For Delaware Valley Concrete (DVC), it was never an issue if the company would add compressed natural gas (CNG) -powered mixers to its fleet, but when and what design. The Hatboro, Pa., producer’s core values hold sustainability efforts in high regard, and management is not afraid to try emerging technologies and gain a competitive edge wherever possible.
“We have been investigating CNG trucks for a couple of years, reading about the technology and talking to manufacturers,” says DVC Safety Director Tim Ketavongsa. “There are many upsides to the design, including fuel savings, operating with a smaller carbon footprint and less complicated emission systems on the engine.”
“It is more important than ever that we look to sustainable and environmentally friendly energy alternatives, especially for industries that consume large amounts of fuel in their operations,” adds DVC President Mario Diliberto.
While environmental benefits were a definite positive, there were a number of business considerations DVC weighed before a transition to CNG power. Location of fuel stations in relationship to where the mixer trucks would operate, justification of paying a premium price for engines, and modifications and costs to remodel the maintenance shop for servicing the alternative-fuel mixers were but a few of the considerations.
Since CNG is an emerging fuel source, fueling stations are not yet widespread throughout North America, so DVC looked for targets located near any of its nine ready mixed concrete plants operating throughout southeastern Pennsylvania. The producer pegged a station at a Philadelphia Electric Company (PECO) site within a mile of its Plymouth Meeting, Pa., plant that allowed outside fleets to refuel their CNG-powered vehicles.
While the CNG engines significantly reduce emissions and complexity of the emission systems found on post-EPA 2010 diesel engines, the clean-running CNG design does come at a premium, according to Dave Rinas, director of Sales and Marketing for Terex mixer trucks. “The average upcharge for the CNG engine is approximately $35,000,” he explains, “or about a 15 percent premium on new trucks and 20 percent increase on gliders.”
After careful consideration of all the business pros and cons of adding CNG-powered trucks to its fleet, DVC converted three of its four-axle diesel trucks from the Plymouth Meeting plant to CNG through a glider program. The mixers began making concrete deliveries in early 2014.
“We determined the 2014 season would be a trial year for our CNG trucks,” notes Ketavongsa.
LACKING POWER
For a company that owns its own aggregate quarries, uses only natural sand in its mixes, conducts quality control testing on all local mixes and employs only American Concrete Institute-certified technicians, quality and service are top DVC priorities. “Our customers set high standards for their concrete delivery service,” affirms Ketavongsa, “and we work hard every day to [meet them].”
So when officials began introducing CNG trucks into the 85-mixer fleet, they wanted to make sure the alternative-fuel trucks would perform to the same standards as diesel-powered models. The first three front discharge CNG trucks were modified with an engine and fuel tank design initially developed for rear discharge trucks and adapted to front discharge models.
Each truck was powered by 9-liter CNG engines and equipped with four fuel tanks to match the 75 diesel gallon equivalent (DGE) capacity of the diesel-powered mixers. “At the time DVC purchased its first CNG trucks,” explains Rinas, “only 9-liter engines were widely available on the market. Terex felt the engines did not deliver the power and torque customers expected from our front discharge mixers, so we purposely held off CNG development until the correct power unit was available for the application.”
After putting some miles on the alternative fuel glider trucks, one of DVC’s initial concerns was put to rest. The trucks’ fueling cycles were nearly the same as the diesel units, which did not affect the number of daily deliveries the trucks could make. “Our drivers tell us that a CNG refueling cycle takes about 15 minutes, and that is with significant truck traffic using the PECO fueling station,” says Ketavongsa. “PECO plans to upgrade the station, so fill-time will be even faster in the future.”
DVC customers started noticing the CNG trucks and began requesting deliveries from the environmentally friendly power units, especially those working on projects targeting LEED (Leadership in Energy and Environmental Design) certification. “We like having equipment that gives us a competitive edge, and it’s a plus having these CNG trucks delivering concrete to projects that meet specifications of the U.S. Green Building Council,” says Ketavongsa.
While the producer reaped significant advantages from the alternative fuel trucks, there was a substantial and noticeable drawback to the design. “The 9-liter engines only offer 320 hp (239 kW), which is low for the mixer truck application,” says Rinas.
