Factors affecting the useful economic life of large MSF distillers

Abstract

Large desalination projects take from 5 to 8 years from initial conception to full water production. It is important that large public utilities can predict the remaining useful life of their existing distillers to allow replacements to be fully commissioned before old plants are retired from further service. The reasons for some early retirements are examined. No single item is considered to be of sufficient importance to lead to the scrapping of a group of distillers. The decision to scrap would depend on a number of factors. Examples are given of plants which have been made redundant while in satisfactory operation. Present maintenance cost would have to be increased by 10–20 times before these would become the major deciding factor, and would be of the order of Dh. 7 million per year per mgd of capacity. This level of expenditure would require major shut down time, and hence the resulting low plant availability would be the most important factor. All existing distillers operated by the WED, Abu Dhabi are giving better output and efficiency than originally specified, and the older ones are operating at higher outputs and PR than in 1984. The oldest WED distillers (STS) have been in service for 15 years, and at present there is no reason to suppose that they will not give a further 15 years of service.