DPF’s, or Diesel Particulate Filters, are required to reduce exhaust emissions on virtually all diesel engines. Whether you have an over-the-road truck or industrial equipment, you likely have a DPF attached to the exhaust system. The real question is do you know how the difference between DPF regeneration and DPF cleaning?

If you’ve researched DPF’s at all, then you’ve probably heard the term “regeneration.” This can be a confusing term, but the simplest way to explain it is that regeneration is the process by which the DPF burns off the emissions that it has filtered from the exhaust. Easy enough, right? The real question is how does it do this and what is the impact on the engine?

DPF Filter

DPF Regeneration Methods

All regeneration methods are designed to increase the temperature inside the DPF to the point where the emissions will combust and burn up. That being said, the different methods have different impacts on the engine that can decrease the life of the engine. The method used is normally determined by the engine manufacturer, in the case of new equipment, since it requires knowledge of engine details and access to the engine control unit. Here are some of the methods that can be used:

Active Regeneration Methods (For On-the-road Vehicles and Equipment with Varied Duty Cycles)

  • Altering the Turbo Boost
  • Intake Air Throttling
  • Late (Post) Injection of Fuel into Combustion Chamber
  • Modification of the EGR Valve
  • Post Catalytic Oxidizer Fuel Injection
  • Retarding of Injection Timing

Passive Regeneration Methods (For Industrial Equipment with Regular Duty Cycles)

  • Precious-metal Substrates are added to raise Exhaust temperatures
  • Off-board Regeneration Stations

Active Regeneration Methods have to be used for equipment when the engine does not operate at a steady pace (accelerates, decelerates, and idles) which does not allow the exhaust to stay hot enough to burn up the filtered emissions. Unfortunately, virtually all of these methods result in additional wear and tear on the engine, reduced fuel economy, and reduced power. The exception to this is the Post Catalytic Oxidizer Fuel Injection which adds fuel directly to the exhaust before it reaches the DPF. This method impacts engine performance the least. However, all methods can benefit from fuel additives that help reduces the temperature needed for emissions combustion (typically 600° C).

Passive Regeneration Methods have no real effect on engine performance, but they can only be used with engines that are run at a steady pace. This is typically only found in industrial equipment like generators and mining equipment. Some trucking companies that use a depot where trucks can sit in between runs may use an off-board regeneration station.

Why Regeneration is not Cleaning

Many people think that regeneration is a sort of automatic cleaning of the DPF. This is not true and can result in significant engine damage regardless of what type of regeneration is used. Regeneration is simply the process of burning up the emissions the filter has trapped which leaves behind ash and soot. Over time, this will clog the filter and create a significant amount of back pressure in the exhaust system. This can lead to a number of problems including:

  • Damage to the DPF, Exhaust System, and/or Engine
  • Reduced fuel economy
  • Loss of engine power

Considering the cost of fixing or replacing the DPF exhaust system can climb over $7,000, you must have your DPF cleaned on a regular basis. “Regular” is a very subjective term since it really depends on how often the equipment is run and whether or not the DPF is allowed to regenerate often enough. Vehicles that are only operated for “in-town” routes that rarely reach highway speeds may never undergo regeneration. Maintenance lapses on industrial equipment may prevent the filter from undergoing regeneration. Diesel engines that aren’t running efficiently may be expelling higher emissions than the filter is designed to handle. All of this can require the filter to be cleaned more often. Check with your equipment’s manufacturer to determine the recommended cleaning frequency.

What is DPF Cleaning?

Now that we understand regeneration simply burns off emissions, we can examine DPF cleaning. Cleaning a DPF requires special DPF cleaning equipment that most shops won’t have lying around. We use the following steps while cleaning these filters.

  1. Place the filter in our DPF cleaning chamber and use an air knife to to clean the filter without damaging it.
  2. Inspect the filter for damages. Damaged filters must be replaced or risk severe damage to the engine or exhaust system.
  3. Bake the filter at 1100° in a special furnace to remove any left behind soot or residue.

Most other cleaning services stop after step two, but we ensure your filter is as clean as possible by taking the extra step to bake off any particles left behind. This gives you the best possible performance for your filter and prevents engine damage from a build up of back pressure caused by a clogged filter. Check out the difference in a filter before and after it is cleaned. You can click on each image for a larger view.

Before

After

In order to get the most out of your equipment, make sure you have your DPF cleaned regularly. If you’d like to schedule a cleaning or have any questions, give us a call at 1-800-223-4299.

(PSTC would like to thank the fine folks at C, G & J Inc for their permission to re post this great article.)

photo credit: Rolls-Royce Power Systems AG via photopin cc  and C, G, & J Inc

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