Technical Bulletin
Diesel Particulate Filter
General Information
National Clean Diesel Campaign
www.epa.gov/cleandiesel
Technical Overview
Diesel Particulate Filters, also known as DPFs, are exhaust
aftertreatment devices that significantly reduce emissions
from diesel fueled vehicles and equipment. DPFs typically
use a porous ceramic or cordierite substrate or metallic
filter, to physically trap particulate matter (PM) and remove
it from the exhaust stream.
After it is trapped by the DPF, collected PM is reduced
to ash during filter regeneration. Regeneration occurs
when the filter element reaches the temperature required
for combustion of the PM. "Passive" regeneration occurs
when the exhaust gas temperatures are high enough
to initiate combustion of the accumulated PM in the
DPF, without added fuel, heat or driver action. "Active"
regeneration may require driver action and/or other
sources of fuel or heat to raise the DPF temperature
sufficiently to combust accumulated PM. The frequency of
regeneration is determined by the engine's duty cycle, PM
emission rate, filter technology and other factors. When
using an active filter, it is particularly important to follow
the manufacturer's instructions for regeneration.
In addition to regeneration, the filter must be periodically
cleaned to remove noncombustible materials and ash. It is
important to avoid excessive PM and ash accumulation in
a DPF, so proper maintenance and cleaning instructions
should be followed closely. Cleaning of DPFs is typically
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Diesel Particulate Filter
required every 6 to 12 months. The cleaning process
involves manually removing the filter element from the
vehicle and placing it in a cleaning station designed
for this purpose. An engine emitting excessive PM or
inadequate filter regeneration will cause a DPF to require
more frequent cleaning. Diagnostics should be performed
to identify the cause for more frequent cleaning intervals.
A backpressure monitoring system should always be
used with a DPF and periodic inspection of the monitoring
system should be performed to confirm proper operation.
Emissions Reduction
The United States Environmental Protection Agency
(EPA) and the California Air Resources Board (GARB)
evaluate the emission reduction performance of DPFs
and identify engine operating criteria and conditions that
must exist for DPFs to achieve those reductions.
DPFs verified by EPA and GARB are typically effective at
reducing emissions of PM by 85 to 90 percent or more.
EPA's Verified Technology List also shows that certain
DPFs reduce emissions of hydrocarbons and CO by 70
to 90 percent. DPFs generally do not reduce oxides of
nitrogen (NOx) emissions. DPFs can be combined with
crankcase ventilation systems for additional emission
reductions.
EPA is aware of concerns that catalyzed DPFs may
increase the nitrogen dioxide (NO2) fraction of total
NOx emissions. Some DPFs generate NO2 as a means
to help filter regeneration at lower temperatures. The
NO2 produced by a DPF is dependent on the catalyst
formulation. EPA and GARB have established a limit on
increases in NO2 emissions from diesel retrofit devices
and all DPFs on the lists of verified products comply with
this limit.
Application
Verified DPFs are available for nonroad and highway
heavy-duty diesel engines including those on buses,
trucks, construction equipment, auxiliary power units and
stationary generators.
EPA-420-F-10-029
May 2010
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Each DPF is verified for use with specific engines and/or
with specific configurations over a range of model years. In
addition to vehicle and engine specifications, the intended
application should be evaluated for exhaust temperature,
duty cycle, fuel sulfur levels, lubrication oil consumption
and engine-out PM emission levels. Exhaust temperature
data logging should be performed with each installation
over a range of vehicle duty cycles and, if possible, over
a range of ambient temperatures. A copy of results and
analysis from data logging should be retained by the fleet
for each installation. EPA and CARB's lists of verified diesel
retrofit technologies define the specific engine operating
criteria required to successfully apply a particular retrofit
technology: www. epa.gov/otaq/retrofit/verif-list.htm.
Fuel
DPFs are verified for use with Ultra Low Sulfur Diesel
fuel (ULSD), which contains up to 15 parts per million
sulfur. Fuel additives should not be used unless explicitly
approved by the DPF manufacturer.
Cost
DPFs generally cost between $5,000 to $15,000 or
more, including installation, depending on engine size,
filter technology and installation requirements. Active
DPF systems are more expensive than passive DPF
systems and can cost up to $50,000 for a large piece of
nonroad equipment. Vehicle inspection, data logging and
backpressure monitoring systems are required with each
installation and these costs are typically included in the cost
of the DPF. Because a DPF is likely to be heavier than a
muffler, it is likely that special mounting is necessary. Costs
for cleaning stations or cleaning services should also be
considered when purchasing DPFs.
Longevity
When properly installed and maintained, DPFs should
remain effective for the life of the vehicle, generally five
to ten years or 10,000 or more hours of operation. Engine
problems with fuel control or oil consumption may quickly
deteriorate the performance of a DPF. Consequently, regular
engine maintenance is essential to DPF performance.
Warranty coverage is typically part of the commercial
contract negotiated between the product suppliers and
their customers. Such warranties typically cover defects in
materials or workmanship fora specified period defined in
years, miles and/or operating hours.
As part of their verification program, GARB has established
detailed warranty periods for CARB-verified retrofit
technologies as shown in the following table.
California Air Resources Board
Warranty Period
Vehicle Category
GVWR > 33,000 Ibs.
hp > 250 hp and miles/
year> 100,000 Vehicle
miles < 300k
GVWR > 33,000 Ibs.
hp > 250
GVWR 19,500 to 33,000
Ibs.
GVWR < 19,000 Ibs.
Warranty Period
Two years; unlimited
mileage
Five years or 150,000
miles
Five years or 100,000
miles
Five years or 60,000
miles
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