EKG III some Questions sep-17

1.   a)  Briefly explain the Concept of Integrated Bilge Water Treatment System (IBTS).                                                                                                                                                                                                  [4 Marks]

b)   Sketch and describe a Pre-treatment unit for oil separation which can be used                   incorporated with IBTS                            [4 Marks]

c)   State the definition of “Oil residue        sludge)”   [3 Marks]

d)  Draw a flow diagram of oil residue (sludge) collection and disposal arrangement which can be used incorporated with IBTS                   [5 Marks]                           

2.           a) 1) List the safety devices fitted on fuel-oil settling tanks, daily service tanks.                          2) State the reasons for fitting such safety devices.                           marks]

                      3) State what attention requires for above safety devices.                                [2 marks]

              b)  Describe with aid of a sketch a fuel oil supply line to a 2-Stroke Cross head type  Marine Diesel Engine indicating the safety devices, position and type of valves were fitted to ensure satisfactory operations of the fuel oil supply system.                                                   [6marks]

                 c) State the routine maintenance and inspections on above (b) mentioned fuel oil supply system to avoid/control any flammable oil spillage.                                                                                                 [6 marks]

3.          a) State how is the capacity of an air compressor specified                                           [2 Marks]

              b) Describe with an aid of a line diagram, the compression process of a two-stage air compressor indicating each stage air pressure and temperature.                                                                     [3 Marks]

              c) Describe how is the running gear of reciprocating air compressors lubricated      [3 Marks]

              d) Describe the bearing replacement procedure of a two-stage air compressor mentioning the necessary inspections and calibrations of its components.                                                                                    [8 Marks]

4.           a) Briefly explain with the aid of sketches, the control mechanism of following Electronic Control Equipment;

                 1) A digital sequential control device                                                    [3 Marks]

                2) An integrated Automation Control and Monitoring System (IACMS)                [3 Marks]

                3) A  Computer programmable                                                                              [3 Marks]

              b) State how Electronic control equipment cited above (a) are utilized for main and auxiliary machineries                                                                                                                          [3 Marks]

               c) Draw and explain a flow chart indicating automatic control system for main engine or generator control system.                                                          [4 Marks]

5.

               a) Briefly discuss the effects of Ozone Depletion substances on human health and environmental.                                                                                           [2 marks]

               b) Explain how to collect the refrigerant into a recovery bottle form a refrigerator plant

                                                                                                                                                                  [3 Marks]

               c) State how make the following leak tests for a refrigerator plant;

                                        1)        Pressure test                                                               [2 Marks]

                                        2)        Vacuum test                                                                                        [2 Marks]

              d) Explain how to charge refrigerant into a refrigerator plant                                        [3 Marks]

              e)    1) State the preparation and precautions for starting a refrigerator plant           [2 Marks]

                      2) State how operating condition of a refrigerator unit is identified in a good working order.                                                                                                                     [2 Marks]

6.           a) Define followings, for an elastic material subjected to a tensile load;

                               1)         elastic limit                                                                                                   [1 Mark]

                               2)         yield point                                                                                                     [1 Mark]   

                               3)         breaking strength                                            [1 Mark]

               b) State how vibration is caused on the elastic materials         [3 Marks]

               c) Describe the main sources of ship vibration                           5 Marks]

               d) Explain how ship vibration may be reduced.                         [5 Marks]

7. With reference to a hydraulic system, suitable for the operation of deck machinery.

                a) Sketch a line diagram showing the layout and components                       [8 Marks]

                b) Describe the operation of the system sketched in above (a)                      [8 Marks]

Section-B

       8. a) name the materials commonly used for the following part of cables.

