Discusses how SCADA data can be used to:
- Determine if machines are operating within their AS4324.1 design load envelope.
- Tracking actual fatigue cycles to the design assumptions.
- Using 3D heat maps to find patterns in overload trips and find root causes
- Increase production rates i.e. digging efficiency via changes to the stockpile shape and reducing "air digging".
Biology for Computer Engineers Course Handout.pptx
Improving Bucketwheel Reclaimer Performance and Asset Integrity using SCADA Data
1. Improving BW Reclaimer Performance &
Asset Integrity using SCADA Data
Bulk Materials Handling
Conference, Perth
Mark Biggs
Adam Mayers
2. Outline
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
• Introduction / context
• Operating within design envelope of machine – AS4324.1 Compliance
o Using SCADA data to compare actual operating loads to design loads.
o Operating loads (conveyor live load, digging loads, etc).
o Machine balance monitoring.
• Capital Planning – When will the machine reach the end of its life?
o Fatigue damage monitoring.
• Improving throughput performance by monitoring SCADA
o Fundamentals of Operation
o Reducing trips and unexpected downtime.
o Alternative control philosophies
o Identify opportunities for performance improvements.
3. Bucketwheel Reclaimers
• Bucketwheel reclaimers are extensively
used in materials handling facilities in
Australia. Predominately slewing, luffing,
long travel machine.
• Large, expensive items of equipment.
Many new machines have been
constructed in last 5 years.
• Typically high required availability and
utilisation.
• Machines typically fitted with SCADA
system (Supervisory Control and Data
Acquisition).
• Data available to optimise performance
within design envelope of machine.
Challenge is to turn this Data into useful
Information.
• Approach can be applied to different
equipment types.
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
4. AS4324.1 Design Envelope
• AS4324.1 – 1995 is the Australian
Standard relating to ‘Mobile
equipment for continuous handling of
bulk materials’
• Specifies how machine structures are
designed for structural strength and
fatigue life.
• New revision to be released in 2015
• Vast majority of new machines in
Australia have been designed to this
standard.
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
5. AS4324.1 Load Combination Table 3.7 – Related to Fatigue and
Strength Design Loads, and SCADA Data
Rare loads and
accidents – strength
design
e.g.
-Flooded Belt
-Collisions
-Grounding
-Cyclone
Operational
loads used for
strength design
-Dead weight
-Conveyor
-Digging
-Dynamics
Loads used to
calculate fatigue
life of machine
structure
-Conveyor
-Digging
Abnormal operation
strength design
-High digging loads
-Slew bearing jacking
Many of the loads can
be related to drive
torque, or production
rate which are data
logged by the control
system (SCADA
system)Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
6. Using SCADA Data to Compare Real Loads with AS4324.1
Luff cylinder
forces:
AS4324.1
-Dead load
balance
-Slew brg loads
-Combined live
loads
-Collisions
Belt weigher tonnes/hr:
AS4324.1
Conveyor live load (F)
Flooded belt (FF)
BW drive power
AS4324.1
Normal digging (U)
Abnormal digging
(UU)
Slew drive power and
angle:
AS4324.1
-Lateral digging (S)
-Lateral collision (FS)
-No. Slew cuts for
fatigue
Bucketwheel boom
Counterweight
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
7. Example – Conveyor Live Loads
Live Load (F) is the
normal operating
load for strength
design.
The load can be
converted to tph
using the belt
speed (green line)
Flooded Belt Load (FF) is
the accidental load used
for strength design
Measured conveyor
throughput is below strength
design envelopes.
Fatigue design to AS4324.1 is
based on 0.8 x (F) = 15,113
tph
Conclusion: Conveyor live load is within strength and
fatigue design envelopes during this SCADA data
sample.
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
8. 0 20 40 60 80 100 120 140 160
0
x 10
5
BW motor current
BW motor current (A)
Bincounts(frequency)
0 20 40 60 80 100 120 140 160
0
50
100
Cumulativesum(%)
Cumulative sum
AS 4324.1 fatigue digging CU
.U
Motor full load current 108 A
AS 4324.1 normal digging U 175 kN
AS 4324.1 abnormal digging UU 239 kN
Example – Digging Loads A histogram is useful for large data
sets as it gives an idea of the
amount of time at each load level.
Green line represents
digging load used in
fatigue calculations.
Blue line represents Normal
Digging Load (U) used in
strength design.
Conclusion: Digging load is higher than assumed in the fatigue
design which may reduce the life of certain areas of the structure.
The loads are generally within the strength design envelope
Magenta line represents the
Abnormal Digging Load (UU)
used in strength design.
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
9. Example – Luff Cylinder Loads
The combined
effect of the live
loads can be seen in
the luff cylinder
pressures/loads.
We can also infer
information about
the dead load
balance e.g.
counterweight trim
compared to design.
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
10. Example – Luff Cylinder Loads
Machine is slightly
discharge boom
heavy compared to
design balance
(green line)
Peak tensile luff cylinder loads
approach the AS4324.1 III/6 Flooded
Belt and Blocked Chute Combination
but are inside the strength envelope
(red dotted line)
Loads exceed the
fatigue design
assumptions quite
often (blue line) Conclusions:
- Strength OK.
- May need CW trim
- Fatigue life may be
shorter than design
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
11. Capital Planning – Remaining Fatigue Life
• Machines specifications typically require 20 years of operation or perhaps 100,000
operating hrs. Typically, primarily limitation on life of machine structure is
accumulated steel fatigue damage which results in cracking, at which point,
machine replacement is often required.
