• Categories
• Neumático
• Camión
• Suspensión (Vehículo)
• Transmisión (Mecánica)
• Carretera

Citation preview

FPO Application Guide Mining Fleet Productivity Optimization Version 11 - 26 November 2004

Table of Contents Nomenclature

2

1. Introduction

4

2. General overview of a typical Haul Road

5

2.1. Load Area & Pit Floor

5

2.2. Main Haul Road

6

2.3. Waste Dump

7

3. Guidelines for collecting representative haul road cycle data

8

4. Composite Pressure Limits

9

4.1. Background

9

4.2. Composite pressure limit values

9

5. Mine Severity Index

11

5.1. Haul Road Condition index

11

5.2. Payload Distribution index

13

5.3. Mine Severity Index estimation

14

5.4. MARC rates estimation using MSI data

15

6. Machine performance and haul road assessment using control charts

18

6.1. Speeds on curves and superelevation

18

6.2. Manoeuvring in dump areas

26

6.3. Gear selection

27

6.4. Crossfall

30

7. Acknowledgements

31

8. References

31

9. Appendices

32

NOTE: This document should be read in conjunction with the FPO User Manual located in the Guides/Tools section of the Caterpillar Knowledge Network Community: “Mining Project Manager’s Toolkit”. For those Cat/Dealer staff with a Corporate Web Security logon, visit:

https://kn.cat.com/guides.cfm?id=6232

Caterpillar Confidential: Green FPO Application Guide

1 of 32

Version 11

Nomenclature Abbreviations LF: Left-Front position.

RF: Right-Front position.

LR: Left-Rear position.

RR: Right-Rear position.

OHT: Off-highway Truck, such as 785, 793 and 797 trucks. GMW: Gross Mass Weight.

Definitions Machine Rack: or just Rack, is the difference between strut pressures diagonally across the centre of the truck; i.e. (LF + RR) - (RF + LR) which tend to ‘twist’ the frame, and highly load machine components. Machine Bias: or just Bias, shows whether placement of the load is central or to one side of the truck during the loading cycle (Payload BIAS). It also shows whether significant ‘dynamic’ loading is occurring as the machine negotiates cross-slopes, or corners at speed where super-elevation is not sufficient; called ‘Machine BIAS’. Both Payload BIAS and Machine BIAS are defined as the difference in strut pressures between the totals down each side of the truck; i.e. (LF + LR) - (RF + RR) Machine Pitch: or just Pitch, is the difference between the totals of strut pressures of both front wheels and both rear wheels; i.e. (LF + RF) - (LR + RR). By design, axle loading should generate rear strut pressures equal to approximately double front strut pressures. Composite strut pressures: Any of the Rack, Bias or Pitch pressures. 10/10/20 payload rule: The mean of the Payload distribution shall not be more than the Rated/Target Payload; no more than 10% of loads may exceed 1.1 times Rated/Target Payload, and no single load shall exceed 1.2 times Rated/Target Payload. Variations in 2-second interval - Frame twisting can be more severe than the overall value indicates if the rate of change is fast. Twisting over a longer time span will cause less distress than a quick reaction. Minimum strut pressure - Values as low as 1800 kPa are cause for concern as this is the approximate charging pressure of the suspension cylinder. A low pressure may indicate that the cylinder piston could be contacting the head. Axle split – Caterpillar trucks are designed to generate a distribution of approximating 33% front axle, 66% rear axle when loaded. Strut pressures in the table approximate this condition. Consistent operation outside this design level will cause a corresponding reduction to the life of the components listed previously, such as frame and suspension cylinders. Rolling Resistance This is described as the measure of force that must be overcome to roll or pull a wheel over the ground. Rolling resistance is effected by ground conditions and vehicle load. The deeper the wheel sinks into the ground the higher the resistance to motion. Effects on Components – Increase in fuel burn with high rolling resistance which inturn reduces engine life. Increased loads on final drives, wheel bearings, tyres and drive train to drive through high rolling resistances. Effects on Production – High rolling resistance increases haulage cycle times and operating costs due to elevated fuel burn rates and reduced production outputs. Super Elevation The purpose of superelevation is to maintain even pressure distribution over the machine suspension and safely maximise the speed of the truck through the radius of the corner. The recommendation of superelevation for a corner depends on the radius and the desired speed to negotiate. Superelevation is incorporated to minimise lateral tyre forces. FPO Application Guide

22 of 32

Version 11

Effects on Components – Too little superelevation increase loads to wheel bearings, steering components, chassis and suspension cylinders. Tyre wear will also increase with poor superelevation. Effects on Production – With negative or little superelevation production costs increase due to increased tyre wear, reduced safe operating speeds and increased cycle times, increase road maintenance due to spillage and gouging from tyres. With correct superelevation operator comfort in improved due to the reduce G-forces and reduced effort of negotiating the corner. Gradient The suggested grade for caterpillar trucks is the one that will keep the truck within second transmission gear. The estimation of such grade should consider a range for rolling resistance, which typically falls between 1.5% to 2.5%. Performance Handbook or FPC software may be used to evaluate these conditions. Effects on Components – Increased gradients increase fuel burn and brake wear, reduce transmission and drive train life due to higher energy shifts up ramps and higher energy braking when travelling down ramps loaded. Effects on Production – Increased fuel costs, increased cycle times, increased spillage requiring more clean up, tyre damage to trailing trucks from spillage and possible bunching of haul trucks if split fleets are working on the same ramp. Crossfall Crossfall is the difference in elevation between the road edges, used to drain water from the haul road. The recommended maximum Crossfall is 3% to allow water drainage [Guiachi, 1990]. Effects on Components – Too much Crossfall increases tyre wear, wheel bearing and final drive loads. Effects on Production – Too much Crossfall increased tyre costs and pending of road base could cause scoring or erosion. Too little Crossfall may causes excessive water accumulation on the Haul Road. Vertical Curves Vertical curves are the curves from the point of flat gradients to either descending or ascending ramps. For instance the top of the ramp and the bottom of the ramp. A general rule is a minimum of 100m of Sag radius and Crest Vertical Curve. Effects on Components – With sharp Vertical curves on the ascend to the ramp can cause harsh down shifts and heavy drive train loads. Horizontal Alignment This relates to switch backs, corners and intersections. The minimum radius of a horizontal curve for a given vehicle speed can be determined on the type of gradients and land available. Effects on Components – Tight sharp switch backs and corners cause severe loads on final drives and wheel bearing parts. Tyre wear increases as well. Heavier braking is required to negotiate sharp corners causing increased brake temperatures and reduced component life. Effects on Production – Increases in spillage can occur when both corners and superelevation is incorrect. This also adds loads and erosion to the road surface as well as increasing cycle times negotiating sharp corners.

