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Equipment design, engineering controls and operator efficiency can help aggregates producers deal with rapidly rising energy costs.

By Mark S. Kuhar

This is the first part of a two-part series. –Ed.

Fluctuating energy costs, especially with regard to diesel fuel, are having a huge impact on the bottom line for aggregates operations. Vulcan Materials, in its fourth-quarter report, noted that “all key labor and energy efficiency metrics” for its aggregates business improved in the quarter and the full-year from the prior year, which “helped offset increases in the unit cost of diesel fuel, a 25 percent increase for the quarter and 35 percent increase for the full year.” In 2012, the company expects energy costs, specifically unit costs for diesel fuel and liquid asphalt, to approximate those increased 2011 levels.

Martin Marietta Materials noted in its fourth-quarter report that “cost management is an enduring area of focus throughout our company. In line with that objective, direct production costs for our heritage aggregates product line increased only 1 percent despite an 11 percent increase in noncontrollable energy costs (principally diesel fuel), which reduced overall earnings by $0.05 per diluted share and was offset by reductions in personnel and depreciation costs.”

Martin Marietta reported that for the quarter, diesel fuel costs averaged $2.95 per gallon compared with $2.32 per gallon in the prior-year quarter. “On a consolidated basis, our cost of sales increased 9.5 percent over the prior-year quarter, reflecting higher raw materials costs, including liquid asphalt, and the impact from rising energy costs,” said company President and CEO Ward Nye. “Diesel fuel and other consumables change production costs directly through consumption or indirectly by increased energy-related input costs, such as, steel, explosives, tires and conveyor belts. Fluctuating diesel fuel pricing also affects transportation costs, primarily through fuel surcharges in the corporation's long-haul distribution network.”

Many other aggregates producers feel the same pain as Vulcan Materials and Martin Marietta. So what can aggregates producers do?

Machine Design
When it comes to rolling stock, how the equipment is engineered can have a significant impact upon fuel consumption. The experts at Caterpillar say that fuel burn rate (gal./hr.) is impacted by four major factors:

  1. Machine application. What type of work is the machine doing? In a difficult load and carry operation down in the quarry, a loader may burn 60-100 percent more than the same machine in a truck-loading application at load-out.
  2. Operator technique. An aggressive truck-loading cycle (20 seconds) can burn 60 to 80 percent more than the same machine in a moderated cycle (30 seconds). Using transmission auto-shift can save a minimum of 15 percent versus manual shifting.
  3. Idle time. The percentage of time a machine is idling has a huge impact on the fuel burn rate (gal./hr.) A mid-sized loader burns less than one gal./hr. when idling, however a larger loader such as Cat’s 980 class working in tough conditions on the quarry floor may burn as much as 12 gal./hr. A typical 980K burns six gal./hr. or less. The higher the percentage of idle time, the more it overall fuel burn average, and 30 to 40 percent idle time is common.
  4. Machine configuration. Machine features impact fuel burn rate but to a far smaller degree than application, operator technique and idle time.

New Machine, New Features
Almost every new loader or haul truck to hit the market these days comes equipped with features designed to reduce energy use and decrease fuel consumption. Caterpillar’s just released 777G haul truck, for instance, realizes fuel savings through features such as auto neutral idle and APECS transmission controls where the truck becomes more fuel efficient at idle in a forward gear and when climbing grades. Customers can choose to engage features like Engine Idle Shutdown and speed limiting to further improve fuel savings.

The Komatsu WA500-7 haul truck features Komatsu Smart Loader Logic, which provides optimal engine torque when the job requires. Komatsu Smart Loader Logic can save fuel by adjusting the engine torque to match the machine application, such as when traveling with an empty bucket high engine torque is not required. Komatsu Smart Loader Logic functions automatically and doesn’t interfere with operation, which results in saving fuel without decreasing production.

John Deere’s new 160G LC and 210G LC excavators feature engine technology that is simple, fuel efficient, fully integrated and supported by the nationwide Deere dealer network. It uses field-proven cooled exhaust gas recirculation (EGR) for reducing NOx emissions, and a diesel particulate filter and a diesel oxidation catalyst to reduce particular matter. Periodic active and passive filter cleaning automatically cleans the filter without the operator having to stop the machine and impact productivity. The hydraulically driven, highly efficient fan at the heart of the excavators’ cooling system also runs only as needed, reducing noise, fuel consumption and operating costs.

The new Case CX210C excavator delivers lower operating costs and higher productivity according to Tim O’Brien, brand marketing manager, Case Construction Equipment. He cited 10-percent fuel economy gains, 3-percent cycle time reductions and 7-percent lift capacity increases among crucial product improvements. “An advanced version of the Case Intelligent Hydraulic System technology reduces total fuel consumption and improves performance,” O’Brien said. Boom Economy Control lowers engine RPMs during the boom down and swing operation, while the Auto Economy Control lowers RPMs when the joysticks are inactive. Swing Relief Control technology manages the hydraulic power allotted at the start of the swing operation, and Spool Stroke Control creates an automatic pressure adjustment during digging operations. These fuel efficiency gains are especially significant. While typical CEGR systems lose fuel efficiency, we’ve actually increased fuel efficiency on our Case CX210C excavator by 10 percent over the previous B Series model. While delivering exceptional fuel efficiency, the Case C Series models continue to be in the top of their class for productivity.”

The Volvo L250G wheel loader is fitted with a fuel efficient Tier 4i/Stage IIIB certified engine that is married to drive train, hydraulics and lifting systems that are all designed and produced by Volvo to “work in perfect, productive, fuel efficient, harmony.” Intelligent load-sensing hydraulics deliver power to hydraulic functions only when needed, without unnecessary oil pumping which burns fuel unnecessarily. The hydraulic pump designs are coupled with the high torque, low rpm engine, and provide full flow at the engine’s optimal working range, eliminating the need to throttle to max rpm for higher flow, drastically saving fuel.

Consisting of a new torque converter with Lock Up and free wheel stator, Optishift is a new system that integrates the Volvo patented Reverse-by-Braking (RBB) function – both significantly reducing fuel consumption together – by up to 15 percent – as well as increasing operator comfort and driveline durability. When changing from forward to reverse (or vice versa), RBB applies the standard service brakes instead of the torque converter, slowing the machine and putting less stress on the converter and transmission. OptiShift can significantly reduce fuel consumption in operations such as load and carry – as well as in short cycle loading. The driveline lock-up, meanwhile, improves drive response, rimpull and incline performance, and fuel efficiency.

Cummins Inc., at last year’s ConExpo-Con/Agg show revealed the latest generation of the QSL9 engine, which is not only capable of meeting near-zero emissions levels and is EPA Tier 4 Final and EU Stage IV compliant, it also incorporates higher fuel efficiency. At Tier 4 Interim 2011 emissions levels, Cummins QSB6.7 and QSL9 engines are capable of achieving up to 5 percent improved fuel efficiency compared to Tier 3, depending on duty cycle and machine optimization. Fuel efficiency will be further increased for Tier 4 Final 2014 by an additional 2 percent to 3 percent.

In the second part of this feature, the link between operator training and fuel efficiency is explored.