Document ID: EPA-HQ-OAR-2008-0708-0377
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-02-23T05:00Z

----- Forwarded by Melanie King/RTP/USEPA/US on 12/08/2009 02:52 PM
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  |"Stachowicz, Bob" <bob.stachowicz@dresser.com>                                                                                            
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  |Melanie King/RTP/USEPA/US@EPA                                                                                                             
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  |12/08/2009 02:39 PM                                                                                                                       
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  |RE: stationary engine malfunction                                                                                                         
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Hello Melanie,

    I apologize for the length of time that I needed to respond.  As I 
indicated in my first acknowledgement, these are not simple issues and there 
is no single "correct" answer.  Also, while I have some knowledge of industry 
practices in general, I can speak directly only for Dresser-Waukesha.  I will 
address each of your four questions:

What are some typical causes of malfunctions in engines (and any associated 
engine emission control system)?  Webster's dictionary defines malfunction 
simply as "to function imperfectly or badly : fail to operate normally".  The 
EPA definition excludes "Failures that are caused in part by poor maintenance 
or careless operation" and appears to include only something "which causes, or 
has the potential to cause, the emission limitations in an applicable standard 
to be exceeded".  This is a much more narrow and directed definition.  There 
are a multitude of potential malfunctions in an engineered product as complex 
as a reciprocating, internal combustion engine system that includes the 
engine, an electronic control system which may control both the engine and 
part - or all - of the aftertreatment system, and the aftertreatment itself.  
A malfunction can occur in any of these areas.  Current and proposed emissions 
standards are so restrictive that there is almost no allowable variation in 
any area in order to continuously comply with the standards -- everything must 
function near flawlessly.  Since a modern SI RICE system is so complex, 
failure/malfunction of almost any component can affect output emissions levels 
although they may not be affected to the point of non-compliance.
    Note that, while I will try to keep the EPA definition of a malfunction in 
mind in my responses, many malfunctions that could meet EPA's malfunction 
definition can be exacerbated by poor maintenance or careless/improper 
operation.  One example of this would be a spark plug that would fail early 
under normal operation but will fail even earlier under improper operation.  
Would the "in part" phrase in EPA's definition exclude this circumstance from 
being considered a "malfunction"?  If so, the EPA definition of malfunction 
may be too restrictive from a practical perspective for an engine system 
versus other types of stationary sources such as large power plants.  This 
sort of circumstance relates to my question to you about how EPA would look at 
a malfunction that was colored, in some fashion, by poor maintenance or 
careless operation.  Specifically, how are "poor" and "careless"
officially defined and who would make the final determination if the 
maintenance was "poor" or the operation was "careless"?
    There are several possible causes of malfunction outside of poor 
maintenance or careless/improper operation.  These can include a manufacturing 
error such as machining a part outside of blueprint tolerances, a part 
inadvertently made of, or including, non-conforming material, statistically 
expected random and early failure such as B10 life for bearings or illustrated 
by the bell-curve distribution, ambient and operating conditions including a 
fuel composition change, human error, and "acts of God".  An example of the 
latter may be a nearby lightning strike that directly or indirectly affects 
electronic controls such that engine operation continues but in an abnormal 
manner.
    Typical gas engine malfunctions originating from any, or other, of the 
preceding causes include spark misfire, spark timing shift, engine 
backpressure increase or decrease, engine crankcase pressure change, abnormal 
coolant temperature, valve train operation out-of-specification, abnormal/high 
vibration levels, air/fuel ratio shift, and breakage of virtually any engine 
component.
    Some issues that can directly affect emissions may not meet the EPA 
definition of "malfunction" but may be considered a "failure" even though that 
failure is normal.  "Normal" in this case means very gradual performance 
degradation, usually of the aftertreatment, due to length of operating time.  
One of the best examples of this is the steady decrease of performance of a 
catalyst due to continuous exposure to heat (resulting in slow sintering and 
loss of performance), particulate (even the cleanest of engine exhaust streams 
contains some particulate from combustion of engine oil which will eventually 
mask the active catalyst material), and chemicals (engine exhaust may contain 
trace amounts of antifreeze if there is a minor, internal, coolant leak and 
all engine oils contain additives which will add known catalyst poisons to the 
engine exhaust stream).  While such a failure could be considered "reasonably 
preventable" from one viewpoint since the processes are known as well as the 
fact that it will happen is known, the way in which these factors combine to 
degrade a catalyst can vary the degradation rate significantly with the result 
that loss of compliance could be looked at as sudden and infrequent.