FPO Application Guide

33 of 32

Version 11

1. Introduction This document builds upon data collected from ‘real-time’ TPMS, or 'data logger' VIMS files that have been analysed using the Fleet Productivity Optimisation (FPO) software program. It allows a quantitative assessment of haul road condition and its interrelationship with the truck. Such analysis can be used to develop improvement strategies, and to trend the effect of past actions and mining programs. Once data has been graphed using FPO, plots can be reviewed to determine whether individual, and/or composite strut pressures are exceeding ‘Management Limits’. It is then possible to identify opportunities for improvement of the haul cycle using a ’Haul Road Condition Index’. The Haul Road Condition Index is then combined with an assessment of Payload data, to establish a ‘Mine Severity Index’. Once an initial ‘index’ has been determined, continued regular analysis of haul road condition and Payload history can be scheduled to help identify areas in need of attention, and to maintain these improvements. Release of VIMS Supervisor has significantly improved a Project Manager‘s ability to analyse Payload data from a fleet of trucks, using the Fleet Payload Summary and Payload Management options. Conformance with CAT’s 10/10/20 Payload policy can quickly be determined. Application Severity Analysis (ASA) is the name for previous versions of FPO. It was found amongst ASA users that by assessing machine severity and reporting the associated values to the customer, it did not provide the correct language to explain to the Truck users how they can reduce the overall cost per ton with ASA. The name ASA was changed to FPO to highlight the opportunity this software provides to improve operating conditions and to create a win-win situation between Truck’s users and Maintenance people. In this new approach, FPO user would analyse where haul road defects are and how machine application can be improved , instead of rating machine severity alone. FPO is increasingly being used in MARC contracts with MARC contract rates conditional on Mine Severity Index ratings for Payload and Haul Road Condition indices. While this move is commendable and a logical extension of the FPO theory it should be remembered that the program was initially intended as a tool to help identify and address haul road design and maintenance issues in a constructive dealer/customer relationship rather than a punitive process. As a result of the push towards better management of MARC contracts there has been an increasing need to quantify Mine Severity ratings against expected increases (and decreases) in contract costs. At present there is nothing more to offer than general comment, as field data to relate these two factors is unavailable. Any data from sites that are in a position to correlate longer term operating costs against haul road conditions will be always welcomed.

FPO Application Guide

44 of 32

Version 11

2. General overview of a typical Haul Road 2.1.

Load Area & Pit Floor

Depending on environmental conditions, the loading tool, and support equipment available. The conditions in the loading area can vary dramatically. Compare the extremes in conditions on Figures 1 and 2. The condition shown in Figure 1 is a hard rock gold mine in Australia with very little rainfall. The second one shown in Figure 2 is an iron ore mine in southern Australia with poor material for building roads, higher rainfall, and environmental regulations that stipulate rainwater must be drained into the pit, not into a closeby river. Look at the floor conditions. What are the differences? Wet floors mean increased chance of tyre cuts. Rough floor conditions are uncomfortable for the operator and production is slowed. Cramped conditions mean truck exchange time is slowed along with production. What are some possible solutions? Change drainage or slope the pit floor to keep water away from the loading zone? Sheet the floor with rock or high-grade ore (if there is concern about ore dilution)? Is the support equipment being utilised effectively if nothing else is possible? Can the operator lock the truck in 1st gear to reduce the impact load on the truck? (Remember impact load is a function of vehicle weight and ground speed)

Figure 1 – Hard Rock Gold Mine pit floor conditions

FPO Application Guide

55 of 32

Version 11

Figure 2 – Iron Ore Mine pit floor conditions

2.2.

Main Haul Road

In some FPO traces, you may find the main haul road does not generate any composite strut pressure spikes outside the management or “limit” lines. However, consider the two primary road features that generate FPO spikes outside the management limits: Off camber corners cause weight transfer to the outside tyres and a bias spike. Use the Caterpillar Performance Handbook (Chapter 26) or table 1 to determine the correct superelevation for a given corner radius and desired travel speed. Table 1 – Superelevation in curves (Taken from Caterpillar Performance Handbook) Turn radius (m)

Truck Speed (kph) 16

24

32

40

48

56

64

72

15

13%

30%

-

-

-

-

-

-

30

7%

15%

27%

-

-

-

-

-

45

4%

10%

18%

28%

-

-

-

-

60

3%

8%

13%

21%

30%

-

-

-

90

2%

5%

9%

14%

20%

27%

-

-

150

1%

3%

5%

8%

12%

16%

21%

27%

200

1%

2%

4%

6%.

9%

12%

15%

19%

300

1%

2%

3%

4%

6%

8%

11%

14%

Potholes and other road defects can generate rack spikes if struck by a single wheel. Potholes should be ripped, filled, watered and compacted to repair them, and the road crown or Crossfall should be checked and repaired if necessary to reduce standing water on the road.

