New heavyweight excavators from Caterpillar
CATERPILLAR are replacing their 365C and 385C heavy excavators with the 374D and 390D. At 72.6 tonnes and 88.2 tonnes, respectively, the D-series machines have put on weight and are said to be up to 20% more efficient than their predecessors.
The 374 gets 18% more power (355kW) which, in mass-excavation form, bigger boom cylinders and increased hydraulic pressure turn into a 19% increase in digging force and a 9% boost in bucket breakout. Coupled with increased stability from the wider (3.41m) track gauge and heavier operating weight, the extra power allows the 374 to use bigger buckets resulting in an overall fuel efficiency gain of 5% compared with the 365.
While the 390 retains the same 390kW engine power as its predecessor, the increased hydraulic pressure boosts digging and bucket breakout forces by 9%. Productivity is also up by 9% and Caterpillar say overall fuel efficiency is 11% higher.
Caterpillar have increased the strength of the boom and dipper to cope with the higher forces and the undercarriage gets cast idlers and redesigned track links to increase durability. The 390 also gets thicker track shoes and both models benefit from heavy-duty track guards.
Central to the excavators’ increased efficiency is an electronically controlled regeneration valve which, when lowering the boom, diverts pressurized oil back into the high-pressure side of the hydraulic system rather than returning it to the unpressurized tank.
A new generation of increased-efficiency buckets are available for both machines and come in four new duty grades (General, Heavy, Severe and Extreme) with increasing amounts of replaceable wear plates.
Significantly, the quarrying industry’s safety concerns have not been ignored and both new models come with walkways widened to 500mm, a rear-view camera is standard (plus optional boom and toolbox cameras) as are time-delayed lights that give the operator 30s to lock up and dismount before turning off.
Both machines have Stage 3A engines which do not require a diesel particulate filter. Caterpillar say they will use the flexibility allowed by the EU regulations to retain these engines through to 2013 when the 374 and 390 will become some of their first Stage 4 machines.