Marine Insight

What To Do During Marine Auxiliary Boiler’s Flame Failure or Fuel Pump Tripping? Marine auxiliary boiler is only used in port and the exhaust boiler caters for all heating and steam needs while at sea. Generally if the burner routines are carried out religiously and the filters are cleaned, there is no major maintenance or routine that needs to be done In this article the author is relating a problem faced on one ship and the troubleshooting done. Scenario One day the boiler shut down after flame failure alarm came. After many futile attempts to restart the boiler on HFO, the boiler was changed over to diesel and manually fired. The auto firing mode was non operational and the FO pressure low alarm was coming and fuel pumps stopping. The following checks were done that helped to restart the boiler: *Correct pressure setting of the boiler: Generally the Fuel Oil pressure at the burner must be between 2 to 4 bars. In case the pressure is too high more fuel will be sent and the air fuel ratio disturbed. Less fuel pressure will give a lean mixture and flame will be unsteady and fail. *The fuel pump might trip on overload. Check the pump for mechanical damage and jamming. It should be free to turn by hand. *The over current relay may be at fault. Check the OCR setting and try increasing it if not correct. There is generally a test lever at back of OCR for testing. *The fine filter also called as dirt trap on the burner may be dirty. *The pressure transmitter may be giving wrong pressure feedback, check the wires. *The pressure transmitter for DO is normally different from FO line, Check this pressure transmitter. *The PLC will give command to stop due to pressure transmitter fault. Try calibrating the transmitter with the Master calibrator and check output. Output should be between 4 to 20 mA. *The fuel oil line may be choked and blocked. This can be ascertained by high back pressure. *The fuel oil temperature should be around 90 deg C. Check heater for correct functioning. High temperature can cause vapor lock that can lead to ignition failure. *The PLC (Programmable Logic Controller) has a reset buttons and resetting it restores the default values, often solving the problem. *Check any error code flashing on the display of the PLC or logic module and consult the manufacturer. *If a fuel oil (FO) low pressure alarm is generated it may be due to restriction in the line going to the pressure transmitter. There are also valves for isolation, they must be open. *Local FO pressure gauge may be replaced with a new / calibrated one to get correct picture. *If the boiler is firing on diesel oil (DO) then the burner should be generally ok, however if filters are partially dirty or the nozzle is partially choked, it may lead to this problem. Overhauling the burners may give correct picture. If the nozzle is choked it will create a back pressure. *There are two fuel oil (FO) pumps, try starting the second pump. *Check supply and return lines for correct functioning of valves. *Check the megger reading of the pump motor. *Check the suction line change over and return line change over valves. *In case the system includes separate pressure control valves for HFO and MDO, change over the three way valve from MDO position to HFO position or close the stop valve before the MDO pressure control valve. *Near the FO change over valves and near the burner assembly, there are pressure regulating valves on MDO and HFO line, try to adjust the pressure within 3 to 4 bars for HFO. Moreover there may be another pressure regulating valve near the pressure gauge of burner assembly. Use this for fine adjustment. *If the fuel pumps are tripping in manual firing then there is pump problem or back pressure. In manual mode PLC should not be involved and as still pump is tripping there is some other fault. *Check the input voltage to the pump and also the current by clamp meter. *If both the pumps are tripping then it indicates Pressure switch or back pressure problem.

The information was related to Saacke boiler on board but may slightly differ with the make of the boiler and the piping system and automation on board.

