***\"Mention of any company name or product does not constitute
endorsement by MSHA.\"***

MNM DPF Filter Selection Guide Explanations

Diesel Particulate Filters (DPF)

Overview

Diesel particulate filters applicable to the equipment used in your
Metal or Nonmetal mine are designed to filter diesel
[soot](../MNM_DPF_Glossary.htm#Soot) from the hot exhaust. They also
replace the muffler. The filter media used in the majority of the
commercially available DPFs is made from a porous ceramic material made
from either [Cordierite](../MNM_DPF_Glossary.htm#Cordierite) or [Silicon
Carbide](../MNM_DPF_Glossary.htm#Silicon_Carbide). The Silicon Carbide
material is more robust, filters slightly more efficiently, but is more
expensive.

The filters work by blocking passage of the diesel soot so that much
less than 10% of the soot in the engine's exhaust is released into the
mine air. Obviously, soot builds up in the filter and something has to
be done to remove it. The process of removing the combustible portion of
the collected soot is called
\"[regeneration](../MNM_DPF_Glossary.htm#Regeneration)\" which is the
burning off of the soot by raising the temperature of the filter element
so that combustion of the soot occurs. When the soot combusts, the soot
which is almost pure carbon is converted to gaseous carbon dioxide
(CO~2~) and carbon monoxide (CO), which pass through the filter. Diesel
soot or [DPM](../MNM_DPF_Glossary.htm#DPM) is not entirely comprised of
combustible carbon but also contains noncombustible
[ash](../MNM_DPF_Glossary.htm#Ash) resulting primarily from the
additives used in crankcase lubrication oils, fuel or intake air
additives, and from the fuel itself. The removal of the ash from the DPF
is called \"cleaning\" and, although necessary to do, is done much less
frequently than regeneration. See the [discussion of ash](#ash) in this
document.

DPF regeneration can occur \"passively,\" or naturally when the engine
exhaust is hot enough during equipment operation. Some DPFs use a
washcoat of specially-formulated
[catalysts](../MNM_DPF_Glossary.htm#Catalyst), [fuel-borne
catalysts](../MNM_DPF_Glossary.htm#FuelBorneCatalyst) (a fuel additive),
or both to reduce the exhaust temperature needed for regeneration.

When natural passive regeneration is not possible, the DPF stores the
soot during machine operation, and a regeneration must be \"actively\"
performed on a *regular* schedule, for example once every shift. Active
regeneration uses electric heating elements and a controlled air flow to
regenerate the filter when the equipment is not in use. The commercially
available systems for active regeneration either incorporate the
electric heating element into the DPF and regeneration takes place
on-board the equipment while the equipment is off duty and parked at a
designated location, or require the exchange of the loaded DPF for a
regenerated DPF. In the exchange scheme, the loaded DPF is taken to a
[regeneration station](../MNM_DPF_Glossary.htm#Regeneration_Station)
located in a designated area (perhaps with other such regeneration
stations) that is ventilated and free of combustibles either underground
or on the surface. Another system uses compressed air, flowing in the
reverse direction from the normal exhaust flow, to blow out the
collected soot and ash into a collection bag.

The exhaust temperature dictates whether passive or active DPFs are
applicable for a specific piece of equipment. Active systems are
universally applicable because they only collect the soot and can be
mounted where convenient, but passive systems impose strict requirements
on exhaust temperatures and must be mounted as close to the engine
exhaust manifold as possible.

You can learn more about regeneration methods
[here](#DPF_regeneration_methods), the effect of a DPF on engine exhaust
back pressure and the need to monitor [here](#Exhaust_back_pressure),
and ash removal [here](#ash_removal), or you can continue to scroll down
and keep reading.

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DPF regeneration methods

The soot that is trapped by the DPF can be removed in several different
ways. The removal of the carbon soot from the DPF is called
[regeneration](../MNM_DPF_Glossary.htm#Regeneration).

