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



# 40 CFR 63 Subpart ZZZZ

The main engines on our rigs are e ither 320mm or 280mm bore. The 320mm bore engines have two separate strokes. 350 & 400mm stroke’s, dependant on the year of delivery; our engines delivered before 2000 tend towards 350 and later engines have a longer stroke of 400. The 350 stroke engine s have a vol of 28.15 L/cyl and the 400mm engines have a vol of 32.17 L/cyl. Given that the limit for category 3 engines is 30 L/cyl, then these engines are either over or extremely close to this limit. And engines of that size are being regulated separately. See below from the EPA

MODU’s run their power plant to suit DP re quirements which, in reality, means that the load on any one engine is never above 50% \2\ Marine diesel engines at or above 30 liters per cylinder, called Category 3 engines, are typically used for propulsion power on ocean-going ships. EPA is addressing Category 3 engines through separate actions, including a planned rulemaking for a new tier of federal standards (see Advance Notice of Proposed Rulemaking published December 7, 2007 at 72 FR 69522 ) and participation on the U.S. delegation to the International Maritime Organization for negotiations of new international standards (see www.epa.gov/ otaq/oceanvessels.com for information on both of those actions), as well as EPA's Clean Ports USA Initiative (see http://www.epa.gov/ cleandiesel/ports/index.htm >).[Recipient Name] April 11, 2012 Page 2

Category 3 marine diesel engines generate NO X , HC, PM and CO emissions that contribute to ozone and CO levels above the National Ambient Air Quality Standards (NAAQS) for ozone and CO (i.e., they contribute to ozone and CO nonattainment) as well as adverse
health effects associated with ambient concentrations of PM. As described in more detail below and in the Final Regulatory Support Document, Category 3 marine diesel engines accounted for about 1.6 percent of nationwide mobile source NO X emissions in 2000. They also accounted for about 2.8 percent of nationwide mobile source PM emissions in 2000. These percentages are expected to increase as a
result of increased trade and decreases in emissions from other nonroad sources. The contribution of Category 3 marine diesel engines to nationwide mobile source HC and CO levels is small, at 0.1 and 0.02 percent, respectively, in 2000.

In writing the ruling, the EPA produced an a ppendicle TO the proposed Toxics rule on inventories. In this, the use of Spark Ignite d (SI) engines was discu ssed and the need for catalyst treatment. Stationary spark ignition engines are used when running on natural gas or methane as opposed to Compression Ignite d (CI) engines that are running on liquid fuel; in the case of Transocean, Ultra Low Sulfur Diesel (ULSD). From the tables included, the source considered was >750 HP (559 kW), no real data was shown from engines of the size used offshore, which range from 3,800 kW to 7,000 kW.

To try and compare using what actual data we have, we find the following:

We compared the calculated fuel consum ption values for an average load and extrapolated over the year and over four engi nes and found that the calculated annual fuel consumption was 7,221 tonnes compared to 2007 figures that give annual consumption of 7,380 tonnes, 98%. Similarly, we extrapolated the NO X readings and calculate that the annual figure would be 372 tonnes. As we don’ t have available CO and VOC data, we extrapolated using ratio’s to give a figure to work from. Th e results show that our VOC reading is 12.5 Tonnes/year/rig. What this shows is that the VOC’s and CO emissions from CI (diesel) engines is significantly lower than similar natural gas SI (generic) engines. However, this data’s far from comp lete, as load, size & fuel consumption are all missing. Incidentally, Drilling rigs is menti oned in the EPA study list but has absolutely
no data or a Source Clas sification Code (SCC).

The above shows that the diesel engine in general is a significantly lower emitter of CO & VOC’s than natural gas engines.

Additionally, to be able to react to highly a ggressive load demands and to ensure that power is always available for thrusters to maintain DP position, the main engines cannot operate above 50% load so that, should ther e be a malfunction and the engine need to[Recipient Name] April 11, 2012 Page 3

Catalyst removed from DD2 SCR. shut down, the remaining engine can accept th e inrushing load. Modern marine diesel engines, that are now used as MODU main engines are designed to run around 85% load, this allows the turbocharger to push in the needed excessive air required to get combustion up closer to stoichiometric condi tion of having an air/fuel mixture of 14.6:1. What this means in practice is that when fuel is injected into the cylinder at 30% load, the air is at 42.3 Bar but at 100%, (from test bed results), the pressure’s 101.8 Bar. This gives the higher load much more “a ir” to combust with, allowi ng much better combustion.

In looking at the EPA’s working document on “proposed toxics rule appendices, it shows that there is very little data from compressi on ignition engines, and the data it does have, show’s that the CO and VOC’s are very low as opposed to spark ignition engines (natural gas engines). The pertinent data has been ex tracted and shown in a spreadsheet with the calculations showing it in comparison to the da ta Transocean has gathered so far from it’s
fleet.

We believe that the use of a oxidizing catalyst is further hampered by the low loads that predominate on offshore platforms. Wartsila, our engine supplier has mentioned that it is better to run above 25% load, but low load operation is expected to foul the catalyst earlier, thus leading to manual cleaning. This is a time consuming and dangerous proposition as the exhaust system is not designed
for removal of a cat alyst. We are of the opinion that the catalyst will need cleaning regularly, similar to what we found with the DD1/2 catalyst in the

SCR that was fitted.

In discussing Oxidation catalysts with our engine supplier, they have brought up the concern that there is a possibili ty that the catalyst, as well as reducing the CO, will also
convert the NO to NO 2 , thus increasing the environmenta l damage from that gas. See
Wartsila letter.[Recipient Name] April 11, 2012 Page 4

In summary, we believe that large offshore di esels should be exempt from CO regulations for the following reasons.

 CI (Compression Ignition, Diesel) engines are extremely low emitters of CO gas by default, and emissions can be further reduced by promoting running at efficient load levels; >50%.

 Unlike CO 2 & NO X , CO is not a GHG but a pollutant. However, our DP deepwater drillships rarely drill in water depths of le ss than 900 M (3,000 ft.), and never less than 500M. This puts the closest a drillship will be to land at approx 150 km. (93 miles) during normal operations, see attached maps.

 On these large engines, the oxidation catal yst is designed to work in conjunction
with an SCR.

 Given the low loads that are normal ope ration in offshore drilling, we believe fouling of the catalyst will be an issue, resulting in a requirement to remove and manually clean the membrane, this has not been accomplished before with this equipment and given the location of the exhaust systems, will introduce a significant dropped object hazard.

 Our Supplier has concerns of unintended consequences of operating an oxidation catalyst without additiona lly using an SCR.