“The engines did not have the right power. The lack of horsepower was quite evident when the trucks climbed hills with a load, and they were underpowered compared to our diesel powered trucks,” Ketavongsa adds, noting how the CNG mixers could not offer the flexibility of being dispatched to every type of job.
MORE POWER
About the time DVC deployed its first two CNG glider trucks, Terex debuted its CNG truck design, powered by a 12-liter engine. “We equipped our front discharge CNG mixer trucks with what we feel is the right power unit, offering the torque required for delivering concrete,” explains Rinas.
“The Cummins 12-liter engine offers 350-400 hp (261-298 kW) options with torque ranging from 1,350-1,450 ft.-lb. (1,830-1,965 nm),” adds Terex Design Engineer Mike Johnson, noting that both CNG packages are similar to the power and torque ratings typical of diesel-powered Terex front discharge mixers.
Mario Diliberto met with Terex representatives at ConExpo-Con/Agg 2014 in Las Vegas to review the five-axle CNG truck on display, noting especially the engine and overall installation. Since Terex did not rush the model to market, company engineers were afforded time to make sure the engine was fully and properly integrated into the truck’s frame. “We took a clean-sheet approach for the CNG front discharge mixers when working with engine and fuel system vendors,” says Rinas.
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| With 2014 being a CNG mixer truck trial year, DVC transitioned from 9-liter to 12-liter engine trucks for the additional power and torque. The Cummins Westport ISX G 12-liter engine powering Terex compressed natural gas trucks offer from 350-400 hp options with torque ranging from 1,350-1,450 ft.-lb., similar to the ratings of Terex diesel-powered trucks. |
As a bonus, Terex also designed the alternative-fuel truck to take full advantage of system improvements and reliability of its diesel-powered model. “Everything below the frame rail and forward of the rear pedestal is the same as our diesel mixer trucks,” affirms Johnson.
The CNG model’s integrated design allows the engines to be equipped on every Terex model from three- to seven-axle, standard and bridgemax configurations, as well as with glider trucks. The design includes major emphasis on weight distribution and positioning within existing configurations. Built to maximize payload capacity, the new trucks use only two Type-4 CNG tanks, positioned low on either side of the rear frame, to meet the 75 DGE. In addition, the new engine cowling design removes approximately 50 percent of the internal steel to further reduce truck weight and increase payload.
DVC ordered three Terex four-axle FD4000 CNG Front Discharge Mixers for its Plymouth Meeting plant. After delivery of the trucks, the producer began realizing the advantages of up to an 80 percent reduction in carbon monoxide and up to 85 percent reduction in nitrogen oxide emissions. “Additionally, the engines are much quieter than our diesel trucks,” Ketavongsa observes. “You mainly hear the tire noise.”
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| To maximize payload capacity, Terex front discharge trucks use only two Type-4 CNG tanks to offer 75-diesel-gallon-equivalent, up to 25 percent lighter than other tank configurations. |
Compared to diesel-powered units, the Terex CNG mixer trucks also provide DVC with similar mileage and performance, he adds, noting, “One of our drivers commented that the CNG trucks seem to have more power than our diesel trucks.”
Staying ahead of the competition curve, not only was DVC the first ready mixed concrete producer to operate CNG mixers in Pennsylvania and Delaware, it has more than a year of experience running alternative-fuel mixers. Upgrading to a more powerful, 12-liter engine, the producer company is now looking ahead to expand the CNG truck fleet and find the best way to refuel the trucks.
“We hope to add CNG mixers as we deplete the older diesel-power units each year until we have a large portion of the fleet powered by the alternative fuel,” says Diliberto. “We are looking at all options, including a fast-fuel station of our own, located at one of our plant locations. The governing factor is the availability of natural gas line service in the areas we are considering.”
Rinas adds that the DVC experience and evolution of thought for fueling stations is similar to other producers operating CNG trucks throughout North America. “We are seeing and expect to see the CNG truck market follow infrastructure development increasing CNG availability,” he says. — Terex Construction, Ft. Wayne, Ind.; www.terex.com/construction