-   **Passive Regeneration** -- Passive regeneration occurs when the
    soot in the DPF spontaneously combusts (burns off) during the normal
    work cycle because the exhaust temperatures are sufficiently hot.
    Techniques have been developed that can lower the temperature
    required for passive regeneration. The most effective technique is
    to coat the surface of the filter media used in the DPF with noble
    metal catalysts such as platinum. This has the undesirable effect of
    increasing NO~2~. In general, the more catalyst used, the lower the
    regeneration temperature and the greater the conversion of NO to
    NO~2~. MSHA has issued a [PIB
    P02-04](http://www.msha.gov/regs/complian/PIB/2002/pib02-04.htm)

> Other ways to reduce regeneration temperatures which do not increase
> NO~2~ include using [fuel-borne
> catalysts](../MNM_DPF_Glossary.htm#FuelBorneCatalyst) (FBC),
> fuel-borne catalyst with a light washcoat of platinum on the DPF, and
> washcoats of a base metal catalyst.
>
> A rule of thumb has evolved for characterizing exhaust temperatures at
> which regeneration occurs for passive DPFs of the different systems
> described above. Specifically it is the exhaust temperature that is
> exceeded about 30% of the operating time during a shift. It this
> document it is called the [critical
> temperature](../MNM_DPF_Glossary.htm#Critical_temperature) and
> represented by T~30%~. The exhaust temperatures required for passive
> regeneration for these techniques range from about 325 to 420^o^ C
> (615 to 790^o^ F)

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**Active Regeneration** -- The term \"Active\" regeneration refers to
the requirement for the active involvement of a person or mechanism to
accomplish the DPF regeneration. Active regenerating DPFs must be used
when the engine exhaust temperature during the work cycle is not hot
enough to burn off the soot being collected. Soot, therefore,
accumulates in the DPF and must be removed. Active regeneration is
usually performed on a set schedule, usually at every working shift. A
set schedule which fits into a regular or natural work pattern such as a
shift, or day, or week, is a must to ensure that regeneration is
performed *without fail*. The DPFs are sized to collect a full
shift-load of soot without creating excessive back pressure on the
engine. Several active regeneration schemes, employing
temperature-controller electric heaters and controlled low air flows to
heat up the DPF to about 800&deg; C to ignite the soot, are currently
available:

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-   **On-board regeneration** -- In this scheme, the electric heater is
    built into the front/upstream section of the DPF. Regeneration takes
    place while vehicle is off duty. The controller and compressor can
    be installed on-board the vehicle or can be a separate unit. If the
    controller and compressor are on-board, the equipment needs only to
    be parked in a ventilated area away from combustible materials and
    where there is a source of electric power. If the controller and air
    compressor are off-board the equipment, it must always travel to the
    location of the control unit. If the equipment cannot be parked at
    the same place at the end of a shift, then additional control units
    need to be purchased or on-board controller should be considered.

> During regeneration the electric heaters heat the DPF to high internal
> temperatures (about 800^o^ C). The outer surface of the filter may get
> hot and combustion gases very slowly flow from the equipment\'s
> exhaust. A regeneration parking area should be designated where the
> appropriate electrical, fire, and ventilation safety requirements are
> in effect. Regeneration times can range from under one hour or two
> (Silicon Carbide media) to eight hours (Cordierite) depending on DPF
> size, filter media, and regeneration system manufacture. This
> regeneration time defines the time required every shift or every day
> that the vehicle must be \"out of service.\"

-   **Off-board regeneration** -- The DPF is removed from the equipment
    (this is most easily accommodated with the smaller DPFs used for low
    horsepower engines) and placed into a filter regenerating system
    designed for it. Such a system will be connected to a source of
    electric power, may incorporate a temperature controller, compressed
    air source and controller, and possibly a catalyst on the outflow to
    eliminate hydrocarbons and carbon monoxide from the combustion
    gases. Some regeneration systems blow out the DPM into a collection
    bag prior to starting the heated regeneration cycle. The
    regeneration units must be properly located to meet proper
    electrical, fire, and ventilation safety requirements. Regeneration
    times are similar to those of the on-board unit.

> The equipment down time can be very short, since a newly regenerated
> DPF can be exchanged for a loaded DPF when the loaded one is removed.
> The exchange scheme doubles the DPFs required for each piece of
> equipment.

**Active-Passive Regeneration** -- In some cases, the exhaust
temperatures are sufficient to combust most, but not all, of the soot
during normal equipment operation. This has been seen to occur in
systems incorporating a fuel borne catalyst and/or base metal catalyzed
DPFs. In this case, the active regeneration of the DPF is required only
after extended periods of operation, say, for example, after 250 or 500
hours and can be performed during the regularly scheduled maintenance.
Active-passive regeneration of the DPF uses the same methods as those
for Active Regenerating systems described above. Monitoring of back
pressure is critical for these systems, because a slight reduction in
the operating cycle load can significantly lower the soot burn off rate
and reduce the operating time before active regeneration is required.

