A hand-held current analyser has been introduced by Tube Lines in an effort to reduce signal failures on the Jubilee, Northern and Piccadilly lines of London Underground.The device was developed by one of the infrastructure manager’s engineers to counter the effect of failed block joints. These insulating joints separate track sections and enable signal blocks to be maintained, but they are prone to contamination by metal filings that bridge the plastic, creating a circuit between two sections and triggering a signal failure.However, identifying this as the cause of signal failures has proved difficult in the past, leading Tube Lines to seek a more efficient method of detecting current flow between track sections. Previously, track had to be inspected at close quarters and filings dislodged from the blocks using a hammer. The current analyser means such laborious inspections are no longer necessary, and it diminishes the risk to track workers of receiving electric shocks. Tube Lines says the hand-held device should also allow at-risk sections to be identified and repaired before they cause a total failure.Tube Lines, UK