MSF Desalination plants. Availability, reliability and safety analysis

Abstract

While good MSF desalination plant performance exerts a positive influence on plant economics, as part of water supply systems in isolated regions, the availability of the desalination system becomes a major design criteria. Reliability problems have historically been a major cause of poor performance for desalination plants. The emphasis of this paper is on the importance of availability modeling methodology to MSF desalination plant reliability problems by providing a context in which the effect of unit unavailability can be quantified. An assessment is made of failures and outages which impact the availability of MSF desalination plants. Limited fault tree logic for system failures is developed and reliability data from the literature is incorporated, where possible. The impact of other water supply system failures on the reliability requirements of the desalination plant is quantified as are the effects of increased average water system demands. The single largest influence on the effective capacity of a water supply system based on MSF desalination of sea water is found to be the availability and maintainability of the desalination plant. Forced outages as a result of equipment failure are significant, but other dominant contributions to unit unavailability include externally caused problems, such as silting. The design configuration of the desalination plant is also found to have an impact on the acceptability of water supply system performance.