Motor Flashcards
(8 cards)
Q1
With respect to Main Propulsion Engines, state the immediate action to be taken as Engineer Officer of the watch in the event of EACH of the following, stating ONE reason why EACH action is necessary:
(a) Turbocharger repeatedly surging. (4)
(b) Air start manifold/branch pipe overheating local to one unit. (4)
(c) Low scavenge air temperature alarm. (4)
(d) Engine misfires, fuel rail pressure low alarm activates, booster pump pressure high. (4)
(a) In the event of Main propulsion engine Turbocharger surging, the immediate action is to reduce the load/ slow down the engine after informing to bridge and CE. Repeated surging causes damage to the turbocharger due to the vibration when spinning back. This could be caused by the propeller being crashed into water in rough weather, causing rapid load fluctuations on the engine. Reducing the speed will reduce load, thus reducing load fluctuations and stops surging.
(b) An overheated air start manifold/ branch pipe has the danger of starting air line explosion. The immediate action would be to inform CE and bridge, request to slow down the engine and if possible, the engine to be stopped. The air start valve has to be repaired or replaced. The engine should not be started until the air pipe is cooled down as it can cause an explosion. If repairs could not be taken place, the engine would have to be run with the fuel pump lifted.
(c) Low scavenge air temperature alarm may be due to low coolant inlet temperature. The immediate action would be to reduce the seawater flow rate to the cooler. Reduce the cooling water flow rate/increase the temperature of the cooling water to prevent water moisture from condensing on the liner and washing off the lubricating oil. This prevents scuffing and corrosion caused by the removal of lubrication oil.
(d)Engine misfires “fuel rail pressure low” alarm activates, and booster pump pressure high may be due to clogged filters or leaks. The immediate action would be to change over to the other filter. If the pressure is low even after changing the filter, then request permission from the bridge to slow the engine down and/or reduce its load and inform CE.
Q2
(a) Sketch and label an obscuration type oil mist detector that incorporates a reference tube. (8)
(b) Explain the operation of the sketch drawn in part (a). (8)
(b) The arrangement of OMD consists of two tubes of the same size, one is called a reference tube and the other one is called a measuring tube. Both these tubes are placed parallel to each other. At one end of each tube, a photo-electric cell is fixed. Photo-electric cells generate an electric current when light falls on their surface. The amount of electric current generated is directly proportional to the intensity of light falling on it. The other ends of both tubes are sealed by fitting lenses that allow light to pass through them.
Equal intensity of light is reflected on the photo-electric cells using a lamp. Light passes through the lenses after being reflected by mirrors. One of the tubes has an inlet and outlet connection for introducing oil mist.
The measuring tube has a connection for oil mist, which is extracted from the crankcase with the help of an electric extractor fan. Samples from each cylinder are monitored by using a rotating selector valve, which connects each cylinder in sequence to the OMD. If the concentration of Oil mist in the measuring tube rises, the intensity of light reaching the photo-electric cell reduces. Now as both the tubes are electrically connected, a reduction in the generation of electric current will induce an electrical imbalance between the two cells, which will lead to ringing of the alarm.
Describe the procedure to change the fuel supply system of the main propulsion engine from high viscosity fuel to low viscosity fuel such as diesel oil whilst on passage. (16)
- Describe the procedure to change the fuel supply of the main propulsion engine from high viscosity fuel to low
viscosity fuel such as diesel oil for manoeuvring purposes (16)
• Check the status of the diesel tank, i.e quantity and quality
• Reduce the heat supply to the HFO heater gradually
• Slowly close the HFO tank valve and slowly open the diesel oil tank valve, leave open the return line to the HFO
tank
• When this procedure is complete, monitor the flow situation with respect to temperature and pressure
• Monitor the visco-therm if fitted
• After a suitable period of time to allow circulation of diesel oil, remove all trace heating
• Change over the recirculating line from the HFO tank to diesel oil tank
• Monitor condition of engine, i.e temps, pressures, sound, etc
Describe the procedure to change the fuel supply system of the main propulsion engine from high viscosity fuel to low viscosity fuel such as diesel oil whilst on passage. (16)
Needs amended
When it is required to change over the main engine fuel system from HFO to MGO, obtain the approximate time from the bridge to enter the SECA area so that we can start purification of the MGO tank for about 48 hours and keep the MGO service tank full.
Changeover from HFO to MGO means changeover from high temperature to low temperature. The changeover should be carried out in a controlled manner at a low load (25 - 40% MCR), and the fuel temperate gradient must not exceed 2°C/ min.
Before the changeover is to be done, check the FOBAS calculator for the change-over time required, and steam heating to the fuel oil heater shall be shut accordingly.
Proceed as follows for the changeover.
Shut the steam to the FO heater tracing lines and wait for the temperature to reach below 90 degrees or wait till the viscosity reaches 18cSt.
Reduce the main engine load to 25 - 40% MCR.
Make sure the temperature reduction does not exceed 2°C/ min.
Open the MGO service tank outlet valve and open the MGO inlet valve to the FO module.
The temperature will now gradually decrease until it reaches the temperature in the MGO service tank.
