Inspection of butyl rubber-coated, glass fibre insulators on Lea Valley line on 5.11.72 (TN-ETR-13)

Tracking has occurred on butyl rubber covered glass fibre under bridge support arms on the Lea Valley line on Eastern Region and on the M.S.J. & A. line on L.M, Region after two years' service (References 1 and 2). Greasing of the insulator surfaces with a silicone grease is being...