FPO Application Guide

66 of 32

Version 11

2.3.

Waste Dump

The waste dump is often a neglected section of the haul cycle. In addition, since dumps are generally flat, loaded trucks can accelerate to higher ground speeds and increase the magnitude of impact on major components. What can be done on waste dumps to improve machine application? Can we build a good quality single lane road most of the way across the dump so loaded trucks can travel quickly to the tip head? Can we sheet the floor with rock? Or even high-grade ore if the customer is concerned about ore dilution? Are operators braking parallel to the tip head, THEN turning to reverse back, or are they generating large bias spikes and frame stresses by conducting high speed turns? Is the support equipment being utilised effectively to minimise the impact of the dump area? Can the operator lock the truck in 1st gear to reduce the impact loading on the truck?

FPO Application Guide

77 of 32

Version 11

3. Guidelines for collecting representative haul road cycle data The following steps provide a guideline to capture representative data, which will maximise the accuracy of sampled haul road condition the machines are experiencing, and importantly, customer credibility will be established and maintained. Ensure the chosen truck to collect the sample data has correct suspension cylinder oil and nitrogen charge, and is considered to be performing normally (i.e.. power, ride, shift points, etc.). All suspension cylinders should be completely discharged, and then recharged with oil, then nitrogen at least once every 12 months or 6000 hours. The condition of the grease relief fitting in front struts is assessed regularly to ensure it is not becoming blocked, as grease can be forced into the oil/nitrogen space if it blocks. There should be small amounts of grease present at the fittings in normal operation. When taking real-time TPMS data, be sure to set the Real Time Log Delay to one (1) second intervals. The FPO program will not accept data if taken at any other time intervals. Be sure that recordings of the haul cycle are truly representative of a typical haul. To ensure this, observe several load cycles before collecting data, and ride with the operator a time or two. When feel comfortable for the cycle, set the recorder (TPMS or VIMS Data Logger) running as the truck waits in the queue about to drive under the loader, then, once loaded, follow along behind in a light vehicle to observe that the truck: o has a typical payload, both in tonnage and load position (i.e. no significant BIAS) o is not obstructed by a grader, or another machine stopped on the haul road o is operated as normal, and is not ‘babied’ just because you are watching Drive the complete haul cycle in a light vehicle and record ‘features’ that may influence the cycle, and their distance from the loading zero point. By recording this haul road features, a better interpretation of FPO data would be done when analysed. Time and distance from the loading zone can be written down using a stopwatch and the pick-up truck’s odometer. It is advisable to record features such as: o the beginning and end of the Loading and Dump zones o the location of all significant corners, curves and switchbacks o the beginning and end of haul road grade changes o any speed restriction zones or Stop / Give Way signs o any road sections with one-way traffic restrictions o any significant humps, gutters, wash-aways, or rough road sections

FPO Application Guide

88 of 32

Version 11

4. Composite Pressure Limits 4.1.

Background

For some time Caterpillar, Dealers, Decatur CMT and several other Caterpillar subsidiaries have been collecting strut pressure data from various mine operations and comparing FPO graphical information with known product performance, component life and actual observations of haul road conditions. Analysis of this data suggests that a direct relationship exists between racking of the machine frame over time, and damage to the frame and other machine components; final drive & wheel bearing components, tyres & rims, steering ball studs, ‘A’ frame bearings, etc. Additional studies have been undertaken regarding haul road assessment and truck interaction on different types of road surfaces. Outstanding work was done by the following authors: Assessment of soft ground roads by using strut pressures and vertical acceleration [Joseph, 2003; Joseph, T.G. and Sharif-Abadi 2003]. Designing and managing haul roads for 300+ tonne trucks for optimal performance [Thompson, R. J. and Visser, A. T. 2002]. Behaviour of OHT pitch on haul roads [Prem and Dickerson, 1992]. Analysis of composite pressure limits for Machine Rack and Bias [Trombley, 2001; and Wohlgemuth, 1997]. There are other factors such as PITCH and BIAS (as a result of poor loading techniques and due to cornering at speed without adequate super-elevation) and the rate of change of strut pressures adversely affects the service life obtained from these components.

4.2.

Composite pressure limit values

From the experience gained by Caterpillar and other authors listed in the previous section, a table of composite pressure limits were established. These limits are intended to promote objective and consistent assessment of haul road conditions and to counter the level of subjectivity that exists when haul roads are reviewed. Studies have been done in the design of haul roads (see for example [Giacchi, 1990], but few studies have been made in proactive haul road maintenance (i.e. Planning and scheduling maintenance in haul roads) for trucks of over 300 tonnes GMW. The proposed composite pressure limits attempt to locate and quantify haul road defects that may be reducing mine productivity. It also attempts to facilitate tasks such as: Creation and scheduling of backlogs associated with haul road pending repair jobs Programmed maintenance (PM) practices for haul road networks throughout the year Develop haul road condition monitoring strategies for haul roads. Values of composite pressures included in table 2 for models 785 to 797 are the result of considerable experience, but we recommend values for trucks smaller than 777 be evaluated and applied carefully. CAT Global Mining welcome comment on the validity of sub-777 and recently developed parameter values and Management Limits for the 797 truck.

