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interaction/interfaces with other systems ? HVAC and ventilation. A full description shall be furnished along with an assessment of ventilation failures, particularly with regard to control equipment ? The effect of an intentional or unintentional ESD has to be assessed, which will include an ESD system description ? DP control systems shall be analyzed. In addition to standard DP system analysis of reference systems, DP computers, and so forth, any vessel-speci c modes shall be reviewed ? Communications. e vesselĀs communication systems shall be identi ed ? Conclusions. A conclusion section on the vessel design and any issues arising shall be provided. Once the FMEA is developed it needs to be proved. is is achieved using proving trials. at is, for the failure modes iden- ti ed, test methods are developed to prove that, under the failure conditions, the expected outcome from the analysis can be prac- tically demonstrated. It is possible that where results are not as expected, further analysis needs to be done to understand the failure mode more thoroughly and the FMEA may need updating. e FMEA is maintained as any other key vessel document. us, as equipment is updated or changed, the FMEA is updated. Further, it is becoming more common for an FMEA to be reviewed and reissued with new proving trials every ve years. It is also a common practice for DP vessels to undergo annual DP trials testing. e purpose of these tests is to provide an annual vessel assessment and review any changes. Annual trials are increasingly required by class and are recommended practice by IMCA. Recognizing FMEA limitations e FMEA does have limitations that need to be understood. It should not be taken as a given that a DP vessel having an FMEA gives any guarantee against a position/heading loss. Not all FMEAs are created equal, and poor designs can still pass FMEA analysis such that WCF is not compromised. ere are no entry criteria to writing an FMEA for a DP vessel. In addition, budgets for writing FMEAs vary greatly. A particular area of interest is the shipyard FMEA. Often, a vessel needs to be delivered with a DP class notation and thus an FMEA will need to be furnished. However, the shipyard has no ongoing vested interest in the DP FMEA process, so documents are written solely for the basis of passing class acceptance and do not consider the operational value-added supporting analysis that may be of insight to the operator. Shipyard FMEA business is an intensely competitive environment with cost pressures. Any reduction of cost only serves to reduce the time allowed for the analysis. FMEA providers working with shipyards have to balance any reductions of cost against maintaining a quality product. An FMEA does not guarantee good design. For example, vessels systems and components can be set up in many di er- ent ways; while a vessel may meet the requirements of DP2 or DP3 it may require signi cant aligning of equipment to correct T3 PORT AZIMUTH THRUSTER AND DRIVE CONVERTERT4 STBD AZIMUTH THRUSTER AND DRIVE CONVERTERDG no. 1DG no. 2DG no. 3DG no. 4T1 FWD BOW TUNNEL THRUSTERT2 AFT BOW TUNNEL THRUSTERFIGURE 04RISK UNDERSTANDING AND RESPONSE CAPABILITY www.sname.org/sname/mt October 2013