Diesel Particulate Filter (DPF) Cleaning Practices Standardized

By Fernando Varela, CEO, RAVHD

If you are in any way involved with heavy-duty clean-diesel vehicles and equipment, you most likely never asked yourself vital and overlooked operational and maintenance questions about DPF cleaning.  If you had however, you could now be saving thousands of dollars, minimizing production downtime and protecting the environment. 

You ask “how does my company start saving money on heavy-duty vehicle repairs, reduce my fleet’s downtime? My company has no standardized way to clean DPFs. Will this really help us?”

The best news is yes!

It is never to late to save money, increase worker productivity, and to do all you can to protect the earth that we inhabit.

Your organization should begin by adopting three principles: 1) use a standardized and trusted DPF cleaning methodology like the one described in this white paper,  2) only use industry leading and trusted DPF cleaning equipment, 3) deploy conditionally-based testing software to track and measure the effectiveness of the entire DPF cleaning process. Then utilize the data gathered to predict future maintenance requirements and replacement parts needed.

This DPF cleaning how-to-document details industry principles that should be adhered to in order to guarantee your DPFs are cleaned properly every-time.

DIESEL PARTICULATE FILTER CONDITION BASED CLEANING – WHAT IS IT?

DPF cleaning is messy, literally and figuratively.  DPF cleaning can be time consuming and is often considered a nuisance by the truck driving community.

Performing periodic maintenance on your DPF and other components of the after-treatment system is comparable to performing an oil change, less frequent, but a necessity. If DPF cleaning is ignored, it can cost the truck driver or fleet manager large sums of money and unexpected downtime.

The following steps ensures a thoroughly cleaned DPF: 1) Visual Inspection 2) Air Flow Pressure Testing 3) PIN Testing 4) Bypass Inspection 5) Air Cleaning and Thermal Cleaning when needed. 

1) A Visual Inspection will reveal the DPF’s surface damage such as cracks, loose ceramic, gouging and or melting. A Visual Inspection step will also reveal any evidence of oil soaking, discoloration, and the number of initial black holes observed.

2) The first recording or the initial results of the DPF’s Air Flow Pressure Test will show how dirty the DPF is. It is this beginning pressure reading that will serve as a benchmark throughout the cleaning process.

After all subsequent DPF cleaning steps have been completed the DPF will fall into either a Red Tag (condemned, do not return to production), Orange Tag (acceptably cleaned, o.k. to return to production) or Green Tag (pass, return to production) category during the Air Flow Pressure Test procedures.

3) PIN Testing is the process of measuring a DPF’s cell depth to verify the health of the cell. It also reveals if a cell is breached.  PIN Test measurement are achieved by inserting a metal PIN into the clean end of variously selected DPF cell ports. An off-the-shelf measurement PIN tool is usually either 10 inches, 16 inches or 20 inches in length.

PIN Tests will show that there is generally a 3/8 inch plug felt at the bottom of most DPFs’ cell when the measurement is taken from the clean end (exhaust side) of the DPF.  At its core, a DPF prevents soot and ash from entering the atmosphere. So there should be no or minimal signs of soot and ash bypassed from one end of the DPF to the other.

4) The Bypass Inspection procedure simulates a DPF’s performance while in production. It measures the bypass of Particulate Matter (PM) through a DPF. This test is done in a two minutes time frame. When completed, it will indicate the number of cells that are defective. Ideally, less than 20 cells should be defective.

5) High Pressure Air Cleaning of both ends of a DPF for 15 to 30 minutes will extract soot and ash from a DPF.  The High Pressure Air Cleaning procedure is done using a pressurized pneumatic cleaning machine. At the beginning of pressurized pneumatic cleaning, any damaged cells will be revealed. A thermal cleaning takes longer than air cleaning, but when used in conjunction with air cleaning this process removes any soot and ash that air cleaning is not able to. 

When all of the above are done in conjunction, the Diesel Particulate Filter will be returned to industry standard operating specifications.

WHEN IS IT TIME TO CLEAN A DPF?

DPFs should be cleaned whenever one or more of the following conditions are encountered:

  • A check engine light condition occurs
  • A turbo goes bad
  • An EGR (Exhaust Gas Recirculation) goes bad
  • Truck is running very sluggish
  • DPF maintenance light is on
  • Miles per gallon has decreased significantly
  • Identify frequency of hauls (Short vs Long). This determines when to clean a DPF.
    • Short Hauls – clean sooner rather than later because increased idling time during short trips, causes more accumulation of soot and ash
    • Long Hauls – it is recommended that the DPF be cleaned annually for best performance results

Please refer to your OEM’s recommendations for maintenance intervals.