                  1)       Conductors                                                                                                                     [1 Mark]

                  2)       Insulation                                                                                [1 Mark]

                  3)     Sheathing                                                                                 [1 Mark]

            b) Explain the following electrical diagrams

                   1)       Block Diagram                                                                                                               [2 Marks]

                   2)       System Diagram                                                                                                            [2 Marks]

                   3)       Circuit Diagram                                                                                                              [2 Marks]

                   4)        Wiring Diagram                                                                                                             [2 Marks]

            c) Sketch a circuit diagram for the following wiring diagram                          [5 Marks]

9          a) Explain the following characteristics of semiconductors 

                             1) photoelectric effect                                                                                                                                  [2 Marks]

                             2) thermoelectric effect                                                                                                 [                         2 Marks]

                               3) Communicating action                                                                                               [2 Marks]

                             4) hall effect                                                                                                                      [2 Marks]

              b) 1) Define Integrated Circuit (IC) and Large Scale Integrated Circuit (LSI) as circuit elements

                                                                                                                                                                          [2 Marks]

                   2) Describe the structure of an IC                                                                                            [3 Marks]

                   3) Describe briefly the functions of the following types of IC Complementary Metal-Oxide Semiconductor (CMOS)                                                                                                                                 [3 Marks]

Section-C

10. a) 1) Define the propeller singing                                                                                                         [2 Marks]

           2) Explain generation mechanism of propeller singing and preventive measures.                 [2 Marks]

      b) Describe with aid of sketches, a controllable pitch propeller (CPP) and its mechanism of changing blade   Angle                                                                                           [         6 Marks]

       c) Explain how propellers fit on propeller shaft.                                            [6 Marks]

11. Explain how external hull corrosion is inhibited by EACH of the following.

       a) Design and maintenance.                                                                                                  [6 Marks]

       b) Impressed current system.     protection.                                      [5 Marks]

       c) Cathode                                                                                           [5 Marks] 

safety valve unstable operation terms

     

Unstable Operation of safety valve

Unstable operation often results from misadjustment.

The following are the state of unstable operation and its remedy.

 Chattering

This is a rapid reciprocating variation in valve lift during which the disc repeatedly

contacts the seat. It is because popping power is weak. In this case, bring up

the lower ring (closer to the bottom face of the disc).

Hunting

This is the state where the disc repeats violent vertical motion during operation as if

it beats the seat violently. This is often caused when there is much flow restriction in the pipings connected with inlet and discharge side of the safety valve or when blowdown period is excessively too short. In this case, open the adjusting cook or throttle valve or bring down the upper ring to increase blowdown. lf hunting is not ceased despite the above adjustment, rechecking of the piping is necessary.

Fluttering

This is an abnormal reciprocating motion in valve lift during which the disc does

not contact the seat.

This is caused by the unbalance of the relative part against valve lifting power.

In this case, bring down the upper ring to increase the valve lifting power.

with canvas or the like to shut off the air.

economizer mounting, preperation,soot fire

       

Economizer installation

The exhaust gas economizer is designed so that it is installed on a strong installation base, and thermal expansion is absorbed by the long holes of the installation bolts provided in the base plate of the exhaust gas economizer.

As reinforcement against the ship's rolling, the structure can be supported by an anti-rolling fixture from the ship's side.

Gas inlet and outlet ducts are equipped so that the flow of gas comes in contact with the heating surface uniformly.

In a case where the inlet duct also serves as a dust catcher, it is provided with a large drain opening from which the washing water used for cleaning of the exhaust section can be discharged satisfactorily.

Cold Starting- of economizer

A CAUTION Before operating the exhaust gas economizer, following checks are to be made

 1. Check to see if the water supply to the steam separator drum (boiler or special-purpose

drum) is normally actuated.

2. Fully open all the valves between the evaporating part of the exhaust gas economizer and

the steam separator drum except the discharge valve of the circulating pump.

3. Open the air vent valve of the evaporating part header, and make sure that the drain valve

is closed and the root valve of the pressure gauge is open.

4. Operate the circulating pump.

5. Gradually open the discharge valve of the circulating pump.

6. Make sure that water spouts from the air vent valve of the evaporating part header, and

then close the air vent valve.

