Cracks have been discovered in casting on Vanguard class Trident submarines. The head of resources and programme finance at the Ministry of Defence, Miss EG Cassidy, said in a letter that the castings "suffered from corrosion problems and would not meet the submarine's required commission lengths, necessitating additional corrosion examinations, implied costs and reduced platform availability".
The original castings were made of Nickel Alloy Bronze (NAB). The Ministry developed an alternative - Copper Nickel Chrome. However the new material was even worse developing "sub-surface cracks and defects." The Ministry then decided to return to the original NAB castings. Both types of casting are now in service on all Trident submarines
The Ministry of Defence claim that the operational effectiveness of NAB "had been maintained by a rolling programme of monitoring and validation. That programme has given us the assurance that any work needed to replace the castings can be managed within the normal refit programme."
This is probably one of the major items which is being considered as part of a maintenance programme which is being carried out on the first Trident submarine HMS Vanguard. Vanguard was reduced to one crew in early May and is undergoing an extensive repair period, part of which will be carried out in the shiplift at Faslane. The vessel carried out its first sea trials in October 1992 and is due to go in for its first refit in 2002.
Reported in the Electronic Telegraph 7 June 98.