£1bn Warships Need Refit After Breakdowns

Six modern warships described as "part of the backbone" of the Royal Navy are to be fitted with new engines, after repeatedly breaking down.

Persistent problems have been reported on board the fleet of Type 45 destroyers, which cost £1bn each to build, and this has led to concerns over how reliable they are.

The Ministry of Defence insisted the refit "will ensure increased availability and resilience over the life of the ships".

A spokesman added: "The Type 45 destroyers are hugely capable ships and have consistently made a difference to our safety and security."

It is expected that the maintenance work on the engines will cost tens of millions of pounds.

The MoD had already committed to improving each warship's integrated electric propulsion systems.

The warships are used in "hunting pirates, drug runners or submarines, defending the fleet from air attack, and providing humanitarian aid after natural disasters", according to the MoD.

To make sure some of the vessels remain operational at all times, the refits will be staggered over several years.


http://news.sky.com/story/1631926/1bn-warships-need-refit-after-breakdowns

Propulsion
Further information: Integrated electric propulsion

The Type 45 is fitted with an innovative integrated electric propulsion (IEP) system. Historically, electric-drive ships (like USS Langley) have supplied power to their electric motors using DC, and ship's electrical load, where necessary at all, was either separately supplied or was supplied as DC with a large range of acceptable voltage. Integrated electric propulsion seeks to supply all propulsion and ship's electrical load via AC at a high quality of voltage and frequency.[N 4] This is achieved by computerised control, high quality transformation and electrical filtering. Two Rolls-Royce WR-21 gas turbine alternators and two Wärtsilä 12V200 diesel generators provide electrical power at 4,160 volts to a high voltage system. The high voltage supply is then used to provide power to two GE Power Conversion advanced induction motors with outputs of 20 MW (27,000 hp) each. Ship's services, including hotel load and weapons system power supplies, are supplied via transformers from the high voltage supply at 440 V and 115 V.[34] The benefits of integrated electric propulsion are cited as:

   The ability to place the electric motors closer to the propeller, thus shortening the shaftline, obviating the need for a gearbox or controllable pitch propellers, and reducing exposure to action damage.[34]
   The opportunity to place prime movers (diesel generators and gas turbine alternators) at convenient locations away from the shaftline, thus reducing the space lost to funnels, while at the same time improving access for maintenance and engine changes.[35]
   The freedom to run all propulsion and ship services from a single prime mover for much of the ship's life, thus dramatically reducing engine running hours and emissions.[34]

Key to the efficient use of a single prime mover is the choice of a gas turbine that provides efficiency over a large load range; the WR-21 gas turbine incorporates compressor intercooling and exhaust heat recovery, making it significantly more efficient than previous marine gas turbines, especially at low and medium load.

The combination of greater efficiency and high fuel capacity give an endurance of 7,000 nautical miles (13,000 km) at 18 knots (33 km/h).[34] High power density and the hydrodynamic efficiency of a longer hull form allow high speeds to be sustained. It has been reported that Daring reached her design speed of 29 knots (54 km/h) in 70 seconds and achieved a speed of 31.5 knots (58 km/h) in 120 seconds during sea-trials in August 2007.
-------------------------------------------------------------
you know i have read these "wiki"specs a couple of times and to be honest
the whole power system seems way under what i think the power requirements needed and looks like very little redundancy has been built in and the whole thing ,every system is dependent on two generators .........that`s very bad practice no wonder the grid keeps tripping And Ac .....spit