David McKenna joked about pulling the shortest straw when it came time to address a standing-room crowd of maintenance managers, and the crowd laughed with him. Other members of his Technology and Maintenance Council panel were discussing emission controls to come, but the director of powertrain sales at Mack Trucks had the unenviable task of listing equipment problems linked to earlier decrees by the U.S. Environmental Protection Agency (EPA).
It was a long list.
The last 11 years have seen the biggest changes in diesel technology since Rudolf Diesel created the first engine of its kind, McKenna said, referring to EPA mandates that came in October 2002, 2007 and 2010. First came Exhaust Gas Recirculation (EGR) systems to lower smog-producing NOx created in the combustion process. Diesel Particulate Filters (DPF) followed those, capturing lung-clogging flakes that would otherwise be released from an exhaust stack. Selective Catalytic Reduction (SCR) and the related tanks of Diesel Exhaust Fluid (DEF) were introduced to transform remaining NOx into nitrogen and water.
New maintenance challenges emerged every step of the way, and with every nameplate.
“Exhaust Gas Recirculation challenged us all,” McKenna said, referring to his fellow manufacturers. Coolers cracked in the face of demands to lower exhaust gases from 1,000 Fahrenheit to 300 Fahrenheit in a space of just 24 inches. Valves failed. Pitot tubes plugged.
The most common hardware-related complaints these days seem to be traced to DPFs. Delta pressure sensors have cracked, filters are plugging ahead of schedule, and fleets report unwanted spikes in the regeneration processes which transform trapped soot into ash. Many shops are cleaning the filters ahead of schedule – after as little as 325,000 km of service — largely to spot emerging problems while the equipment is still under warranty. Meanwhile, engines are being de-rated to sloth-like speeds when “drifting” NOx sensors generate faulty engine codes. No clean air? No speed for you.
Engineers have hardly been sitting idly by. The diameters of pitot tubes were enlarged to keep them clear. EGR coolers have been remounted to protect against cracks, and new software and upgraded sensors are addressing DPF challenges. The addition of Diesel Exhaust Fluid has also allowed earlier EGR rates to be lowered, reducing the strain caused by that process.
The experience with 2010 mandates was probably the smoothest because manufacturers were able to draw on past experience in Europe and Japan, McKenna added. Then again, Navistar ultimately had to abandon its plans to create an EGR-based system that would meet these emissions standards without SCR.
Why did these problems happen in the first place? The EPA’s October 2002 deadline forced manufacturers to rush new components into production ahead of an original 2004 schedule, but there was plenty of testing behind the systems which followed. “There was a lot of learning,” Detroit Diesel engineer Chuck Blake explained in an interview. Sometimes, equipment which performed well during many miles in test fleets would struggle in a wider rollout, requiring further upgrades. On Series 60 engines, for example, the EGR valve was moved from the hot side of the engine to the cold side and back again, largely in a bid to keep it free of blockages. Detroit reprogrammed engine software to switch specific components on and off to force unwanted blockages out of the system. And if coolant temperatures appear to climb too fast, a fan might turn on at 205 Fahrenheit rather than 225 F.
Other engine makers have examples of their own.
As much as the equipment has evolved, many Canadian fleet managers continue to struggle with components introduced in the name of cleaner air. When asked about the overall experience, several laughed outright.
“I’m very frustrated with the engines,” says Tim Harkness, director of maintenance with Cavalier Transportation Services in Bolton, Ont. In one week alone, five of his trucks broke down because of failing DEF lines. “Everything to do with emission controls is what causes us the problems nowadays,” he says.
Steve Sharpe, Cooney Transport’s manager of fleet maintenance, refers to engine failures involving everything from EGR valves to coolers, DPFs and turbochargers. Oil change intervals at the Ontario-based fleet have dropped to 40,000 km compared to the 60,000 km enjoyed before the air-clearing mandates emerged. “I’m still pushing that out farther than the engine manufacturer would like it to be,” he says.
Steve Haus, service manager for the Erb Group of Companies in New Hamburg, Ont., describes his experience in three words: “Frustrating as hell.” Every time one emission-related challenge is addressed, another seems to emerge. First, EGR valves and coolers were failing. Then problems emerged where cooled exhaust was fed back into the engine. Drivers also had to be discouraged from a long practice of topping up any low coolant. “If you’re adding antifreeze and you don’t see a leak, it’s going internally, and [then] it’s messing up sensors,” Haus says.
One of the biggest challenges of all has come in the form of added weight. The latest SCR-era equipment is adding about 450 lb. to the truck. Coupled with the weight of tools like chains for northern routes, it can be tough to fit 43,000 lb. of cargo in the trailer, he says.
Mullin Trucking’s biggest issues tended to involve failing sensors. Luckily, maintenance director Kelly Scheer says the components linked to SCR systems have been relatively trouble-free, other than a batch of trucks that had problems with heated lines used to deliver the DEF, causing engines to de-rate.
The latter issue bothers Gary McLean most of all. “The units that work seem to work well,” says the maintenance supervisor with Steinbach, Man.-based Penner International. “When they have a problem, you are up the creek.” Stuck with a de-rated engine that can barely limp off a highway, drivers can face long delays to address issues like a split DEF line – especially in areas where shops are stretched to the limit. “It would be nice if that de-rating would start after 2,000 km,” he muses. “If [a driver has] to spend five days in Edmonton when his home base is somewhere in Manitoba … you’re looking at a big cost.”
Outside of cracking EGR coolers, XTL Transport’s maintenance director, Jason Wood, struggles with drivers who ignore the warning lights that call for a DPF to be manually regenerated. The solution has come in the form of added inventory and a pair of extra DPF units for each model of truck. But now he’s worried about what the fleet’s experience will be with SCR. “It’s not so much the cost. It’s giving the driver a responsibility to make sure the tank is full.”
As much as components have evolved, there’s no mistaking that fleets shoulder new responsibilities with every new piece of exhaust-handling equipment.
McKenna stressed several times that fleets need to watch for updates to the engine software stored in Electronic Control Modules. Service bulletins also need to be monitored for advice on caring for everything from delta pressure sensors to seventh injectors. Coolant must be free of any air, and the related pressure cap needs to have the proper rating and sit securely in place. Diagnostic trees also have to be followed to the very last step, addressing any underlying causes of different symptoms, he added.
Even the quality of the fluid needs to be monitored. “A $150 refractometer will give you a very good idea of the water content in the DEF,” McKenna said.
In the meantime, fleets are cautiously waiting for the 2014-model-year engines, which promise to reduce Greenhouse Gases (GHG) and improve fuel economy &nda
sh; a welcome step given that some fleets have only recently recovered fuel economy lost in the name of cleaner exhaust. Compared to their 2010 counterparts, 2014 engines will need to be 3% more fuel-efficient; the 2017 models will need better the 2010 models by 5%. Canada recently agreed to adopt the same rules.
These engines could carry some new maintenance needs of their own. A label inside the driver’s door on every GHG-reducing truck will include every piece of equipment used to meet the standards. Fleets are expected to maintain every related component, whether it is an aerodynamic device or fuel-efficient tires, although enforcement strategies have not been set. Some engine parameters – like speed limiters that top out at 65 mpg, or automatic shutdowns that kick in after 5 minutes of idling – may also be in place.
They will hardly replace today’s systems. Aftertreatment systems like DPFs and SCR are here for the “foreseeable future”, says Vic Meloche, manager of technical sales and support for Detroit Diesel.
It will be up to maintenance managers to decide if this is a reason to breathe easy.
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