Foreign material exclusion (FME) failures of large turbo alternators.

Abstract

Synchronous turbo alternators form the basic building block of a generation scheme. Turbo alternators are highly susceptible to foreign material ingress. In industry this phenomenon is on the rise. We evaluated the effects of foreign materials on the generator and condition monitoring equipment. The sources of foreign materials and methods to reduce ingress were investigated. We further evaluated industry best-practices on foreign material exclusion. Information is scarce, as no classic research material is available on foreign material exclusion. We therefore used industry foreign material exclusion best-practices and expert opinions were gathered. Eleven global incidents of foreign material exclusion failure were investigated. The areas of interest were: types of foreign material, area of ingress, condition monitoring response, component damage, root cause and prevention. We point out that turbo alternators are vulnerable to foreign material ingress mainly due to weak foreign material exclusion practices. We categorised the foreign materials and their effects on the operational parts of the turbo generator. We found that the air gap was the most susceptible to ingress. We identified the Generator Core Monitor as a possible solution to minimising foreign material damage.