From: "Robertson, Dougie (Houston)" <Dougie.Robertson@deepwater.com> To: Melanie King/RTP/USEPA/US@EPA Cc: "Pelley, Darrel (Houston)" <Darrel.Pelley@deepwater.com>, "Hayes, Dennis (Houston)" <Dennis.Hayes@deepwater.com>, Kelly Fortin/R4/USEPA/US@EPA, Jessica Montanez/RTP/USEPA/US@EPA

Date: 05/25/2012 12:01 PM Subject: RE: Quad Z CO emissions paper.

Melanie,

Further to our discussion this morning, here’s a quick synopsis on low load operations of our main engines.

Regards

Dougie

Douglas A Robertson Senior Engineering Specialist

Room 741 4 Greenway Plaza

Houston TX 77046 Direct Line 1(713)232-7120 dougie.robertson@deepwater.com 80% Preparation, 20% Application...

From: Melanie King [mailto:King.Melanie@epamail.epa.gov] Sent: Thursday, May 24, 2012 15:17 To: Robertson, Dougie (Houston) Cc: Pelley, Darrel (Houston); Hayes, Dennis (Houston); Kelly Fortin; Jessica Montanez Subject: Re: Quad Z CO emissions paper. Question, this analysis seems to focus on the main power engines on the vessels. So am I understanding correctly that those engines are your main concern, and not other engines on the vessels that would also be subject to subpart ZZZZ, crane engines for example?

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

"Robertson, Dougie (Houston)" ---05/18/2012 11:51:04 AM---Melanie, Rather than delay further with gathering further input, here's our concerns with introducin

From: "Robertson, Dougie (Houston)" <Dougie.Robertson@deepwater.com> To: Melanie King/RTP/USEPA/US@EPACc: "Pelley, Darrel (Houston)" <Darrel.Pelley@deepwater.com>, Kelly Fortin/R4/USEPA/US@EPA, "Hayes, Dennis (Houston)" <Dennis.Hayes@deepwater.com>

Date: 05/18/2012 11:51 AM Subject: Quad Z CO emissions paper.

Melanie,

Rather than delay further with gathering further input, here’s our concerns with introducing CO regulations to offshore regulations. Can you take this into consideration when instigating CO regulations next year.

Regards

Dougie

Douglas A Robertson Senior Engineering Specialist

Room 741 4 Greenway Plaza

Houston TX 77046 Direct Line 1(713)232-7120 dougie.robertson@deepwater.com 80% Preparation, 20% Application... CONFIDENTIALITY NOTICE: The information contained in this email and any attachments may be privileged, confidential, or proprietary to Transocean. If you are not the intended recipient, you are prohibited from using, copying, relying upon, or disseminating the information, and the sender disclaims any liability for such unauthorized use. Further, if you are not the intended recipient, please notify the sender immediately and delete the message from your computer. Thank you. [attachment "40 CFR 63 Subpart ZZZZ discussion.docx" deleted by Melanie King/RTP/USEPA/US] [attachment "Emissions comparison.xlsx" deleted by Melanie King/RTP/USEPA/US] [attachment "proposed_toxics_rule_appendices.pdf" deleted by Melanie King/RTP/USEPA/US] [attachment "Region 4 drilling limit print.pdf" deleted by Melanie King/RTP/USEPA/US] [attachment "Topgrahical G of M print.pdf" deleted by Melanie King/RTP/USEPA/US] [attachment "IOXI drawing.pdf" deleted by Melanie King/RTP/USEPA/US] [attachment "NOR with integrated Oxi W32 dimensions.pdf" deleted by Melanie King/RTP/USEPA/US] [attachment "toioxycat2 doc.pdf" deleted by Melanie King/RTP/USEPA/US] CONFIDENTIALITY NOTICE: The information contained in this email and any attachments may be privileged, confidential, or proprietary to Transocean. If you are not the intended recipient, you are prohibited from using, copying, relying upon, or disseminating the information, and the sender disclaims any liability for such unauthorized use. Further, if you are not the intended recipient, please notify the sender immediately and delete the message from your computer. Thank you. (See attached file: Marine Engine Low load operations.docx)(See attached file: operational compressor map.pdf)(See attached file: Test bed charge air pressure.pdf)

## Transocean Offshore D eepwater Drilling, Inc.
Engineering and Technical Support Corporate Engineering



# Marine	Engine	Low	load	operations

Modern marine diesel engines are designed with high thermal efficiency, now over 60%, where smaller, higher speed diesels are in the 40-45% range. The major difference in the design is in the combustion space design.

In smaller, higher speed diesels, they use a high swirl piston or prechamber design that is highly efficient in mixing the air and fuel to achieve combustion closer to stoichiometric combustion. However, in designing these compli cated chambers, this reduces the strength of either the piston or the cy linder head. In larger diesel engines, a quiescent combustion system is used, in this the combustion space is much simpler and as such has inherent strength built in.

The reason that the marine diesel engine gets such high efficiency is that as th e combustion space is designed with inherent strength, the air that is fed into the cy linder can then be mu ch greater. This is accomplished with high gain modern turbocharger s that are capable of raising the charge air pressure to historically high values. For example, the Vasa 12 V 32 charge air pressure rises from 1.8 Bar (26 PSI) to 2.65 Ba r ( 38 psi) when the load rises from 75 % to 100%. This air pressure and volume allows the engine designers to obtain these high thermal efficiency figures.

However, to get the turbocharger to get up to sufficient speed to generate the required air flow, the engine needs to be loaded up to allow sufficient gas flow to spin the turbocharger; the attached turbocharger map shows the great difference between the designed running position of 85% and a MODU’s 25%. This leads to a much reduced air

flow.[Recipient Name] May 25, 2012 Page 2

This reduced air flow then lowers the actua l air/fuel mixing in cylinder and leads to additional partially unburned hydrocarbon’s pass ing into the exhaust stream. This then leads to fouling of any obs truction in th e gas path.