Small Changes To Fueling Process Saves Millions of Dollars
Every time you take a truck out of the production circuit you lose tonnes. By making adjustments to your operation’s refuelling practices, your trucks are kept in the production circuit longer, making better use of them and your operating costs.
Many years ago, I worked on a project at Freeport’s massive Grasberg open pit operation in Indonesia. There, I calculated the savings derived from purely better use of their FMS refuelling functionality and it equated to tens of millions of dollars. At the time, Grasberg was one of the largest open pit operations in the world. Using the methodology described below, can you estimate the savings available at your mine?
Some mines refuel all trucks at the same time every day – even if a truck just came out of the workshop with a full tank of fuel. In that scenario, a sub-optimal queue of trucks waiting for their turn to get refuelled is created, costing millions of dollars in wasted operating hours.
Let’s work through an example with the following assumptions:
Empty travel time to fuel bay: 12 minutes.
Queue at fuel bay: 10 minutes
Refuel time: 26 minutes.
Empty travel time back to production circuit: 12 minutes.
Total time lost due to refuel event: 60 minutes.
One full hour of lost available time every single day, equating to 365 lost truck hours per year, per truck. Multiplied by the number of trucks you have working. Multiplied by your operating cost per hour. Now you start to see why truck refuelling really is costing money.
Assuming you have 100 trucks, and you are refuelling all trucks at the same time each day, let’s crunch some numbers.
Operating Cost: $200/ hour
Production Loss: $6 million/ year
Imagine if you could cut the number of refuel events per year in half! Which is not an unreasonable assumption in operations where there is not already a disciplined approach to refuelling.
You would SAVE $3 MILLION annually in operating costs (in the example above)
return over 15,000 hours of trucking resources to the production circuit every year.
How much is that extra production worth to your operation?!
If your mining operation has a fleet management system (FMS) such as Wenco, Modular, MineStar or Jigsaw they all have functionality to manage the refuelling process. The concept is simple: use the FMS to make truck assignments to the fuel bay only when the trucks are running low on fuel. And only when there is not a long queue of trucks already waiting to refuel.
Level A (in the diagram) is used to determine whether a truck should be considered for a refuel assignment.
If remaining fuel is above Level A, send the truck to a loading unit for another load – don’t even consider it for refuelling.
If the fuel level is between Level A and Level B, consider sending the truck to the fuel bay, if and only if that assignment decision does not result in an excessive queue at the fuel bay. This is often referred to as ‘opportune fuelling’, meaning the truck still has enough fuel to operate, but if there is no queue at the fuel bay, the truck should take this opportunity to refuel, thus optimising operation, production, and queue times.
If the fuel level is below Level B, the truck does not have enough fuel to continue operation and needs to be sent for refuelling, regardless of the resulting fuel bay queue time.
In an ideal world, the truck would arrive at the fuel bay on it’s last drop of fuel. Of course, mining is far from an ideal world; we need a margin of safety so we do not leave haul trucks stranded out of fuel, blocking haul roads. These fuel levels are configurable, and need to be set as low as possible to achieve the savings in operating costs and increase in production, but high enough so that a truck is not left out of fuel at the bottom of the pit.
The trick to managing refuelling with a FMS is to make sure we are working with accurate, up to date information. It is critical to know exactly how much fuel is left in the truck. Some truck OEMs (Caterpillar, Komatsu, Hitachi) have functionality that allows your FMS to connect to the OEM system (such as Cat VIMS) on board and query what the fuel level is. Other third party products exist if your truck does not have the functionality.
This is the best practise of haul truck refuelling. Working with real-time fuel levels. It allows you to query the actual fuel level in the truck when the truck is dumping its load, then decide if you want to send that truck back to be loaded again, or if it is necessary to proceed straight to the fuel bay.
If there is no functionality to read the actual fuel level from the truck, the FMS will try to approximate the fuel level remaining using theoretical fuel burn rates, operating hours, etc. Being an approximation, it is safer to set the refuel trigger points higher if your mine relies on this method.