FPO Application Guide

99 of 32

Version 11

Table 2 – Composite pressure limits for Caterpillar OHT (Pressures in kPa) Parameter

769 - 777 Management limit

785

789 - 793

797

± 6000

± 8000

± 8500

± 12500

Warning limit

± 10000

± 12000

± 12000

± 16500

Action limit

± 14000

± 16000

± 16000

± 20000

Bias (loading stationary truck)

± 3000

± 3000

± 4000

± 5500

Max. variation in 2 sec interval

± 5500

± 7000

± 8000

± 12000

± 12000

± 14000

± 14000

± 22700

Rack and Bias (Moving truck)

Maximum Strut Pressure

The Management, Warning and Action limits shown above are used in assessing dynamic machine loading situations, as measured using ‘real time’ TPMS or VIMS Data Logger data taken during the ‘Travelling Loaded’, and ‘Travelling Empty’ cycles. Loading stationary truck Bias pressure limit is to be used during the loading phase. By assigning limit values to composite pressure graphs during plotting and printing, control charts can be easily generated to assess and analyse machine and haul road performance. It is important to note that the Haul Road Condition Index shown in the next section used to rate a particular haul road cycle are not absolute numbers, but are intended to establish criteria that help indicate where the opportunities for improvement are. They have been developed by comparing practical field data with historical component life data on many mine sites around the world. It is also advisable to use these limits in conjunction to RAC FELA numbers to provide a holistic assessment of the haul road/truck interaction. Refer to RAC Application Guide for more information.

FPO Application Guide

1010 of 32

Version 11

5. Mine Severity Index Haul Road Condition index and Payload Distribution index are used to estimate the Mine Severity Index of the haul road under consideration.

5.1.

Haul Road Condition index

Once suspension cylinder pressure data has been assessed using the limits shown in Table 2, a Haul Road Condition (HRC) index can be assigned to rate the condition of the haul road. HRC index uses data from the composite pressures control chart of the FPO analysis, and looks at peak values, or spikes in Machine Rack and Machine Bias pressure traces that exceed management, warning and action limits. Table 3a – HRC index logic table number 1 Rating 1 2 3 4 5 6 7 8 9 10

Spikes > ML 0 1 or 2 3 or 4 5 or 6 7 or 8 9 - 10 11 - 13 14 - 16 17 - 19 20

AND AND AND AND AND AND AND AND AND AND

Spikes > WL 0 0 0 0 0 0 0 0 0 0

AND AND AND AND AND AND AND AND AND AND

Spikes > AL 0 0 0 0 0 0 0 0 0 0

Table 3b – HRC index logic table number 2 Rating 1 2 3 4 5 6 7 8 9 10

Spikes > ML

Spikes > WL 1 2 3 4, 5 or 6 7, 8 or 9 10, 11 or 12 13, 14 or 15 16, 17 or 18 19

Spikes > AL AND AND AND AND AND AND AND AND AND

0 0 0 0 0 0 0 0 0

Table 3c – HRC index logic table number 3 Rating 1 2 3 4 5 6 7 8 9 10

Spikes > ML

Spikes > WL

Spikes > AL

1, 2 or 3 4, 5 or 6 7

Table 3a, 3b and 3c were developed to provide a coherent definition of HRC index under all of the possible combinations of peaks and pressures. The logic structure presented in tables 3a, 3b FPO Application Guide

1111 of 32

Version 11

and 3c is more suitable to be translated in computer language than previous versions and is therefore more easily incorporated in FPO. Cells shown in grey are not considered during calculation of rating when other logic events take place. ML, WL, and AL represent Management, Warning and Action Limits respectively. Table 3a covers conditions where composite pressures exceed ML but there are no spikes exceeding WL and AL. If one or more of the spikes exceed WL but none exceed the AL, table 3b should be also considered. When composite pressure spikes exceed AL, table 3c must also be used. The HRC index should be evaluated for each of tables 3a, 3b and 3c. The HRC index will be the highest index obtained from each of the tables individually. Table 4 provides examples of how table 3a, 3b and 3c can be used when composite strut pressure is given. Table 4 – Examples of Haul Road Condition (HRC) Index evaluation Condition

Rating value

Rating yielded by

There are only 6 spikes over ML, no WL, no AL

4

Table 3a

10 spikes over ML and 1 over WL, no AL

6

Table 3a

13 over ML, 16 over WL, and 1 over AL

9

Table 3b

12 spikes over ML, 3 over WL and 1 over AL

8

Table 3c

There are only 4 spikes over AL

9

Table 3c

FPO Application Guide

1212 of 32

Version 11

5.2.

Payload Distribution index

An index value can be assigned to Payload Monitor Summary data (through either TPMS or VIMS) in the same way. The index is called Payload Distribution (PLD) index, and it is based on Caterpillar's 10/10/20 Payload Rule. PLD index is generated using a similar logical approach than HRC index (Table 5). PLD index uses the two payload limits described in 10/10/20 rule. Table 5 – PLD index ratings Rating Conditions A

100% of loads less than 110% of Rated Payload.

B

95% of loads less than 110% of Rated Payload, and none exceeding 120%.

C

90% of loads less than 110% of Rated Payload and none exceeding 120%.

D

85% of loads less than 110% of Rated Payload and none exceeding 120%.

E

80% of loads less than 110% of Rated and/or up to 2% of loads exceeding 120%.

F

75% of loads less than 110% of Rated and/or up to 5% of loads exceeding 120%.

G

70% of loads less than 110% of Rated and/or up to 10% of loads exceeding 120%.

H

65% of loads less than 110% of Rated and/or up to 15% of loads exceeding 120%.

I

60% of loads less than 110% of Rated and/or up to 20% of loads exceeding 120%.

J

55% of loads less than 110% of Rated and/or 20+ % of loads exceeding 120%.

It is highly advisable to evaluate the PLD index using VIMS payload data of the chosen truck only (not the whole fleet) of the previously used FPO sample record, i.e. weekly fortnightly or monthly.

FPO Application Guide

1313 of 32

Version 11

5.3.

