Class IIIPreferencial Test.docx

1、Class III Preferencial TestClass III Marine Engineer ExaminationBoilerQ.1 What will you do if no water shown in the water gauges?Check the water gauges; if it blows steam, this is a very dangerous emergency.First, the fire should be immediately extinguished and the boiler should be isolated from the

2、 steam supply system.Switch off the feed pumps. Turn off the feed water valve and fuel supply valve.Wait for the slow cool down. Check to see if there is any damage to furnace, internal structure and other p arts of the boiler.Check the tripping of fuel supply valve as it should cut the supply of fu

3、el oil when water level reaches low low levelAfter the problem is fixed, boiler could be put back to service.Q.2 What are boiler trips & alarms?Boiler trips are actions that will occur under undesired situation of boiler. Boiler alarms are audible and visual signal about a problem or a condition.For

4、 example, when the boiler is in the low water level condition, alarm will occur. When the boiler is in the low low water level condition, trip and alarm will occur togetherQ.3 How to start up the boiler?First check the safety valves, air vent, manhole cover, steam valve, feed water pump, thermometer

5、 pressure gauge and water level gauge are in good condition. If all are ok, open the air vent. Then check the fuel oil system and circulate the fuel oil with heater to warm it to the required temperature and viscosity.Then run the force draft blower to purge the combustion area of any explosive gas

6、accumulation.Put the flame spill in low position and open the fuel valve to fuel spray nozzle. Then press the ignition switches.If the fuel fails to ignite, close the fuel valve and repeat the procedure. To prevent thermal stress, the temperature should be raised slowly. Also, in order to let the ai

7、r to release from the system, the air vent should be kept opened.When the pressure builds up, one should close the air vent and turn the flame spill to high position.Once the service pressure is reached, the steam valve should be opened slowly. If necessary, open the steam valve to oil tank carefull

8、y in order to prevent water hammering.Q.4 How to trip the boiler?Low low water level, high steam pressure and flame failure will also trip out the burner.Q.5 What is boiler blow down & why is it needed?Blow down of the boiler is done to remove scum and bottom deposits. This means that blow down is d

9、one either for scum or for bottom blow down.The reasons for boiler blow down are:1. To remove the precipitates formed as a result of chemical addition to the boiler water.2. In case of pollution from sea water, regular blow down is necessary to low the chloride level.3. To remove solid particles, di

10、rt, foam or oil molecules from the boiler water. This is mainly done by scum valve and the procedure is known as “scumming.”4. To remove excess water in case of emergency.chroideQ.6 What is boiler water treatment & why is it needed?On pacific Java, the chemicals MULTI-PLUS and OXYTREAT are newly emp

11、loyed. MULTI-PLUS is for adding phosphate and alkalinity to minimize scale-formation, corrosion and sludge accumulation, while OXYTREAT is for adding tannin to remove oxygen in the system. By blowing down the boiler, the precipitates can be removed.Liquid treate: precipitates, alkanityCondensate: Ph

12、Treatment is needed because forming of scale and corrosion would reduce efficiency and damage the boiler.Scale would thermally insulate the heating surface, so rise the metal temperature and the exit gas temperature.Corrosion would thinner the metal, or even made holes on tubes or surfaces, so as to

13、 endanger the boiler structure.Q.7 How to blow boiler water gauge glass?Check for the leak of the cocks. First close team and water cocks, open the drain, nothing should blow out if steam and water cocks are not leaking.In order to check the water cock connection to the boiler is clear, open and clo

14、se the water cock to see if water blow out.In order to check the steam cock connection to the boiler is clear, open and close the steam cock to see if steam blow out.Close the drain.Open the water cock. Water should then gradually rise up to the top of the gauge glass. Then open the steam cock and t

15、he water in the glass should fall to the level of the water in the boiler.Q.8 Describe how to manual ignite the boiler? First check the boiler pressure and temperature are in normal condition under heating from the economizer. Circulate the boiler fuel through the heater to ensure suitable temperatu

16、re and viscosity is reached. Check for the pressure of the circulated fuel.Then switch the control of the boiler into manual. Then start the forced draught fan and pass the air through the furnace for several 5-15 minutes to purge it of any exhaust gas or oil vapors.Then manually adjust the air inpu