Fuel dribble (dripping) after injection This occurs when the fuel supply is not precisely cutoff at the end of fuel injection and fuel particles are accumulated on the tip of the nozzle. If fuel dribble occurs after fuel injection, the fuel in the cylinder will not burn completely. This will result in the emission of black or white smoke being exhausted. To prevent fuel dribble, the relief valve of the delivery valve is designed to draw back any fuel that may drip out of the nozzle after injection. Fuel dribble occurs if there is any failure in the delivery valve or injection nozzle, as the residual pressure remains in the injection pipe after fuel injection. Diesel EngineBleeding Air for the Fuel System 1. Bleeding the air between the fuel tank and the injection pump (low pressure side) (1) Repeatedly push down and release the pump handle. (2) Gradually the pump handle resistance will become higher, and the pump will seize to operate. Then the air flows with the fuel into the fuel tank via the return pipe. (3) Bleeding the air is completed when the pump handle becomes hard to operate. SERVICE HINT: In following cases, bleed the air between the injection pump and injection nozzle (high pressure side). When the engine does not operate properly after the engine is warmed up When a part on the high pressure side of the fuel system are replaced 2. Bleeding the air between the injection pump and the injection nozzle (high pressure side) (1) Loosen all injection pipe union nuts on the nozzle holder side. (2) Crank the engine to force the fuel out of the injection pipe and bleed the air. (3) Tighten the injection pipe union nuts. NOTICE: In the case of the common-rail type, use the hand-held tester and operate the injector to bleed the air. Do not bleed the air with the injection pipe union nuts loosened.

10 Precautions to Take Before Operating Controllable Pitch Propeller (CPP) on Ships The driving force of a ship comes from the rotation of propeller(s), which is attached to the main engine of the ship. The two main types of propellers that are used in merchant vessels are: 1. Fixed Pitch Propeller (FPP) 2. Controllable or Variable Pitch Propeller (CPP) As the name suggest, in fixed pitch propeller, the blades are fixed with the propeller boss and hence their pitch cannot be changed. However, in Controllable or Variable Pitch Propeller (CPP), the propeller blades are attached to the boss and their pitch can be altered via the hydraulic system. Both the types of propeller systems have their own advantages and disadvantages. In Controllable Pitch Propeller (CPP), the main engine can be started with blade pitch set to 0. This decreases the fuel consumption and also reduces the load on various engine bearings and its shafting during the starting procedure. If you are working on a ship with a Controllable Pitch Propeller (CPP) drive, do ensure to take the below mentioned precautions before operating it: 1. Operation from Remote Position: Operate the CPP from Remote control position for ahead, astern and stop position and check the pitch position indicator located near the stern shaft. 2. Operation from Emergency Position: Operate the CPP from Emergency control position which is located near the stern shaft for ahead, astern and stop position and check the pitch position indicator. 3. Check for Leakages: Ensure their is no oil leakage from the system. Even a small leakage can lead to failure of the system at later stage of operation. 4. Maintain the oil level: Check and maintain the oil level in the hydraulic tank of the system at all times. Also, ensure that all the alarms in the tanks are in working condition. 5. Check the pressure: Ensure their is no loss of pressure once the desired angle of pitch is achieved. 6. Start The Engine At Zero Pitch Angle: Always start the main engine at zero pitch angle as their will be a zero propeller resistance during the start, leading to less load on the shaft bearings. 7. Check all the Parameters: Check all the parameters of the main engine are within limits and check the temperature of all bearings including the shaft bearings. 8. Carry out Hydraulic Oil Analysis: Analysis of hydraulic oil used in the Controllable Pitch Propeller (CPP) system to be carried out onboard to check the condition and water intrusion. 9. Run Engine At Constant Speed: If shaft generator is fitted with power Take off/ Gear constant ratio for power production, the engine with CPP should be run at constant speed even at reduced load. This will ensure the efficiency of Controllable Pitch Propeller (CPP) and engine is maintained. 10. Perform Frequent Overboard Checks: Frequent overboard checks near the stern area to be performed during starting of the Controllable Pitch Propeller (CPP) for oil leakage from the sealing ring. Controllable or Variable Pitch Propeller (CPP) eases the use of other fuel efficient machinery such as shaft generator and also reduces load on the ship’s engine. It is a complex and expensive installation as compared to the Fixed Pitch Propeller (FPP) and hence engineer officers onboard must be skilled enough to ensure no breakdown takes place by knowing the system inside-out.