Mine Severity Index estimation

The concept of a Mine Severity Index (MSI) acknowledges the fact that machine application severity is related to both haul road condition, and machine payload. Previously, both parameters have been rated on a scale from 1 to 10. HRC and PLD indexes are then compared together to generate the Mine Severity Index (MSI). To avoid confusion when reporting the Mine Severity Index (eg. when entering values into SIMS), the PLD index scale has been changed to a letter scale, i.e. A to J. It is the intent of the analysis to establish a baseline index of the current haul cycle, then to reassess conditions at regular intervals to identify, and rectify areas of the haul road causing significant machine stresses. Feedback of this data to a customer’s Mine Planning and Haul Road Maintenance departments has proven to be a constructive way of improving both haul road condition, Payload management, and also in: Reducing operating costs through extending component life (for customers and sites under dealer MARC contracts). Improving productivity (through increased average road speed and reduced cycle times). Reduced fuel consumption through reduced rolling resistance. Improving operator comfort and safety (through reduced effort and the onset of fatigue). Proving the value to the customer of the Caterpillar / Dealer value chain. In order to remain within design and Gross Vehicle Weight parameters, PLD index should not exceed a Rating of C. Similarly, HRC index should not exceed a Rating of 5. Therefore, the highest acceptable MSI would be C5, being the combination of these two Rating numbers. J I

PAYLOAD INDEX

H G

UNACCEPTABLE RANGE

F E D C B A

ACCEPTABLE RANGE 1

2

3

4

5

X

6

7

8

9

10

HAUL ROAD CONDITION INDEX Figure 3 - MSI Rating map This may be represented graphically, as shown in Figure 3. Using the graphical method shown in Figure 3 has proven to be a very useful way to illustrate current Payload management and Haul road conditions to mine management. Using green in the FPO Application Guide

1414 of 32

Version 11

‘Acceptable Range’ area, red in the ‘Unacceptable Range’ and placing a yellow ‘X’ to show the current site conditions allows easy identification of current haul road and machine application situation. In the example shown in Figure 3, a MSI of C6 has been added, showing that Payload is being managed within Caterpillar’s 10/10/20 payload rule, but haul road conditions are in need of attention to bring the HRC index back into the acceptable range.

5.4.

MARC rates estimation using MSI data

Figure 4 – Haul Road and Payload distribution sensitivities concept Two new parameters can be defined to show the influence on Haul Roads and Payload distribution in MARC associated costs: Payload distribution sensitivity (SPL) SPL is the estimated percentage of additional cost MARC rates will increase when trucks are overloaded while haul roads are in good conditions. In other words, it is evaluated under the following conditions: Payload distribution rated as maximum “J” Haul road index rated as “5”, which correspond to an acceptable level.

FPO Application Guide

1515 of 32

Version 11

Haul Road sensitivity (SHR) It is the estimated percentage by which MARC rates would increase if trucks were experiencing the poorest haul road conditions at a normal payload distribution. In other words: Haul road index rated as maximum “10” Payload distribution rated as “C”, which correspond to an acceptable level. SPL and SHR define two lines that can be integrated to generate a surface for the whole range of HRC and PLD indexes combinations (Figure 5).

Figure 5 – A surface is generated from the two lines defined by SPL and SHR If the PLD index is changed to a numeric scale, such that: A=1 ; and C=3 ; and J=10 then the equation for the plane generated would be: z

1 1 S HR ( x) S PL (y) - S HR 7 5

3 S PL 7

…………… (Eq. 1)

where, x: Haul Road Condition index y: Payload Distribution index z: resulting MARC rate increment axis Equation 1 can then be integrated back in the MSI rating map (Figure 3). Tables 6 provides an examples, where: SPL=17 and SHR=10 Both lines shown in Figure 5 are highlighted in this table. FPO Application Guide

1616 of 32

Version 11

Payload Distribution Index

Table 6 – MARC rates variations using a planar distribution. SPL=17 and SHR=10. J = 10

9

11

13

15

17

19

21

23

25

27

I =

9

7

9

11

13

15

17

19

21

23

25

H=

8

4

6

8

10

12

14

16

18

20

22

G=

7

2

4

6

8

10

12

14

16

18

20

F=

6

-1

1

3

5

7

9

11

13

15

17

E=

5

-3

-1

1

3

5

7

9

11

13

15

D=

4

-6

-4

-2

0

2

4

6

8

10

12

C=

3

-8

-6

-4

-2

0

2

4

6

8

10

B=

2

-10

-8

-6

-4

-2

0

2

4

6

8

A=

1

-13

-11

-9

-7

-5

-3

-1

1

3

5

1

2

3

4

5

6

7

8

9

10

Haul Road Condition index

Notice that negative values of SPL and SHR can also be used; for example when contract availability would be plotted instead of MARC rates. This approach facilitates how the map shown in Table 6 can be generated. There are only two values needed to generate the whole set of values for a given MSI map. What it does not provide are both Payload distribution and Haul road sensitivities, which must be estimated according to each particular mining operation.

FPO Application Guide

1717 of 32

Version 11

6. Machine performance and haul road assessment using control charts The most important factor is being familiar with the site’s haul roads. In particular, it is important to be aware of the site conditions during the data logger run that was used in order to generate a verbal or written description of the features on the haul road that are generating spikes on the FPO control charts. FPO generates a number of control charts for a variety of purposes, which are described in the FPO User Manual. It is very difficult to provide suggestions for machine application improvement while the truck is travelling empty. Impact loads on trucks due to poor road conditions are the result of vehicle weight and ground speed. Therefore, many of the FPO control charts used in this section comprise machine loaded. Many studies have been previously done using control charts to manage engineering processes, for example [Oakland, 2003]. The following sections analyse FPO control charts and their application to optimise machine application. It is highly recommended to use this section in conjunction to the FPO User Manual.

6.1.

