Guide
How to run a loader cycle time study
A cycle time study replaces opinion with numbers. Two shovels can look equally busy from the ramp, yet one may load a truck in three passes at 26 seconds and the other in four passes at 33. Only disciplined timing shows it. Here is a method that works at the face.
1. Define the phases before you time anything
A loader pass has four phases. Agree on the start and stop of each so every observer cuts the cycle in the same place.
| Phase | Starts when | Stops when |
|---|---|---|
| Dig | Bucket teeth enter the muckpile | Loaded bucket clears the face |
| Swing loaded | Bucket clears the face | Bucket is centred over the truck body |
| Dump | Bucket over the truck | Material is discharged |
| Swing empty | Empty bucket clears the truck | Teeth re-enter the muckpile |
Pass cycle time is the sum of the four phases. Gross cycle time is dig to next dig, including every interruption. The gap between the two is time lost to repositioning, waiting for a truck or housekeeping, and it is usually a support problem, not an operator one.
2. Choose a safe observation spot
Stand where you can see the bucket and the truck body at the same time, outside the swing radius and the haul road, and follow the site's safety rules. Never trade a safe position for a better view.
3. Record the interruptions as they happen
Do not discard slow cycles. Tag them: waiting for a truck, dozer cleaning the floor, a hard dig, a blast hold. Later you can report the clean pass time and the delay time separately, which is the only fair way to compare operators.
4. Know how many cycles you need
Thirty cycles is a habit, not a rule. The sample size depends on how variable the machine is.
where s is the standard deviation of your sample, x̄ the mean, r the accuracy you accept (0.05 is 5%) and t about 2 for 95% confidence. Example: mean 28 s, standard deviation 3.2 s, 5% accuracy gives n = (2 × 3.2 / (0.05 × 28))² ≈ 21 cycles. A noisier shovel with s = 6 s needs about 74.
5. Common mistakes
- Changing phase boundaries mid-study. Write them down and keep them.
- Timing only the best operator. Cover shifts, crews and materials.
- Ignoring conditions. Record fresh waste, ore, hard dig, so comparisons are fair.
- Studying too little. A few cycles on one afternoon will mislead you.
6. Turn the numbers into action
Compare the mean pass time with the target, look at which phase is longest, then check the delay list. A long swing-loaded phase points to a wide spotting angle. A long dig phase points to a poorly blasted or badly dressed face. A big gross-versus-pass gap points to truck supply or auxiliary equipment.
Time your own cycles. CycleStudy Pro records loader and truck cycles offline and does this maths for you. Get the Android app or try the free calculators.