17、t into the lighting up mode, open the fuel valve, press the ignition button, then press the fuel injection button and then leave the ignition power of the boiler.Then adjust control to normal service so that the air input and other parameter could be put into normal service.Check to see if the flame

18、 is steady.Q.9 What are the reasons caused low low water level?Low low water level may be caused by many reasons:1. Blow down valve is accidentally opened2. Feed water system- feed tank is empty, feed pump failure, automation control failure or other isolation from the feed system3. Serious leakage

19、on the water contacting areaQ.10 What is boiler carry over (priming)?It is a harmful condition in which water is carried over from the boiler to the steam space.Cause of it may be contamination of boiler water by excess of salts or oil. Foaming occur because of them. Also, too high of the water leve

20、l, excessive boiler loads, and sudden load changes could also lead to this problem. If it really happens, perform the water test and check the result, check to see any contamination for the water treatment equipment, chemical and the procedure. Check the steam loading, check the operator to see if h

21、e have made any sudden load changes before, etc.Q.11 What is cross-blow?Cross blow is blowing the steam through the steam terminal cock and steam pipe, to the water cock, through the glass column to the drain, and also, blow the water through the water terminal cock and water pipe, to the steam cock

22、, through the glass column to the drain.Open steam terminal cock, water cock and the drain, close other cocks, the steam terminal cock, steam pipe and the column are clear. Then close back and open water terminal cock, steam cock and drain, close other cocks, the water terminal cock and water pipe a

23、re clear.Q.12 Sketch the boiler inters structure & explains the difference between fire tube boiler & water tube boiler.Main EngineQ.13 What are the causes of crankcase explosion, 1st & 2nd explosion?For the first explosion, usually a hot spot could be possibly created in the crankcase. If the hot s

24、pot comes in contact with the lubricating oil, vaporization takes place. The vapour then circulates to a cooler place and condenses into white oil mist. The white oil mist would accumulate to create a higher concentration of the mist, and upon the explosive limit is reached, the crankcase explosion

25、occur.The primary (first) explosion produces a shock wave which propagates inside the crankcase and it has a breaking effect to reduce the size of oil droplets, producing more fuel for ignition. The pressure is followed with a low pressure area which tries to suck more air from outside. If there is

26、leak from relief valve, the stuffing box and crank case vent, a good environment with more few and air would be present. Usually the crankcase door may be rutureThe hot spot then ignite the flame and cause a very serve damage in the engine room.Q.14 What the causes are of scavenge fire?The cause of

27、scavenge fire is blow-by of combustion product between liner and piston into the scavenge air spaces. This fouling will be greater if soot is produced because of incomplete combustion of the fuel injected.There are some causes of blow-by of combustion product, they areWorn, sticking or broken piston

28、 rings,Lubricating quills on liner are not working,Damage to the running surface of liner,The symptoms includes surging of turbocharger, rises of scavenge air temperature and exhaust temperature.This problem could be prevented by careful maintenance, which includes draining the scavenge cock, regula

29、r inspections and cleaning of scavenge spacesDetail refer to Marine Engineering Series Diesel Engines A.J. WhartonQ.15 Compares the 2-stroke & 4-stroke engine advantages & disadvantages.For a 2-stroke engine, 1 stroke is for compression of gas and explosion, another stroke is for the exhaust gas to

30、leave and the fuel-air mixture to be inserted into the cylinder.For a 4-stroke engine, there is 1 stroke for compression and then explode, 1 stroke for return, 1 stroke for pushing exhaust gas to leave, and the last 1 for the air and fuel to be inserted into the cylinder.The advantages of 2-stroke e

31、ngine includes higher power to weight ratio and less moving parts such as exhaust valve, however, there may be problem of fuel-air mixture escaped with exhaust gas as there is relatively shorter time for scavenging to take place.The advantage of 4-stroke engine includes less chance for the fuel-air

32、mixture escaped, but there is a problem of low power to weight ratio.Q.16 What is A/E scraper ring function? / Why the lube oil levels of main engine sump tank suddenly drop down rapidly?Oil scraper ring is on the piston that scrapes the excess oil off the liner wall on the down stroke of the piston. This is done to remove excess oil from combustion chamber to enhance a uniform oil layer formation.The lube oil level drop may because of leakage from sump tank or burning of the lube oil.Q.17 What wi