With the recent introduction of stringent environmental regulations, such as those from the IMO, ship owners and operators are increasingly obliged to operate their MAN B&W two-stroke main engines on ultra-low sulphur fuels in defined marine zones. Furthermore, CARB (the Californian Air Resource Board) has enforced the use of diesel oils (MDO) or gas oils (MGO) in Californian waters since 1 July, 2009, while European harbours introduced similar requirements at the start of 2010. These new requirements ultimately mean more frequent, running changeovers in fuel type aboard marine vessels.
When entering/leaving such defined marine zones, the changeover from preheated HFO to cold MDO/MGO and vice versa represents a risk for fuel-pump sticking or seizure if not performed properly due to the very small clearances within fuel pumps. In response, MAN Diesel & Turbo has developed the Diesel Switch, building on its own patent, to handle this fuel changeover in a controlled way and avoid rapid temperature deviations and fuel-pump seizures.
In particular, the changeover between HFO and distillate fuels can be problematic for fuel equipment, with a high degree of automation necessary to avoid negative incidents. The Diesel Switch ensures the necessary flexibility and safety when changing between HFO and MDO/MGO and comes in two variants: for retrofits and newbuildings.
While MAN Diesel & Turbo currently recommends vessels to reduce loads to 25-40% before changing fuel type, the Diesel Switch retrofit enables a controlled and safe changeover independent of engine load. It does this through continuously checking temperature versus time. If the fuel temperature at the engine inlet exceeds 2 degrees/minute, the Diesel Switch emits an alarm and automatically halts the changeover process. 9/2010
The Diesel Switch also logs the entire changeover process for subsequent use as official documentation for port authorities if required.
The Diesel Switch hardware is controlled by a touch-screen control panel and has software to operate an MGO cooler to adjust fuel temperatures. The changeover valve uses magnetic couples that dispense with mechanical seals and are 100% leak-proof. It also has integrated sensors for detecting current and end positions. As back-up, the entire system has a manual override.