Failure of A21 Doulton porcelain insulators on eastern region in tension applications (TM-ETR-113)

A number of porcelain fractures occurred in crossovers, in which the insulators were loaded almost entirely in tension, on Eastern Region in May/June 1977 and 1978. The units were type A21 with a tongue at each end and had been made by Doulton Insulators Ltd in Nov and Dec 1959.