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Exhaust back pressure

As the DPF collects soot, the passage of exhaust gas through the pores
of the filter element is progressively blocked and the pressure required
to maintain the exhaust flow increases. This pressure that the engine
exhaust must work against is called \"back pressure.\" Engine
manufacturers place limits on the exhaust back pressures for their
engines. Beyond a certain limit, excess exhaust back pressure increases
engine exhaust temperature, CO, and particulate matter (soot) emissions.
The additional soot emissions loads the DPF up even faster. Because of
detrimental effects of excessive exhaust back pressures on both engine
and DPF (discussed below), a back pressure monitoring system must be
installed with the DPF.

The exhaust back pressure increases for two reasons:

-   short term build up of soot, remedied in the short term by
    [regeneration](#DPF_regeneration_methods); and

-   long term build up of ash, the noncombustible component of soot,
    remedied by [cleaning](#ash_removal).

Need for back pressure monitoring

Overloading the DPF with soot can be detrimental to the life of the DPF.
When the DPF is overloaded, spontaneous
[regeneration](../MNM_DPF_Glossary.htm#Regeneration) in passive DPFs
becomes difficult to control and may become too vigorous causing the
filter media to melt or crack. For both the protection of the engine and
the DPF, all DPF installations *require* a system to monitor engine
exhaust back pressure continuously during engine operation. Back
pressure monitoring systems can range from those consisting of a simple
mechanical gage with the high level marked on the dial to systems using
electrical pressure sensors in a sophisticated electronic data loggers
and a display multiple alarm set points. Some can incorporate an exhaust
pressure measurement into the electronic engine control system to cut
back the fueling rate when exhaust back pressures exceed the safe level.
Back pressure monitoring systems are offered by most DPF manufacturers
as part of the DPF installation and is one criteria to be used for
selecting a DPF supplier.

Exhaust back pressure monitoring is also a must because of the slow
increase of the back pressure in a regenerated DPF caused by the build
up of [ash](../MNM_DPF_Glossary.htm#Ash). At some point in the service
life of any DPF, the regenerated DPF back pressure will be too high to
allow the normal build up of soot without exceeding the back pressure
allowed by the engine. When this happens the ash must be removed from
the DPF by following the manufacturer\'s instructions for cleaning. The
ash build up will not occur if the regeneration process includes an ash
removal step in the routine regeneration process.

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Ash Build-up and Removal

**Ash Build-up**

Not all of the soot can be removed from the DPF by regeneration which
combusts the carbon portion of the soot. A small fraction of the soot is
not combustible, the ash. The primary source of ash in diesel exhaust
soot are the additives in the crankcase oil. This oil lubricates the
cylinder walls, and a small part of it is combusted with the fuel.
Additional (repairable) lube oil leaks from worn piston rings or valve
guide seals can add significant contributions to ash. Ash is also
created by the use of any metal-based fuel additives or by additives to
the combustion air.

Unless the engine is consuming lube oil or is a 2-stroke engine, the
build up of ash is a slow process and demands no action for several
hundred hours or even a thousand hours of operation. Since the life of a
DPF is several thousand hours (10,000 or more), the ash must be removed
several times during the useful life of a DPF.

**Ash Removal (DPF Cleaning)**

Ash can be removed from the DPF by several different methods. The DPF
manufacturers will provide the hardware, instructions, or a service to
remove the ash from the DPFs they supply. The alternatives include back
flushing with compressed air into a collection bag or placing it on a
special regeneration and cleaning station which uses a vacuum cleaner to
reverse flow the air through the DPF as part of the regeneration
process. It is not a good practice to reverse the DPF on the engine and
use the engine exhaust flow to purge the DPF of ash unless this is done
in an open space outdoors and is recommended by the DPF supplier.

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Explanations specific to MNM DPF Selection Questions

**Why is it important to have a site champion?**

The successful implementation of diesel particulate filters requires the
coordination and cooperation of several departments within a mine
operation. It was pointed out in a discussion group at MDEC 2003, that
the introduction of DPFs will require a \"cultural shift\" of the entire
mining organization, but in particular, those responsible for
maintenance and operation of the equipment. The mine management should
designate a single person who will be responsible for the selection and
implementation of diesel particulate filters at a specific mine and for
providing the training to implement the necessary cultural changes. This
person should then be given the authority, responsibility and time to
perform this function.

The list below provides some indication of the variety of people and
disciplines involved in the control of DPM.

-   Presumably the vehicle(s) targeted (by the **ventilation or health
    and safety** department) as candidates for DPF installation was/were
    selected as a result of a survey of area or personal exposures to
    DPM (Total or Elemental Carbon) and the knowledge of the local
    ventilation.

-   **Engine mechanics** need to be involved to ensure that the engine
    is in proper working order. These may be either mine employees or
    contractors.