Speeds on curves and superelevation

Switchbacks can be identified using FPO by looking at Bias and Rack values. The relationship between Rack and Bias when a lateral force is applied to the truck can be estimated using the following methodology. Machine Bias attempts to evaluate force reaction induced by lateral forces. Figure 6 illustrates typical forces on a truck when a lateral force is applied; for example when the truck is bouncing side ways or when cornering.

Figure 6 –Forces on an OHT when bouncing transversely (Front view) FPO Application Guide

1818 of 32

Version 11

The following expressions are then found from Figure 6:

RR

W …………………….………. (Eq. 8)

RL

RR

L

F H

RL

L ………..…………….. (Eq. 9)

Combining equations 8 and 9: RR

W H F …………………………. (Eq. 10) 2 2L

RL

W H F …………………………. (Eq. 11) 2 2L

Notice that reactions RL and RR vary in the same proportion when a lateral force “F” is applied. The second term at the right side of equations 10 and 11 adds and subtracts the same magnitude when the truck is bouncing or cornering. Given that Bias is the difference between left and right strut pressures, Bias will be direct proportionally to the difference RL-RR, therefore: Machine Bias

RL

RR

H L

F …………………… (Eq. 12)

Equation 12 shows a linear relationship between any lateral force and Machine Bias values for small amounts of truck bouncing. Therefore, it would be expected to observe symmetrical positive and negative values of Bias in the control charts when the truck has no payload imbalance and bounces sideways or negotiates a corner.

Figure 7 – Rack forces on an OHT under normal payload distribution If payload imbalance is introduced, the first term at the right side of equations 10 and 11 (i.e. W ), will decrease in one and increase in the other, causing machine Bias to fluctuate 2 symmetrically about a non zero pressure value. Machine Rack is also close related to Bias variations, when the truck bounces sideways or during cornering. FPO Application Guide

1919 of 32

Version 11

Figure 7 shows a top view (figure on the left) and left side view (figure on the right) of an OHT, where reaction forces are illustrated. Lets assume that the longitudinal weight distribution is twice on the rear axle than on the front, then:

FPO Application Guide

2121 of 32

Version 11

Machine Bias

1 RL

2 RL

1 RR 3 (RL

2 RR

………..……….. (Eq.13)

RR ) …………….…… (Eq. 14)

Similarly, Machine Rack

(1 RL 1 (RL

2 RR ) (1 RR

2 RL ) ……… (Eq. 15)

RR ) …………………………… (Eq. 16)

Equations 14 and 16 comprise the common factor (RL

RR ) . Notice that Bias and Rack from

these equations always have opposed signs and Bias magnitude will be three times more than Rack.

Figure 8 – Rack and Bias relationship Therefore, it would be expected that Rack and Bias traces would have opposed signs when the truck bounces sideways or turns a corner, assuming that: Truck has a weight distribution of one-third at the front and two-thirds at the rear There is no longitudinal acceleration Slight forces are introduced to unbalance the truck transversely. Equations 14 and 16 are plotted in figure 8 using the parameter (RL the lineal relationship of both magnitudes. FPO Application Guide

2020 of 32

RR ) at the x-axis to show

Version 11

Figure 9 illustrates Rack and Bias relationships with an example. Notice the mirror-shape of both traces, where Bias (blue trace) magnitude is mostly higher than Rack (green trace) at the peaks.

Figure 9 – Example of Rack and Bias relationship. Notice the Rack and Bias mirror-shape The current analysis shows the behaviour of Rack and Bias pressure traces for an OHT when slightly bouncing or cornering. In order to identify in which case the truck is turning, we need to use additional data from VIMS regarding rear wheel speed.

Figure 10 – OHT rear wheel speeds when turning Figure 10 shows the relationship between left and right rear wheel speeds on a truck when turning about an instantaneous circle. The two vertical vectors shown in Figure 10 represent the instantaneous displacement of each individual wheel around the associated center of rotation, where: R: FPO Application Guide

Turning circle radius around the instantaneous center of rotation 2121 of 32

Version 11

e:

Truck tyre tread distance

T:

Instantaneous time

WR, WL:

Right and Left wheel speeds respectively

From Figure 10: T WR R

T WL …………………..……. (Eq. 17) R-e

Therefore: Instant. turning diameter

2 R

2 e

WR W R - WL

…….… (Eq. 18)

Equation 18 provides the instantaneous turning diameter based on truck tyre tread distance and wheel speed. Notice that the turning diameter will be infinite when the truck follows a straight line so both left and right wheel speeds are the same. Minimum turning diameter (2R) and tyre tread distance (e) can be found in the Performance Handbook. Values for OHT are listed in table 7: Table 7 – Values of Minimum turning diameter and tyre tread distance for OHT 769D/

773E/

777D

785C

789C

793C 797B

771D

775E

Machine clearance turning circle (m)

20.3

23.8

28.4

30.5

30.2

32.4

42.1

Front tyre tread (m)

3.10

3.28

4.17

4.85

5.43

5.61

6.51

Using the front tyre tread from Table 7 as ‘e’ in equation 18 and rear wheel speeds as WL and WR in equation 18, the instant turning diameter can be evaluated for different truck conditions. Wheel speeds need to be exported from VIMS database. Figure 11 shows the screen on VIMSpc from which data can be exported. Speed data can then be saved in a spreadsheet to integrate equation 18. Figure 12 shows an example of how VIMS data can be manipulated in this manner. Wheel speed differential is the arithmetic difference between left and right rear wheel speeds. When this value is plotted in conjunction with Bias and Rack, the following events can be determined: Traction loss (Wheel spin): Rack and Bias follows the predicted relationship of equation 14 and 16 near to zero, but the wheel differential show high values. Switchbacks: Rack and Bias show big spikes with opposed signs, and wheel differential speed also show high values, either positive or negative.