 Operation of Economizer

1. After preparations for operation, start the main engine and allow the exhaust gas to pass.

2. If the steam separator drum is not under pressure, open the air vent valve of the steam

separator drum, and when steam starts spouting, close the air vent valve.

3. When the pressure of the steam separator drum reaches the specified pressure, gradually

open the steam valve so as not to cause water hammer.

4. If the exhaust gas economizer includes a superheating part, open the drain valve of the

superheating part header to discharge all drainage.

Keep the air vent valve open.

When the exhaust gas temperature at the exhaust gas economizer inlet exceeds the steam

separator drum's saturation temperature under the specified pressure, gradually open the

superheating  inlet valve to allow steam to pass.

When steam starts spouting fiom the air vent valve, close the air vent valve, and finally

open the steam outlet valve gradually to begin normal operation.

SOOT FIRE [IMPORTANT]

The exhaust gas economizer operator is requested to take the following precautions to allow the

exhaust gas economizer to perform its full functions and for safe operation.

A CAUTION If soot is left adhering in the exhaust gas economizer, there is a strong

possibility that a soot fire (meltdown of heating tube) resulting from

soot burning will occur.

Soot will easily catch fire if the equipment is often used with the circulating pump stopped as when the ship enters and leaves port, during low speed operation (sailing on canal or river) or during

shifting, where a large amount of soot is generated.

Ifthe circulating pump is stopped, the cooling effect of the heating surface is lost, which will cause a serious accident leading to a meltdown of the heating tube (s).

Since a soot fire is an accident which should occur least, make every effort to prevent soot, one of the three burning elements, from adhering.

1. Scot is generated by incomplete combustion of the main engine, and is affected by the fuel,

handling of it, conditions of the main engine, combustion of lubricating oil, etc. A large

amount of soot is generated especially when the load on the main engine has dropped and

when the supercharger has been cleaned.

2. Adjusting the main engine in good condition is the method for preventing soot from

adhering, and strict observance of soot-blowing and water-washing when the ship is

anchored are methods for removing soot.

Soot-blowing is effective in removing unadhered soot, but it cannot totally compensate for

poor operation of the main engine. Soot which cannot be removed by soot-blowing should

be removed by water-washing when the ship is anchored.

Handling a soot fire

Soot that catches fire is detected by the exhaust gas high temperature alarm (if

available) or another method such as sparks coming out of funnelincreased economiser back pressure. the following emergency measures are taken immediately.

1.       Bypass the exhaust gas (if a bypass device is available at the exhaust gas pipe

side). If it cannot be bypassed, stop the main engine, and cover the air suction port

with canvas or the like to shut off the air

2.       Continue the operation of the circulating pump. If possible operate both pumps in

parallel. (Lower the temperature in the exhaust gas economizer.)

3.       Continue the operation of the circulating pump. If possible operate both pumps in

parallel. (Lower the temperature in the exhaust gas economizer.)

Do not operate the soot blowers. Also, if soot-blower is operating, immediately

stop it.

fin stabilization

) why  Bilge keels are considered as an effective method of roll stabilization in ships 02

      b)   what are the types of tank stabilization                                                                    03

   c)    With reference to fin stabilisers:

      Sketch a block diagram showing an automated control system;                                 (4)

d)With reference to activated fin stabilisers give reasons why:

            i)for large vessels fin stabilisers are preferred to passive tanks;                          (4)

            ii) fin stabilisers are preferred for passenger and fast cargo ships;                    (3)

           

a)      bilge keels

l  up to 30% roll reduction

l  cheap and easy to maintain

l  effective whether making headway or not

l  simple in construction

b)      Pure Passive

            water movement controlled by baffle plates or manually operated valves

Controlled Passive

            water movement controlled by air or water valves

Active

            water moved by an impeller or pump

d)

         i)Fin stabilisers require much less internal volume than tank stabilisers and the internal space taken up by fins is not usually required for cargo.  Typically, the space taken by a passive tank stabilising system is approximately 900m3 which equates to approximately 20 containers.