-   **Vehicle and engine maintenance** persons need to be consulted on
    the placement of the DPF on the vehicle so as to not cause undo
    impediment to routine vehicle or engine maintenance.

-   The **production or operations people** need to be involved because
    the DPF may require adjustments to vehicle operation and production
    schedules to accommodate active regeneration systems.

-   The **equipment operator(s)** needs to be involved so he/she
    understands the importance of a DPF to air quality and to learn the
    importance of back pressure alarms or gages and actions to be taken
    if exhaust back pressure is exceeded during production.

-   Finally the **ventilation or health** department needs to conduct
    post installation surveys to verify reductions in DPM, and if
    necessary, when precious metal (i.e., Platinum) catalyzed DPFs are
    used, verify that the workplace NO~2~ concentrations are at safe
    levels.

It is the responsibility of the site champion to gather together all of
these persons who are directly involved with the DPF and fully explain
each person\'s role and responsibility, to solicit suggestions, and gain
their acceptance and cooperation. It is the site champion who must
maintain and operate with the knowledge of the full picture required for
successful implementation of a DPF on a single or several vehicles.
Without such a person to coordinate the application of DPFs, successful
implementation is less likely.

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Explanation of Engine Questions

**Why is the type of engine important?**

Two-stroke diesel engines emit exhaust particulate matter (PM) than
equivalent 4-stroke engines, and the PM contains lubrication oil. This
affects the diesel particulate filters (DPF) in two ways:

-   the size or capacity of the DPF must be larger for a 2-stroke engine
    to provide adequate service time between regenerations for active
    DPF systems; the larger size increases the cost of the DPF and
    requires more space for installation.

-   the lubrication oil contains ash which cannot be removed by thermal
    regeneration; frequent maintenance to remove the ash would be
    required to maintain an acceptable exhaust back pressure.

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**Why be concerned with engines that burn oil?**\
\
The excessive burning of oil contributes to the engine\'s particulate
matter (PM) emissions reducing the service time between regenerations in
DPF systems that must be manually regenerated (active DPF system).
Generally, the capacity (and thus the running time between
regenerations) of active DPFs are sized for the PM emissions rate for a
specific engine model *in good working condition*. The lubricating oil
also contains metals which create an ash residue in the DPF that is not
removed by simple thermal regeneration. Thus ash accumulates much faster
than it should, increasing the back pressure of a fully regenerated DPF,
shortening the service life between regenerations in active DPFs, and
requiring more frequent maintenance to remove the ash for both active
and passive DPF systems.

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**Why must the exhaust CO concentration be at an acceptable level?**

The carbon monoxide concentration in the raw exhaust is a good indicator
of engine condition and/or engine tune. Higher than normal CO
concentrations in the engine exhaust at full engine load (torque stall)
indicates incomplete combustion of the fuel. Incomplete combustion also
causes high diesel particulate matter (DPM) emissions which means the
DPF will load up with soot more quickly which will be detrimental to the
successful functioning of a DPF. Monitoring engine-out (before any after
treatment) CO concentrations in the exhaust forms the basis for
[emissions-based
maintenance](../MNM_DPF_Glossary.htm#Emissions_Based_Maintenance).

CO is also a toxic gas and must be controlled so that the workplace CO
concentration does not exceed that allowed in §57.5001 (50 ppm).

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Exhaust Temperatures

**Why do I need to obtain an exhaust temperature profiles of my
equipment?**

Exhaust temperature profiling, that is, obtaining a set of exhaust
temperature vs. time logs, is needed primarily for determining the DPF
regeneration method alternatives that will work on the target equipment.
In addition, the DPF supplier can use this information to estimate
engine loading and particulate matter emissions to assist in sizing the
DPF for the application. Temperature traces or logs need to be obtained
for several shifts to provide a valid representation of the variety of
situations in which the equipment is used.

The temperature of the engine exhaust is the most critical parameter in
determining whether the target equipment can utilize a [passive
regenerating](../MNM_DPF_Explanations.htm#PassiveRegen) DPF or must use
an [active regenerating](../MNM_DPF_Explanations.htm#ActiveRegen) DPF.
With one exception a fuel burning active regenerating DPF active
regenerating DPFs cause a greater impact on vehicle deployment,
maintenance, and operation than passive systems. Whether a DPF can
successfully regenerate using exhaust temperatures alone, is highly
dependent on the length of time the exhaust is above a certain threshold
temperature and on the catalyst formulation of the DPF system.

Successful use of a passive DPF also requires that the equipment on
which it is installed operate at high loads for **every** shift; ***the
equipment cannot be reassigned without a reassessment of exhaust
temperatures***.

