The LEMAG CONTROLmag with an integrated LEMAG DIESELswitch fuel change-over system is designed to carry out the change-over process between heavy fuel oil and low sulphur fuel automatically and safely. LEMAG CONTROLmag also enables the operator to switch fuels running at full load, as sensors will detect if the fuel temperature changes too rapidly. The system will then freeze the position to protect the engine’s fuel injection system from a thermal shock and generate an alarm. For safety the fuel change-over process can also be stopped manually.

The system is safe and simple to operate.
All you have to do is:

  1. Choose time frame for change over
  2. Choose change over direction
    (HFO -> DFO or DFO -> HFO)
  3. Start the process!


The integrated LEMAG DIESELswitch system ensures an absolutely linear change-over process to avoid any scuffing or blocked plunger and barrels or nozzles. Different tank levels can lead to substantial differences in fuel pressure that can be difficult for ball valves or standard change-over system to control. Tests have shown that only 4% movement of a lever of a 3-way valve can cause 90% change-over as shown in the following graph.

LEMAG DIESELswitch however controls the change-over process with its especially designed 3-way valve and exchangeable orifice inserts. These inserts have special opening surfaces that cause a controlled pressure difference to be able to control the change over and can be applied for all fuel systems.


LEMAG CONTROLmag does not only concentrate on the gradual change-over of fuel, but also takes the entire process into account as the following problems can occur if e.g. the cooler is not controlled automatically:

  • Heat energy from the booster pumps
    During low load operation the supply and circulating pumps create a lot of heat energy, which heats up the MDO. In many cases the fuel temperature cannot be reduced sufficiently by just adding just new fuel.
  • Risk of DFO temperature drop
    If the cooler is started too early, the temperature drop can be more than 12°C / min, which can severely damage the engine.
  • Risk of DFO cooler blocking
    If the cooler is operated incorrectly and at the wrong time the fuel flow can easily be blocked by HFO cooling down too rapidly.

LEMAG has already recorded many DFO temperature high alarms and has managed to avoid any resulting safety risks accordingly. To date these situations were always created by incorrectly operated (trace) heating systems.

LEMAG CONTROLmag also has an extensive safeguard system integrated with over 50 alarm parameters, which also takes all necessary precautions against black-outs to ensure a safe fuel change-over process.

LEMAG CONTROLmag is simple to install on both newbuilds and existing vessels and can handle different tank levels up to 25 m without additional MDO/MGO pumps. The basic system consists of:

  • Safety change over valve
    with magnetic coupling to prevent leakages
  • Static mixing tube
  • Electronic cabinet with advanced software

The LEMAG DIESELswitch fuel change-over system can also be delivered on a foundation containing all system components, pipes and internal cabling. All systems are equipped with a tamper-proof data logger to prove that the correct fuel was used in regulated areas. It is also possible to integrate a flow and density meter to calculate total fuel consumption.

Before shipment each system is pressure tested by Germanischer Lloyd (other classification societies on request).


  • Automatic and controlled change-over from HFO to MDO/MGO and vice versa
  • l Minimized risk of damages due to abrupt temperature changes
  • l Change-over at full load possible
  • l Integrated data logger
  • l Sealed by magnetic coupling
  • l Integrated safeguard functions