ONLINE LASTEST E- PARIKSHA QUESTIONS

Why crank pin bolts are not uniform? Changing cross section of Connecting rod bolts ? Structure of connecting rod bolt.

First of all, Connecting rod bolts are not given a uniform crosssection from bottom to top TO PREVENT STRESS CONCENTRATION, and FRETTING. shank of the bolt is less in diameter at the botttom core by a marginal 10% which reduces stress concentrations in the bolt, and increases EXTENSIBLITY. note the term extensiblity used here. it accounts for elongation of the bolt wen needed, and thus increases fatigue strenght. it inturn reduces the area in direct contact with the bolt, reducing fretting.

The main design feautures of the bolt are:

1. High UTS alloy steel having higher fatigue strength.
2. Long thin elastic bolts for higher percentage of elongation and fatigue strength.
3. High degree of surface finish bolts is used to reduce stress concentration.
4. Bolts are free with very little fitted portion, to reduce stress concentration.
5. Shank of bolts is less in diameter than the core diameter at the bottom of the thread by 10 %, which increases extensibility.
6. Well-formed fillet at place of change of section and between the shank and bolt head to prevent stress concentration.
7. Bolt has smooth change of section.
8. Bolt stiffness is less than component stiffness.
9. Rolled thread and three or four additional thread and gradual transition.
10. Dowel pins are fitted to reduce shear load on bolts and bolts are provided with interlocking arrangements

Muff coupling and emergency astern arrangement

         muff coupling and emergency astern arrangement

what does it mean by saying sulzer RND 68 ?

When looking at Sulzer engine’s specifications, there is always some ambiguity. MAN B&W is very clear with its specifications, however Sulzer never gave one. That doesn’t mean MAN B&W is better than Sulzer engines.

The letter ‘R‘ in the engine designations goes back to the Sulzer RSD two-stroke low-speed engine types introduced in 1950. The letter ‘R‘ stood for ‘Revidierter’, so the RSD types were ‘revised’ versions of the SD engine types that had been developed since 1930. Built in two bore sizes, 58 and 76cm, the RSD engines were the first two-stroke low-speed engines designed and built by Sulzer that had fully welded structures (columns and bedplates). Turbocharged versions followed in 1956 with the RSAD engine types.

The number given after RND specifies the cy;inder bore. So RND 68 means 68 cm cylinder bore.

You can see the parameters of the engine , mayb asked by the survoyers, in the table given in the end. 

Year	Type of Engine	Cylinder diameter in cm

1967 – 1981

RN (RND, RNF, RNMD)

68,76,90,105

The letter ‘R‘ was then retained over the following years in the RD, RND, RND..M, RLA, RLB, RTA and RT-flex engine types. Yet after the RSD and RSAD designations, the letter lost any connotation of ‘revised’. It was simply kept as an easily-recognised identifier for Sulzer low-speed engines. When electronically-controlled common-rail systems were applied in 1998, the designation RTA was adapted to RT-flex to emphasise the key feature of flexibility given by the new technology.’

Parameters for the engines are 

Parameters	RD	RND	RTA	RT-FLEX
Turbocharger	Pulse (No auxiliary Blower)	Constant Pressure	Constant Pressure	Constant Pressure
Scavenging	Loop	Loop and Under piston space	Uni flow	Uni flow
Exhaust valve	Rotary flap valve	Exhaust ports	Hydraulic operated	Hydraulic operated
Stroke Bore Ratio	1.7	1.7	3 to 4.2
Piston	Convex shape	Convex shape	Concave shape	Concave shape
Piston cooling	Water	Water	Oil	Oil
Fuel pump	Suction valve control, no spill valve	Suction valve and spill valve	Suction valve, spill valve and VIT	Common rail system (jerk type)
Drive	Chain	Gear	Gear	Gear
Cylinder Lubrication	Mechanical drive	Mechanical drive	Load dependent, Electric motor driven
Cylinder quills	Quills at upper part	Quills only at upper part	Quills at two level
Cross head bearing	Two piece type	Two piece type	Continues bottom half type	Continues bottom half type
Piston skirt	short	Long	Short	Short
SFOC	208 g/bhp/hr	203 – 208	115	118
MEP	8.6	10.6 – 12.3	17	19.5
Peak Pressure	76 bar	84 – 94 bar	140 bar	150 bar
Power/ cycle	1700 KW	2100 – 2500 KW	3700 KW	2100 – 5720 KW
Piston Speed	6.1 m/s	6.3	8	8 – 8.5

Turning gear

A Jacking gear (also known as a Turning gear) is a device placed on the main shaft of an engine or the rotor of a turbine. The jacking gear rotates the shaft or rotor and associated machinery (such as reduction gears and main turbines), to ensure uniform cool-down. Without turning, hogging or sagging can occur. Additionally, the jacking gear's assistance in rotation can be used when inspecting the shaft, reduction gears, bearings, and turbines. As an auxiliary function, the jacking gear also helps to maintain a protective oil membrane at all shaft journal bearings.