• Fatigue is caused by stress fluctuations at the welds. The magnitude of the stress
range and the number of cycles are important.
• For a Bucketwheel Reclaimer, the stress fluctuations and cycles are mainly
proportional to the number of slew cuts i.e. the digging and conveyor load cycles,
and magnitude of loads. The designer therefore converts the 20 year life
requirement to a number of slew cut cycles for the fatigue design calculations. The
conversion is based on the annual throughput rate, stockpile shape and digging
parameters.
• SCADA data can be analysed to count the number of slew cuts that actually occur
per million tonnes reclaimed and estimate the magnitude of loads, to estimate
remaining life based on historical throughput data.
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
12. Example – Remaining Fatigue Life
0 90 180 270 360
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Slew passes at slew angle
Slew angle (deg)
Slewpassespermilliontonnesreclaimedperquadrant
Statistic can be
calculated for
number of slew cuts
per million tonnes
reclaimed e.g. 4,300
slew cuts per Mt
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
13. Example – Remaining Fatigue Life
Historical
production records
converted to
accumulated slew
cuts e.g. 4,300 x
annual production.
Variations in the
production rate are
captured.
Current point in
time
Estimated point in time
when the design
fatigue life will have
been consumed.
Suited to longer term
capital planning i.e.
approximate machine
replacement
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
14. Example – More Detailed Fatigue Assessment
SCADA analysis and FEA can be used
together to derive stress/cycle
distributions as inputs to fatigue life
calculations.
More accurate because it includes the
load variations and cycles.
Suited to life extension studies and
targeting resources for asset integrity
inspections.
Finite Element Structural ModelFinite Element Structural Model
LoadsLoads
Stress cyclesStress cycles
Fatigue life
calculation
Fatigue life
calculation
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
15. Improving Performance - Fundamentals of Operation
Re-positioning
Losses at ends of
cut
Trips result in
production
losses
Geometric & Control
opportunities
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
16. Example – Modifying the Geometry of the Reclaim Process
SCADA data review
and subsequent
reclaim simulation
indicated that a
Stacker-Reclaimer
was under-
performing. One
suggested change
including moving
from 4 bench to 3
bench reclaiming –
estimated 10%
improvement in
average reclaim rate.
Change implemented
in early 2015. SCADA
review confirmed
approx. 10% increase
in average rate!
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
17. Example – Troubleshooting Trips to Minimise Production Delays
using 3D Graphics: Slew Clutch Alarms
Colour scale shows SCADA parameter as a function of 3D boom tip position e.g. BW
current, throughput, slew torque
Black dots are logged alarms/trips which represent production delays (lost revenue)
Concise way of finding patterns using very large data sets e.g. ~5 million data points in
picture below
Easy to see that trips mainly occur at outer edges of lower benches using this technique
Not easy to look at these patterns using normal “trend” software
1 month of 1Hz data1 month of 1Hz data
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
18. Example – Troubleshooting Trips to Minimise Production Delays
using 3D Graphics: Slew Clutch Alarms
Trips occur when slew speed is changing
quickly.
Zooming in on individual trips found that
the slew brakes were being applied
incorrectly.
Brake always applies
before trips
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
19. Example – Troubleshooting Trips to Minimise Production Delays
using 3D Graphics: Luff Cylinder Trips
Machine balance is boom heavy
Luff cylinders trip the machine due to
spikes in the digging load
Each black dot is a trip which stops the
machine until it is re-set. The average
delay is 3 mins
195 alarms in 90 days
195 alarms x 3 mins x 8,500 tph x $60/t
= $5M potential lost revenue per quarter
$20M annualised
195
trips
Trip frequency
vs duration
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
20. Example – Troubleshooting Trips to Minimise Production Delays
using 3D Graphics: Luff Cylinder Trips
Add 2 tonnes to
counterweight
Trips reduce from 195 to
69
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
21. Example – Troubleshooting Trips to Minimise Production Delays
using 3D Graphics: Luff Cylinder Trips
Add 8 tonnes to
counterweight
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
22. Example – Identification of Repositioning Losses
12 second delay
between weightometer
and BW. Consider incl.
some BW torque
feedback or relocate
weightometer.
Significant
repositioning losses,
particularly at far end
of slew cut.
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
23. Additional Opportunities
• Throughput measurements typically lag behind reclaim operation → slows control
system response. Alternative more direct feedback, such as bucketwheel current
or torque arm feedback control can be effective.
• Using SCADA data to benchmark performance against similar machines in fleet.
Recent example showed two identical machines were performing differently:
Reclaimer 1 average = 2815 TPH, Reclaimer 2 average = 3050 TPH → 8%
difference.
• Learn mode algorithms can be implemented to provide predictive feedback based
on SCADA data. Control of one slew reclaim cut is influenced by previous slew
reclaim cuts (e.g. pile edges, soft / hard sections of stockpile etc).
• Good stacking is very important!
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data
24. Summary – Benefits of SCADA based Engineering Analysis
Asset Management
• Understand whether operating machines are compliant with AS4324.1
• If not full compliant, risks can be explored
• Targeting structural integrity inspections to fatigue prone areas
• Understanding machine balance via the luff cylinders.
Capital Planning
• Estimate when machine may need to be replaced in the future based on remaining
fatigue life.
Production
• Reduce production losses due to overload trips
• Identify under-utilisation within the design envelope and opportunities to increase
production rates.
• Benchmark production performance against similar machines in the fleet
• Highly cost effective method of “sweating the assets” for maximum productivity.
Improving BW Reclaimer Performance & Asset Integrity
using SCADA Data