I’ve heard longwall crews described as the fighter pilots in their F/A18s strutting down to the dolly car with Maverick, Goose and Iceman on their hard hats, the development crew as the B52 bomber, big, heavy, slow and very expensive to run, and gas drainage and conveyors as the ground crew – no one gets off the ground without them.
Let’s have a look at the development unit delivering a panel on time, to longwall specification and at or below the dollar per metre budget preferably 4000m long rather than 800m.
Utopia is roaring down a 28 pillar gate road in record time and hanging a left or right to knock out a 300m face road with very little gas and good roof, and in 2015 there are some teams that can do just that, giving the longwall department a face road 90 days ahead of the LW changeout so that the second set of gear can be installed and commissioned.
On the other hand if you have a block of coal that is high in methane or carbon dioxide (or hydrodgen sulphide, that really makes you Mr Popular at the pub as you smell of the stuff) and or strata that is on red or double red support, well it requires a more complex plan and can be difficult to manage.
Development can have a nasty habit of not delivering the metres and using up all of the allocated cash.
You can always remember the big hitters:
- The major roof fall that the Sunday night shift deputy found in the belt road;
- The water event that flooded the panel; or
- The dyke that was as hard as iron and took a month to shot fire out.
But we tend to forget or not notice the “chronic” delays, a few minutes here, 30 minutes there that cumulatively add up to many days lost.
And you know what ... at some point I’ve been all of those people, from whacking the boot with a car to asking people to go to the other panel to grab some of the other panels gear.
So to correct our bad habits and to aim for best practice, what does a good plan look like? See table on right.
Three hundred metres in 300 hours was a catch cry that a very good mine manager ran with and an average 12.5 day pillar cycle will deliver a cost effective panel with longwall continuity and without “flogging people or machinery”
So putting my data analyst hat on here, what is required to knock out a 10 day pillar cycle? Well unfortunately 1.8m per operating hour (MPOH) won’t cut it.
Your 125m pillar with cut-throughs and any stubs adds up to around 300m of drivage, Your week has 168 hours in it less all planned and unplanned delays.
- 40% utilisation allows the CM to cut for 67 hours.
- Best practice 50% utilisation gives 84 hours average.
- Best practice outlier is 100 hours per week and these do deliver the 220 to 270m weeks, but they are few and far between.
Good operating hours and a top end production rate is the desired combination, you need the high MPOH to balance the low rate shifts.
Look on my website (Blackboxadvisory.com.au) for a best practice Sandvik chart showing what 5.0MPOH looks like – a pretty impressive result with 50 cutting cycles in almost 10 operating hours, the number at the top of each column indicates that all but a couple of cycles were at 100cm so the full 1m roof mesh is achieved with minimal overlap.
The blue line indicates that the team used auto cut for 80% of the time, which is great – a bit like using cruise control on the freeway, same speed, same Shuttle Car loading characteristics and the same roadway profile – and a happy production manager.
Getting the plan, people and processes aligned delivers the results and will also highlight your next constraint.
A development unit delivering regular 5MPOH shifts will have the supply chain waving the white flag, but what a great flag to see ...
Jim Curtis is a director of Black Box Advisory (business, planning, transformation and risk)