Hogging is when the shaft bows upwards due to thermal stratification.

On the engine shaft of a marine vessel, this process also prevents the shaft from warping when a ship is preparing to achieve maneuvering status.

Thrust block

A thrust block, also known as a thrust box, is a specialised form of thrust bearing used in ships, to resist the thrust of the propeller shaft and transmit it to the hull.

Early screw-propelled steamships used a thrust block or thrust box composed of perhaps a dozen lower-rated plain thrust journal bearings stacked on the same shaft.[These were problematic in service: they were bulky, difficult to dismantle, wasted power through friction and they had a tendency to overheat. The thrust box was built of a box-like cast iron housing with a radial bearing at each end and a number of collars formed on the shaft between them.This shaft was often a short section of removable shaft called the thrust shaft, linking the engine ahead to the propeller shaft astern. A series of iron horseshoe-shaped collars fitted over the small diameter of the shaft and bore against the forward face of the shaft's collars. Each horseshoe was faced with a low-friction pad of babbitt metal. Lubrication was by an oil bath in the box and a plentiful volume was important for cooling purposes too.

Although lignum vitae wood was used for the radial stave bearings in the stuffing box, cooled directly by seawater itself, this material wasn't capable of withstanding the force needed for the thrust blocks of any but the earliest screw vessels.

Each horseshoe was independently adjustable forwards and back, by either wedged gibs or a screwed adjustment. A particular problem with these thrust boxes was in adjusting them so that the force was shared equally between all the collars. Adjustment was often done on the basis of their operating temperature, gauged with the engineer's hand.


Improved understanding of the theory of lubrication films (initially by Reynolds) allowed the development of much more efficient bearing surfaces. This allowed the replacement of multiple collars in a thrust box by a single thrust block.

Fluid-film thrust bearings were invented by Australian engineer George Michell who patented his invention in 1905. Michell bearings contain a number of sector-shaped pads, arranged in a circle around the shaft, and which are free to pivot. These create wedge-shaped films of oil between the pads and a rotating disk on the shaft. Each lubricant "wedge" can only be of a limited length (in the direction of travel, i.e. circumferential) so multiple pads are needed rather than a single ring. No lubrication pump is needed, the rotation of the shaft itself is sufficient.

Strait

A strait is a naturally formed, narrow, typically navigable waterway that connects two larger bodies of water. It most commonly refers to a channel of water that lies between two land masses, but it may also refer to a navigable channel through a body of water that is otherwise not navigable, for example because it is too shallow, or because it contains an unnavigable reef or archipelago.



strait of malaca


Straits used for international navigation through the territorial sea between one part of the high seas or an exclusive economic zone and another part of the high seas or an exclusive economic zoneare subject to the legal regime of transit passage (Strait of Gibraltar, Dover Strait, Strait of Hormuz). The regime of innocent passage applies in straits used for international navigation (1) that connect a part of high seas or an exclusive economic zone with the territorial sea of coastal nation (Strait of Tiran, Strait of Juan de Fuca, Strait of Baltiysk) and (2) in straits formed by an island of a state bordering the strait and its mainland if there exists seaward of the island a route through the high seas or through an exclusive economic zone of similar convenience with respect to navigational and hydrographical characteristics (Strait of Messina, Pentland Firth). There may be no suspension of innocent passage through such straits.

What is difference between MC and MC-C engine in MAN B&W???

These are the physical differences between the two.

The first MC-C engines to be introduced in 1988 were K80MC-C and K90MC-C engines. They were almost identical to the MC engines of the time, but the layout was optimised for container vessels (at that time the -C stood for "container"). I 1994 the K98MC-C engine was added to the programme.

