The term DPF in most industries will give people chills. It’s a technology that most people want to avoid and hope will never come up in conversation. In reality, it’s a wildly complicated but simple system that by understanding just a few basic principles can greatly influence your bottom line… in a good way.
A study conducted recently by Webasto Thermo & Comfort North America, in conjunction with a major industry media partner, suggests that over 75% of the fleet and maintenance managers surveyed did not know how much they were spending annually to clean or replace DPFs.
“Today’s DPFs are engineered to reduce pollution by trapping particulate matter (PM), the byproducts of diesel engine exhaust gases, before they can be released into the environment,” said Duane Bratvold, Western regional business development manager for Webasto Thermo & Comfort North America, Inc. “Engine combustion releases exhaust gases which are channeled through the DPF and converted to ash through regeneration and stored until they are cleaned.
During engine operation, soot deposits form on the walls of the filter and continue to build up over time. Once exhaust gases reach a predetermined temperature and backpressure, the regeneration process begins. Deposits of the ash remain in the filter cavities until they are removed by periodic cleaning. Engine age, condition and duty cycle all contribute to the need for DPF cleaning. These factors should be monitored closely to avoid costly downtime and DPF replacement.
Running Hot and Cold
“A DPF’s operational efficiency and is wholly dependent upon it reaching the proper operational temperature. If exhaust gases are not hot enough, the DPF may not function as desired,” Bratvold said. “The DPF is at particular risk when the engine it serves is started cold.
Cold engines can release un-combusted fuel, engine oil, and PM into their DPF, coating them with a thick, wet heavy soot that often leads to face plugging and filter overload. The result is decreased vehicle performance, additional DPF cleaning and/or replacement costs and downtime. These costs can range from $2,500 to $8,000 including downtime, per vehicle.
Cold engine starts are one factor when calculating DPF overhead costs, but engine idling has to be part of the equation as well. Some industry professionals contend that idling time can account for as much as 45 to 50 percent of a vehicle’s operational life. In fact, according to the U.S. Department of Energy, a long-haul truck spends approximately 1,800 hours per year idling, consuming about 1,500 gallons of fuel in the process.
“Unfortunately, an idling engine never reaches temperatures high enough to trigger DPF regeneration and therefore, the abundance of contaminates accumulate in the DPF, overwhelming it and causing it to lose efficiency,” Bratvold said. “The most efficient regeneration sequence commonly begins at or about 450 to 600 degrees Celsius (842 to 1,112 degrees Fahrenheit), temperatures generally achieved only at highway speeds and well above idling temperatures.”
Temperature-related DPF issues are also prevalent in vehicles with low duty cycles. With the increase in home deliveries, precipitated by the e-commerce revolution, many vehicles have been refocused on last-mile delivery routes with shorter duty cycles. A truck that might have been operating on long distance routes with no DPF issues can begin to have DPF problems if it is assigned shorter routes with frequent stops, increased idling or engine-off sequences. Sub-optimal temperatures and increased emissions are the result and the DPF becomes overloaded and plugs frequently.
Bratvold suggests that to help minimize the impact of increased idling time, fleet maintenance managers can ask drivers to alert them of any engine or DPF warning lights. “Through teamwork, all stakeholders can help their fleet minimize DPF-related damage, repairs and downtime” he added.
Keeping It Clean
Cleaning a DPF incorrectly can result in a voided warranty and if proper cleaning methodologies are not employed, a DPF may be damaged, resulting in greatly reduced efficiency and service life. Cleaning a DPF requires significant skill and knowledge and a specific understanding of the manufacturers recommendations. Powdery ash may be relatively easy to remove, but carbon deposits can cling to and remain lodged in the DPF’s ceramic surface and pores.
Bratvold noted that for the DPF to function properly after cleaning, the majority of contaminants must be extracted, while leaving the filter’s catalytic coating intact. Cleaning approaches are dependent on the DPF make, model and may include compressed air, heat or a combustion cycle booth. “Cleaning should only be performed by a qualified person or service facility,” Bratvold said.
Pre-Conditioned for Success
One way to protect a fleet’s DPF investment is to use an engine-off coolant heater like the new Webasto Thermo Top Evo. Pre-heating or pre-conditioning a diesel engine with a fuel-operated heater (FOH), allows the engine and its fluids to warm to about 165 degrees prior to engine starting. This greatly reduces noxious waste moving into the exhaust system, commonly associated with cold starts. Fuel-operated heaters are quickly becoming a reliable tool among fleets for controlling DPF maintenance costs, idling times and fuel costs.
For more information on Webasto’s full-line of fuel-operated heaters, including no-idle bunk heaters and engine-off coolant heaters, visit Webasto.com.