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Technology News

From the Bureau of Mines, United States Department of the Interior

13 developments from Bureau of Minos programs. itis published to encourage the

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No. 431, April 1994

Apparatus for Sampling and Measuring
Diesel Tailpipe Emissions

Objective

Develop a portable emissions measurement apparatus
to sample and measure tailpipe concentrations of diesct
particulate matter (DPM), carbon monoxide (CO), carbon
dioxide (CO,), nitric oxide (NO), and nitrogen dioxide
{NO,) under steady-state engine load and speed conditions
during a 1-minute test.

Background

The U.S. Bureau of Mines (USBM) has a comprehen-
sive research program to develop ways to reduce exposure
of miners to diesel exhaust pollutants. Engine mainte-
nance has been shown to have important effects on such
exposure.

Accurate measurements of tailpipe emissions are
becoming an essential part of a good maintenance
program for underground mines that use diesel-powered
vehicles. Past studies of particulates in U.S. underground
coal mines have shown that DPM alone may be present at
concentrations greater than 1 milligram per cubic meter
(mg/m), half the 2-mg/m? limit for respirable coal mine
dust. A poorly tuned (smoking) diesel engine may be the
sole cause for respirable dust concentrations exceeding the
limit. Although there is currently no standard specifically
for DPM in U.S. mines, regulatory steps are underway,
and significant reductions of DPM levels in both coal and
metal mines will most likely be required.

Tailpipe emission measurements can provide diagnostic
information lo identify engine malfunctions such as

clogged air cleaners, faulty injectors, or incorrect injection
timing. In some cases, mine vehicle tailpipe DPM concen-
trations have becn reduced up to 50 percent by engine
maintenance and adjustments.

An accurate measuring instrument would also be useful
for determining the cffects of exhaust control devices on
tailpipe emissions. Little information is currently available
about the overall effectiveness of exhaust controls after
long-term use. Raw exhaust concentrations with and with-
out the control device can be measured in underground
mincs, and from these data a control efficiency can be
calculated. Knowledge of the effectiveness of exhaust
control devices over time is needed to make intelligent
decisions on how to use and maintain these devices, and
when to replace them.

Approach

The design and development of the emissions measure-
ment apparatus was undertaken by Michigan Technological
University, under sponsorship by the USBM.! The ap-
paratus consists of (1) a dilution system, (2) a sampling
system with a particulate filter to collect DPM and a gas-
sampling bag to collect gaseous emissions, and (3) a meas-
urement system consisting of portable gas instruments, a
DPM filter conditioning chamber, and a balance to weigh
the particulate filters.

‘This research has been supported by the U.S, Department of the [n-
terior’s Mineral Institute Program, administered by the USBM through
a subcontract from the Pennsylvania State University’s Gencrie Mineral
‘Technology Center for Respirable Dust under grant G1115142.

This document was prepared by the U.S. Bureau of Mines. Neither the United States Goveroment nor any person acting on behalf of the United
States Government assumes any liabiity resulting from the use of the information contained in this document, or warrants that such use be free from

privately owned rights.



How It Works

The emissions measurement apparatus (fig. 1) contains
an ejector that dilutes and cools a portion of the exhaust
with nitrogen and passes the mixture through a prewcighed
particulate filter, where a weighable quantity of DPM is
collected, A portion of the filtered exhaust is collected in
a gas-sampling bag. The concentrations of CO, CO,, NO,
and NO, in the bag are analyzed by portable gas instru-
ments. The DPM mass collceted is determined by condi-
tioning and weighing the filtcr before and after sampling,
The DPM concentration is then calculated from the mass,
the volume of exhaust flowing through the filter, and the
dilution ratio.

The emissions measurement apparatus is designed to be
used only during a stationary test of an underground mine
vehicle. In-mine tests are conducted by operating the
mine vehicle engine under high load at a single speed with
the vehicle in a safe condition. This condition, represent-
ing the torque stall condition, is attained by depressing the
vehicle’s brake, engaging the transmission in high gear,
and pressing the accelerator pedal ta the Qoor. Loading
the engine in this manner is necessary to attain a fucl-to-
air ratio (detcrmined by CO, concentration) that produces
higher CO and DPM concentrations than lighter load con-
ditions, Engine faults increase these pollutant concentra-
tions at this condition and allow the cmissions measure-
mert apparatus to make meaningful measurements.

Testing the Design

Comparisons were made between the emissions meas-
urement apparatus and laboratory instruments at the
USBM Diesel Emission Research Laboratory. Current
measurement accuracy and precision are adequate, but
attempts are still being made toward simplifying and
automating the emissions measurement apparatus for ease
of use. The apparatus has been used to measure the tail-
pipe concentrations of diesel-powered vehicles in a number
of U.S. underground coal and noncoal mines, and plans
arc being made to integrate it into periodic maintenance
of engines and vehicles at these mines.

Future Applications

The cmissions measurement apparatus is applicable to
underground mine vehicles and to other diesel-powered

equipment such as railroad locomotives, ships, off-highway
vehicles, and heavy-duty trucks. Michigan Technological
University is currently seeking a partner to enter into a
cooperative agreement to develop the emissions measure-
ment apparatus into a commercial product.

For More Information

More information is available in USBM Report of
Investigations 9422, "Apparatus for Measuring Diescl
Tailpipe Emissions in Underground Mines.” For answers
to technical questions or for additional information,
contact Todd Taubert, U.S. Bureau of Mines, Twin Cities
Research Center, 629 Minnchaha Avenue South, Minnc-
apolis, MN_ 55417-3099, (612) 725-4766; or John H.
Johason, Presidential Professor, Mechanical Engineering,
Enginecring Mechanics Department, Michigan Technolog-
ical University, Houghton, MI 49931, (906) 487-2576,

Ejector-Dilution Chamber

poe Cecsocpon: - Dilution
Flow
(Nitrogen)

Quick- —Critical
~._ Connect Flow
Fitting Nozzle
1 Exhaust Probe

Filter <<

~~ Holder

Filter Holder

_-~ Retaining Clip

Gas-Sampling Bag

Excess Diluted
Exhaust Sample

xy

Figure 1.—Emissions measurement apparatus,

81

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