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Sketch and describe the Cylinder Lubricating System used in new generation marine diesel engines

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  • Sketch and describe the Cylinder Lubricating System used in new generation marine diesel engines

    Sketch and describe the Cylinder Lubricating System used in new generation marine diesel engines
    Last edited by mohit; 12-21-2017, 11:47 AM.

  • #2
    Pump station and starter panels: The pump station consists of two individually operating pumps, heating coil, filters and a suction tank. The power supply to the pump

    station starter panels is taken from two separate circuit breakers, one supplying each pump.


    Lubricator units: The lubricator units, one for each cylinder, each comprise two lubricators for 9870 bore engines and one lubricator for medium and small bore engines.

    Each lubricator

    unit is equipped with one accumulator with nitrogen pre-pressure of 2530 bar on the inlet side, and one accumulator on the outlet side of each lubricator, with nitrogen

    pre-pressure of

    1.5 bar.


    Each lubricator features 3, 4, 5 or 6 lubricating pistons, depending on engine type, a feedback pickup and a solenoid valve.

    Alpha lubricator control unit –ALCU: The three main electronic components for controlling the lubricating oil are comprised of one steel cabinet – the so-called ALCU

    unit. The three units

    are;


    - MCU(Master Control Unit)

    - BCU (Backup Control Unit)

    - SBU (Switch Board Unit)

    A terminal block interfaces all electrical connections to the engine. The 24 V DC power is supplied from two individual power sources, from different breakers in the UPS

    unit.


    Load transmitter: The load transmitter is connected to the fuel rack, thereby continuously transmitting the fuel index % to the MCU, which calculates the engine load

    from this information and the detected engine rpm.


    Trigger system (Shaft encoder): The shaft encoder is connected to the fore end of the crankshaft, and the signals are transmitted to the computer panels via a terminal

    box. For engines on which the crankshaft fore end is not available for angle encoder installation, a trigger ring and tacho pickups are installed at the turning wheel.


    Backup trigger system: The backup trigger system comprises two tacho pickups in a box at the turning wheel, thereby transmitting the engine rpm to the BCU. The

    backup pickups are also connected to the MCU for surveillance purposes.


    Human Machine Interface (HMI) panel: On the HMI panel, individual cylinder lubrication adjustment is possible, various values and alarms are displayed, control

    buttons for the pump station are available, and manual execution of prepublication is possible


    Working principle

    o The pump station supplies the Alpha Lubricators with 4050 bar oil pressure.

    o The MCU controls the oil injection by activating a solenoid valve situated on the relevant lubricator.

    o A feedback signal from each lubricator indicates that oil injection has taken place (motion sensor for the piston inside). This is shown by Light Emitting Diodes (LEDs)

    on intermediate boxes for each cylinder.


    o Timing is based on two signals from the angle encoder, a TDC cyl. 1 marker and a crankshaft position trigger. The Alpha Lubricator system is normally timed to inject

    cyl. oil into the piston ring pack during the compression stroke.


    o The cylinder lubrication is based on a constant amount of oil being supplied per injection. The specific feed rate is controlled by variation of the injection frequency.

    o The injection frequency is calculated from index and speed, and is normally proportional to the engine MEP. However, a power Mode or RPM Mode is possible.

    o The basic cylinder oil feed rate at MCR (100%) is calculated as a correlation between a number of injections / rpm and the stroke of the lubricators.

    o On the HMI panel, adjustment of lubrication feed rate for individual cylinders is possible between 60% and 200%. Default value is 100%.

    o During normal operation the system is controlled by the MCU. If any failures are detected in the system, a common alarm is activated in the control room. The

    detailed alarm reference is displayed on the HMI panel.


    o If a critical failure in the MCU is detected, the BCU automatically takes over (Note – control switch must be in “auto” position). An indication lamp “BCU in control” is

    lit on the panel that contains the HMI panel. Note that on older installations, the indication lamps can be situated elsewhere.


    o The BCU is based on random timing and RPM Mode. The injection frequency is adjustable on the BCU and is normally, as minimum, set to the basic cylinder oil feed

    rate for the engine, plus 50%.


    o Alpha Adaptive Cylinder oil Control: ACC
    • The Alpha Lubricator System has an algorithm controlling cylinder oil dosage proportional to the sulphur content in the fuel. This algorithm is referred to
    • as Alpha Adaptive Cylinder oil Control (Alpha ACC).
    • The cylinder oil amount is controlled such that it is proportional to the amount of sulphur entering the cylinder with the fuel.
    The following two criteria determine the control:
    • The cylinder oil dosage shall be proportional to the sulphur percentage in the fuel
    • The cylinder oil dosage shall be proportional to the engine load (i.e. the amount of fuel entering the cylinders).
    The implementation of the above two criteria will lead to an optimal cylinder oil dosage, proportional to the amount of sulphur entering the cylinders.

    The above principle is founded on the observation that the main part of the cylinder liner wear is of a corrosive nature, and the amount of neutralizing alkaline

    components needed in the cylinder should therefore be proportional to the amount of sulphur (generating sulphurous acids) entering the cylinders.


    A minimum cylinder oil dosage is set in order to account for other duties of the cylinder oil (securing sufficient oil film, detergency, etc.).

    The above described Alpha ACC is implemented with the so-called “Sulphur Algorithm” The crew onboard vessel inputs the “HMI setting” based on the sulphur

    percentage of the fuel used and a conversion table. This is done by one input on the HMI panel of the Alpha Lubricator System each time the fuel specification is

    changed
    Last edited by deepak; 12-21-2017, 11:46 AM.

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