         The mass of the fin stabiliser system is also very small compared to the deadweight, whereas passive tank stabilisers take up approximately 1.5% of the displacement.

         Since fin stabilisers are also much more effective than passive tanks, there is less chance of cargo movement/damage and crews are more likely to work at optimum efficiency.

(ii)     In passenger ships, comfort is of prime importance and this necessitates the best roll reduction system available.  Activated fins are the most effective method of roll reduction throughout all periods of wave encounter, mainly due to their rapid response time.  There are also considerations of financial income with regard consumption of food/drink and other purchases.  It has been shown that excessive ship motions have a marked effect on income.

bulbous bow

a) “bulbous bow (bulb) used as a important part of the hull “ discuss the reasons in support of this statement                                                                            04

b) explain the reasons that in modern ship construction sometimes , bulbous bow is completely eliminated or existing ones are being modified                        04

c)        

a)      the properly designed bulbous bow reduces wave-making resistance by producing its own wave system that is out of phase with the bow wave from the hull, creating a canceling effect and overall reduction in wavemaking resistance. as it can potentially reduce the hull resistance considerably this lead to better fuel economy for the vessel that are moving at speed thus it help in reducing co2 emission.   In addition bulbous bow gives additional buoyancy to the vessel at the forward end. Strong bulb gives addition protection to the vessel in the event of the damage in under water area of the forward

b)     it has been found that bulbs are not efficient at all service speeds (relate it to Froude numbers). In very low ship speeds, bulbous bows have found to increase the drag. Because a bulb is only effective when it makes its own wave, along with the bow wave. But at very low Froude numbers, wave making hardly occurs. But the bulb still being below the waterline, increases the total wetted surface area of the ship, therefore contributing to increase in its skin friction resistance.

Currently large ships are being built that are moving at super slow speed slow steaming is becoming a preferred option. It reduces consumption and emissions. Container ships and bulkers now are so large that they need not go fast because their attractiveness is the amount of cargo they can shift, reducing shipping costs.

So these large ships are , timetabled to deliver their goods at, more economical rate. The bulbous bow then becomes superfluous and can actually hamper efficiency as the ratios no longer mean it does its job. Due to above  on those ship bulbous bow is modified or eliminated

in refrigeration under cooling supercharging

Q5 With reference to a vapour compression refrigeration plant

a)Explain why Each of following is desirable

i) undercooling of the refrigerant at the condenser outlet    02 marks

Undercoolingor sub cooling  is defined as the reduction in a refregerent below its saturation temperature.  undercooling is measured in °C. undercooling of the refrigerant is necessary to avoid vapour bubbles in the refrigerant ahead of the expansion valve. Vapour bubbles in the refrigerant reduce capacity in the expansion valve and thereby reduce liquid supply to the evaporator. undercolingcooling of 4-5K is adequate in most cases. that will increase the net refrigeration effect. 

ii).supercharging at the compressor suction        02 marks

 Expansion valve ensure that the refrigerant gas leaving the evaporator is superheated by 5 to 7 ^OC to ensure that maximum utilization of the latent  heat of evaporation at the cooling compartment also the super heat will ensure the gas entering the compressor will behave as a gas. Any condensation of the refrigerant at the compressor inlet will lead to excessive pressure build up inside the compressor. It will lead to lifting up of the safety head without compressing the refrigerant. Due to liquid entering the compressor cylinder Consequently it may cause damage to the compressor body. 

b) Describe with the aid of a sketch how a   heat exchanger could be incoperated in the circuit to enhance undercooling.

