This year ushered in Europe’s Stage II and America’s Tier 2 off-highway emissions regulations. Most engine manufacturers are well ahead of the game so the advances in technology should offer far-reaching benefits to the mobile crane sector. While the crane’s initial price may increase, the performance and lifetime cost is likely to improve.
Typical in the crane industry, and also in the off-highway sector in general, most vehicle manufacturers rely on engine suppliers. At least one crane manufacturer, however, does not: Liebherr makes its own engines. So it is with this German OEM that we begin to look at the technology being used, and what is expected to be used, to meet the increasingly strict emissions limits.
Euro III engines already power all Liebherr’s new mobile cranes. The company met the requirements by using injection systems with variable injection start, electronic ignition map control and optimised turbocharging. Further, Liebherr will introduce four-valve technology in the next generation of engines. This step will optimise fuel consumption.
‘Every application of a higher pollution level did result or results in greater fuel consumption,’ reports Liebherr’s technical department. ‘Optimisation measures and improved injection systems, however, can reduce that increased consumption.’
Four-valve technology will also enable Liebherr to comply with Euro IV limit values (if required), increase performance and torque, reduce fuel consumption at an equal pollution level, or reduce the greater consumption from higher pollution levels.
Liebherr concedes that these advanced designs will raise the engine’s price. But, it adds, the new technology will contribute to easier and safer crane operation. Also, extras such as cruise control, automatic track control and speed limiters will not cost more.
Engine manufacturers
Among engine manufacturers, Mercedes-Benz, part of DaimlerChrysler Powersystems, is a leading supplier for mobile cranes. Its off-highway engines satisfy Euro II standards, and can meet future emissions guidelines, the company claims. Full electronic engine management enables vehicle users to obtain the exact power required.
Besides electronics, Mercedes-Benz has satisfied emissions criteria by using multiple valves per cylinder, pump-line-nozzle technology with pump units for each cylinder, and eight-hole injection nozzles. These features not only reduce emissions, they also result in low fuel consumption and better reliability.
Mercedes-Benz’s latest engine, the OM 926 LA, is based on the OM 906 LA in-line version. The newer model has six cylinders and a higher displacement – 7.2 litres – producing 240kW and 1,300Nm of torque. According to Mercedes-Benz, both the power output per litre and the torque per displacement are among the best in this category. Yet dimensions and weight are claimed to have remained low.
‘The OM 926 LA serves as a power source suitable not only for cranes but for universal off-highway use,’ Grosch says. ‘It has proven its high power capacity, reliability and economy in its first application, a piste machine, in constant full-throttle operation at an altitude of 3,000 metres.’
The 500 series from Mercedes-Benz is its most powerful, serving mobile cranes as well as other heavy-duty vehicles. Power outputs range from 230kW to 420kW, in closely spaced steps.
Mercedes-Benz goes a step further, offering custom-made drivetrains. ‘The engine and transmission are ideally matched to each other and communicate electronically,’ Grosch says. ‘This results in harmonious gear changes with operating convenience and little stress on the clutch. It also prolongs the useful life of the drivetrain and saves fuel.’
Volvo Penta’s introduction of four- to seven-litre engines has greatly broadened the Swedish company’s industrial range. The new five model series has an injector for each cylinder to give injection pressure high enough for low emissions and low fuel consumption.
In addition to modern injection technology, Volvo Penta’s latest engines include integrated oil coolers and easy-access service points. For the crane operator, exchangeable cylinder liners and standard poly-V-belts lessen cost and maintenance requirements.
Volvo Penta has also introduced an industrial version of its D12 engine. Again, it offers lower emission levels and better fuel consumption – 6% less than its predecessor. The engine features EMS (Engine Management System), which improves performance and allows full integration with the vehicle. ‘We can deliver D12 engines as a component of our customer’s systems,’ Westlund says, ‘either partly integrated or free-standing.’
US manufacturers
In America, Cummins recently confirmed it would meet the deadline for lower-emission engines, as outlined in a consent decree signed in 1998. Four other engine manufacturers also signed similar consent decrees; over the past months, however, a few have asked the Environmental Protection Agency (EPA) and the Department of Justice (DOJ) to delay this agreement.
Under the decrees, manufacturers agreed to produce engines meeting the 2.5g/bhp-hr standard for NOx emissions and non-methane hydrocarbons (NMHCs) by October 2002. The decree means a further 38% reduction in NOx emissions from current off-highway emissions standards. Cummins expects to be the first US engine manufacturer to meet the standards, and it received a boost in early June when the EPA and the DOJ reaffirmed the government’s intention to enforce the decree.
