform material tests, analyse the
welds or inspect the bolting holes.
We have found that the client does not follow OEM-approved procedures to refurbish their
screens, replace parts, or reassemble components that came loose. Not following OEM
procedures could place components of these screens under excessive stress, which will reduce
their fatigue life.
We have performed fitness checks on four screens that have encountered cleat failures thus
far. These screens are listed as follows:
1. 4C-SC-102 (SLO4361)
2. 4C-SC-201 (SLO4361) (Loose huck bolts on the left-hand feed crossbeam and a missing
huck bolt on the right-hand center beam. The client should replace these bolts)
3. 4C-SC-202 (SLO4361)
4. 4D-SC-104 (SLO4361-3)
The main issues that we have found with these screens are that three of the four screens are
running out of phase. The only screen that runs in phase is screen 4C-SC-201. The maximum
permitted phase difference of these screens is 5 degrees. Screen 4C-SC-201 has a maximum
phase difference of 2 degrees. Screen 4C-SC-104 has a maximum phase difference of 7
degrees. Screen 4C-SC-102 has a maximum phase difference of 8 degrees. Screen 4C-SC-202
has a maximum phase difference of 22 degrees. From this, we can see there exist phasing
issues in the majority of the screens tested. When these screens run out of phase, the body
of the screen will entail additional bending, subjecting the screen components to additional
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
•
5
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
stresses, and the fatigue life of these components will be affected. The main reason for
screens not operating in phase is due to exciters' misalignment. We have checked the
alignment of screen 4C-SC-102 and have found that the exciters are misaligned. This
misalignment error could result when connecting these exciters to the drive unit via the
intermediate shafts. It could be that one or both driveshaft spline connections came apart
during the connection procedure, and when they re-engaged the spline connections, they did
not align the holes on the left and right-hand flanges first. Therefore, they had to rotate the
segments on one exciter relative to the other to enable the bolting holes on the shaft flanges
to align with the bolting holes on the exciter and layshaft hubs.
We have found that competitor exciters are being used on Schenck Process supplied vibrating
screens. Since we do not have access to these exciters' technical specifications, we cannot
access the effect of such exciters on our products. However, we know that defective or
incorrect exciters can severely affect the integrity of our vibrating screens or their
components.
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
Conclusions
This investigation aimed to find the possible causes of the cleat failures on the SLO4361 screens. We
have found a pattern in the position of cleat failures, and the failure modes are consistent. If the
failures occurred in more random positions, one could have argued that the material of the cleats and
the welds on the cleats are not according to specification. However, this is not the case. Only the cleats
on the right-hand side of the discharge beams fail. The failure modes are such that a moment force is
acting on these failing cleats. During the normal operation of these screens, no such moment forces
should exist in these cleats. However, we have found numerous signs of discharge side liners coming
loose. If these side liners come loose, they can no longer hold the discharge panels in position. If one
end of the panels is loose and bolted on the other, its pivoting motion will include moment forces in
the right-hand discharge cleats and affect their fatigue life. Hence, these cleats are experiencing
fatigue failures.
Further, we have found that the client does not follow OEM-approved procedures to refurbish their
screens, replace parts, or reassemble components that came loose. Not following OEM procedures
could place components of these screens under excessive stress, which will reduce their fatigue life.
We have found that the client uses competitor exciters on our screens. Therefore, we are not able to
guarantee the operational performance of our components used in conjunction with competitor
exciters. We have also found that the majority of the screen tested is running out of phase due to
exciter misalignment, affecting the screen components' fatigue life.
Based on the findings in this report and the above conclusions, Schenck Process Africa rejects the
warranty claim against them.
Recommendations
To prevent similar failures in the future, we recommend the following:
•
•
•
Ensure that no components come loose during the operation of the screens. This can be done
using OEM parts that entail critical design aspects that allow for proper fixture and
performance.
Ensure always to follow OEM-approved procedures when refurbishing screens, replacing
parts, or reassemble components that came loose.
Ensure that all the screens run in phase. One can achieve this by correctly aligning the exciters
when connecting them to the drive unit.
Vian Kotze
Applications Engineer.
Schenck Process Africa Pty Limited
1 Crusher Road
Crown Mines, Johannesburg, South-Africa
Cell: +27714927731
v.kotze@schenckprocess.com
6
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
Pictures
Flat plate
Angle iron
Point of break
FIGURE 1: CROSS SECTIONAL VIEW OF THE CROSSBEAM CLEAT ASSEMBLY
7
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Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FIGURE 2: CROSSBEAM CLEAT FAILED AT CURVED SECTION OF THE
ANGLE AND THE CLEAT IS STILL INTACT
8
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Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FIGURE 3: RIGHT HAND DISCHARGE LEDGE ANGLE DAMAGED BY LOOSE
PANEL.
9
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FIGURE 4: DAMAGED BOLTING HOLES ON DISCHARGE DECK RUNNER
DUE TO LOOSE PANEL.
10
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Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FIGURE 5: ANGLED WEDGE BRACKETS USED TO FIX THE STEPPED SIDE LINERS.
11
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FIGURE 6: COMPETITOR PANEL NOT SITTING FLUSH ONTO THE DECK RAIL AND LEDGE ANGLE
12
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FIGURE 7: LEDGE ANGLE DAMAGED BY LOOSE PANELS
13
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Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FIGURE 8: DAMAGED COMPETITOR PANEL DUE TO IT COMING LOOSE.
14
we make processes work
Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FIGURE 9: COMPETITOR STEPPED SIDE LINERS NOT SECURELY CLAMPING THE DISCHARGE
PANELS DOWN. THESE SIDE LINERS ARE PRONE TO COMING LOOSE AND FALLING OUT.
15
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Schenck Process Africa (Pty) Ltd
P O Box 35380,
Booysens, 2016
1 Crusher Road
Crown Ext. 3
Johannesburg, 2092
www.schenckprocess.com
sales.pza@schenckprocess.com
T +27 11 837-9656
F +27 11 837-7458
Reg. No. 1929/001731/07
VAT No. 4160102051
Board of Directors
W.L. Kempen (Managing)
M.O. Issing
*(German)
Vibrating Screens & Feeders
Static Weighing
Continuous Weighing
FIGURE 10: BONDING/SEALING AGENT APPLIED TO SIDE LINERS
16
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