As shown in the diagram below refrigerant liquid leaving the condenser is further cooled by removing sensible heat, using an internal heat exchanger here the cooling medium is the superheated refrigerant gas returning from the evaporator.

internal heat exchanger

c) Explain the possible consequences of the refrigerant having a dryness fraction at the compression suction    02 marks

Wet compression cycle is not preferred since liquid droplets of refrigerant will damage the valves and moving parts of the compressor, liquid refrigerant carrying lubricating oil from compressor would adversely affect the heat transfer rates, has low volumetric and mechanical efficiency Effect of operating variables on performance of vapour compression cycle are super heating of suction vapour increase refrigerating effect,.

hollow type coupling bolt and the hydraulic head/nut

Q4. With regards to main transmission shaft flange coupling arrangement :

a) Sketch a hollow type coupling bolt and the hydraulic head/nut and loading rod which are

 used to fit it; [4 Marks]

b) Describe how the bolt is fitted  [4 Marks ]

High pressure oil pumped into the head pushing down seal piston and rod this acton stretches the bolt (within its elastic limit)and reduces it diametersufficently to make a running fit into the hole. When the fluid pressure is released bolt will expand tightly into the hole with a radial grip simalutaniously  longitudinal contraction with the hand tight nutmaking a complressive load on the face of the nut hydralic head and loading rod is remved and  protective cap and seal is fitted to complete the assembly

c) state the advantage of the hollow coupling bolt as compared to the traditional type of

 coupling bolt [2 Marks ]        

Reduction in fitting and dismantling time, bolts can be used repeatedly.  During installation of traditional bolts, tight tolerance fit into the bolt hole will sometimes cause damage to both the bolt and hole During repeated fitting and removal. Also during the tensioning process the bolt is stretched and reduced in cross section which leads to reduction in the friction between the surfaces of the bolt and the bolt hole Dismantling in.

increasing its deadweight capacity without altering the ships length.

CE20175

Q1       You have been appointed as Chief Engineer to a dry cargo vessel recently purchased by your  shipping company.  The Company requests that you examine the vessel with a view to increasing its deadweight capacity without altering the ships length.  Outline the suggestions that you would make, justifying your proposals

To increase the deadweight through increasing the size of the ship requires an increase of either length, breadth, draught or block coefficient.

                The question rules out an increase in length.

                Of the remaining three parameters, it would seem to be totally impractical to convert the ship by increasing breadth or block coefficient.

                To increase the draught requires a reduction in freeboard, thus by considering the Load Line Regulations, there may be scope for a freeboard reduction.

                The vessel is a dry cargo ship, hence Type B, therefore attracts the maximum freeboard.

                If the vessel had wooden hatch covers fitted, then the replacement with steel, gasketed covers would reduce the freeboard. 

                In the design/build stage the Assigned freeboard is increased if the design is deficient in sheer, extent of superstructures and bow height.  Thus, if any of these deficiencies existed, there is capacity for structural alteration - adding superstructure - increasing deck sheer - adding a forecastle, (although the first two of these options would be very demanding). 

                The ship could also be deficient in depth and this could be increased (there have been conversions of this type carried out) which would raise the freeboard deck and, for the same freeboard, increase the draught.

                The ship may be an open shelter deck type which could be converted by ensuring all the openings had permanent means of watertight closing, thus raising the freeboard deck, effectively increasing draught.

                It may be possible to modify the structure to a bulk carrier and have Type B-60 assigned which would allow a reduced freeboard.

                Although an increased draught by decreasing freeboard would seem to be the only option, there are some modifications that can be made.  Sponsons have been fitted to some vessels (notably RO-RO's) to improve stability.  However, the extra buoyancy provided could be used to increase deadweight.  Other hull protuberances could be fitted for some other reason than extra buoyancy and allow an increase in deadweight.  For instance, a bulbous bow may be fitted to reduce wave making resistance, but it does add extra buoyancy.

6. With reference to the metallurgy of plan carbon steel

a) Sketch an iron carbon equilibrium diagram , labelling the salient point ;    [ 6 Marks]

b) Explain EACH of the following terms

         I.            Austenite                   [ 2 Marks ]

When steel heated, above the critical temperature of 723°Ca  non-magnetic solid solution of carbon and iron that exists in steel. Its face-centred cubic (FCC) structure allows it to hold a high proportion of carbon in solution. As it cools, this structure breaks down into a mixture of ferrite and cementite usually in the structural forms pearlite, or undergoes a slight lattice distortion known as martensitic transformation. The rate of cooling determines the relative proportions of these materials and therefore the mechanical properties (e.g. hardness, tensile strength) of the steel. Quenching (to induce martensitic transformation), followed by tempering (to break down some martensite and retained austenite).