In 1996 and onward the MC-C versions of the small and medium bore engines were added to the programme. In this case the -C stands for "compact", as the engines were intended to be lighter, cheaper and yet more powerful. They feature an integrated camshaft housing, simplified cross-head and a variety of other smaller changes to facilitate the "compact" concept. In exchange the fuel injection system was simplified and the VIT system was made an option. The small and medium bore MC-C engines are thus best suited to vessels operating for prolonged periods at the power at which the engines are optimised.

The engine types prior to the introduction of the MC-engines were designated e.g. EF, FF, GF, GFCA, GB. The first letter was an indication of the mean pressure, while the subsequent letters were an indication of the application and turbo charger efficiency. This system was increasingly difficult to maintain as the engines were being developed and it had earlier been decided to reduce the designation to two letters. Some letters were already in use to designate stroke or used in 4-stroke designations. It was thus decided to name the new engine type MC, where M indicates the mean pressure (but not strictly according to the previous system) and the C indicated the turbo charger efficiency. This was at the same time the last engine designation according to the old system.


MC-C is more compact and produces more power compared to an MC engine.

Tonnage- Net tonnage, Gross tonnage, Gross Register Tonnage (GRT) and Net Register Tonnage (NRT)

Gross tonnage (GT) is a function of the volume of all ship's enclosed spaces (from keel to funnel) measured to the outside of the hull framing. The numerical value for a ship's GT is always smaller than the numerical values for both her gross register tonnage and the GRT value expressed equivalently in cubic meters rather than cubic feet, for example: 0.5919 GT = 1 GRT = 2.8316 m³; 200 GT = 274 GRT = 775,88 m³; 500 GT = 665 GRT = 1,883.07 m³; 3,000 GT = 3,776 GRT = 10,692.44 m³), though by how much depends on the vessel design (volume). There is a sliding scale factor. So GT is a kind of capacity-derived index that is used to rank a ship for purposes of determining manning, safety and other statutory requirements and is expressed simply as GT, which is a unitless entity, even though its derivation is tied to the cubic meter unit of volumetric capacity

Gross register tonnage (GRT) represents the total internal volume of a vessel, where a register ton is equal to a volume of 100 cubic feet (2.83168 m³), which volume, if filled with fresh water, would weigh around 2,800 kg or 2.8 tonnes. The definition (and calculation) of the internal volume is complex; a ship's hold can, for instance, be assessed for bulk grain (accounting for all the air space in the hold) or for bales (omitting the spaces into which bulk, but not baled cargo would spill). If V stands for the total internal volume in m³, then the GRT equals V / 2.83168, so for a ship of 10,000 m³total internal volume, the gross register tonnage is 10,000 / 2.83168 = 3531.47 GRT. Gross register tonnage was replaced by gross tonnage in 1994 under the Tonnage Measurement convention of 1969, and is no longer a widely used term in the industry.

Net register tonnage (NRT) is the volume of cargo the vessel can carry; i.e., the gross register tonnage less the volume of spaces that will not hold cargo (e.g., engine compartment, helm station,crew spaces, etc., again with differences depending on which port or country is doing the calculations). It represents the volume of the ship available for transporting freight or passengers. It was replaced by net tonnage in 1994, under the Tonnage Measurement convention of 1969.

What is condensate treatment in boiler?how condensation will take place?

we have a dump condenser using sea water. it cools the bypassed steam from dump valve, From heater, steam trap sends only condensate to the hotwell. In this hotwell we add certain chemicals like phospates,alkanline materials, oxygen scavengers such as hydrazine, coagulants to bind all precipated salts in order to prevent deposition so that which can be extracted during blow down.

More Class 4 questions Here

Main Engine cooling system V/S Auxiliary engine cooling

The cooling water pump which may be engine driven or be a separate electrically driven pump pushes the water around the circuit. After passing through the engine, where it removes the heat from the cylinder liners, cylinder heads, exhaust valves and sometimes the turbochargers, it is cooled by seawater and then returns to the engine. The temperature of the cooling water is closely controlled using a three way control valve. If the water is allowed to get too cold then it will cause thermal shocking which may lead to component failure and will also allow water and acids to condense on the cylinder bores washing away the lubricating film and causing corrosion. If it gets too hot then it will not remove the heat effectively causing excessive wear and there is a greater danger of scale formation. For this reason the cooling water outlet temperature is usually maintained at about 78-82°C. Because it is at a higher temperature than the cooling water used for other purposes (known as the LT cooling), the water for cooling the engine is known as the HT (High Temperature) cooling water.

Main engine cooling system

Auxilliary engine cooling system.

