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Operational failure prevention methodology for offshore systems using multiple criteria decision-making process

Dagkinis I., Lilas T., Nikitakos N.

Journal of Polish Safety and Reliability Association

2012

Vol. 3, No. 1

15--22

A framework for decision analysis, which has been applied on an operational offshore system and is based on a multiple criteria decision making (MCDM) process, is presented in this paper. This provides a generic methodology for the evaluation of alternatives and implementation of operational and design improvements based on the experience gained from past failures. The Failure Modes and Effects Analysis (FMEA) method is modified and used as a significant criterion together with Analytic Hierarchy Process (AHP) in order to enhance the decision making process. The mathematical model of AHP identifies and combines the weight of changes, as well as the results of modified FMEA. This combination takes into account possible interactions among the causes of failure by integrating several elements, enhancing the FMEA method. Next, the paper describes a decision model that incorporates also decision maker’s subjective assessments and is suitably applied to an autonomously operating floating structure. This decision making technique, enables the manipulation of both qualitative assessments and quantitative metrics in order to improve final judgments and, in general, advance the operation of the complex floating system.

Apply FMEA modeling to a floating ecological desalination unit

Dagkinis I., Lilas T., Nikitakos N.

Journal of Polish Safety and Reliability Association

2011

Vol. 2, No. 1

73--82

Water scarcity in small Aegean islands is considered a major problem for their development. On the other hand high potential renewable energy sources are available. Therefore a floating desalination unit was developed in order to treat the problem in an ecological manner. The floating unit has been operating for four years at sea close to a small island. Marine environment and autonomous remote operation led to a more complex design with several sensors and safety mechanisms. This paper illustrates and applies Failure Modes and Effects Analysis (FMEA) modeling to Floating Ecological Desalination Unit. FMEA is based on monitoring data and also taking into account failure dependencies between components during the assessment of desalination system reliability. Then two systems, one with safety mechanisms and one without are analyzed by Reliability Block Diagrams (RBD) and the reliability of each system is computed. The comparison between a simple system and the remote autonomous system illustrates the implications of the additional monitoring mechanisms and the impact of these mechanisms to reliability and risk assessment on the floating wind powered offshore desalination unit.

Modelling ship’s diesel electrical system using Markov theory

Mennis E., Dagkinis I., Nikitas N., Platis A.

Journal of Polish Safety and Reliability Association

2008

Vol. 2

241--245

One of the most critical systems for a ship operation is the diesel generator set. This is why the ship preserves four different diesel generators except the power battery packs. The paper describes the generator operation and the main failure conditions. Assuming that the failure rate of the system parts is constant the paper shows how the diesel generator system could be modelled in the context of Markov theory.