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Further Learnings from the Fundamental Analysis of Development Cycles ACARP Roadway Development Operator Workshops March 2009. 13/2/08. Introduction. From late 2007 and through 2008 development processes at all Xstrata mines were benchmarked.
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Further Learnings from the Fundamental Analysis of Development CyclesACARP Roadway Development Operator WorkshopsMarch 2009 13/2/08
Introduction • From late 2007 and through 2008 development • processes at all Xstrata mines were benchmarked. • In each mine data was gathered on times to perform each of the small steps in the process. • This included loading, wheeling, bolting etc. • The findings were presented at this forum in March 2008. • This presentation is an update of further learnings and analysis arising from this benchmarking. • Firstly, a brief recap on last year’s presentation..
Effect of Support Density on Rate Mine B Mine D Mine E* Mine A* Mine F Mine C Mine E Mine G
Equipment Observations • Three pieces of equipment in the cut and load sub-process: • Miner – 4 types in XCN, each with different load out capacity, which varied ~100% • Car – both car capacity and car speed varied ~100% • Feeder – discharge time through the feeder (or boot) varied ~ 150% • Combination of these has a major effect on process rate • This combination is expressed as the rate at which the roof can be exposed for one round of support
Effect of Equipment on Rate – Normal Support Mine B Mine D Mine E* Mine A* Mine C Mine E Mine F Mine G
Process Observations • Once support variations and equipment variations are levelled, the remainder of the variation is process application
Effect of Manning on Process Rate (or so I thought then) Manning has no clear relationship to process rate, but the process must be manned so that it works as designed.
Findings • Three measurable elements affect cycle time: • Support density • Equipment selection • Process application • You cannot affect the support density • You can design your process • You can select your equipment to achieve your process • You must man your process to achieve it
Using these building blocks • Each of these four basic build-ups of the cycle can be examined to see where an improvement in rates can be delivered, or where speed humps have been put in. • With them in mind you can systematically and critically examine each process. • This has been done at a number of mines
1. You cannot affect your support density… • ….unless it is over engineered: • One operation was using lots of roofbolts and tendons and long ribbolts. • There was an alternative area to work that could require less intensive support, and operations were moved to there. • A program of rationalisation of support using risk assessment, monitoring and a trial was implemented • Process rates increased markedly.
1. You cannot affect your support density… • …but you can look at how it is achieved: • A mine was putting in 6 bolts/m at 1 m spacing and had to widen the heading from 4.8m to 5.5m, so put in a 7th bolt. • This last bolt led to the process being unbalanced, with a lot more serial tasks required on one side of the miner. • Consideration is being given to reducing the spacing to 0.85m, so the bolts remain at 6 per row, density remains at 6 bolts/m, and the process is balanced again.
2. You can design your process… • Off standard driveages cost time. • I watched a box niche take 90 minutes to complete as the miner operator had a lot of trouble slewing the machine, dodging roofbolt tails and roof and rib bolting it, including moving the machine for each single bolt. • Other operations drive a box niche simply by overdriving the cutthrough. This happens in 15 – 20 minutes because it is standard driveage. • Cable boats save the need for some niches too.
2. You can design your process… • One mine was cutting 60cm of very hard roof, which was adding about 4 - 5 minutes to every car. They had the lowest exposure rate of any mine. • The longwall had demanded the height because their equipment was too big for the seam section. The longwall was having a serious impact on development rates, and perversely affecting its own float. • They moved to an area that had a thicker section. Loading a car returned to normal times, and rates improved. • Examination started on getting a lower BSL.
2. You can design your process… • How far you can productively overdrive depends on whether you are wheeling constrained or bolting constrained. • If the process is bolting constrained throughout, it does not matter if you overdrive until the car runs out of cable. • This is particularly the case if the process is set up to start the belt move only when certain conditions are met. • However if the process is wheeling constrained, productivity would drop off as the overdrive lengthens.
The Effect of Overdriving If you overdrive when you are wheeling constrained you add in the worst rates from one pillar, and lose the best rates from the next pillar. Both pillars suffer. The case above may be worth half a shift.
2. You can design your process… • One operation was routinely putting in secondary support off the miner. • By using another crew, the miner crew stayed on primary support and went forward faster, while the secondary support still went in a few days later. • The secondary support was designed off the critical path. Support time decreased, and cutting time increased.
2. You can design your process… • The support rules of one operation required tendons to go in between rows of roofbolts. • This led to a surprising amount of shuffling of the miner, dodging VTs, pulling cables etc, and then returning the miner to the face. • Unless you sit on a miner for a while you don’t notice these things.
2. You can design your process… 6.1m tendon next to 1.8m bolt They now simply replace a roof bolt with a tendon, and leave the miner where it is.