The amount of operating time during a shift that the engine is heavily
loaded provides an indication of the particulate loading of a DPF for a
shift and affects the sizing (soot holding capacity) of the DPF for most
active DPF systems.

The variability of engine temperatures and loading experienced from
shift to shift is of critical importance in assessing whether normal
operation can support a passive DPF. If the equipment occasionally works
one or more shifts with lighter loads, exhaust temperatures may not be
sufficient to regenerate the DPF with the result of excessive exhaust
back pressures and potential for destruction of the DPF.

The Compliance Assistant, and most reputable DPF suppliers and
manufacturers, insist on having a valid and representative temperature
profile for the vehicle targeted for installation of a DPF prior to
making a recommendation of a DPF system for the target application.

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**What are the differences between getting temperature traces myself and
using a DPF supplier or independent consultant? What does the Compliance
Assistant suggest?**

Below are some things to consider when choosing whether you gather
exhaust temperature profiles yourself or let an a DPF supplier or
consultant do it.

When you collect temperature traces yourself

-   **Disadvantages**

-   You must invest in equipment (a little over \$250 for a \"kit\");

-   You must train personnel to use the temperature logging equipment
    and software.

-   You must give the person time and responsibility to do this task.

-   **Advantages**

-   Collecting exhaust temperature profiles is simple; it is the
    analysis that is the challenge;

-   You are free to move the temperature logging kit from one piece of
    equipment to another as needed;

-   You gain a person on your staff and on-site who is trained in
    temperature logging and can expand to other activities for DPF
    support;

-   You own all of the data and can share it with all potential DPF
    suppliers or consultants for analysis;

-   You can collect over more shifts;

-   You can log temperatures after installation, upon redeployment of
    equipment (a necessity with passive DPFs), and anytime temperatures
    are needed;

-   You will need to establish exhaust temperature logging capabilities
    in any case in the long run.

When you contact a DPF supplier or consultant to collect the exhaust
temperatures:

-   Ask for an on-site visit either to actually perform the temperature
    profiling and/or to train your personnel to continue after the
    visit;

-   Ask whether you or they supply the temperature profiling
    instrumentation;

-   If the instrumentation is supplied by them, ask how long you can
    keep it;

-   Negotiate for your ownership of the raw temperature data in
    electronic form compatible with popular spreadsheet programs
    (separate data collection task from that of data analysis);

-   Ask whether the data analysis results in a DPF recommendation and/or
    consists of exhaust temperature analysis such as histograms,
    cumulative frequency analysis, moving averages, etc. which provides
    the basis for DPF selection.

-   **Disadvantages**

-   The contractor\'s time available to remain on-site to collect
    exhaust temperatures is limited. To continue with gathering
    additional traces on this or other equipment, *you will have to do
    it yourself*.

-   The contractor may not be able to profile the equipment for
    sufficient number of shifts to cover the variety of tasks
    encountered;

-   Unless you own the logging equipment, you have no opportunity to
    profile other equipment or log exhaust temperatures after DPF
    installation.

-   **Advantages**

-   Minimum investment of your time and personnel when the DPF supplier
    can come on site and collect temperature traces.

-   The temperature profiling can be part of the DPF system purchase
    with the DPF supplier assuming the responsibility for a successful
    DPF application.

In sum, the Compliance Assistant believes that the optimum arrangement
would be for you to acquire the equipment and collect the temperature
data yourself. MSHA or NIOSH can assist you in this task. Also see
[taking exhaust temperatures myself](../MNM_DPF_Actions.htm#Get_Temps).
You can then provide the temperature profiles to all of the potential
DPF suppliers for their analysis and DPF option recommendations.

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DPF System Configuration Details

Passive DPF Systems Descriptions & Considerations

::: Definition-Term
**Un-catalyzed DPF**
:::

An un-catalyzed DPF consists of Cordierite or Silicon Carbide ceramic
filter media that has not been catalyzed; it is bare and hence the
nickname of \"bare trap.\". This DPF will regenerate when exhaust
temperatures exceed 450 to 500&deg; C for at least 30% of the engine
operating time per shift.

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**Considerations for Un-catalyzed DPF**

-   It is rare that these exhaust temperatures (450 to 500&deg; C) can
    be achieved with today\'s modern turbocharged engines. Because the
    exhaust temperatures are marginal for passive regeneration, there is
    a risk that a slight or subtle decrease in equipment work load would
    decrease the exhaust temperature below that needed for regeneration.
    Back pressures and exhaust temperatures would have to be carefully
    monitored.

