Lean Crushing

AggMan Staff | Published on August 1, 2008

Save your capital and maximize your equipment investment through the implementation of lean crushing processes.

by Todd Creasy, Ph.D.


Infomercials. You know what I’m talking about. You can’t sleep, and there you are thumbing through the channels only to land on a 30-minute infomercial about some exercise contraption designed to help you lose weight and tone up. You’re almost persuaded to pick up the phone and dial to begin the “three easy payments automatically billed to your credit card.” The 30-minute spot promises to make you leaner, which is the opposite of…well, you know…rounder. In the end, however, it sounds too easy to be true and you decide against it. What if I were to tell you that you could substantially reduce your operating costs per ton by increasing your tons produced or tons per man hour, and the concepts to get there are easily understood and, with a little management, quickly implemented? Would you be interested?

To understand lean crushing, you must first understand what “lean” is. A few years ago, some researchers at the Massachusetts Institute of Technology (MIT) began to study the differences between domestic automobile producers (such as General Motors and Ford) and Toyota. After several months of analysis, they observed that Toyota had fewer suppliers, fewer defects, less turnover, fewer quality issues, took less time to bring a new product to market with less cost and less effort, and it even had fewer employee injuries. They puzzled and concluded, “they seem so lean.” And just like that, the term “lean” was launched and made popular throughout the world via the book entitled The Machine that Changed the World. Since that writing, companies within most industries have been chasing lean and finding substantial areas to save capital, maximize returns, and gain market share.

So what does “lean” mean then? Lean means less of many things – less waste, less lead time, shorter cycle times, fewer suppliers, and even less bureaucracy. Ultimately, however, lean means less cost. Lean is concerned with two fundamental operating issues – waste and flow. Lean seeks to reduce waste in all its forms and improve product flow. So how does lean fit into the aggregate industry?


The aggregates industry

When you consider the multiple steps and processes necessary to take rock from a wall and process it into clean stone for a concrete producer, the opportunities to reduce waste and improve flow are plentiful. Most aggregate professionals refer to the processes of loading shot rock, hauling it to the primary crusher, and crushing it as “load, haul, and convey.” For simplicity’s sake, let’s examine that segment or phase of the crushing process and see where lean principles could apply.

Have you watched your load, haul, and convey processes recently? If so, what did you see? Was one haul truck running faster than the others, or did trucks constantly have to wait at the primary to dump their loads? What about your loader operator? Was he digging deep holes into the shot pile while loading trucks? Did he have a load up and waiting period when the haul truck was positioning himself to back up? If you examine the behaviors of these operators closely and do some timing, you may be surprised at the amount of wasted time and equipment under-utilization you see. Both of these types of inefficiencies are targets of lean.

To be a lean crushing aggregates operation, the loader operator has to understand that no truck should ever be left waiting for him to do his job. Those trucks hauling material to the primary crusher are the quarry’s life blood. When the primary runs dry or experiences “black belt,” the whole quarry process is under-utilized and, hence, production drops, thereby increasing per-ton incremental costs. The loader operator should be able to routinely – in a standardized (and safe) manner – load every truck in two minutes or less. Every few seconds you shave off his average load time ultimately increases tonnage up the hill and, subsequently, tons on the ground and ready for sale. Production is up and per-ton costs are down.

To be a lean crushing aggregates operation, the aggregates professional needs to pay attention to the condition of the quarry, specifically the haul roads. The first question you should ask yourself is, “Are loaded haul trucks given priority over all other vehicles in proximity?” If not, production is being sub-optimized while the primary is being starved for product. Can the haul trucks safely pass one another when opposing one another on the haul roads? Are your haul road turns super-elevated? If you’ve got haul trucks waiting on one another in route from the loader to the primary or on the return trip, most likely either the primary crusher is experiencing black belt or the loader guy is waiting for a truck to show up. In either instance, you have waste – under-utilization of equipment and time. Both of these productivity detractors are enemies of a lean facility.

