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.