From Wikipedia for what it's worth . .
The Northrop Grumman intercooler as fitted in the WR-21, on Type 45 destroyers, were not designed to operate in water temperatures beyond 30c. Rolls-Royce said that the NG intercooler had been built as specified, but that conditions in the Middle East were not "in line with these specs". The House of Commons defence committee had in 2009 warned that "persistent overoptimism and underestimation of the technical challenges combined with inappropriate commercial arrangements" would lead to increased costs. The Northrop Grumman intercooler of the first Type 45 destroyer, HMS Daring, failed in the mid-Atlantic in 2010 and had to be repaired in Canada, with further repairs for intercooler failure in 2012 in Bahrain. The Type 45's pioneering Integrated Electric Propulsion (IEP) system uses two WR-21s and two Wartsila 2MW diesel generators to power everything on board, including weapons systems in addition to propulsion and other functions, leaving the ships vulnerable to "total electric failure". The Ministry of Defence said: "The Type 45 was designed for world-wide operations, from sub-Arctic to extreme tropical environments, and continues to operate effectively in the Gulf and the South Atlantic all year round."[6]
The Rolls Royce turbines themselves are extremely well-designed, but the Northrop Grumman intercooler has a design flaw causing the turbines to fail occasionally. [7]