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December 4, 2009

VIA E-MAIL

Ms. Melanie King

Energy Strategies Group

U. S. Environmental Protection Agency

Mail Code D243-01

Research Triangle Park, NC 27711

Re: EMA Response to Questions Regarding Crankcase Emission Controls

Dear Ms. King:

On a recent conference call between your office and the Engine Manufacturers 

Association (EMA), you requested some information and recommendations from EMA 

regarding the control of crankcase vent emissions from existing stationary compression ignition 

(CI) engines. Our understanding is that EPA is exploring options and possible controls to reduce 

the emissions of hazardous air pollutants (HAP), in particular metallic HAP emissions, from 

existing stationary diesel engines. EPA would adopt any potential controls in the upcoming final 

NESHAP for stationary CI engines to be released in February 2010. 

I have discussed the issue with EMA member companies that manufacture the vast 

majority of in-use and new stationary CI engines sold in the United States. EMA has the 

following information and recommendations regarding the control of crankcase vent or blow-by 

emissions.

· The crankcases of all engines, including compression ignition engines, must be vented 

so that pressure within the crankcase remains within tolerance levels. Without 

venting, high pressures from combustion gases that enter the crankcase through 

piston-cylinder gaps would quickly build to levels that exceed crankcase and 

crankcase seal specifications. Seal failures and external oil leaks would result. 

Consequently, all CI engine crankcases are vented to relieve such pressures. 

Historically, the normal practice had been to vent the crankcase directly to the 

atmosphere, but many newer model engines have incorporated some mechanism to 

reduce blow-by emissions.

· This crankcase venting or blow-by adds only a very small amount of airborne 

emissions to the total emissions from CI engines, on the order of 0.01% of total 

emissions. However, as exhaust emission standards have become increasingly more 

stringent, blow-by emissions have become a larger percentage of total emissions, even 

though they are still small in absolute terms. Blow-by emissions are largely composed 
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of oil mist. It is likely that metallic HAP are also emitted since engine lube oil and the 

wearing of surfaces in the crankcase (bearings, rings, and liner interface, etc.) are 

believed to be the major source of metallic compounds in engine emissions.

· Older CI engines are likely to have higher levels of blow-by emissions because 

increased deterioration and wear of the piston ring and liner interface over time 

increases crankcase pressure and the amount of oil emissions. This mechanism is a 

natural part of engine operation and can only be mitigated by engine overhaul.

· More recently, engine manufacturers have developed open and closed crankcase 

systems to reduce the amount of oil mist escaping into the atmosphere, and therefore 

other compounds carried in the blow-by in the oil mist. Closed crankcase systems are 

more common on heavy-duty on-highway applications while open crankcase systems 

are used on larger engines. Newer CI mobile source engines used in both on-highway 

and nonroad applications have addressed blow-by emissions by collecting the oil mist 

and returning it to the crankcase, by directing the blow-by emissions back to the 

combustion chamber on naturally aspirated engines, by directing the blow-by 

emissions to the exhaust system, or by collecting the oil droplets for re-use or liquid 

disposal. As you may be aware, current EPA regulations for new CI engines require 

that blow-by emissions be addressed by the application of closed crankcase systems or 

by requiring the engine manufacturer to account for blow-by emissions as part of the 

total system-out emissions of the engine (See the EPA 2007 heavy-duty on-highway 

emission regulations and the Tier 4 nonroad regulations for details of the requirements 

for new engines).

· EMA members have very limited direct information available on metallic constituents 

contained in blow-by emissions. This has not been an area of focus for manufacturers

nor has there been a requirement to measure those constituents. However, metallic 

HAP constituents have considerably different characteristics compared to the oil 

which contains and transmits the HAP. Wear metals in lube oil are thought to be in 

the 2-20 micron range whereas the oil mist itself is closer to 300 nanometers. Thus 

wear metals are nominally 6 to 60 times larger than the oil mist. Consequently, since 

capture and return systems for the oil mist are more efficient at capturing larger 

particles, it is reasonable to conclude that they would effectively return a very high 

percentage of the relatively large metallic HAP particles to the crankcase.

· In applying crankcase vent emissions controls to existing engines, the options 

available depend on the age of the engine, the fuel used, the size of the engine, the 

amount of blow-by and whether the engine is naturally aspirated or turbocharged. 

Controls are generally more difficult on turbocharged engines since blow-by 

emissions cannot be recirculated into the intake air due to turbocharger fouling and 

reductions in performance (NOTE: For a discussion of those issues, see the EMA 

written comments on the Nonroad Tier 4 NPRM in EPA docket EPA-HQ-OAR-2003-

0012, those comments dated August 20, 2003 and submitted by Jed Mandel, Page 50).
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Considering the issues described above, and if EPA decides that blow-by emissions from 

existing stationary CI engines are a significant source of metallic HAP emissions that require 

further controls, then a potential way to reduce emissions is to consider retrofitting existing nonemergency CI stationary engines that do not have a crankcase filtration control system with such 

a system. EMA believes that appropriate systems exist in the form of open crankcase oil 

separators that can significantly collect and reduce the oil mist in crankcase blow-by vents. Such 

systems are designed to either return the collected oil to the crankcase or condense the oil 

droplets for collection and proper re-use or disposal. 

EMA does not believe that such systems should be applied to emergency stand-by 

engines because such engines operate so infrequently, and the addition of crankcase filtration

systems would not be cost effective, in the same manner that exhaust aftertreatment systems on 

emergency engines are not justified. 

Open crankcase filtration systems are effective in reducing blow-by emissions but must 

be sized properly to avoid significant crankcase pressure increases that can be detrimental to the 

engine. In general, such systems can remove upwards of 60-80% of the oil mist and return it to 

the crankcase or collect it for liquid disposal, depending on flow rates and engine operation. In 

general, the more efficient the collection system, the more restrictive it is. A balance between 

removal efficiency and increased backpressure needs to be maintained. As noted above, 

engineering judgment suggests that metallic HAP emissions would be decreased at a higher rate 

than the oil flow in general. Such systems are relatively simple and are designed to maintain 

engine performance without operator intervention.

Should EPA decide to require open crankcase filtration controls on existing stationary 

engines, EMA recommends that such systems:

· Apply to non-emergency engines that are not currently equipped with crankcase oil 

filtration systems,

· Meet a minimum performance standard of 60-80% oil removal efficiency, 

· Be verified to meet the oil removal performance standard, perhaps through EPA’s

existing retrofit verification process,

· Be applied to both naturally aspirated and turbocharged engines, and

· Have an effective installation date at least three years after publication of the final 

regulation in order to allow manufacturers time to develop and verify the systems and 

owners and operators to purchase and install the systems.

EMA believes that retrofitting non-emergency stationary CI engines with open crankcase 

filtration systems is a technically feasible method to reduce oil-related crankcase blow-by 
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emissions as well as metallic HAP emissions from existing CI engines. Open crankcase 

filtration systems can be applied to virtually all existing non-emergency engines and provides 

a flexible solution that can be adapted to site-specific conditions.

Please feel free to contact me if you have any questions regarding the information 

provided or EMA’s recommendation to address blow-by emissions.

Sincerely,

Joe Suchecki

Joseph L. Suchecki

Director, Public Affairs