2. Consistently and without overloading / damage
3. How to minimize hauler / loader cycle time
4. What loading equipment is the best under the circumstances?
Load Size : Issues
1. Minimize under / over load conditions
2. Bucket / box volume to reflect material properties
3. Loading/hauling equipment match is important
Correct and Incorrect
Basic Considerations
1. We loose money if we underload:
a. Capacity paid for is not utilized
b. Resources involved are underutilized
c. Incremental production increase directly affects profits
2. We (likely) loose money if we overload:
a. Mechanical / structural failures result in
b. Downtime - production loss
c. Added repair cost
Volumetric Load
1. Struck vs. heaped capacity
a. bucket/box volume
b. standard definition SAE, others
c. heap defined by material
d. we always carry a “heap”
2. We always load “by volume”
a. no easy & reliable means to determine load
b. exception: truck load weighing system??
3. We need to make sure that the volumetric load matches the weight carrying capacity
How Much Load Does the Bucket / Box Carry ?
1. The load carried is the product of:
a. Volume carried and
b. Material density
2. We need to know both
a. Volume of heap is a site-specific value determined
* By material angle of repose / surcharge
* Loading practice
b. Material density is a site specific value
* Material type & properties
* Degree of fragmentation
Site Specific Factors
1. Angle of surcharge (not: a. of repose)
a. Differs between various materials
b. Need to be defined to facilitate definition of the actual heap size
c. May change the volume carried by up to 30 - 40%
d. Always load eq’t up to (near) full volumetric capacity
2. Material density
a. We carry volume, but truck is designed to carry a specified load
b. Load carried is a function of:
* Carried volume
* Material density
c. We need to make sure that the load is:
* Below the limit specified for a unit
* Close to nominal
How Do We Control the Load ?
1. Customize bucket / box volume.
a. To fit material properties.
b. To fit vehicle payload.
2. Assure optimum loading equipment match.
3. Control the loading operation.
a. Use weight measuring systems.
b. Train shovel / truck operators.
c. Secure good working conditions in loading areas: light, floors, etc.
So What Is the Actual Load ?
1. The actual load is a random variable
a. Variations of bucket fill factor
b. Variations of material density/swell
c. Other variables
2. To optimize load we need:
a. To assure that the average load is close to the nominal one
b. To minimize the load variability
c. To assure that no severe overload takes place
Theory and Practice
Overloading ??
Compare : More payload delivered for each cycle versus :
1. Slower speed - quantifiable
a. Especially so on uphill ramps
b. Thus less cycles per hour
2. More wear and tear – difficult to quantify
a. More wear & tear, thus maintenance
b. Lower mechanical availability
3. May increase loading time - quanitfiable
a. Thus longer cycle time / less cycles
This is a site & equipment specific decision
“The business is to make money”
CAT 10/10/20 Rule
It is acceptable :
1. For 10% of loads
2. To exceed Rated Payload by 10%
3. With no loads to exceed Rated Payload by 20%
Note: use statistics to define control limits and loading strategy
What Box Do We Need ?
Box/body/bowl/tray
1. Is Standard Box Good Enough?
2. Do We Need a Custom Designed One?
Choose a “Standard” box ? CAT 793 Example
Lightweight Boxes For Trucks
1. Increased payload potential
a. Lighter box means more lo
2. Unique set of engineering, design and construction problems
a. Careful loading, thus longer loading time
b. Shorter life of liners / beds, thus more maintenance & cost
Lightweight Boxes
1. High strength steel boxes
a. First bucket load to be placed carefully
b. No load at the front headache rack
c. Problems with exhaust-heated boxes?
d. Life of liners?
2. Rubber-like material (example: Skega)
a. Abrasion vs. wear & tear
b. Durability / life
Example: Lone Tree Mine, NV (After Evatz & Mills, SME 01-83)
1. Westech Inc. high-strength steel boxes on 785 trucks (ULW for ultra light weight)
2. TPMS system adjustment philosophy
a. Introduced at the same time
b. Use 10/10/20 CAT rule
3. Average load increased from 138 to 150 tonnes for 8.5% improvement
4. Payback in 2.4 years (at 9% discount rate)
5. Could have been up to 13% but for 2. above.
Do You Need a Tailgate? A Customized Box ?
Komatsu 930E in a Wyoming coal mine
Matching the Truck & Material
Watch the Center of Gravity !!
Truck Wieghtometers
1. The system: automatic load weighing & display to communicate with the shovel
2. Lights are of help :
a. Green light - load.
b. Amber light - one more bucket.
c. Red light - no more.
3. How are the lights set-up.
a. Your task: define maximum load a truck can carry.
b. Set the lights to reflect this and the bucket size.
4. Does it help? - Depends on …..
Case Study : Intercor Improvement Program
1. Define achievable targets - benchmark
2. Investigate use of truck weight measuring systems
3. Sample actual loads & communicate the information
a. % bucket fill, %box fill, load distribution, weight carried
4. Sample the loading and travel times & communicate
5. Monitor wear & tear; control TKPM (TMPH)
6. Monitor material fragmentation, communicate & insist on good fragmentation practice
7. Educate shovel and truck operators
a. weekly “communication” talks
b. identify good performers
c. “trainers” selected from the best operators
Case study : Intercor Progress
Case study: Intercor Results