What about your haul roads and quarry floor? Are they smooth and level for comfortable riding? Imagine yourself bouncing around the cabin of one of your haul trucks for 8 to 10 hours a day. At the end of the day, it’s not so much the stress of the job that has taken its toll on you; it’s the physical beating of riding on your haul roads or quarry floor. Take some time and invest in smoothing out those surfaces. Establish a practice for keeping them smooth, well drained, and comfortable. Driving the haul trucks at slower speeds because of poor conditions is another form of waste that lean scrutinizes.

You say, “I’ve never noticed any black belt on my conveyor.” No, you probably have not, and the reason why you have not is that your whole production system is being slowed to the biggest bottleneck within your production system. Take the bottleneck out with the help of lean tools and expertise; watch your production rates climb. Lean takes waste out of your value stream and improves product flow.

If you are considering how waste equates to financial returns, simply consider the savings on labor and equipment expense. If you can get the same production (using lean philosophies and management techniques) but with two fewer hours of production daily – that’s 12 hours weekly of saved equipment/fuel expense and 12 hours of labor expense for the same (or improved) production. Repeat after me, “Ka-ching!!”


Next steps

Let us suppose you won the lottery and are now the proud owner of an offshore power boat. You have a racing crew and the boat/crew manager says that with the money you have invested, you should have engines that, combined, generate at least 1,250 horsepower, which enables sustained speeds in excess of 125 miles per hour. You are told this is what you should be getting from the capital you have spent on your rather expensive hobby. Because you have a good business head on your shoulders, you ask the obvious question, “Are we getting 1,250 and 125?” That same sort of question applies in the aggregate business. Most quarries have a secondary plant which further crushes the rock into a product more suitable for its customers. Within the principles of lean, the act of measuring is critically important. To understand the impact of our decisions, we must understand our “baseline” and to understand our baseline performance, we must measure it. An old axiom goes, “if you don’t measure it, you can’t manage it.” Measuring can be accomplished in a number of ways, but the most common within a quarry environment is belt scales.

So, in consideration of our power boat example above, your desire would be to see the radar-measured speed your boat is generating rather than listen to the experienced manager say what speed he thinks you are getting – data over intuition. It’s with this data mindset that this author first realized the lack of measurement within a quarry, specifically at the secondary plant. There was a belt scale measuring the tons per hour leading into the tower, but despite there being several conveyors protruding from the tower, only one had a belt scale on it. I asked the operator, “How do you know what’s on the other belts?” The answer wasn’t specific or impressive. The lesson learned was to put belt scales on final product conveyors or where measurement is necessary. This act had indirect benefits as well – it helped in measuring and managing inventory.

Now that we can measure, we can get back to asking ourselves some questions about the plant. If a manufacturer of a cone says that it can produce 450 tons per hour, are you getting 450 tons per hour? How do you know if you don’t measure downstream within your production system? Are your screens efficient or are they “blinding over?” Once again, measuring can indicate if you’re making the product you most need or if you’re sending good rock into the base stone pile.

Does your operator have to intentionally slow down the plant because some conveyor belt is undersized? Are you assisting your operator and their running of the plant by utilizing technology (cameras, sensors, amp gauges, etc.)? If the answer is “no,” then you may be costing yourself more money than you know in unnecessary labor hours, unnecessary equipment hours, unnecessary electricity, and suboptimal product flow. A holistic examination of your plant using industry software and lean principles may be warranted to achieve your full return on investment. Get your 1,250 and 125!


Investment or optimization?

Within the industry, a tug-o-war exists over whether to invest in bigger equipment or rolling stock to get productivity improvements or emphasize best practice techniques together with prudent on-the-ground management. While there are advantages to capital investment, this author proposes optimizing what you have before going to the bank with hat in hand to finance plant or rolling stock improvements. It’s important to note that within the lean methodology, the need for investment (and employee training) may become quite apparent, and you should follow common return on investment calculations to help in the decision process. But if you’re not sure what your plant and equipment can actually produce, by all means try these techniques first. In the vast majority of cases, you will be pleasantly surprised. The good news is, unlike the infomercials often seen on television, these lean techniques put money in your pockets, not charge you in equal month-to-month installments.


Todd Creasy, Ph.D., is a master black belt in Six Sigma and Lean Professional with approximately 10 years experience in the aggregates and construction industry. He can be reached via telephone at 615-476-5706 or via e-mail at todd.creasy@bridgepointllc.com.


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