Delivering a Safety Justification and Navigating Closure of Dependencies (from an Earthing and Bonding Perspective)

The earthing and bonding (E&B) on the Elizabeth Line is everywhere, consequently it is extensive and highly integrated, it is essential as a primary safety system to prevent electrocution and fire. Development of the E&B Safety Justification was time consuming and involved creation of a spreadsheet of reference documentation (circa 2000+ items listed).

The majority of the Safety Justifications (SJs) were written by the Engineering Safety Management Team (ESM), however, just two weren’t – those for Earthing and Bonding (E&B) and Electromagnetic Compatibility (EMC) were written and delivered by the Chief Engineer’s Group (CEG) respective Heads of Discipline (HoDs). This paper covers both the delivery of an SJ and closure of dependencies from the perspective of the CEG HoD E&B plus support team. We also discuss lessons learnt about the process and the possible concept for a future project of assurance leading delivery.

As the SJs are written for the final state, ahead of actually achieving it, each SJ is accompanied by a list of dependencies (items that are outstanding). An intricate process of closing these dependencies evolved through the lead up to Entry into Trial Running (EiTR) with both Safety Justification Engineering Judgement (StEJ) panels and the SJ Joint Dependency Closure Workshop (SJJDCW) running, leading to some overlap. In this paper we also discuss the importance of integration, proper records, interface management, tracking of outstanding items and good practice for getting approval at StEJ and SJJDCW.