Manufacturers in this case need to determine the alternate useful life based on the documented hourly service life of these engines in the field. This may in some cases be much less than 10,000 hours of operation. To prevent abuse of this provision, we won't approve any useful life less than 1,000 hours and we will require that the manufacturer display the certified useful life on the engine label. Also, the shortened useful life may not be less the manufacturer's recommended overhaul interval or mechanical warranty for that engine.
2. Warranty Periods
Tied to the useful life is the minimum warranty period imposed under the Clean Air Act. The warranty periods for marine diesel engines are based on the ratio of useful life and warranty periods established for land-based nonroad engines. Specifically, we are setting a warranty period that is 50 percent as long as the useful life (in both operating hours and years) for both Category 1 and Category 2 engines. Also, the emissions warranty may not be less than any mechanical warranties offered by the manufacturer. This applies whether the mechanical warranty is published or negotiated, and whether it is offered for a fee or at no extra charge. Table 5 summarizes the useful life and warranty values that apply.
We are also including defect reporting requirements in the final rule. We require engine manufacturers to tell us whenever they identify a specific emission-related defect in 25 or more Category 1 engines, consistent with the provisions that apply to highway and land-based nonroad engines. Similarly, we require notification for specific emission-related defects in 10 or more Category 2 engines, which is the same threshold that applies to locomotives. This is not limited to a single engine model or model year.
3. Deterioration Factors
To further ensure that the emission standards are met in use, we require the application of a deterioration factor (DeF) in evaluating emission control performance during the certification and production-line testing process. The emissions from new engines are adjusted using the DF to account for the expected deterioration in emissions over the life of the engine due to wear and aging of the engine and emission controls. The resulting emission level (i.e., the final deteriorated emission level) represents the expected emissions at the end of the useful life period. New emission control technologies such as aftertreatment, sophisticated fuel delivery controls, and some cooling systems, may lose some of their effectiveness as they age. DFs are already required for highway vehicles and engines, land-based nonroad engines, and locomotives. We are extending this approach to marine diesel engines.
Marine diesel engine DFs will be determined by the engine manufacturers in accordance with good engineering practices. Consistent with the land-based nonroad and locomotive programs, we are not specifying a detailed procedure. In generating DFs, however, manufacturers must observe some general guidelines and get our approval. In particular, the DF must be consistent with emissions increases observed in-use based on emission testing of similar engines. Additionally, the DF should be calculated for the worst-case engine calibration offered within the engine family. 8 DFs must be calculated as an additive value (i.e., the arithmetic difference between emission level at full useful life and the emission level at the test point) for engines without exhaust aftertreatment devices. In contrast, DFs must be calculated as a multiplicative value (i.e., the ratio of the emission level at full useful life to the emission level at the test point) for engines using exhaust aftertreatment devices. This is consistent with the DF requirements applicable to other diesel engines, based on observed patterns of emission deterioration.
It is not our intent to require a great deal of data gathering on engines that use established technology for which the manufacturers have the experience to develop appropriate DFs. New DF testing may not be needed where sufficient data already exists. However, we are applying the DF requirement to all engines to be sure that manufacturers are using reasonable methods to ascertain the capability of engines to meet standards throughout their useful lives. Consistent with the land-based engine programs, we will allow marine diesel engine manufacturers the flexibility of using carryover and carryacross of durability emission data from a single engine that has been certified to the same or more stringent standard for which all of the data applicable for certification has been submitted. In addition, we are allowing deterioration data from highway or land-based nonroad engines to be used for similar marine diesel engines.
Service accumulation is necessary to generate DFs from engines in the laboratory. Consistent with the land-based nonroad rule, we are specifying minimum allowable maintenance intervals for marine diesel engine service accumulation to ensure that durability data represent in-use performance (see 40 CFR 94.211(e)). These minimum intervals for marine diesel engines are equivalent to those required for nonroad and highway diesel engines (40 CFR 89.109; 40 CFR 86.094-25). For Category 2 engines, we will allow engine manufacturers to request alternate minimum maintenance intervals at the time of certification, subject to our approval. This allowance for Category 2 engines is necessary to allow harmonization with locomotive maintenance practices (63 FR 18978, April 16, 1998).
8 The worst case would be the engine calibration expected to generate the highest level of emission deterioration over the useful life, using good engineering judgement.
4. Rebuilt Engines
It is common for marine diesel engines to be rebuilt several times during the course of their lifetimes. Similar to land-based nonroad engines, we have two concerns regarding the rebuilding of marine diesel engines. First, there may not be an incentive to check and repair emission controls that do not affect engine performance. Second, there may be an incentive to rebuild engines to an older configuration due to real or perceived performance penalties associated with technologies used to meet the new emission standards.
