PS Diggers Not Digging

Owned by iarmstrong
Dec 01, 2021
4 min read

How to resolve poor digger utilisation in a period.

Check 1: Refresh your knowledge on the scheduling engine

Steady States

  • Schedules are composed of increments of time called “Steady States”.

  • In every steady state, the diggers choose what block/parcel to mine.

  • After all diggers have nominated their target block/parcel, the optimisation runs to determine the destinations.

Optimisation Failures

  • Steady state optimisations can sometimes fail to find a destination for ore. For example:

    • Crusher is full.

    • No capacity at stockpile A.

    • Grade is out of spec for stockpile B.

    • Material type is not accepted at stockpile C.

  • If no destination can be found, the digger records a “Do Nothing” delay and moves zero volume.

Spinning Wheels

  • A digger can get into the following state:

    1. Select parcel X.

    2. Optimisation fails to find a destination for parcel X.

    3. Report “Do Nothing” delay and return to 1.

  • In this state, the digger will remain on standby until a destination opens up for parcel X.

Resolution

  • Consider adding an Overflow stockpile to avoid this issue.

  • If any material goes to the Overflow stockpile, then there is some kind of issue with the destinations.

Even in a Mining Mode scenario, mining is still dependent on the drilling delay time. If a shot has drill meters remaining, they deplete at the rate specified in Calendar > Default Rates.

Check 2: Setup > Loaders > Loadable Trucks

  • Check the digger has loadable trucks.

Check 3: Schedule > Calendar > Agents

  • Confirm the dig rates are set to a reasonable number.

Check 4: Schedule > Calendar > Truck Assignments

  • Confirm the digger has assigned trucks in the period.

Check 5: Setup > Equipment Rosters

  • Confirm the digger has available hours in the period.

Check 6: Setup > Destination Rules

  • Confirm the digger has an applicable destination rule for the pit and material.

  • Double check that parcel subsets (such as “Ore”) actually contain the relevant materials.

Check 7: Check stockpile accepted parcels

  • Setup tab > Destination Rules step > see if stockpiles are listed as destinations.

  • Setup tab > Stockpiles step> check the chunk template for the stockpile.

  • Setup tab > Stockpile Chunks step > check the Accepted Parcels column includes the material the digger is mining.

If a destination rule sends HG to a stockpile, but HG is not an accepted parcel, then the digger may shut down from lack of destinations.

Check 8: Check stockpile build/reclaim type

  • The Blended, FIFO Mutex, and LIFO Mutex type stockpiles cannot build while reclaiming, and cannot reclaim while building. This can make the stockpile inaccessible as a destination.

Check 9: Schedule > Gantt

  • Drag the Gantt slider to when the digger shuts down and check:

    • Is there a dig sequence in the lane at that time?

    • Is there a rostered delay in the lane at that time?

    • Is there a manual delay in the lane at that time?

    • Is there a blast window in the blasting lane at that time?

    • Is the dig sequence empty at that time? (Grey hatching indicates all blocks in sequence are finished).

    • Is there a schedule issue at that time? (Yellow and white hazard tape warnings on the Gantt timeline).

Check 10: Schedule > Animation

  • Find the time:

    • In the Gantt, move the time slider to when the digger shuts down.

  • Find the location:

    • Double click an agent in the Agent List to zoom to it.

    • Double click a block in the Record tree to zoom to it.

    • Look for the block which fails to mine.

    • Drag the animation slider back and forth to get a visual on what is happening.

  • Quick Checks:

    • Is the block underground? (Check for batter trims and skins along the pit wall)

    • Is it drilled and fired?

    • Is another agent in the way?

    • Is it within the blast radius of a shot being fired?

  • Right click > “Show Dependencies”:

    • Look for red dependencies.

    • Expand the dependency to see X waits for Y waits for Z.

    • Find the issue (expand distance, time delay, drill proximity, etc).

  • Right Click > “Show Trace Messages”.

    • If there are messages, read them. This dialog is blank by default.

Trace messages dialog example

Check 11: Check optimisation

  • Setup tab > Flow Optimisation step > cash flows > make sure filtered parcels match the destination rules.

  • Schedule tab > Calendar tab > Optimisation field > change all cash flows to positive and run.

  • Schedule tab > Calendar tab > Optimisation field > set all content deviation penalties to zero and run.

  • Setup tab > Flow Optimisation step > disable all grade targets and run.

  • Make an overflow stockpile and run.

Maximum grade targets are honoured even if the deviation penalty is zero.

Maximum grade targets are honoured even if the deviation penalty is zero

Check 12: Haul Infinity > check routes

  • Confirm a path exists between the source and the destination.

  • Check the Error List panel for ramps that are too steep for the truck to traverse.