A. Introduction
Fleet-management data becomes useful only when the underlying KPIs are clearly defined.
This article covers the most important production-control concepts:
- Production
- Productivity
- Equipment time states
- Physical Availability (PA)
- Use of Availability (UA)
- Loader and truck cycle time
- Excavator productivity
- Truck productivity
- Match factor
The exact definitions may vary between mine sites. Every operation should maintain an approved KPI and time-classification dictionary.
B. Production
Production measures the total material moved during a defined period.
Common units include:
- Tonnes per hour
- Tonnes per shift
- Tonnes per day
- Bank cubic metres per hour
- Number of trips
Production should be compared with:
- Shift target
- Daily plan
- Material target
- Source and destination plan
A high tonnage result is not enough if the wrong material was moved.
C. Productivity
Productivity is output per unit of productive time.
Possible units include:
- tonnes/hour
- BCM/hour
- trips/hour
Example:
A loader produces 1,050 tonnes during seven working hours.
Always state the time basis. Productivity based on working hours is different from production divided by total scheduled shift hours.
D. Equipment Time States
A simplified time relationship is:
MOHH = WH + SH + BD
Scheduled Time = Working Hours + Standby Hours + Breakdown/Repair Hours
Different sites may use different terms, such as:
- MOHH (Machine on Hand Hours)
- Scheduled Machine Hours
- Available Hours
- Operating Hours
- Mechanical Downtime
Do not mix these terms without checking their definitions.
Working hours (WH)
Working time is the period in which equipment performs productive activities.
For a haul truck, this may include:
- Spotting
- Loading
- Hauling loaded
- Dumping
- Returning empty
Some sites also count queueing as operating time. Others classify it separately.
Standby (SH)
Standby means the unit is mechanically ready but not working.
Examples:
- No operator
- No production requirement
- Waiting for instruction
- No supporting equipment
Standby is not always waste. Some standby may be planned. Usually, a delay is categorized as SH too.
Delay
A delay is an interruption to productive work.
Examples:
- Meal break
- Prayer break
- Shift change
- Refueling
- Blasting clearance
- Road obstruction
- Waiting for supervision
A delay may be classified as controllable, uncontrollable, planned, unplanned, internal, or external.
Breakdown and maintenance downtime
Downtime occurs when equipment cannot operate because of a mechanical or electrical condition.
Examples:
- Unscheduled repair
- Planned maintenance
- Tyre repair
- Component replacement
- Electrical troubleshooting
Many sites separate planned maintenance from breakdown, so the site definition must be checked.
E. Physical Availability (PA)
A common simplified formula is:
Example:
- Scheduled time: 12 hours
- Downtime: 2 hours
Physical Availability answers:
How much of the scheduled time was the equipment mechanically available?
F. Use of Availability
A common simplified formula is:
Example:
- Scheduled time: 12 hours
- Downtime: 2 hours
- Working time: 7 hours
Use of Availability answers:
How much of the available time was actually used?
G. Payload Performance
Average payload alone can hide inconsistency.
A better payload review includes:
- Average payload
- Median payload
- Standard deviation
- Percentage underloaded
- Percentage within target
- Percentage overloaded
- Payload by loader, operator, truck, and material
The objective is not the highest possible payload. The objective is stable loading within the approved range.
H. Loading-Unit Cycle Time
A typical excavator bucket cycle includes:
- Digging
- Swinging loaded
- Dumping
- Swinging empty
[
CT_b =
t_{dig}
+
t_{swing\ loaded}
+
t_{dump}
+
t_{swing\ empty}
]
Truck loading time consists of several bucket cycles:
[
\text{Loading time}
\approx
\text{Number of passes}
\times
\text{Average bucket cycle time}
]
Other factors include:
- Truck spotting
- Truck exchange
- Loader repositioning
- Face cleanup
- Fragmentation
- Bucket fill
- Operator technique
Cycle time can be measured through manual observation, video, onboard systems, or FMS events.
Manual observation remains useful for validating automatic timestamps.
I. Haul-Truck Cycle Time
A truck cycle usually includes:
- Queueing at loader
- Spotting at loader
- Loading
- Travelling loaded
- Queueing at dump
- Spotting at dump
- Dumping
- Returning empty
[
CT_{truck}
t_{queue\ loader}
+
t_{spot\ loader}
+
t_{load}
+
t_{loaded\ travel}
+
t_{queue\ dump}
+
t_{spot\ dump}
+
t_{dump}
+
t_{empty\ travel}
]
The start and end points must be consistent. Different reports may use arrival-to-arrival, dump-to-dump, or loading-completion-to-loading-completion definitions.
