Public Transit Station Construction Getting Cleaner with Caterpillar’s New Hybrid Excavator

Tuesday, May 21, 2013

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Caterpillar Inc. recently performed productivity tests on its new hydraulic hybrid excavator, the 336E-H with contractor, Kiewit Corporation, at the site of the regional transportation system (BART) extension near Fremont, California.  Kiewit is building BART’s Warm Springs extension which will bring the system further south toward San Jose. The development and evaluation of this machine is part of the California Energy Commission’s Medium- and Heavy-Duty Vehicle Demonstration Program which is being administered by CALSTART.  

Kiewit has been using the 336E-H hybrid excavator for the past several months at the site to do regular earthmoving tasks.  For the productivity tests the crews brought in a conventional Cat 336E as a control machine and collected copious amounts of performance data.  The crew worked on a long, 15-foot high hill, excavating it down to grade and then loading dirt on to a long line of trucks, which took the excavated material away from the site.  The 336E was used in the morning and the 336E-H was used in the afternoon.  The same operator worked both machines.  Caterpillar brought in portable scales and each truck was weighed as it left the site.  They measured fuel use and also timed each dig/load operation which was divided between scooping and dumping components.  They also measured the density of the soil as they moved along the hill in order to maintain consistent calculations.

Overall, the data for the hybrid machine met or exceeded expectations. Fuel consumption (gallons per hour) was lower with the hybrid machine and fuel efficiency (tons of dirt moved per gallon of fuel) was better than the conventional machine.  The actual test results were better than Caterpillar’s marketing literature which indicates that the 336E H fuel consumption will be up to 25% less than the standard 336E.   Essentially, the hybrid excavator is performing as advertised.  Productivity (the amount of dirt moved by the machine per hour) was slightly better, with the hybrid completing its tasks slightly faster.  

CALSTART’s Steve Sokolsky observed the work, and spoke a bit with the operator. The operator was impressed with the performance of the 336E-H and felt that certain operations were smoother and quicker with others having a slightly different feel.  He also said that the noise factor was different, because the engine is running at a lower rpm on the hybrid (1500 vs. 1800) the engine noise is lower so he can now hear the pumps more.  Observing from the outside, the hybrid seemed substantially quieter to Sokolsky.  Overall the operator felt the hybrid offers a nicer environment inside the cab.  The machine operations are identical and he did not need any additional training before using the hybrid, which construction crews will likely appreciate.

Finally, Caterpillar’s local maintenance rep reported no maintenance issues at all with the hybrid system and uptime has been identical.  The Caterpillar crew was very happy with the tests (they’re collecting a bit more data in further tests at the BART station). 

Check out Caterpillar’s video about the excavators in use at the transit station, and photos of the day CALSTART's Steve Sokolsky spent with the crew: