You may recall when the EPA mandated that, starting in 2007, all new on-highway diesel engines must limit the emission of particulate matter. To comply with this regulation, OEM’s incorporated diesel particulate filters (DPF’s) as part of a comprehensive emission’s control system. DPF’s trap diesel particulates (soot) in the engines exhaust through an extensive filtering process that burns off (oxidizes) the soot before it can escape into the atmosphere. To support this new filtration technology, ultra-low sulfur diesel (ULSD) fuel was introduced for use with the DPF equipped engines. ULSD is a cleaner burning diesel fuel that contains 97 percent less sulfur than low sulfur diesel fuel. ULSD was developed to allow the use of the improved pollution control devices that reduce diesel emissions more effectively but can be damaged by sulfur.
Today, as many stationary, mobile, and off-road engines become affected by Tier 4 emissions regulations, depending on the horsepower, much can be learned by looking in the rearview mirror at the experience of the on-highway sector. This is what we have learned.

  1. The DPF technology and the emissions control systems are working. DPF technology and other emissions control systems are working. This technology is effectively filtering diesel exhaust. Clear evidence is building that cleaner diesel exhaust helps remove major health risks caused by prolonged exposure to diesel exhaust, such as increased risk of cardiovascular, cardiopulmonary, and respiratory disease, and lung cancer. Truck driver life expectancy is also beginning to climb; more evidence that diesel exhaust after treatment systems do the job.
  2. Does a clean DPF improve fuel efficiency? Many fleets are now reporting fuel efficiency gains from 3 percent to as high as 5 percent when DPF’s are cleaned regularly.
  3. How often does a DPF need cleaning? Years ago wrong assumptions were made about DPF service intervals. Perhaps the most damaging assumption was because the DPF could inventory a lot of ash, then service intervals could be extended out to 15,000 hours or more on off-road applications. At the time, on-road mileage recommendations could run as high as 400,000 miles. Both assumptions have since proven false. Ash left too long in the DPF will gradually solidify into a hardened “ash island” causing permanent backpressure, as well as a host of other problems from cracking to melting. Remember, you may not have anywhere near 100 percent ash load on your DPF, but the 30 percent you do have may have solidified, rendering your expensive DPF uncleanable. Bottom line: DPF filters must be cleaned early and often while the ash is soft and pliable. Service intervals can vary depending on the application. (Check the service manual for specific recommendations for your vehicles or equipment.)
  4. What happens when DPF cleaning is ignored altogether? 1) Back pressure causes the trucks active regeneration system to over engage adversely affecting fuel efficiency, 2) Heat shock encourages substrate cracking, low temperature glass formation (glazing), and melting. All destroy the DPF resulting in vehicle downtime and added expense. DPF’s should be “inspected and verified suitable for reuse,” advises David McNeill, parts and service manager at Cummins Service Solutions. DPF’s that are improperly cleaned or not cleaned at regular intervals are most likely to require replacement. Filters cleaned at proper intervals “result in improved DPF reliability and durability, as well as reduce the likelihood of frequent regenerations, poor fuel efficiency, and downtime,” he notes.
  5. Should I clean my DPF in-house or contract it out? Prices charged for DPF cleaning range between $350 and $500, depending on location and the cleaning method used. Some manufactures offer exchange programs in lieu of cleaning, which usually run between $600 and $800 per filter. It has been our experience at FSX that when a fleet requires 100 or more cleanings per year, it is cost effective to own their own cleaning system. Such a fleet would pay for the cleaning equipment in about 1 year.
  6. Is the ash material hazardous? California classifies the waste ash as “low level hazardous” and thus must be disposed of through licensed waste disposal companies. All other states allow for the dry ash to be disposed of as regular refuse in the landfill. However, always check state and local regulations for handling hazardous waste in your area first, as local regulations can change without notice.
  7. What DPF cleaning equipment should I purchase? DPF cleaning systems have been in use for years now and there is a variety to choose from. Do your homework before purchasing one. Key things to keep in mind include: 1) Is the DPF cleaner OEM tested and recommended? 2) What is the method of cleaning? 3) What size compressor does the cleaner use? Check CFM/PSI rating. The more powerful the compressor, the more effective and complete the cleaning. The more complete the cleaning, the better the fuel efficiency, and the less chance for in-service downtime, and lastly, the longer the DPF lasts, which is an important consideration when reselling your power units or trucks. 4) Is the DPF cleaning process visible to the technician? Visible cleaning is the only way to truly determine when cleaning is complete and if cracking of the substrate has occurred.

When Choosing a DPF cleaning system, remember: YOU GET WHAT YOU PAY FOR! Careful attention needs to be paid to choosing a DPF cleaning service, as well.
In conclusion: Much has been learned and wisdom has been gained on the actions necessary to safeguard your exhaust filter investment. The Interim Tier 4 exhaust after treatment filters is complex and expensive, yes; but vastly better for the air we all breathe. Become familiar with the exhaust after treatment on your equipment. Be proactive in maintaining your DPF’s and DOC’s and you will be surprised at how durable, trouble-free, and cost-effective this technology can actually be. ■
For more Information or more information about DPF cleaning systems, contact FSX Equipment, Inc. at 360.691.2999, or visit

Modern Contractor Solutions, August 2014
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