Excavator Productivity
There are several valid calculation methods.
Bucket-based estimate
[
Q_{excavator}
\frac{3600}{CT_b}
\times q
\times FF
\times \rho_l
\times E
]
Where:
- (CT_b) = bucket cycle time in seconds
- (q) = bucket capacity in loose cubic metres
- (FF) = fill factor
- (
ho_l) = loose density in tonnes per loose cubic metre - (E) = efficiency factor
This method is useful for estimating potential capacity.
Truck-service method
[
Q_{loader}
\frac{3600}
{t_{loading}+t_{truck\ exchange}}
\times
\text{Average payload}
]
This method is useful when loading-event and payload data are reliable.
Actual productivity
[
Q_{actual}
\frac{\text{Actual tonnes loaded}}
{\text{Actual working hours}}
]
This method is best for reporting achieved performance.
These formulas answer different questions and should not be treated as interchangeable.
Truck Productivity
For one truck:
[
Q_{truck}
\frac{3600}{CT_{truck}}
\times P
\times E
]
Where:
- (CT_{truck}) = truck cycle time in seconds
- (P) = average payload
- (E) = efficiency factor
Be careful not to double-count losses. If actual cycle time already includes normal delays, applying another general efficiency factor may reduce the result twice.
For identical trucks:
[
Q_{fleet}
N
\times
Q_{truck}
]
For mixed fleets:
[
Q_{fleet}
\sum_{i=1}^{n}Q_i
]
Match Factor
Match factor compares hauling capacity with loading capacity.
A simplified formula is:
[
MF =
\frac{N_t \times Q_t}
{Q_l}
]
Where:
- (N_t) = number of trucks
- (Q_t) = productivity per truck
- (Q_l) = loader productivity
Interpretation:
- (MF < 1): hauling capacity is lower than loading capacity
- (MF \approx 1): capacities are approximately balanced
- (MF > 1): hauling capacity is higher than loading capacity
Under-match
Possible effects:
- Loader waiting
- High hanging time
- Underused loading capacity
- Lower production
Over-match
Possible effects:
- Truck queueing
- Increased idle time
- Higher fuel use
- Lower truck productivity
Exactly 1.00 is not always the practical optimum.
The best target depends on:
- Cycle-time variability
- Equipment reliability
- Mixed truck fleets
- Material priority
- Haul distance
- Cost of truck waiting
- Cost of loader waiting
A control band such as 0.90–1.10 may be useful at one site, but it is not a universal standard.
Worked Example 1: Under-Matched Fleet
Given:
- 3 trucks
- 55 tonnes/hour per truck
- Loader productivity of 250 tonnes/hour
[
MF =
\frac{3\times55}{250}
0.66
]
The fleet is under-matched.
With four trucks:
[
MF =
\frac{4\times55}{250}
0.88
]
With five trucks:
[
MF =
\frac{5\times55}{250}
1.10
]
The correct choice depends on production requirements, variability, and cost.
Worked Example 2: Over-Matched Fleet
Given:
- 6 trucks
- 60 tonnes/hour per truck
- Loader productivity of 300 tonnes/hour
[
MF =
\frac{6\times60}{300}
1.20
]
The fleet is over-matched.
With five trucks:
[
MF =
\frac{5\times60}{300}
1.00
]
Under stable assumptions, five trucks provide a theoretical balance.
Cost per Tonne
High production does not always mean economic efficiency.
[
\text{Cost per tonne}
\frac{\text{Total operating cost}}
{\text{Total tonnes moved}}
]
Operating cost may include:
- Fuel
- Tyres
- Maintenance
- Labour
- Equipment ownership
- Road maintenance
- Support services
Production, productivity, and cost should be reviewed together.
Conclusion
Mining KPIs are useful only when their definitions are consistent.
Before comparing equipment, shifts, or fleets, confirm:
- What time basis is being used
- How delays are classified
- Whether payload data is reliable
- How cycle time is defined
- Whether efficiency losses are already included
- Whether the fleet is homogeneous or mixed
A correct formula with inconsistent inputs still produces a misleading result.