Cooling can be achieved by using a dedicated cooler or by mixing in some of the water from the LT cooling circuit. The LT cooling water is then cooled in the sea water coolers. The temperature is controlled using cascade control which monitors both the inlet and outlet temperatures from the engine. This allows a fast response to any change in temperature due to a change in engine load.

To make up for any leaks in the system there is a header tank, which automatically makes up any deficiency. Vents from the system are also led to this header tank to allow for any expansion in the system and to get rid of any air (if you are familiar with a domestic central heating system then you will see the similarities). The header tank is relatively small, and usually placed high in the engine room. It is deliberately made to be manually replenished, and is fitted with a low level alarm. This is so that any major leak would be noticed immediately. Under normal conditions, the tank is checked once per watch, and if it needs topping up, then the amount logged.

The system will also contain a heater which is to keep the cooling water hot when the engine is stopped, or to allow the temperature to be raised to a suitable level prior to starting. Some ships use a central cooling system, whereby the same cooling water is circulated through the main engine(s) and the alternator engines. This system has the advantage whereby the engines which are stopped are kept warm ready for immediate starting by the engines which are running.

A fresh water generator (FWG) which is used to produce fresh water from sea water is also incorporated.

A drain tank has been included. This is for when the engine is drained down for maintenance purposes. Because of the quantities of water involved and the chemical treatment, it is not economically viable or environmentally responsible to dump the treated water overboard each time. This way the water can be re used.

More Class 4 questions Here

Minimum requirements for certification of officer in charge of an engineering watch

Minimum requirements for certification of officer in charge of an engineering watch in a manned engine room or designated duty engineer in a periodically unmanned engine room ( Marine Engineer Officer Class IV)

1. Every officer in charge of an engineer watch serving on a sea- going ship powered by main propulsion machinery of 750 KW propulsion power or more shall hold an appropriate certificate of contemporary in form 8.

2. Every candidate for the certification shall -
(i) be not less than 18 years of age on the last date prescribed for receipt of application;
(ii) have completed approved education and training for a period of at least thirty months as provided in an approved training and assessment programme including on-board training documented in an approved training record book and meet the standards of competence as specified in section A-III/1 of the STCW Code;
(iii) have completed approved sea-going service for a period of not less than six months in the Engine Department of a sea -going ship powered by main propulsion machinery of 750KW propulsion power or more, closely supervised and monitored by a marine Engineer Officer Class I or an officer of the Engine Department holding certificate of competency under rule 5 and which is duly documented in an approved training examination, assessments and meets the standard of competence as specified in section A-III/1 of the STCW Code.
Source : www.mmd.gov.in 

Checklist for applying for COC

Click here for More on MEO CLASS IV Questions.

Random questions on Function 3 and Function 5 faced by Sumit Dalal on 07/05/12 (Mumbai MMD-Orion sir and Piplani sir)

 Answers will be published in corrosponding sections soon; keep watching for updates marines..

Fn 3

1.What is imdg code? List of books and description? And how is this information useful to you as an engineer?
2. What is annex 3? Their regulations? List of harmful substances?
3.what is annex 1 and its discharge criteria from engine room?
4. Acoording to annex 1 what are the constructional requirements of the engine room? And how is it decided?
5. IOPP certificate and what all things are described in it?
6.ORB entries and what do you write under code I and H?
7. Bulbous bow and its construction?

Function 5
1. AVR its diagram and functioning?
2.synchroscope its dia and working?
3.earth lamp dia and working?
4. Power triangle. Wht is the the relation btw them.? Can u measure reactive power
5. Power factor and how will you increase it.?
6. Emerg gen regulation?
 7.MSB safeties?
8. 3 wire system and 4 wire system and how will you take 220 from three wire system and where do you
measure the voltage in both?

Answers will be published in corrosponding sections soon; keep watching for updates marines..

Where To Stay in Mumbai While giving Class 4 MEO Orals ?

Where to stay ??

If you are giving your exams in Mumbai you can stay at the Seamans club which is nearer to MMD, in CST Station, Mumbai.This is just for your information.If are making your own arrangements well and good.
Seaman's Club (Mumbai) Phone Numbers: 022-22612260, 022-22624960

Procedure for applying for part A excemption for Class 4 MEO.

Following procedures are required to be followed for giving Class IV part A to the candidates, who have undergone GME course with embedded on board ship training;

1. On completion of the structured training ashore, the institute will send a list of successful candidates to the Mercantile Marine Department (Mumbai, Chennai, Kolkatta, