Environmental matters: Engines

09 November 2015

The new 12-cylinder Liebherr stage IV / Tier 4 final diesel engine

The new 12-cylinder Liebherr stage IV / Tier 4 final diesel engine

New regulations for engines used in construction equipment are expected to be introduced in Europe in 2019 and 2020. Whereas Europe currently only regulates diesel engines from 19 kW to 560 kW, the new laws will cover all engine sizes and all fuel types used in off-highway equipment.

In the USA, the Environmental Protection Agency (EPA) is yet to announce any plans to implement any equivalent to the European Stage V regulations. As it stands, Tier 4 Final engine exhaust emission regulations will remain in place.

Tier 4 Final engines reduce particulate matter (PM) and create half the oxides of nitrogen (NOx) compared to the 2011 EU Stage IIIB and EPA Tier 4 Interim levels. The laws came into effect in January 2014 for engines rated between 130 and 560 kW. Engines rated in the 75 to 129 kW power band were required to comply from January 2015.

Compared to Stage IV and Tier 4 Final, the European Stage V laws are designed to reduce the amount of particulate matter (PM) even further, making Europe the most stringently regulated market in the world. According to Richard Payne, Cummins Europe off-highway regulatory affairs director, Stage V will require the use of diesel particulate filters (DPFs) across all engine sizes. “This will push everyone to go to diesel particulate filters. There is no other way to do it,” Payne says.

The final version of the Stage V laws is expected to be published in 2017, following the European Union’s drafting and decision-making process. Under current laws, machine owners can replace an existing engine in their equipment with the same stage model as was originally installed. The proposed Stage V laws, however, rule out this provision. In worst case scenario, in many cases if an engine couldn’t be repaired the entire machine would have to be scrapped.

Keeping it simple
To meet the latest emission regulations, manufacturers have gone down a number of routes. Cummins, for example, unveiled a new after treatment module at the 2015 Intermat exhibition in Paris, France, to meet Stage V. The module combines selective catalytic reduction (SCR) and a DPF in a single unit, as opposed to the current two exhaust canisters. According to the company, it is 60 % smaller, 40 % lighter and offers 20 % less back pressure than its current after treatment systems.

Crane manufacturers are also looking at new ways to meet emission regulations. Liebherr, Terex and Manitowoc, for example, are designing all terrain cranes with a single engine. By removing one of the engines, the overall weight of the crane should be reduced, maintenance time is cut down and only one after treatment package is required.

Historically AT cranes have been powered by two engines; one for crane operations and one for moving the vehicle. For slewing and lifting there is a lower power demand and, as a result, less engine power is required, so a smaller engine is needed. For driving there is a higher power demand so a more powerful engine is required.

For models with a single engine, power needs to be transferred from the carrier to the upper structure. To transfer this power additional components and engineering are required. Some manufacturers argue that this adds weight back on and that how much weight saved varies depending on the make and model.

German crane manufacturer Liebherr, for example, has been implementing the single engine design in its new models. Instead of the twin-engine design normally used on cranes in the 160 tonne class, for example, the Liebherr LTM 1160-5.2 is powered by a single engine with a mechanical shaft. A gear shaft is routed from the distributor gear in the chassis via two right angle gearboxes through the centre of the slewing ring up to the pump distributor gear in the crane superstructure. The 300 tonne capacity LTM 1300-6.2 also uses one engine.

Wolfgang Beringer, Liebherr sales promotion, explains, “A mechanical shaft ensures a particularly high efficiency level and low engine speeds in the chassis engine provide sufficient power for crane work. This ensures the economy of the new concept in terms of fuel consumption. The benefits of omitting a separate superstructure engine include a reduction in the amount of maintenance work and a reduction in weight. The omitted weight can be used for load-bearing components, thus increasing the crane's load capacity.”

Andreas Cremer, Manitowoc Cranes global product director of all terrains and truck mounted cranes, adds, “The single engine concept does not only save the weight of the second engine that usually was built into the crane to operate the superstructure, it also saves the weight of all the exhaust after treatment, which became necessary over the past years when emission regulations changed from Tier 3 to Tier 4i, and Tier 4 Final today. In addition to this, the missing engine in the superstructure also allows for more space in the superstructure, which also gives more design options.”

Besides the weight gains there are other benefits to the single engine concept as well, as Cremer points out, “On larger cranes idle times of the superstructure engine are up to 70 even 80 % of the usage, meaning a large four- or six-cylinder engine is running most of the time for power supply and air conditioning only. Our opinion on this is that this can be done in a more efficient way, especially as operating the crane functions with a larger engine on lower rpm is more fuel efficient than running them on high rpm with a smaller engine.”

Manufacturer Terex also believes that having a single engine is the better option. Terex has implemented the single engine design into its Explorer range. Rüdiger Zollondz, Terex product marketing director, says, “At Terex Cranes, we strongly believe in the single engine concept. The new range of Terex all terrain cranes, the Explorer series, has been developed according to a single-engine concept, which lowers the total cost of ownership and requires high reliability. Altogether we can say that having a single engine provides a better performance for crane operation with enough power for all conditions. At the same time the one engine concept provides less fuel consumption on its best duty point compared to the former two engine concept.”

Dr Jan Wieser, Matthias Roth and Frank Wernicke, experts that lead engine implementation projects at Terex Cranes, add, “Weight savings by having one engine can be negligible with old technology engines, but it is definitely not the case with Tier 4 Final and above. Think of having all those peripheral systems in duplicate: exhaust treatment, big cooling system, urea tank and intake. These peripheral arrangements are much wider than the connection between the carrier engine and the superstructure.”