‘We have invested heavily in emission-control technologies,’ says Tim Solso, CEO and chairman of Cummins. ‘The cost to develop and refine the technology to meet these ambitious NOx emissions reductions will alter the competitive landscape if compliance delays are granted. It is critical the EPA enforces industry-wide compliance with the letter and the spirit of the consent decree so we achieve all the environmental and consumer benefits.’
Like most engine manufacturers, Cummins will use cooled exhaust gas recirculation (EGR) to hit emissions targets. EGR technology allows for a portion of exhaust gas to be reused, effectively reducing exhaust emissions.
The company, which first used EGR in the mid-1990s to meet California’s TLEV (Transitional Low Emissions Vehicle) standards in the Dodge Ram pickup truck, says it reached a milestone in this technology for its B Series and other medium- and heavy-duty engines. Fuel economy improved by 2%, NOx emissions fell by 50%, and unaided cold-start time lessened by 60%, it is claimed. In addition, variable geometry turbocharging enabled Cummins to enhance the engine’s throttle response.
‘The only feasible technology for meeting the 2.5 gramme (NOx + NMHC) levels in the timeframe is EGR,’ explains John Wall, vice-president and chief technical officer at Cummins. ‘No other option provides the benefits of fuel economy, cost, responsiveness and overall performance.’
America enforced Tier 2 limits this year on 225kW to 450kW engines, and will expand these next year to cover the 450kW to 560kW band. Starting in 2003, the 75kW to 225kW range will come into force. In Europe, Stage II limits for small engines (18kW to 37kW) became effective this year, while standards for 130kW to 560kW engines begin next year.
Cummins designed its Tier 2 engines, with outputs of 44kW to 560kW, to offer more power and torque from the same-size package. ‘The technical jump from Tier 1 to Tier 2 has added full-authority electronics, as well as air-to-air aftercooling, on many of these engines,’ says Kevan Browne, publicity manager at Cummins. ‘This improves durability, reliability and fuel economy. Also, the automatic engine protection, instant diagnostics and trip data help improve engine availability and reduce equipment down-time.’
To extend a crane’s useful lifetime, Cummins engines offer a re-power option. They come either as new engines or remanufactured units built to as-new specifications. An engine can be upgraded to one with lower emissions. ‘Re-powering lets the operator take advantage of technical and emissions upgrades,’ Browne says, ‘while also extending the useful life of the equipment.
Caterpillar, on the other hand, has gone a different route. It will meet Tier 3 and Stage III emissions regulations using Advanced Combustion Emissions Reduction Technology (ACERT), rather than with EGR. ACERT combines advanced combustion, next-generation fuel systems, integrated electronic controls and after treatment.
By improving engine combustion performance, Caterpillar has also lowered noise emissions. Further, ACERT improves overall engine performance and has the capacity to eliminate exhaust odour without affecting engine reliability and durability, the company claims.
‘OEM customers will not have to make major changes in application engineering and installation when they switch to ACERT-equipped engines to comply with Tier 3 and anticipated Stage III regulations,’ says Roberto Dionisio, Power Systems manager at Caterpillar SARL which covers Europe, Africa and the Middle East. ‘The installation simplicity offers a smooth transition to the next emissions regulations, without expensive EGR systems.’
One reason ACERT engines will be more cost-effective, contends Siamak Mirhakimi, industrial engine business manager for Caterpillar SARL, is that they allow for significantly fewer components than EGR-based engines, thus minimising new hardware requirements. ‘Customers can respond quickly to emission regulations at lower overall costs’, according t Mirhakimi. ‘Moreover, the transition from current production engines to ACERT-equipped ones will have little effect on installation.’
Caterpillar’s latest industrial engine range, the C series, uses electronic controls, advanced fuel injection systems and air-to-air aftercooling (ATAAC) to meet Stage II and Tier 2 regulations. All five models include Caterpillar’s ADEM III Electronic Control System, which provides crane and other vehicle operators with systems and site integration, diagnostics and prognostics, and programmable application parameters.
Reduced weight means better fuel economy, Dionisio says: ‘The C-9, for example, with a dry weight of just 681kg is almost 30% lighter than the Cat 3306’. ‘Specific fuel consumption at full load and 2,100min-1 is 10% less than its predecessor at the same speed and output.’
Caterpillar has also introduced the 3126B, an in-line six-cylinder turbocharged engine. Ratings range from 131kW to 205kW at speeds of 1,800min-1 to 2,500min-1, with peak torque of 697Nm to 1,166Nm. The 3126B has a displacement of 7.2 litres, and uses the ADEM III Electronic Control System, ATAAC and HEUI fuel system.
Crane manufacturers, contractors and users can expect many emissions-driven improvements from today’s engines. While the price will be higher, with lower fuel consumption, longer life, sophisticated electronic systems – and vehicles with less environmental impact – it seems a fair, even exciting, trade-off.