2. You can design your process… • The support rules specify the maximum spacing of rows of bolts. • About half our mines don’t achieve this spacing, because of how far the sheets are overlapped. • One mine specifies 1m spacing, supplies 1.15m sheets, overlaps them 0.25m, and so puts up bolts at 0.9m centres. • This mine actually purchased in a year 29% more mesh than metres that they drove.
2. You can design your process… Another mine specifies 1.2m spacing for one level of support, 200mm overlap of sheets At the time of my visit the rows were at 1.0m centres!! and supplies 1.3 m sheets, so reducing their spacing to 1.1m.
2. You can design your process… • Some mines parallel ribbolting with roofbolting. Both Joy and VA machines can do this. • It has a remarkable effect on process time. • It requires deliberate attention to an expectation and then deliberate attention to having enough men in the crew to do it. • You can risk assess when not to do it.
3. You can select your equipment… • One mine led the way with matching miner, car and feeder capacities, and got the benefits. • Others are now much more conscious of designing their process and getting the right sized car and the right sized feeder. • They aim to get one round of support into two (2) trips to the boot, and to get rid of the coal out of the car in fast tram.
3. You can select your equipment… • One mine was using a feeder that was too small. • They redesigned their boot to the widest they could get it, fitted a plate to catch carryback from the flight chain, bolted a wheelstop to the floor, and got rid of the feeder. They now discharge the whole car at high tram. • However the gains were not a big as expected, and on further examination it appears that there are less flights in the conveyor chain than previously, and this may be rectified. • Nevertheless, they get coal out of the car a bit quicker, and don’t have to worry about moving the feeder every sequence move.
3. You can select your equipment • If you select or put up with a machine that is poorly designed ergonomically, you will get a human reaction. • Men can only work with the tools they are given. • Throughout all the studies I have done, wherever human interaction with the machine is poor, tasks simply take longer, and men will be more prone to injury. • One of the longest bolting processes required men to reach at an awkward angle, put chemicals into holes at about 30 degrees to vertical, and pick up bolts placed badly behind them.
3. You can select your equipment… • One mine had no hungryboards on the car in a 2.6m seam and ran to the boot 10% more often. • Coal in the car could only have been brushed off by the VTs in about 10m of a 240m sequence, but the whole 240m was made slower because someone didn’t like flat tubes. 150mm hungryboards would have added over 1t to the car, the heaped coal would have fitted under flat tubes, and the process would have been balanced at two cars/m.
3. You can select your equipment… • I revisited a mine and found that the feeder was heavily choked off and discharge rate much slower than previously. • The panel belt fed onto two jiffy drives put in ‘temporarily’ at the start of the panel while the longwall belt drive was away being given a birthday. Unfortunately its return was delayed. • At the time of my visit the panel was at 17c/t. • Slower production had been noticed, but it was not caused by development people. • At the same time poor floor conditions had slowed the car down – a double whammy on exposure rate.
4. You have to man your process… • I didn’t fully appreciate the effect of manning until I saw it at its lowest. • One crew had three men – car driver, miner operator/RH bolter operator, and LH bolter operator (who was also a novice). • The support required was 6 roofbolts and 4 ribbolts every metre, and 2 * 6m tendons every 2 m. • The machine was also one of the worst ergonomic setups I had seen. • Every task was dependant on its predecessor as there was simply no other person to parallel anything. • The men worked hard, but their progress was small.
4. You have to man your process… • One mine had to double their weekly metres. • They compiled a 20 point plan staged over a period. • The first step they recognised was to “man all units consistently”. • They did achieve their plan. • An added incentive may have been their plan was plastered to the CEO’s office wall.
4. You have to man your process… • All tasks require some manpower and manhours. • So the fewer the men in a panel, the longer it will take to put in the manhours. • If you put x men in a crew, • they can only do the work of x men • and you will only get the metres of x men. • The process needs to be designed to optimise • the tasks, • their sequence, • their dependencies on each other, • who is to do them, • and how many men and machines are required
Process Success Story #1 • A mine selected an ABM25 for purchase. • Four (4) employees spent a month in Austria ensuring the machine work platforms were built to suit how the crew would work it. • Great emphasis was placed on ergonomics. • The machine produced good results almost at once. • The process uses six bolting rigs simultaneously. • This mine puts up more support than another with the same equipment but produces more metres.
Process Success Story #2 • One mine had carefully and purposefully selected and matched its miner, cars and feeder. • Their process was well designed and producing good results. Crew manning totalled 11 – deputy, operators and tradesmen. • Ways of improving the process were identified, but involved increasing the crew size to 13. An economic case was made out to justify this. Two temporary employees were employed and proved the improvements were being achieved. • The temporary crewmen were made permanent. • The improved results were locked in.
Acknowledgements • Thanks to development operators, engineers and superintendents for their help in providing data and comment for this presentation. • My apologies to anyone I’ve embarrassed. • Deming: • “If you can't describe what you are doing as a process, you don't know what you're doing.”
