By reducing the risk of ash clogging in diesel particulate filters, ultra-low ash lubrication technology has the potential to save waste collection and landfill fleet operators’ equipment downtime, and provide longer DPF service life, longer equipment life and lower fuel consumption.
By Dan Holdmeyer
Lower carbon emissions, cleaner air and fuel efficiency are goals we can all get behind. However, manufacturers and operators of diesel-powered waste hauling fleets and landfill equipment have struggled to reconcile these goals with the cost of achieving them.
Legislation on air quality has had a far-reaching impact on diesel engine design and maintenance. The EPA 2010 emission rules governing on-highway vehicles and 2014 Tier 4 Final rules for off-highway equipment mandated sharp restrictions on nitrogen oxides (NOx), carbon monoxide, soot, sulfur and particulate matter in diesel engine exhaust. Meeting these standards has required a well-coordinated effort among engine manufacturers, fleet operators, energy companies and lubrication producers. And, although we have made great strides in reducing harmful emissions from diesel-powered vehicles, changes in engine design have placed an increased burden on waste vehicle maintenance teams to learn how to properly care for the new engines.
To meet these stricter standards, OEMs introduced exhaust aftertreatment systems or EATS. The evolution of EATS began with the introduction of exhaust gas recirculation (EGR) systems, which return exhaust to engines to be further combusted. It continued with the addition of diesel particulate filters (DPFs) and selective catalytic reduction (SCR). Implementation of off-highway standards proceeded at a slower pace, but on a parallel track with similar types of technologies. Today, virtually all OEMs have incorporated a combination of EGR, DPF and SCR systems into their designs.
DPFs, first installed in 2011, have proven effective in removing as much as 98 percent of particulate matter from diesel engine exhaust. A portion of the particulate matter captured is non-combustible ash produced by metallic additive materials and detergents in engine oils. Heavy-duty engine lubricants contain metallic additive materials that are essential for protecting metal surfaces in the engine, but the ash they generate can plug up emission control filters, creating maintenance headaches and driving up operating costs.
Photo courtesy of Chevron Lubricants.
The Impact on Waste Haulers
Waste management maintenance crews find they have to clean DPFs frequently through an expensive regeneration process. Regeneration refers to the process in which the temperature of the engine is elevated to the point that it burns off the accumulated soot. Passive regeneration often occurs naturally in the course of normal operations in on-highway trucks running at sustained high speeds. However, waste collection trucks tend to run at slower speeds and in a stop-and-go mode as they make pick-ups. The same is true of dozers, compactors, excavators and tractors working at landfill sites. As a result, they may not experience passive regeneration and have to be taken out of service for active or forced regeneration. That means downtime and under-use of equipment on top of direct costs for labor.
Moreover, many maintenance managers have found that even after the DPF has been removed, cleaned and re-installed, not all the sulfated ash has been removed, and the expected service life of a DPF is diminished compared to a new, clean filter.
DPF units that have become excessively clogged are prone to cracking and may require replacement, at a cost ranging between $3,000 and $7,000. Besides the direct costs, a DPF replacement will likely take a waste hauling vehicle out of service for at least one or two full days.
A number of waste hauling fleets across the country have turned to biodiesel fuels, an effective use of renewable resources with the added advantage of less toxic emissions than fossil fuels. However, some operators are under the mistaken impression that biofuels keep the engine cleaner, which is not the case. Because biodiesel exhaust atomizes into larger droplets, DPFs tend to accumulate more unspent fuel in the form of soot. Biodiesel vehicles may in fact require more regeneration than a normal diesel-powered vehicle.
In addition to the added maintenance burden, ash and soot accumulation in DPFs also impedes fuel efficiency by forcing engines to work harder. While fuel cost efficiency is less of an issue in waste and recycling than for long-haul fleet operators, fuel is still a major operating expense and any savings would go straight to the bottom line. This is simply another reason for a concerted effort to mitigate the problems caused by clogged aftertreatment systems.
Rethinking the Oil Itself
While vehicle manufacturers continue to evolve and refine their engine designs to address carbon emissions and fuel efficiency, producers of heavy-duty diesel lubricants also have a role to play in this effort. That means looking at the source of the problem: the oil itself. As much as 90 percent of non-combustible matter in a typical DPF are the result of lubricant additive materials. Detergents such as calcium and magnesium and anti-wear additives such as zinc contribute significantly to ash accumulation and DPF clogging.
Oil specifications have changed over time to keep up with lower emission demands, but have not specifically addressed EATS. The maximum ash content allowed in diesel engine lubricants has remained at 1 percent under the API CK-4 standard, introduced in 2016. But not all CK-4 oils are formulated the same. Certain types or higher amounts of metallic additives will result in faster rates of ash accumulation. Engine load can also be a factor—the more stress an engine is under, the more ash is likely to accumulate.
Even with modern lubrication advances, DPF maintenance, repair and replacement costs related to ash accumulation continue to burden many equipment managers. The challenge for lubrication producers is to further reduce ash content without compromising the protective benefits of additives that waste equipment operators count on.
Reducing the Risks
Chevron has devoted substantial research and development hours and dollars to this issue over the past decade. In the course of our research, we learned that by replacing metallic additives with organic compounds that are equally effective in engine protection, we could reduce the sulfated ash content of a typical CK-4 oil by more than half, from the maximum mandated 1 percent to 0.4 percent. In extensive bench and field testing, we found that oils produced using this ultra-low ash technology met or exceeded CK-4 performance standards for wear protection, oxidation and deposit control.
By reducing the risk of ash clogging in diesel particulate filters, ultra-low ash lubrication technology has the potential to save waste collection and landfill fleet operators significant sums in the form of reduced maintenance and equipment downtime, longer DPF service life, and longer equipment life in general, in addition to lower fuel consumption.
Working together with waste equipment OEMs and waste management companies, we believe we can realize the dual benefits of reduced carbon emissions and lower operating costs across the industry. | WA
Dan Holdmeyer is the Industrial and Coolants Brand Manager at Chevron (San Ramon, CA). With more than 40 years in the oil and gas industry, Dan Holdmeyer has worked for Chevron the past 19 years, serving in a variety of capacities with the company in addition to his current post as Industrial and Coolants Brand Manager where he works as a lubrication engineer that supports Chevron Delo and other related lubricants brands. He plays an integral role in supporting and managing a variety of programs related to off-highway and on-highway lubrication needs. Dan also works as Chevron’s Training Specialist for their Global Lubricants division since joining the company. Chevron and their peers in the lubrication industry are committed to clean air standards and reducing the cost of implementing them. These are not mutually exclusive goals. Chevron has recently introduced the first generation of heavy-duty lubricants using this technology, specifically targeting DPF performance and maintenance issues and are continuing R&D efforts in this area. For more information, visit chevronlubricants.com.