When the viscosity is reached below 8cst, open the valves to the cooler so that viscosity does not drop too much, as this will cause the problem of lubrication to the fuel pumps.
Wait until all the fuel in the system is flushed with MGO.
The load can now be slowly increased up to a max of 75% as long as the temperature change gradient is kept below 2°C/min.
Change the 3-way valve to the MGO cooler slowly to avoid thermal shock and temperature gradient and confirm cooling water valves are open.
After the changeover is complete, inform the bridge and note down the following.
Date and time of completion of fuel changeover
Ships position - latitude and longitude
The volume of MGO in each tank on completion of fuel changeover
Tank identity
Tank quantity
Signature of a responsible officer.
As engineer officer of the watch explain the procedure to be followed in the event of a crankcase oil mist alarm on a bridge controlled, constant speed, main propulsion engine fitted with a controllable pitch propeller. (16)
On activation of the main engine oil mist high alarm fitted with a CPP, the engine load will be reduced automatically - This is because reducing the load on the engine will reduce the loading on the bearings (usual location of hotspot)
The standby generator should start automatically and parallel with the running generator. If it does not start automatically, start it manually - this is because additional power will be required as auxiliary blowers and boiler will be started.
Inform bridge, C/E and 2/E about the situation, if the vessel is not in navigational danger, stop the engine. This will help in cooling the hotspot.
Evacuate all personnel from the engine room. If there is a secondary explosion, this will cause injury to personnel.
Leave the lubricating oil pumps running to help cool down the hotspot.
Do not go near crankcase relief valves. This is to prevent injury in case there is an explosion.
Wait at least 1 hour before opening the crankcase doors. Allowing oxygen by opening the doors may cause an explosion.
Isolate the engine (shut off start air, stop LO pumps, engage turning gear) this is to prevent accidental start
Open the crankcase door and find the cause of overheating.
Repair/ rectify the cause of overheating. This could be due to a bearing or chain rubbing or piston rod fouling on the stuffing box or a cracked piston etc. This may involve taking a unit out of operation. The engine should not be restarted until the cause is established and corrected.
Before restarting check the oil flow through the bearings, chains/ jet sprayers, and piston cooling return. Turn the engine and monitor the load on the turning gear motor (to check the engine is not binding on the tight spot)
When restarting, keep a close eye on any repairs. Use an IR temperature gun to monitor the location of overheating. Stop the engine after 30 seconds, 2 minutes and 10 minutes running at low load and check for overheating. To prevent reoccurrence.
Increase the load gradually over 2 hours, keeping a close eye on the temperature and oil mist detector. If running with the unit out of operation, then must remain in Engine room control with conventional watch keeping. Look out for excessive vibration and T/C surging. Damage may be caused otherwise.
If the engine is fully operational, when Chief Engineer is satisfied with the running of the engine, hand it back to bridge control.
As engineer officer of the watch explain the procedure to be followed in the event of a crankcase oil mist alarm on a bridge controlled, constant speed, main propulsion engine fitted with a controllable pitch propeller. (16)
- Enumerate the important actions to be taken by the Engineer Officer of the Watch in the event of an alarm
condition activated on the oil mist detector (16)
(i)Inform the bridge and request the engine to be slowed down, they should inform Chief Engineer and Master
(ii)If the engine cannot be stopped, evacuate the engine-room shut and secure all doors, open skylights, set up boundary cooling
ensure to keep clear from all doors
(iii)Start Emergency Generator
(iv)Once engine is stopped, Stop auxiliary blowers
(v)Shut off fuel supply
(vi) Stop all engine room fans
(vii)Maintain lubrication
(viii)Maintain cooling
(viiii)Engage turning gear and start
(a) State the name given to the water level indicators mounted on a boiler. (2)
(b) State why at least two of the items stated in (a) are fitted. (4)
(c) List FIVE boiler mountings which are subject to survey, other than those stated in (a). (10)
a) The name given to the water level indicators mounted on a boiler is “Water Level Gauge Glass”
(b)Two gauge glass is fitted to the boiler because:
If one gauge were to crack or become inoperable, there is redundancy until a repair can be made
To allow the water level to be monitored in the event of a severe roll
To enable the level of boiler water to be monitored in the event of one glass failure
Both gauges should read the same so if they don’t an investigation can be made into why
(c) FIVE boiler mountings that are subject to survey are:
Pressure Gauge Connections
Boiler Vent Cock
Main Steam Stop Valve
Safety Valves
Blow Down valve connection
(a) State the name given to the water level indicators mounted on a boiler. (2)
(b) State why at least two of the items stated in (a) are fitted. (4)
(c) List FIVE boiler mountings which are subject to survey, other than those stated in (a). (10)
State the name given to the water level indicators mounted on a boiler. (2)
Water Level Gauge Glass
b) State why at least two of the items stated in Q (a) are fitted.(4)
• To enable the level of boiler water to be monitored in the event of glass failure
• To allow the water level to be monitored in the event of severe roll
c) List FIVE boiler mountings which are subject to survey, other than those stated in Q (a) (10)
• Pressure Gauge Connections
• Boiler Vent Cock
• Main Steam Stop Valve
• Safety Valves
• Blow Down valve connection