The addition of  manganese and nickel, can stabilize the austenitic structure, facilitating heat-treatment of low-alloy steels. In the case of austenitic stainless steel, much higher alloy content makes this structure stable even at room temperature. On the other hand, such elements as silicon, molybdenum, and chromium tend to de-stabilize austenite, raising the eutectoid temperature (the temperature where two phases, ferrite and cementite, become a single phase, austenite).

Austenite can contain far more carbon than ferrite, between 0.8% at723°C and 2.08% at (1148°C). Thus, above the critical temparture, all of the carbon contained in ferrite and cementite (for a steel of 0.8% C) is dissolved in the austenite.

      II.            Cementite          Cementite is iron carbide with the formula Fe₃C. It is a hard, brittle material, essentially a ceramic in its pure form. It forms directly from the melt in the case of white cast iron. In carbon steel, it either forms from austenite during cooling or from martensite during tempering. Cementite contains 6.67% Carbon by weight; thus above that carbon content in the Fe-C phase system, the alloy is no longer steel or cast iron, as all of the available iron is contained in cementite. Cementite mixes with ferrite, the other product of austenite, to form lamellar structures called pearlite and bainite. Much larger lamellae, visible to the naked eye, make up the structure of Damascus steel. Fe₃C is also known as cohenite, particularly when found mixed with nickel and cobalt carbides in meteorites

  [ 2 Marks]

2Ekg 20175

 12

Ships hull is designed to withstand  stresses caused due to external forces such as weather therefore normally  a ship structure can remain intact provided that the load distribution requirements are met.

However in nomal operation it is quite difficult to maintain uniform load distribution  due to the nature of the loading unloading programmes, type of cargo or pre stowage of cargo as in the case of containers

In bulk cargo vessel Pouring the cargo through a shooter or via a conveyor belt does the loading. while doing so it is difficult to achieve even load distribution.In loading high density cargo such as steel makes it even more difficult. Above work is made worse as the owners are always trying to load the maximum cargo capacity.

In container cargo vessels load distribution makes more difficult due poor load ditrbution of cargo inside the container. Also due Wrong weight declaration. in general cargo ship different typs of cargo loaded in the same hold make it difficult to obtain the required load distribution.

In order to satisfy the stability requirements when water ballast is taken the always ditrbute on large tank areas making it difficult to reach the right balance. Some additional stress are induced to the hull when the cargo is loading and discharging as port operation demands fast turnaround of ships

As per above given conditions in operation of a ship it is difficult to meet the load distribution intended by the designer. the gap between designer anticipated load distribution and actual load distribution  is widened.. More than the external factors these factors contribute to structural failures of the hull

Large bulk carries transporting either liquid or dry cargos bear ample evidence of the irralavnce of  sheer

26.7.6 Correction for sheer profile (Regulation 38) Sheer is defined as being the curvature of the freeboard deck in a fore and aft direction. Benefits of sheer include: * Greater reserve buoyancy at the ends of the ship, particularly forward, ensuring good lift in a head/following sea; * Reduces water shipped on deck; * Reduces risk of foredeck being submerged after collision thus improving survivability in the damaged condition and helps to maintain an acceptable angle of heel at which progressive downflooding takes place. The tabular freeboards are based upon a standard sheer profile (standard ship), measured at seven equally spaced stations along the hull. A process based on Simpson’s 1331 Rule of area estimation is applied separately to the sheer measurements from the aft Fig. 26.17 perpendicular to amidships and the forward perpendicular to amidships to produce measures of effective sheer aft and forward respectively. Any deficiency in sheer will result in an increase in freeboard. Excess sheer will result in a deduction in freeboard. The amount of the deduction or increase in freeboard is determined by formulae in regulation 38.