-   The CO, unburned hydrocarbons (HC) responsible for diesel odor, and
    the health impact of the equipment emissions would be reduced if a
    diesel oxidation catalyst (DOC) were used either before or after the
    DPF.

-   Given the above it is worth considering using a lightly catalyzed
    (platinum) DPF (without a fuel additive). A lightly Pt-catalyzed DPF
    would (1) regenerate at a lower exhaust temperature providing a
    margin of safety and (2) would also remove CO and HC.

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::: Definition-Term
**Base Metal Catalyzed DPF**
:::

Some DPF suppliers offer a DPF with a Cordierite media coated with a
base metals which act to reduce the exhaust temperatures required to
initiate and sustain regeneration. The exhaust temperatures need to
exceed 400 to 420&deg; C for at least 30% of the engine operating time.

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**Considerations for Base Metal Catalyzed DPFs**

-   Achieving 420&deg; C consistently is not common but achievable in
    shifts with heavy work loads relative to the available engine
    horsepower.

-   Base metal catalysts do not reduce CO or unburned hydrocarbons (HC).
    Therefore a diesel oxidation catalyst (DOC) could be added upstream
    or downstream of this DPF with some health benefit and odor
    reduction. Such systems are offered by some DPF manufacturers.

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::: Definition-Term
**Lightly Catalyzed DPF plus Fuel Additive**
:::

The \"Lightly Catalyzed DPF + Fuel Additive\" is a system consisting of
a ceramic filter element that has been given a light wash coat of
Platinum- (Pt-)based catalyst. Additionally, a \"bi-metallic\" [fuel
borne catalyst](../MNM_DPF_Glossary.htm#FuelBorneCatalyst) is used in
the fuel to provide a regeneration temperature of about 360&deg; C,
which falls between that of the base metal catalyst and the highly
catalyzed DPF.

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**Considerations for Lightly Catalyzed DPF plus Fuel Borne Catalyst
(FBC)**

-   Recent (February 2003) data seems to indicate that this system will
    passively regenerate when the exhaust temperatures are above the
    360&deg; C (30% of the time) or 335&deg; C (40% of the time).

-   It has also been the experience for some installations that although
    regeneration is not quite keeping up the soot accumulation, manual
    regeneration needs only to be done at an interval that corresponds
    with the scheduled 250-hr maintenance.

-   Preliminary MSHA tests at A&CC indicate that the conversion of NO to
    NO~2~ is not significant (in contrast to the heavily catalyzed DPF
    system discussed below). It is currently unknown to NIOSH whether
    the build up of the catalytic metals from the fuel additive in the
    filter element would affect the NO to NO~2~ conversion increasing it
    as the ash accumulates. A cleaning of the DPF to remove the ash
    would remedy this easily.

-   The light coating of noble metal catalyst does reduce CO and
    hydrocarbons resulting in odor reduction and additional health
    benefit.

-   The [fuel-borne catalyst](../MNM_DPF_Glossary.htm#FuelBorneCatalyst)
    (FBC) must be continuously present in the fuel. Various methods are
    used to accomplish this. Some manufacturers offer on-board automatic
    dosing systems which sense the fuel level in the equipment\'s tank
    and meter out the appropriate quantity of FBC additive as the fuel
    level increases upon refueling. Manual dosing can be achieved by
    metering the fuel during refueling and adding the proper quantity of
    FBC based on the fuel delivered. The third alternative is to add the
    FBC to the bulk fuel that is subsequently kept separate from the
    fuel for other equipment not using this or any other DPF.

-   It is very important not to use fuel doped with a fuel-borne
    catalyst in equipment which is not equipped with a DPF.

-   Using a fuel-borne catalyst increases the rate of ash accumulation
    in the DPF. The dosing level for some FBC additives (the bi-metal
    FBC in particular) is quite low, which minimizes ash build up
    reducing the effect on the period between
    [cleaning](../MNM_DPF_Glossary.htm#Cleaning).

The DPF prevents the fine ash particles of the FBC from being emitted
into the workplace air. Although it is an MSHA requirement that the fuel
borne catalysts be approved by the EPA, their release into the air is
not desirable. Therefore, there is a slight additional diligence needed
to ensure that the DPF is not cracked and is filtering properly.

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::: Definition-Term
**Catalyzed DPF**
:::

A catalyzed DPF system consists of a ceramic media coated with
sufficient Platinum (Pt) catalyst to produce soot burning (regeneration)
at exhaust temperatures at about 325&deg; C. Substantial amounts of Pt
are used, hence these systems are often called \"heavily\" catalyzed
DPFs to distinguish then from the lightly catalyzed DPFs.

