Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

FMECA study of Cruise ship Pod propulsion system based on real-ship accident using
Type-2 Fuzzy expert system
Shoaib Ahmed a, Tie Li a,b*, Shen Wu aaState Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, PR China
bCollaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai Jiao Tong University, Shanghai, PR China

the Carnival Triumph engine room fire (IMO (GISIS), n.d.). Suchaccidents caused a serious threat to the safety of the passengers, crew
members onboard, environment as well as inflicting mechanical damage,
ship operational disruptions, and other financial losses.
In order to eradicate such incidents, today’s modern cruise liners are
subject to a plethora of standards and regulations governing almost every
element and technical aspect of ship design and operation. Since thecruise ships consist of technically complex machines, minor fires, power
outages, and propulsion issues do occur, however, unlike most of theother kinds of vessel accidents such incidents rarely jeopardize cruise
safety. The reason for improved safety of cruise vessels at sea is wide
ranging adopted safety rules and regulations for minimizing marine
accidents and adaptation of latest innovations such as Pod Propulsion.
From 2025 onwards, all applicable ships must reduce Greenhousegas (GHG) emissions by 30 percent, as stipulated by the International
Maritime Organization (IMO) (Nuchturee, Li, and Xia 2021), This is oneof the reasons cruise fleets are becoming increasingly electrified, as theiritineraries are increasingly concentrated on restricted waterways and, inmany cases, moored near various cruise terminals. With around 30 yearsof experience, pod propulsion has changed the ship propulsion andmanoeuvring operations, ultimately improving ship safety, reliability,energy efficiency and overall vessel performance. According to ABB(ASEA Brown Bover) (ABB Group n.d.), since first Azipod installationin 1990, Azipod electric propulsion and steering system with around 20percent fuel saving compared to traditional shaft line propulsion systems
is still breaking ground. With availability for 25 different vessel types,
Azipod propulsion system is still considered favorable to Cruise ships
due to its simple, yet highly robust design. As latest and one of theworld’s largest cruise vessels “Symphony of the seas” is equipped withthree 20-MW Azipod units, considering manoeuvring with incredible
precision and accuracy (ABB Group n.d.).

ABSTRACTThis research is based on the real-ship accident report of the Cruise
vessel Norwegian Star, which resulted in the loss of ship propulsion. For
performing this FMECA study of the thirteen failure modes (FMs) ofpropulsion module sub-system, experts' team comprised of fourteen
professionals from the Ship's Marine Engineering department provided
their insight and input for completing this research. However, for the
calculations of FRPN values, the risk assessment parameters such as
occurrence (O), severity (S) and non-detection (D) are used. Artificial
intelligence technique such as the Interval type-2 (IT-2) fuzzy expert
system is integrated with FMECA (Failure mode, effects, and criticalityanalysis) for performing quantitative risk assessment. Based on theresults obtained, the Propulsion stator failure had the highest FRPN
(Fuzzy risk prioritization number) values.

KEY WORDS: Maritime safety; Cruise ship accidents; Ship Pod
Propulsion; Type-2 Fuzzy expert system; Marine Machinery operation,
Integrated Electric Propulsion, Propulsion module system FMECA.

INTRODUCTION
Forewords
The subject of ship safety, in particular Marine systems safety issignificant in the Cruise shipping business in order to avert serious
marine accidents and their impacts on cruise industry, the environment,crew and the passengers being transported. Cruise shipping carries
significant hazards and in past it experienced catastrophic accidents suchas historical titanic disaster of 1912, which resulted in the loss of 1,503
lives, and two other high-profile recent incidents of Costa Concordia and3748