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 retrofit
technologies that reduce emissions from diesel fueled
vehicles and equipment. DPFs use a porous substrate,
typically a ceramic or wire mesh filter, to physically trap
particulate matter (PM) and remove it from the exhaust
stream.
As a DPF collects PM, the passage of exhaust gas through
the pores of the filter element may be progressively
blocked, causing an increase in exhaust backpressure.
Backpressure increases, caused by the short term build
up of PM, are remedied in the short term by regeneration.
Long term build up of ash is remedied by periodic cleaning.
An exhaust backpressure monitoring and operator
notification system must be installed with every DPF so
when exhaust backpressure exceeds certain thresholds
the operator is notified that filter maintenance is needed.
Regeneration occurs when the filter element reaches the
temperature required for combustion of the carbon in the
PM, converting it to gaseous carbon dioxide (CO2) and
carbon monoxide (CO). "Passive" regeneration occurs
when the exhaust temperatures during the normal duty
cycle are hot enough to sufficiently raise the temperature
of the filter element. Metal based catalysts applied to
the filter alter the combustion chemistry and reduce the
exhaust temperature needed for passive regeneration.
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Diesel Particulate Filter
"Active" regeneration must be used when the engine
exhaust temperature is not hot enough to initiate
combustion of the collected PM, and an additional heat
source is required to sufficiently raise the temperature of
the filter element. The minimum frequency of regeneration
is determined by the rate of PM build-up and is generally
once per day or shift.
In addition to regeneration, the filter must be periodically
cleaned to remove noncombustible materials (ash) resulting
primarily from lubrication oil and fuel additives. Cleaning
is required much less frequently than regeneration and
requires manually removing the filter element from the
vehicle and placing it in a cleaning station designed for
this purpose.
Emissions Reduction
The United States Envirnomental 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 80 to 90 percent, with
some nonroad applications achieving 25 to 50 percent PM
reductions. EPA-verified DPFs also reduce emissions of
hydrocarbons and CO by 70 to 90 percent. DPFs generally
have no impact on nitrogen oxide (NOx) emissions. DPFs
can be combined with crankcase ventilation systems for
additional emissions reduction.
EPAis aware of concerns that catalyzed DPFs may increase
the nitrogen dioxide (NO2) fraction of total NOx emissions.
The catalyst generates NO2 as a means of regenerating
the filter at lower temperatures. The NO2 produced by a
DPF is dependent on the catalyst formulation. EPA and
GARB have established a limit on incremental NO2 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 from a wide range of model
years, including buses, trucks, construction equipment,
auxiliary power units and stationary generators.
Each DPF is verified for use with specific engines and/or
with specific configurations over a wide range of model
EPA-420-F-09-007
February 2009
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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. 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.aov/otaa/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 and their installation generally range from $5,000 to
$10,000 or more, depending on engine size and whether
installation is a muffler replacement orcustom configuration.
Active DPF systems are more expensive than passive DPF
systems and can cost up to $50,000 for a large piece of
nonroad equipment. Backpressure monitoring systems and
mounting brackets are offered by most DPF manufacturers
as part of the DPF installation. Costs for cleaning stations or
cleaning services should be considered when purchasing
DPFs. *
California Air Resources Board Warranty
Requirements
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 Requirement
Two years; unlimited mileage
Five years or 150,000 miles
Five years or 100,000 miles
Five years or 60,000 miles
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.
Warranty coverage is typically part of the commercial
negotiated process between product suppliers and their
customers. Such warranties typically cover defects in
materials or workmanship for a specified period defined in
years, miles and/or operating hours.
As part of their verification program, GARB has established
detailed warranty requirements for CARB-verified retrofit
technologies as shown in the following table.
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