An STN Webinar dove into the polarizing and challenging issue of diesel particulate filter (DPF) maintenance, and how school bus operators can extend their service life and reduce repair costs.
Webasto Thermo & Comfort North America sponsored the webinar, Extending Maintenance Intervals & Lowering Maintenance Costs of DPFs, with 120 attendees joining the live event on Thursday. The recording is archived for 24/7 viewing and sharing.
Paul Baczewski, national account manager at Webasto, began the presentation by providing a brief overview on how Webasto’s pre-conditioning solutions work with the existing coolant system and differ from an engine block heater. Then, diesel emissions expert Duane Bratvold spoke for nearly an hour on how engine pre-conditioning warms the engine to optimal operating temperatures before school bus ignition, allowing for passive regeneration to occur and for the DPF to operate efficiently.
This, he added, can reduce or eliminate DPF clogging that leads to expensive maintenance and even equipment replacement, not to mention save fuel over idling the engine or even using an engine block heater option.
Bratvold. He said a common misconception regarding pre-conditioning systems or other engine heaters is that they are only necessary in cold weather. Not true, he said. In fact, he said tail-pipe emissions are highest when engine temperatures are the coldest. He also pointed out that the typical operating temperature range for diesel engines is between 150 and 180 degrees, so preheating the engine before ignition, even during summer months and in warm climates, eliminates cold start the burdens they place on DPFs.
He said the No. 1 DPF failure he sees across the country is a result of operator ignorance, as the industry often failed to adequately educate drivers about warning indicators on the driver dash, where they were located and want they mean. He added that the results were often reports of “failure after failure after failure.”
He explained that not all DPFs are alike, as they have varying controls and coating. As a result, fleet operators need to understand which ones they use in their buses, as well as how existing maintenance practices and process might damage DPFs and promote failure.
As diesel emissions characteristics are based on vehicle duty-cycle, Bratvold shared that fleets should know how crankcase emissions, injectors, turbochargers and even EGR contribute to emissions. He also discussed how DPFs melt and how districts can take steps to avoid these costly incidents, including limiting the use of additives and repairing exhaust leaks to avoid introducing foreign elements, oxygen, excessive soot, engine oil and more that can increase exhaust heat past the maximum threshold of 450 to 600 degrees Celsius that a diesel engine can operate under in real-world applications.
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