FPO Application Guide

2222 of 32

Version 11

Figure 11 – Exporting wheel and ground speed from VIMSpc

Figure 12 – Calculated data from VIMSpc used to assess traction loss and switchbacks

FPO Application Guide

2323 of 32

Version 11

Figure 13 – Example of traction loss effects on OHT Figure 13 shows an example of traction loss found by using this methodology. Severity of traction loss can be evaluated easily by looking at the blue trace and its location on the haul road. Traction loss has a direct impact in tyre life, and can be corrected when the areas where tyre slippage occurs are identified and fixed. The truck’s Traction Control module will apply individual right or left parking brakes to the wheel that is rotating at higher speed when the ratio between both speeds is higher than 1.6 and the truck travels slower than 19 kph.

Figure 14 – Typical traces of truck bouncing and switchbacks On the other hand, when wheel speed differential stays close to zero, Bias and Rack follow the predicted relationship given by equations 14 and 16 within management limits, it is most likely that the truck is just bouncing within limits, as shown on the left marked area of figure 14. When there is a significant difference between wheel speeds followed by Bias and Rack peaks, it is most like that the truck is turning as shown on the right marked area of figure 14, which has FPO Application Guide

2424 of 32

Version 11

been expanded for analysis in figure 15. A table showing calculated values has been added to indicate the instantaneous turning circle values, as given by equation 18.

Figure 15 – Instantaneous turning circle diameter estimation on switchbacks The minimum turning diameter in the example shown in Figure 15 is 79 meters when the truck is travelling at a ground speed of 20.5 kph. By interpolating Table 1 values, it can be found that for a curve of 79 meter radius and when the truck is travelling at 20.5 kph, a superelevation of 4.5% is recommended. This can then be compared with the actual superelevation for that particular curve. If the actual superelevation is higher than 4.5% for this example, the superelevation should be reduced in that particular curve until the Bias and Rack traces approach the management limits. FPO Application Guide

2525 of 32

Version 11

6.2.

Manoeuvring in dump areas

In some application trucks require significant manoeuvring at the dump area because the: Dump area is too small for the truck size There is a number of support equipment working in the area Poor operating skills of the truck operator The methodology described in the previous section can be used to assess machine application at the dump area to estimated the minimum turning circle diameter and compare it with values shown in table 7. Figure 16 shows an example where Bias and Rack traces show elevated values (spikes) while the truck is travelling loaded at low speed.

Figure 16 – Example of heavily manoeuvred truck at the dump area The trace shows the effect of brake application in both Bias and Rack traces. Ground speed drops from 8 kph to 5 kph creating a peculiar trace signature that is reflected in Bias and Rack. Using the methodology explained in the previous section, turning circle diameter can be estimated for this example. Resulting values are shown in table 8

FPO Application Guide

2626 of 32

Version 11

Table 8 – Calculated values of identified curves in figure 16 Parameter

Curve location – meters from loading equipment 345m

368m

383m

5:14:01 am

5:14:13 am

5:14:26 am

Left

Right

Left

Ground Speed (kph)

12

8

5

Turning circle diameter (m)

56

-43

28

Time Direction

Important parameters to assess machine application in the dump area are time between curves, ground speed and turning circle diameter. From Table 8, it can be seen that the operator switched from a curve of –43m (right turn) to the 28m turning circle diameters in less than 15 seconds. The severity of the combination of these hard right to left turn can be assessed by comparing the time taken with steering cycle times from the SIS, which falls between 7 to 9 seconds. It can be seen that in the last two curves, the operator needs to turn from right to left in around 13 seconds, which might be consider as a hard turn. It may also indicate a safety hazards and machine abuse. In addition, it was also observed that the operator applied the brakes while turning hard at the same time. Both events (hard turn and brakes) contribute to build up RACK and BIAS spikes seen in this example.

6.3.

Gear selection

Gear selection is done automatically at the truck by the electronic transmission control according to machine speed and other machine operational conditions. The operator can limit the maximum transmission gear using the shift lever located in the cab, for example to prevent transmission hunting. Detailed information can be found in the associated service manual. The selection of the correct gear shift to machine application provides the following advantages: Extends transmission life by decreasing then number of transmission shifts Optimise truck productivity when severe transmission hunting is observed FPO provides a control chart showing actual gear and machine speed vs. haul distance, which can be used to quickly evaluate if machine operation can be improved by limiting gears or selecting the right gear at the right place in a particular haul road. If a more detailed analysis is needed, Performance Handbook and FPC software would be needed. Rimpull curves can be found in the Performance Handbook for each model of the OHT. Figure 17 illustrates Rimpull characteristics for 793C, where ground speeds for each of the six transmission gears are shown. There is a ground speed overlap region for each gear change as shown in figure 17, where transmission hunting could be observed under some particular machine operational conditions. There are six combinations of total resistance (grade plus rolling resistance) and machine gross weight that induce transmission hunting in these regions. The combination for an 8% of total resistance and MGW of 383 ton is shown in Figure 17 (red arrows) as an example. Notice that at this point the transmission will be changing from 2nd to 3rd gear (hunting). This condition may be eliminated by: Decrease rolling resistance Modify or smooth ramp grade Limit gear selection to 2nd gear FPO Application Guide

2727 of 32

Version 11

Table 9 provides the full list of machine operational combinations that will induce transmission hunting to a 793C. Table 9 – Transmission hunting conditions (Taken from CAT Performance Handbook) Hunting condition

Gross Weight (kg)

Speed (kph)

Total Resistance (Grade + Rolling Resistance in %)

1st TC and 1st DD

383 727

8

15

1st DD and 2nd

383 727

12

11

2nd and 3rd

383 727

16

8

3rd and 4th

383 727

21

6

4th and 5th

383 727

27

4.5

5th and 6th

383 727

37

3.5

In order to analyse if the impact on machine productivity by limiting gear shifts, FPC should be used. The haul road details, such as grades and distances, can then be defined using FPC. The haul road can be segmented in accordance with (Figure 18): Distance of the segment (meters) Rolling resistance (%) Grade (%) It is highly advisable to use FPC and Rimpull curves to make the decision whether it would be better to limit the transmission to the lowest gear and therefore elimination transmission hunting. The overall performance can be assessed in terms of increased cycle time and associated cost per tonne.

