Inspection of butyl rubber insulations on the Lea Valley line on 22 May 72 (TN-ETR-8)

There are 26 butyl rubber covered under-bridge arms and about 20 butyl rubber covered tension insulators installed on the Lea Valley line of Eastern Region. The majority of these insulators were inspected for tracking on 28 Feb 71 and 4 Jul 71 and reported in Research Department Technical Notes ELD/246/71...