Field service technicians are trained from Day 1 to leave their truck's engine running in order to power the PTO, thereby powering all hydraulic and pneumatic tools needed in field repair. This adds more engine hours and wear to a truck's drive train than is necessary. A new, truck-integrated power source—EnPak® Mechanic Series designed and manufactured by Miller Electric Mfg. Co.—has proven to reduce engine hours, idle times and fuel use, and figures to substantially extend the life of a mechanic's truck at Brandeis.
Brandeis Machinery and Supply, a construction/mining equipment dealer based in Kentucky and Indiana, recently analyzed 170,000 work orders spanning over 10 years in order to better understand how field service technicians used their trucks. In addition to equipment use and field practices, Brandeis began to examine idle times and the resulting effects on engine wear and fuel use.
"These trucks are constantly idling, and that represents fuel burn," says Todd Coffey, corporate service manager, Brandeis Machinery and Supply. "A couple of years ago we put together a service initiative team to identify potential inefficiencies. The dilemma we always ran into was that, I'm running anywhere between a 200- to 250-horsepower engine (to power the mechanic's tools) where a far lower horsepower will take care of it. That's just not good."
This led Brandeis to explore options for running air tools, crane hydraulics and power tools in the field without relying on a power take-off (PTO) system, thus allowing field service technicians to turn the truck off while working. Brandeis worked with Miller Electric Mfg. Co. to install the new EnPak Mechanic Series, a truck-integrated power system run by a 27-HP engine that includes a rotary-screw air compressor, hydraulic pump and a generator.
After six months of data, the results speak for themselves: a 55-percent reduction in idle time, a 36-percent reduction in overall engine hours, preliminary fuel-savings estimates that, conservatively, pay for the system's premium on its own, and the expectation of a longer service life and longer service intervals due to these efficiencies. Combining asset life extension, fuel savings, reduced maintenance costs and the potential to transfer the EnPak from one chassis to another yield a potential total system payback of less than 2 years.
"We're looking at a pretty impressive piece of information," says Coffey. "It's definitely going to have a positive effect on what we're able to do."
Integrated Power Source Offers Addition by Subtraction
Prior to EnPak, Brandeis' mechanic's trucks (Ford F650s and F750s) featured PTOs, a hydraulic pump for the hydraulically run air compressor and crane (10,000 to 12,000 lb.), a 40-cfm air compressor and a separate welder/generator. The welder/generator had its own engine and fuel tank while the hydraulic crane and compressor required the truck's PTO to operate.
The independently-run power source eliminates the need for a PTO by plugging directly into the truck's fuel and electrical systems, and powering all of the pneumatic, hydraulic and electric components off its own 27-HP Kubota diesel engine. With its internal generator (6,000 watts), hydraulic pump (20 GPM max flow, 3,400 PSI max pressure) and rotary screw air compressor (40 CFM), it eliminates the need for each of those separate pieces of equipment while taking up less space on the truck as the previous welder/generator and air compressor did.
"The first thing we were able to do was pull the compressor and the welder off of the side pack," says Coffey. "We put a smaller hydraulic tank on there, so that allowed us to carry less fluids and less weight around. It got it down to a much cleaner package. And when we installed it, we were wondering about the plumbing and how it was going to work, and it's a much cleaner installation than what we had previously, so we were very happy with that. It's allowed us to minimize the number of units on the truck."
Operating a power source that runs independently of the truck's engine required a behavioral shift for Kevin Conner, field service technician, Brandeis Machinery and Supply. Prior to his new set-up, Conner pulled into a site and left the truck running all day—a learned habit repeated daily by field service technicians everywhere. Now, he turns off the truck, fires up EnPak and operates the air compressor and crane, and welds using a portable welding inverter running off the unit's generator.
Eliminating PTO Achieves Tangible Reductions in Engine Hours
Coffey tracks his fleet's data meticulously and, at nearly six months, shows us what happens when the field service technician is able to turn the truck off while working:
|Ford F750 w/Cummins CM850
||Truck 1/1/06 – 9/18/09 Per Day Average
||Truck w/EnPak 9/19/09-3/9/10 Per Day Average
|Total Engine Run Time/Hrs
|Total Idle Time/Hrs
Fig 1. Reductions in idle time and engine hours with EnPak compared to Truck/PTO.