FPO Application Guide

2828 of 32

Version 11

Figure 17 – 793C Rimpull-Speed-Gradeability curves (Performance Handbook, edition 34)

Figure 18 – Haul road simulation using FPC. Speed limit and rolling resistance can be defined at each haul road segment. FPO Application Guide

2929 of 32

Version 11

6.4.

Crossfall

The purpose of the Crossfall is to drain water from the haul road. However, there are some applications where the Crossfall angle is too high may induce higher pressure values to one side of the truck than the other side (Figure 17).

Figure 17 – Effects of Crossfall in pressure readings Bias and Rack will be affected under this condition, because even that the payload mass is centred in the truck’s body there will be positive or negative Machine Bias trace consistently along the haul road under these circumstances. Figure 18 shows an example from a mine site where the Crossfall is excessive causing a considerable positive pressure offset on machine Rack and negative pressure offset on machine Bias.

Figure 18 – Example of high Crossfall angle Both Machine Bias and Rack have clear negative and positive trends. Notice the number of spikes out of the Management Limits caused by the induced Crossfall pressure offset. HRC index for this Haul Road is 10, because the excessive Crossfall.

FPO Application Guide

3030 of 32

Version 11

7. Acknowledgements This document should be used in conjunction with the Fleet Productivity Optimisation (FPO) Program and Users Guide, and the document “Assessing the effects of a mine profile on the performance of Off-Highway Trucks”, by Denis Mills. Assistance is gratefully acknowledged from Denis Mills, Keith Williams, John Saban, Jason Price, Geoff Perich and Jim Davey for their work in developing the Management Limits, and creating useable information from extensive information of VIMS dataloggers, and real-time TPMS data.

8. References [1]. Joseph, T.G., “Large Mobile Mining Equipment Operating On Soft Ground”, 18th International Mining Congress and Exhibition of Turkey, IMCET (2003), pp 143-147. [2]. Joseph, T.G.; and Sharif-Abadi, A.D., “Large haul truck strut pressures in soft and firm ground conditions”, Mining Industry Conference & Exhibition, Montreal (2003). [3]. Thompson, R. J.; and Visser, A. T., “An integrated Haul Road Design System to Reduce Cost per Tonne Hauled”, World Mining Equipment Haulage 2002 Conference, Tucson, Az., USA., 19-22 May (2002). [4]. Prem, H; and Dickerson, A.W., “A study of steady state roll-response of a large rear-dump mining truck”, SAE International Off-Highway and Powerplant Congress and Exposition (1992), Document number 921735. [5]. Trombley, N., “Vital Information Management System”, Co-Op work term presentation at Syncrude (2001). [6]. Wohlgemuth, P., “Structural fatigue Cracking trends”, M.Eng. Thesis, University of Alberta (1997). [7]. Giacchi, A., F., “Guidelines to the Design, Construction and Maintenance of Haul Roads”, Caterpillar of Australia Pty Ltd publication (1990). [8]. Oakland, J.S., “Statistical Process Control”, Fifth Edition. ISBN 0 7506 5766 9.

Butterworth-Heinemann (2003),

[9]. Caterpillar Inc., “Performance Handbook – Edition 34” Caterpillar Inc., Peoria Illinois, USA. SEBD0344 (2003).

FPO Application Guide

3131 of 32

Version 11

Appendices Table 10 - Document Change Chronology V2 – 14 Oct 99

Expanded to include the introduction of VIMSpc99

V3 – 26 Apr 00

Improved explanation of Management Limits Expanded Management Limits into smaller OHT models

V4 - 19 Jan 01

Corrected 10/10/20 policy, clarity of Mine Severity Index limit

V5 – 20 Jun 01

Mine Severity Index changed to include alpha characters in Payload Index Data export procedures changed to delete VIMS 2.4X references and include data export from pre & post V2.0.3 versions of VIMSpc99 Expanded Management Limits, and export procedures for 797 truck

V6 – 19 Nov 01

Modified to include the introduction of VIMSpc2001 & VIMS Supervisor, and to clarify 10/10/20 Payload Rule range definitions

V7 - 26 Apr 02

Modified to include exporting from VIMSpc2001

V8 – 16 Oct 02

Modified to correct export parameter detail [need Engine Speed, not Engine Load] and to include release of VIMSpc2002

V9 – 28 Mar 03

Modified to include revised Haul Road Condition Index Rating criteria Inclusion of data collected using TPMpc and notes covering use of ASA in MARC management Significant Pressure criteria and clarification of Composite Strut Pressure trace interpretation

V9b – 25 Jun 03

Modified to correct 797 pressure value typo in Haul road Condition Index note

V10 – 23 Oct 03

Modified to include the use of RAC FELA data

V11 – 26 Nov 04

New software version: PFO V1.5 New logic tables to assess Haul Road condition index References from other authors included Analysis of MARC rates planar distribution Analysis of switchbacks, gear selection, wheel spin, and Crossfall using FPO RAC FELA data extracted to another separate document

For comments, questions or errors, please contact: Matt McLeod Regional Equipment Management Consultant CAT Global Mining Asia Pacific [email protected]

FPO Application Guide

3232 of 32

Oscar Villalobos Equipment Management Consultant CAT Global Mining Asia Pacific [email protected]

Version 11