Appendix F

Exhaust Temperature Data Analysis for Portable Diesel-Fueled Engines
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Exhaust Temperature Data Analysis for Portable Diesel-Fueled Engines

The University of California at Riverside’s Center for Environmental Research

and Technology (CE-CERT), working with ARB staff, recently conducted a

stack-temperature profile (i.e., percentage of time at various exhaust

temperatures) study to determine if passive diesel particulate filters (DPFs) are a

feasible PM control technology for diesel-fueled portable engines. The success

of a DPF is dependent on whether an engine achieves and maintains the

minimum average exhaust temperature set by the DPF manufacturer. If engine

exhaust temperatures are equal to or higher than the minimum temperatures,

then passive DPFs could be considered as a potential retrofit control device. If

engine exhaust temperatures are below the minimum requirements, then

carbonaceous material may accumulate, increasing exhaust back pressure and

possibly causing serious engine damage.

Currently, three manufacturers of passive DPFs have submitted their technology

to ARB for verification for on-road diesel engine applications. These

manufacturers are Johnson-Mathey, Cleair and Englehard. The required

minimum average operating temperatures and duration per duty cycle vary

among these DPFs. For example, the Johnson-Mathey DPF requires 270

degrees Celsius (C) for 40 to 50 percent of the duty cycle, the Cleair DPF

requires 300 degrees C for 30 percent of the duty cycle, and the Englehard DPF

requires an average of 225 degrees C. To date, these manufacturers have not

requested ARB verification of their technologies for off-road applications, which

would include portable diesel engines.

In the study, CE-CERT gathered exhaust temperatures during normal duty cycles

from about 80 portable diesel engines in Northern and Southern California. The

engines ranged from 77 to 2151 horsepower. The tests consisted of inserting a

temperature sensor into the exhaust stream of a diesel engine, after the turbocharger or exhaust manifold, and measuring the exhaust temperature in oneminute intervals for at least 20 hours of engine operation. Exhaust temperature

data was stored on an in-line data logger. The data were downloaded from the

data logger to a laptop and a frequency distribution test was applied using a

spreadsheet. A frequency distribution test was used on the data to determine

what temperature range each engine operated at and the percentage of time it

operated within each temperature interval. The resulting data were graphed by

temperature verses percent engine operation (See Figures 1-80). Table 1 is a

summary of the equipment categories that were tested, the number of engines

tested per category, and the percentage of those engines tested where the

minimum operating temperature was high enough to install a passive DPF.
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Table 1: Results of Exhaust Temperature Tests

Category Industry Number of

Engines

Tested

Passive DPF

Yes

 (%)

Wood Chippers Arborist, University,

Govt.

7 43

Generators Motion Picture,

Construction, Sand &

Gravel, Oil & Gas

29 73

Paint Stripers

(Compressors)

Govt. 6 83

Compressors Govt., Construction 11 55

Pumps Govt., Oil & Gas,

Agricult.

8 63

Grinders Govt. 3 100

Grader/Shovel Govt. 2 50

Welder Sand and Gravel 1 100

Crane Construction 1 0

Jet Washer Oil & Gas 3 0

Drilling Rig Oil & Gas 1 0

Clamshell Dredger Construction 2 0

Bow Anchor Winch Construction 1 0

Truck Mounted Vacuum

Pumps

Govt. 5 0

The staff assumed that a minimum average operating temperature above 225

degrees C was needed to successfully retrofit with a passive DPF. The results of

the test data showed that not all engines could be retrofitted with DPFs. The

duty cycle appears to be the key to determining a successful retrofit of a passive

DPF. Although some of the categories did show 100 percent of engines tested

were capable of being retrofit with a passive DPF, Grinders and Cranes (Figures

61, 62 and 67), there wasn’t enough of a population base to test and confirm if

this was true for all engines in this category.

Some categories would be good candidates for a passive DPF, paint stripers for

example (Figures 36-41). Paint stripers are either painting or turned off. There is

a minimum amount of idling, so that the average exhaust temperatures are

higher. As the data shows, 83 percent of these paint stripers could be retrofitted

with a passive DPF.

In some categories retrofitting with a passive DPF is on a case by case basis.

The generator category (Figures 8-35) is an example of the need to test before
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installing a passive DPF. From the test results, 73% could be retrofitted with a

passive DPF. For the other 27%, generators appear to run at idle for long

periods of time and when electrical power is needed then they are operated at

full power. This appears to be the case in the movie industry, where generators

of the same horsepower rating had very different duty cycles. Some had very

low average exhaust temperatures while other generators maintained operating

temperatures much higher than the minimum required temperature. Operators

of generators would need to perform exhaust temperature tests to determine if

their engine would be a candidate for a passive DPF.

Some categories would not be good candidates for a passive DPF, vacuum

trucks for example (Figures 76-80). These trucks vacuum leaves and debris

from storm drains, keeping storm drains clear. Data indicated that these vacuum

pumps had engines that were larger and more powerful than what was needed to

remove the average amount of obstruction. These trucks were designed with

reserve power so that if a large amount of debris was in a storm drain it could be

removed quickly. During testing, these engines never reached the minimum

temperature of 225-degree Celsius for the minimum amount of time.

Based on the exhaust test results, the ARB cannot recommend the use of a

passive DPF for all portable diesel engines because in many cases the duty

cycle of an engine may not reach the minimum temperatures required for a

passive DPF to perform its function. If an operator decides to use a passive

DPF, an engine exhaust temperature study is highly recommended to determine

if the average engine exhaust temperatures for individual engines do meet the

minimum requirements for a passive DPF.