"We're trying to crack down on excessive idle times where there is no payback," says Coffey. "It's all cost recovery, really. If something on that truck is mechanically operating, it needs to do the best it can do so that we have payback. The amazing data is the 55-percent reduction in idle time and then almost a 40-percent reduction in overall engine time. This will extend the component life for the engine and the transmission, and it will cut down on our service intervals."
Extended service intervals are a major benefit and potentially save as much as $1,000 per truck over the course of the year, but overall asset life extension is the true goal of the reduction in engine use/idling. Old trucks nickel and dime service departments to death with repairs, but Conner sees this system as having a lasting effect on his truck.
"The useful life of a service truck typically is cut short by how much maintenance you keep having to throw into the engine," he says. "With EnPak you're taking that wear and tear and those hours off of the engine and prolonging that useful service life. The truck should last a lot longer."
"We're at eight to ten years with our current set-up," adds Coffey. "We're realistically thinking, with a couple other things we've done, we may be able to go 12 to 15 years. Chassis life and how well the bodies hold up will be the telling tale on that. We still have to consider all that, but I think component-wise we're doing a lot of things that could definitely extend us into that range."
There are additional factors to take into account when weighing the benefits of turning off the engine.
By reducing truck engine idling, EnPak will reduce regen cycles. It also eliminates a costly PTO system that involves numerous mechanical parts that will cripple a service truck if it breaks down—an unacceptable occurrence for field techs sent to fix other people's equipment. It also centralizes all functions in one self-contained unit that can be serviced without interfering with the truck's functions. If something happens with the truck, EnPak still powers all of the mechanic's equipment.
"If you're running off the PTO, you're spinning that transmission the whole time," says Coffey. "Working clutches and drives, it's not the most efficient system. And if the PTO breaks down, that's not something I can walk up to and work on. I have to be under the truck. If the transmission goes, then I have to take off all the PTO stuff, replace the transmission, and then re-install all the PTO lines and drives and make sure they match up correctly."
Reduction in Fuel Use and Maintenance Provides Measureable Payback
Fuel savings alone will also achieve payback (and savings) over the life of the truck. At idle with the hydraulic pump engaged, EnPak uses ¼ gallon/hour less than the truck at idle (PTO engaged). When you flip the compressor to stand-by with EnPak, its engine idles at 2600 RPM and draws over ½ gallon/hour less than a comparable load off the truck's PTO. At work, with the air compressor in full use, EnPak draws almost 2/3 gallon/hour less than the truck/PTO. "In the six months we've been running it," says Coffey, "the off season and the economy have put us in a position where we're probably not running the truck as hard. The numbers that we have gotten back are very conservative compared to what it will be when things pick up, but we're possibly talking $750 to $1,000 a year in fuel savings. And that is particularly significant when I look at my fleet and I start talking about putting an EnPak on 60 trucks." Calculating the potential fuel savings for an independent power source over the course of a whole year, at full use and taking in to account engine size and local fuel prices, shows a potential annual savings of $1,741.23 (Fig. 2). Using Coffey's conservative numbers, the fuel savings alone would pay for the unit within 7-10 years. Using full production numbers, as in Figure 2, the fuel savings would pay for the unit in four years, and that doesn't include the savings from the reduced service intervals and overall extended truck life. On fuel savings alone, it has the possibility to pay for itself twice over the life of the truck.
Fig. 2: Estimated annual fuel savings with EnPak, taking into account diesel fuel prices in Indianapolis, Indiana on 4/14/10, 250 working days/year and a 6.0 liter engine
Extrapolating this Brandeis' model out over a truck life of 10 years, Enpak has the potential to have six years of pure savings on fuel use alone—or $10,447.38 per truck. Going one step further, assuming Brandeis would add EnPak to an entire fleet of 60 trucks, potential fleet-wide savings from fuel alone could be as high as $626,842.80 over 10 years.
Even if the currently realized savings of $750- to $1,000/year during the company's slow season are as high as the savings ever get, Coffey is still happy with the results.
"That's just from the standpoint of what we're going to save on fuel," he says. "If you add in engine maintenance costs, oil change costs, filters and everything else, it's a significant savings overall."