Diesel Switch solves fuel changeover problem

17 Sep 2010

MAN Diesel & Turbo has developed a system known as Diesel Switch to handle changeover between high and low sulphur fuel in a controlled way to avoid rapid temperature deviations and fuel-pump seizures.

MAN says that with the recent introduction of more severe environmental regulations, shipowners and operators are increasingly obliged to operate two-stroke main engines on ultra-low sulphur fuels in defined ECA zones. Furthermore, CARB (Californian Air Resource Board) has enforced the use of diesel oils (MDO) or gas oils (MGO) in Californian waters since mid-2009, while European harbours introduced similar requirements at the start of 2010. These new requirements ultimately mean more frequent onboard changeovers of fuel type with engines remaining running.

When entering or leaving these defined marine zones, the changeover from pre-heated 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 particular, the changeover between HFO and distillate fuels can be problematic for fuel equipment, with a high degree of automation necessary to avoid risks. The Diesel Switch is claimed to assure the necessary flexibility and safety when changing between HFO and MDO/MGO. It 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 against  time. If the fuel temperature at the engine inlet exceeds 2°/min, the Diesel Switch emits an alarm and automatically halts the changeover process.

The Diesel Switch also logs the entire changeover process for subsequent use as official documentation for port authorities if required. The hardware is controlled by a touch-screen control panel and is programmed to operate an MGO cooler to adjust fuel temperatures. The changeover valve uses magnetic couples that dispense with mechanical seals and are claimed to be 100% leak-proof. The unit includes integrated sensors for detecting current and end positions. For back-up, the entire system has a manual override.

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