Diesel Switch Offers Safe Fuel Changeover: MAN Diesel & Turbo developed the Diesel Switch to change from preheated HFO to cold MDO/MGO in restricted areas
by bo svensson
With the recent introduction of 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 sulfur fuels in defined marine zones, said Peter Rytter Jensen, manager, retrofit products, MAN Diesel & Turbo. “These new requirements ultimately mean more frequent, running changeovers in fuel type aboard marine vessels, and we have seen a growing interest in retrofitting components allowing for a safe diesel switch,” he said.
MAN Diesel & Turbo mentioned Californian waters as one such defined marine zone, where the California Air Resource Board (CARB) has enforced the use of diesel oils (MDO) or gas oils (MGO) starting July 1, 2009. In European harbors, similar requirements were introduced at the beginning of 2010. 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.
To avoid such problem, MAN Diesel & Turbo has developed its PrimeServ Diesel Switch. The system builds on the company’s own patent to handle the fuel changeover in a controlled way, avoiding rapid temperature deviations and risk for fuel-pump seizures. “In particular, the changeover be-tween HFO and distillate fuels can be problematic for fuel equipment, with a high degree of automation necessary to avoid negative incidents,” said Rytter Jensen. “Our Diesel Switch system ensures the necessary flexibility and safety when changing between HFO and MDO/MGO.”
While MAN Diesel & Turbo currently recommends vessels to reduce loads to 25 to 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°C/min, the Diesel Switch emits an alarm and automatically halts the changeover process. Two variants of the system will be available one for retrofits and one for newbuilds. The Diesel Switch hardware is controlled by a touchscreen 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 designed to be 100% leak-proof. It also has integrated sensors for detecting current and end positions. As backup, the entire system has a manual override. Another important feature is that Diesel Switch also logs the entire changeover process for subsequent as official documentation for port authorities if required.