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**Considerations for Heavily Catalyzed DPF**

-   The heavily catalyzed DPFs offer the lowest regeneration
    temperatures of the systems available for mining. The
    Johnson-Matthey CRT® system designed for city buses has a lower
    regeneration temperature but has a high conversion of NO to NO~2~
    that is not controllable nor desirable in underground settings.

-   Heavily Pt-catalyzed DPFs obey the principles of chemistry and
    readily convert the NO in the exhaust stream to NO~2~. The
    conversion rate, which directly affects the amount of NO~2~ that is
    emitted, varies with the DPF temperature and peaks at temperatures
    slightly above that for minimum regeneration. The NO~2~ is consumed
    somewhat by the soot in the regeneration process, thus the
    concentration in the tailpipe may vary depending on the amount of
    accumulated soot in the DPF. Since the compliance level for NO~2~ is
    5 times lower than for NO, the health effects of NO~2~ are more
    serious. In sum, the above together strongly indicate the need
    consider seriously the (active) DPF alternatives or to monitor NO~2~
    in the workplace when heavily catalyzed DPFs are used.

-   Several mines have tried the heavily catalyzed system on their
    equipment because it is the simplest to install and maintain.
    Because of the lack of data, it is not clear whether NO~2~ is a
    problem.

-   If this system does not regenerate reliably, then the only option is
    to use an active DPF system.

-   Link to [installation
    precautions](../MNM_DPF_Actions.htm#Cat_DPF_Precautions) for heavily
    catalyzed DPF.

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Active DPF Systems Descriptions & Considerations

::: Definition-Term
**Systems with off-board regeneration**
:::

Off-board regeneration is used to describe an active (regenerating) DPF
system in which the DPF must be removed from the equipment for
regenerating.

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::: Definition-Term
**DPF Exchange or Swapping**
:::

Off-board DPF regenerating requires the removal of the DPF for
regenerating, usually by placing the DPF in a special regenerating
\"station\" designed for that purpose. Because the time involved in
transporting and regeneration usually exceeds the between-shift down
time of the equipment, the DPF supplier usually recommends two (or more)
DPFs so that when a loaded DPF is removed from the equipment it is
immediately replaced (exchanged or swapped) with a regenerated DPF.

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**Considerations for Off-board DPF Swapping**

The introduction of DPFs requiring active regeneration demands a
\"culture shift\" in mine operations and personnel. Implementation of
this culture change is one reason for having a site champion. The
implications of an off-board regenerated DPF are the following:

-   Because the weight, size, and cost of a DPF increases with engine
    power, DPF swapping can be limited to equipment with engines of less
    than about 150 hp.

-   DPF swapping produces the least downtime of the equipment of any of
    the active DPF systems.

-   Unless the downtime of the equipment exceeds the regeneration time
    of the DPF (regenerating times vary between about one hour to eight
    hours depending on filter composition), you will need at least two
    DPFs for this equipment.

-   DPF swapping requires the easy and convenient access to the DPF on
    the equipment. Some thought should be given to this factor when
    designing the installation layout and the design of the DPF
    connection to the exhaust system. The connection between the exhaust
    system and the DPF must not leak.

-   The logistics (the when, where, and how) of DPF exchange must be
    carefully thought out. The DPF exchange should be (actually, must
    be) scheduled and performed regularly; therefore, it must be set up
    in such a way to ensure that DPF exchange occurs on schedule without
    fail.

-   Transportation of the DPFs between the equipment and regeneration
    station must be thought about. This factor influences the location
    of the regeneration station so that transportation of DPFs is
    minimized to reduce risk of breakage and inconvenience.

-   As a consequence of the above, equipment most suited to DPF swapping
    are the following in order of suitability:

-   utility vehicles (small horsepower, well exposed access to DPF,
    regular parking place between shifts)

-   production equipment with engines smaller than 150 hp, which park at
    an established location between shifts, and with easy access to DPF
    for its removal

-   remote, roaming, or isolated vehicles which are fueled by a visiting
    fuel truck which would be able to carry a DPF for exchange at every
    fueling

-   The equipment least suited for off-board regeneration (DPF exchange)
    would be those with any one of the following characteristics: a
    large engine, no convenient location of DPF for easy access, are
    parked anywhere at the end of the shift, or are fueled by the
    operator from any fuel tank that is convenient at the time of need.

