Method and control device for operating a common-rail fuel supply system

A method for operating a common-rail fuel supply system of an internal combustion engine configured as a diesel internal combustion engine of a ship, the common-rail fuel supply system having a low-pressure region (4), a high-pressure region (6) and a high-pressure pumping device (3) having at least two high-pressure pumps (2), with the help of which fuel from the low-pressure region (4) of the fuel supply system is deliverable into the high-pressure region (6) of the fuel supply system, wherein in the high-pressure region (6) between the high-pressure pumping device (3) and injectors (1) assigned to cylinders, a pressure storage system (7) that is under high pressure is provided, and wherein a rate of delivery of the high-pressure pumping device (3) is adjustable by way of throttle valves (13) upstream of the high-pressure pumps (2), the method comprising:

• determining, dependent on a requested operating point of the internal combustion engine, a set point rate of delivery of the high-pressure pumping device (3), and a set point pressure for the pressure storage system (7) under high pressure,
• determining, dependent on the set point rate of delivery of the high-pressure pumping device (3) for all throttle valves (13), a control portion for the position of the respective throttle valve (13), and activating the respective throttle valve (13) with the determined control portion,
• determining, dependent on a deviation between the set point pressure and an actual pressure in the pressure storage system (7) under high pressure, for a first part quantity of the throttle valves (13) a closed-loop control portion for the position of the respective throttle valve (13), and activating the first part quantity of the throttle valves (13) with the closed-loop control portion in addition to open-loop control for only the respective throttle valve (13) of the first part quantity of the throttle valves (13), whereas the, or each, throttle valve (13) of a second part quantity of the throttle valves (13) is exclusively activated with the open-loop control portion, and
• exchanging or replacing, the, or each, throttle valve (13) of the first part quantity of the throttle valves (13), with a throttle valve of the second part quantity of the throttle valves (13).