What usually happens when these malfunctions occur?  The results of 
malfunctions are as varied as the possible malfunctions themselves and will 
cover the entire spectrum from no practical effect to significant effect on 
either engine performance, engine emissions, or both.
Malfunction of a non-critical component, such as breakage of an air filter 
brace, may increase local vibration levels but will have no discernable effect 
on engine operation or emissions.  Other malfunctions can have an immediate 
and direct effect on engine operation and output emissions.  Examples of the 
latter would be a sensor or control wire breaking or shorting due to vibration 
or a spark plug failure resulting in a severely misfiring or dead cylinder.  
In these latter cases engine emission levels and, of course, engine 
performance can change drastically and suddenly.

Does the engine typically shut down automatically, or does it have to be 
manually shut down?  This will depend on the exact nature of the failure and 
the safety and operational control scheme applied to the engine system.  Most 
modern stationary engines have some level of electronic control in addition to 
mechanical safety and operational sensors and controls.  The control response 
algorithms will determine whether the engine shuts down automatically or is 
allowed to operate until a manual shut-down is performed to investigate the 
malfunction.  Malfunctions determined by the control algorithms to be critical 
will likely result in an automatic shut down to protect the engine or 
aftertreatment or both.  See also the following question / response.

Can the engine still continue operating even if it is malfunctioning?
Simplistically, of course the answer is yes.  However, again, reality will 
depend on both the specific nature of the malfunction and the specific control 
scheme applied to the engine system.  Some malfunctions are considered non-
critical and the engine will be allowed to continue operating.  Note that a 
secondary function of a control system/scheme may be to send a signal to a 
monitoring station indicating a malfunction has occurred even if the engine is 
allowed to continue operation.
Other, more significant, malfunctions may call for an emergency stop to 
prevent a possible catastrophic failure.  If the malfunction is serious enough 
it may cause the engine to cease operation - sometimes catastrophically - 
independent of any control and shutdown scheme.
Usually, significant parameters such as temperatures, pressures, speeds, 
vibration, knock, etc are monitored rather than trying to detect malfunctions 
themselves as most malfunctions that will affect engine performance and/or 
emissions will manifest themselves as a detrimental shift in one or more of 
those parameters.  The algorithms programmed into the control scheme will 
decide whether to allow continued engine operation, allow operation and send a 
warning, or immediately stop engine operation.  Older engines, those with 
mechanical/hydraulic control systems, function the same in principle but have 
much less response flexibility compared to engines with at least some 
electronic control.  In either case, "nuisance" shut-downs -- those not due to 
a true malfunction issue -- must be minimized as far as practical without 
putting the engine, driven equipment, or operational limits in jeopardy.
Nuisance shut-downs can become very expensive to an owner/operator if allowed 
to continue.

    I hope that this adequately addresses your questions.  If I can contribute 
anything further please let me know.

Sincerely,
Bob Stachowicz
______________________________________________________________________________
____________________________________________________
Robert Stachowicz, PE | Staff Engineer | Dresser, Inc., Dresser Waukesha
| 1101 West St. Paul Avenue, Waukesha, WI, 53188 | 262.549.2753 |
262.549.2705 (fax)

From: King.Melanie@epamail.epa.gov [mailto:King.Melanie@epamail.epa.gov]

Sent: Tuesday, November 24, 2009 8:21 PM
To: Stachowicz, Bob
Subject: stationary engine malfunction

Hi Bob,
Hope you are doing well.  Can you help me with a question about stationary 
engine malfunctions?  What are some typical causes of malfunctions in engines 
(and any associated engine emission control
system)?   What usually happens when these malfunctions occur?  Does the
engine typically shut down automatically, or does it have to be manually shut 
down?  Can the engine still continue operating even if it is malfunctioning?  
I'm asking about malfunctions as defined by EPA for the MACT program, the 
definition is:

"Malfunction means any sudden, infrequent, and not reasonably preventable 
failure of air pollution control and monitoring equipment, process equipment, 
or a process to operate in a normal or usual manner which causes, or has the 
potential to cause, the emission limitations in an applicable standard to be 
exceeded. Failures that are caused in part by poor maintenance or careless 
operation are not malfunctions."

So I'm interested in failures that would not be caused by poor maintenance or 
improper operation of the engine, since by the EPA definition, that wouldn't 
be considered a malfunction Thanks and have a great Thanksgiving,

Melanie King
Energy Strategies Group
Sector Policies and Programs Division
Office of Air Quality Planning and Standards U.S. Environmental Protection 
Agency

Mail Code D243-01
RTP, NC  27711

Phone:  (919) 541-2469
Fax:       (919) 541-5450
king.melanie@epa.gov