To distribute power from the engine to the upper structure, Terex uses a design where power is transferred from an hydraulic pump next to the engine. Wieser, Roth and Wernicke, explain, “The power is transferred via hydraulic lines to the hydraulic control block on the super structure. We chose this system as having a shaft means that there is power inertia from the rotating shaft; this inertia translates into less precise ‘jittery’ crane movements. With no shaft inertia between engine and pump the crane movements are more smooth and precise. In the case of an emergency there is an electrical system which brings the crane down, even when the main engine is non-operational.”

Double lifetime
The single engine concept is nothing new for on road cranes such as truck cranes and small all terrains. The single engine concept in larger all terrains, however, is a more recent development. Not all manufacturers are convinced by the concept. Link-Belt and Tadano, are continuing with the twin engine design.

Rick Curnutte, Link-Belt product manager for telescopic truck and all terrain cranes, explains why, “It would seem logical that emission mandates are what drive the single engine debate as much as anything and, perhaps, manufacturing cost. The engineering required to keep in compliance with two different emission standards (off-road and on-highway) for one model is a challenge for some, but one Link-Belt is able to meet. Single engine machines in this class may sound simple on the surface, but they require their own additional technology and hardware.

“Link-Belt has been very successful with the two engine system in its all terrains; keeping the smaller fuel efficient engine in the upper, and separate dedicated systems built from the start to match power demands.”

With regard to the advantages and disadvantages of having a single engine to save weight, Curnutte adds, “The loss of redundant crane features like two cooling and emissions packages is an advantage of a single engine all terrain crane, especially given the rate at which emission standards continue to mandate engine upgrades by manufacturers. A major disadvantage of a single engine, however, is the discrepancy of engine size between the carrier and upper engines. For a single engine all terrain crane this means using an engine that is sized for transport for crane operation; crane operation typically requires half of the horsepower that is needed for transport. Link-Belt does this commonly on truck cranes, but on larger cranes like the ATC-3210 and ATC-3275 that would mean committing a 15 litre, 550 hp engine to do the work required for both the carrier and upper of the crane.”

Manufacturer Tadano agrees with this principle and is continuing with the twin-engine design. The new Tadano ATF 600G-8 all terrain crane with Triple Boom System, for example, is powered by two Mercedes Benz Euromot 4 engines. A 460 kW (626 hp) unit is in the carrier and a 260 kW (354 HP) engine in the superstructure is for crane operations.

Thomas Schramm, Tadano general manager sales and marketing, explains why the company is continuing with the twin-engine concept, “Cranes are viewed as an investment and having two engines compared to just one has a number of benefits. First gain is that having two engines gives the crane a double lifetime. For example, if a crane has two engines the big engine clocks 300 hours of running time and the super structure engine clocks 1,500 hours. For a single engine concept there will be 1,500 plus 300 hours of running time all on the carrier engine. This will mean that engine maintenance will have to be carried out sooner. For people that change cranes frequently, this is not so much of a problem, but is a disadvantage for second-hand buyers.

“In addition, although there have been improvements with larger engines for fuel consumption, smaller engines are still more economic,” Schramm adds. “For a smaller engine, three litres less fuel consumed per hour over 1,500 hours is 18,000 litres saved. Over 10 years, this is 45,000 litres of fuel saved.”

Engine investment
To continue in engine development, Liebherr is heavily investing in its Bulle site in Switzerland. Liebherr Group will be investing more than €160 million (US $179 million) in the site. Out of this investment, €85 million ($95 million) has been dedicated to the expansion of a modern competency and a 5,800 square metre development centre for engines and drive system technology. A further €35 million ($39 million) is being invested into the logistics centre, which will have a new 6,000 square metre building, with an automatic pallet and container warehouse and a 1,500 square metre commissioning zone.

Arno Dalheimer, Liebherr Machines Bulle managing director, says, “In essence, the concept for factory development comprises the expansion of our development centre and an extension to the production facilities, which enables us to extend the diesel engine portfolio and our activities in the field of common rail systems. The investments also comprise the construction of a logistics centre as well as a new training centre. These investments will be supplemented by additional projects within the factory infrastructure.”

One of the main reasons behind the Bulle expansion project was to expand the Liebherr V-engine model series, increasing its engine portfolio in the performance range. New to the V-series are a V16 and a V20 engine, both part of the new D96XX model series. The D9616 with an overall displacement of 36 litres will be in the 900 to 1,200 kW power range. From a displacement of 45 litres in total, the D9620 engine returns 1,125 to 1,400 kW of power. The new engines will be deployed in off-road equipment, including crawler vehicles, large cranes, maritime cranes as well as in large material handling and forestry equipment. The first applications are due by the middle to the end of 2016.

Rudolf Ellensohn, Liebherr Machines Bulle managing director, adds, “To stay within the emissions thresholds throughout the rest of Europe and in North America, we are relying on SCR-only technology for our engines which, apart from an SCR catalyst, does not need any other systems. Our standard solution for exhaust gas after-treatment, therefore, dispenses with the need for a particulate filter.

“To improve this situation and to meet the demands of tunnel applications as well, we are currently developing a solution that combines the SCR catalyst and particulate filter in one: The SCR-coated particulate filter. Together with a DOC catalyst, this SCRF system will enable us to comply with the future stage V specification. Based on the current status, the directive due to take effect in 2019 will include, above all, lower thresholds on engines in excess of 560 kW of power. The directive will also contain specifications in terms of the number of emitted particulates.

“Since we had already planned on introducing the SCRF system in Switzerland and applications in tunnels and other enclosed systems prior to the introduction of stage V in Europe, we are putting a lot of weight behind its development and will be able to deploy the first test equipment using the system in 2015.”

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