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::: Definition-Term
**On-board active regenerating DPFs**
:::

Active DPF systems in which the DPF remains on-board the equipment
during the regeneration process are termed \"on-board regenerating DPF
systems.\" Because the DPF remains on board the equipment, the electric
heating element must be built into the DPF on the upstream end of the
DPF. However, the heater element temperature controller and air
compressor or regulator can be either on-board the vehicle or in a
separate off-board unit. These two systems are described below.
Regeneration requires the vehicle to be out of service for the period of
the regeneration which can range from as little as one to as much as
eight hours depending on system selected.

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::: Definition-Term
**Active on-board regenerating DPFs with on-board controllers**
:::

These systems have their temperature controller and combustion air flow
source (a small pump) on board the equipment and only require connection
to a source of electric power.

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::: Definition-Term
**Considerations for on-board controller systems**
:::

::: Definition-Term
Here are some things to consider with the on-board controller system:
:::

-   ::: Definition-Term
    All the operator needs to do to start regeneration is to connect the
    unit to an appropriate source of power.
    :::

-   ::: Definition-Term
    The equipment therefore must be parked between shifts at a source of
    electric power suitable for powering the regeneration unit. This has
    a number of ramifications:
    :::

-   ::: Definition-Term
    A parking area has to be established that provides the power to as
    many pieces of equipment that may need it.
    :::

-   ::: Definition-Term
    The parking area should be adequately ventilated to remove
    combustion gases from the regenerating DPF.
    :::

-   ::: Definition-Term
    The internal temperature of the DPF will reach 800&deg; C or greater
    during regeneration. Depending on the DPF design, the surface
    temperature of the DPF may also be extremely hot. Precautions must
    be taken both in locating the DPF on the equipment and in the
    parking area to ensure that flammable material is not near or in
    contact with the DPF during regeneration. Normally this should pose
    no problem.
    :::

-   ::: Definition-Term
    The regeneration control unit, because it is mounted on-board the
    equipment, is subjected to the vibrations of the equipment on which
    it is mounted. This has proved to be a weak point in the systems
    tested in the past by DEEP. Suitable engineering can rectify this
    problem.
    :::

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::: Definition-Term
**Active on-board regenerating DPFs with off-board controllers**
:::

These systems have their temperature controller and combustion air flow
source and controller as a unit separate from the diesel equipment. An
umbilical containing heater power, temperature measurement signal, and
air hose as a minimum connects the DPF on the equipment to the control
unit.

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::: Definition-Term
**Considerations for off-board controller systems**
:::

::: Definition-Term
Here are some things to consider with the off-board controller system:
:::

-   ::: Definition-Term
    All the operator needs to do to start regeneration is to connect the
    unit to the umbilical cable from the regeneration controller and
    start the controller.
    :::

-   ::: Definition-Term
    The equipment therefore must be parked between shifts at the site
    where the regeneration controller *for that DPF system* is located.
    This has a number of ramifications:
    :::

-   ::: Definition-Term
    A parking area has to be established that provides the connection to
    the regeneration control unit. There must be one regeneration
    controller for each piece of equipment that requires regeneration at
    that location.
    :::

-   ::: Definition-Term
    If operating scenario for the equipment places it at different
    locations at the end of a shift then each location needs to be
    equipped with a regeneration controller for that equipment. For
    example, if a vehicle works on several different levels and cannot
    take the time to travel to another level at the end of the shift, a
    regeneration facility needs to be made at each of the working levels
    for that vehicle. It may be advantageous in this case to consider
    on-board regeneration controllers since only a source of electrical
    power is needed for their operation.
    :::

-   ::: Definition-Term
    The parking area should be adequately ventilated to remove
    combustion gases from the regenerating DPF.
    :::

-   ::: Definition-Term
    The internal temperature of the DPF will reach 800&deg; C or greater
    during regeneration. Depending on the DPF design, the surface
    temperature of the DPF may also be extremely hot. Precautions must
    be taken both in locating the DPF on the equipment and in the
    parking area to ensure that flammable material is not near or in
    contact with the DPF during regeneration. Normally this should pose
    no problem.
    :::

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::: Definition-Term
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:::

Acknowledgments

::: Definition-Term
***This document was authored by George Schnakenberg, Jr. in
consultation with Aleksandar Bugarski, both with NIOSH, It was reviewed
by Larry Patts of NIOSH and James Angel of MSHA. It represents the state
of knowledge at the time of writing. Please address any comments about
this document to [George Schnakenberg,
Jr.](mailto:gschnakenberg@cdc.gov), NIOSH-PRL, P. O. Box 18070,
Pittsburgh, PA 15236, 412-386-6655.***
:::