GATHER YOUR FACTS AND DETERMINE THE REASON A DPF FAILS

Start by asking:

  • What kind of fuel was the truck using?
  • What kind of oil was being used?
  • What kind of antifreeze was being used?
  • Was the regeneration process skipped regularly?
  • Was the after-treatment system serviced before?

Possible causes for a DPF to fail:

  • The truck driver neglected to adhere to regular maintenance schedules.
  • The DPF cleaning facility neglected to properly inspect the DPF. A thoroughly inspected DPF can reveal discoloration and internally plugging. A failure to inspect the DPF can result in a plugged DPF being reinstalled on a truck. This creates more back pressure internally which causes the turbo and other upstream engine components to fail.
  • A proper DPF inspection can also show a technician that a problem is looming inside the truck’s engine which requires immediate attention. For example, if the engine injectors are leaking too much diesel, this leakage will eventually make its way into the DPF.  This liquid settles and bakes solidly inside the DPF. The exhaust flow system becomes plugged. If the DPF is simply returned to service, this blockage increases back pressure and will cause the turbo and other engine components to malfunction.

THE DATA BEHIND DPFTRAC’s TECHNOLOGY

DPFTRAC software processed over 10,000 DPF work orders through its production systems in the United States and Canada for 16 months.  Each DPF cleaning produced quantifiable data markers that directly correlated to when and where monetary resources could be saved and/or productivity could be enhanced and uninterrupted. DPFTRAC showed:

  • Optimal DPF cleaning intervals
  • A fleet’s maintenance practices
  • A truck’s engine performance
  • The life expectancy of the DPF being cleaned

DPFTRAC used the data it obtained from DPF cleanings from one fleet of 125 trucks (model years 2008 to 2016), DPFTRAC found:

  • 85% (106) of the trucks were brought in for DPF cleaning service once during the 16 month period
  • 60% (64) of the trucks had their DPF cleaned multiple times
  • 9% (10) of the trucks were equipped with a new DPF (different serial number from the prior DPF cleaning) or the owner installed a swap-out DPF since their last DPF cleaning.

DPFTRAC found filter conditions a predictor of future expenditures or savings:

  • Red Tagged DPFs that were cleaned but whose truck had engine issues that were subsequently rectified, the DPF returned for service one year later for a DPF cleaning. This was expected.
  • Red Tagged DPFs that were cleaned and whose truck had engine issues that were not addressed, the DPF returned for service two months later. The DPF required another cleaning.
  • Red Tagged DPFs that were cleaned but showed no improvement after cleaning and then returned to production, these filters progressively deteriorated.  This usually means the vehicle will use more fuel or may not operate at all.

HOW SMART IS DPFTRAC – DIESEL PARTICULATE FILTER TRACKING SYSTEM – WILL IT HELP ME?

DPFTRAC standardizes the DPF cleaning process in an automated step by step format. DPFTRAC can:

  • Conditionally diagnose a DPF’s condition based on data entered by the DPF technician
  • Track DPF cleanings by work order number
  • Track DPF cleanings by purchase order number
  • Track DPF cleanings by customer/company name
  • Track DPF cleanings by DPF part number
  • Track DPF cleanings by DPF serial number
  • Track DPF cleanings by DPF manufacturer
  • Track DPF cleanings by Truck (VIN, Vehicle Number)
  • Track DPF cleanings across the country with two pieces of information (part number and serial number)
  • Email PDF created versions of DPF Cleaning History Worksheet (for customer and office records)
  • Wireless printing of compliance forms, FAQs, and DPF measurements instructions

CONCLUSION

Truck drivers, fleet managers, maintenance shop owners and dealerships must all be proactive. Recognize when its time to clean a DPF. What causes the DPF to go bad? Is it time to replace the DPF? What conditional parameters must be met in order to properly clean a DPF? Is cleaning the DPF again after cleaning it a short period ago economically wise? This DPF Cleaning whitepaper answers all of the above.

Proactive managers should deploy DPFTRAC, Diesel Particulate Tracking System, to ensure their technicians are using an industry standardized step by step process to clean DPFs. A DPFTRAC cleaned DPF is done properly and conditionally every time. A clean DPF equals a happy trucker.