The UK Royal Navy’s third Vanguard class ballistic missile submarine (SSBN) HMS Vigilant will begin sea trials in March 2012, marking the completion of the £300m Long Overhaul Period (Refuel) (LOP(R)) programme.

Babcock project manager Phil Smith said that HMS Vigilant will be ready to leave Devonport next month, capable of fulfilling its mission well into the 21st century.

The three and a half years’ refit and refuel programme, undertaken by Babcock, the UK Ministry of Defence (MoD), Rolls-Royce and ship’s staff at Devonport Royal Dockyard, involved incorporation of around 200 design alterations and additions (A&As) and class modifications to maximise the submarine’s operational capability.

The upgrades included installation and commissioning of the combined oxygen generation system, and a modification to the control rod drive mechanisms to improve nuclear safety during maintenance periods.

As part of the programme, the company undertook a structural survey using ultrasonic phased array and time of flight diffraction techniques to validate the submarine’s hull.

Additional upgrades included the modernisation of the reactor core as in Astute class submarines, overhauling tactical and strategic weapons systems, including replacement and integration of sonar 2054 inboard and installation of improved chilled water plants and system.

The project involved engaging more than 80 subcontracting companies, the overhaul of 26,000 items of equipment and replacement of pressure hull plating to reactor primary circuit pipework as well as testing of some 400 systems by the Babcock commissioning teams.

A formal Pre-Sea Trials Inspection was recently completed while the submarine was refuelled in November 2010, followed by steam machinery trials in dry dock and flood-up in June 2011.

The submarine is currently undergoing Power Range Testing (PRT) to validate its propulsion plant and supporting sub-systems.
Post-LOP(R) trials of the submarine at sea and alongside at Faslane, UK will be supported by Babcock and MoD.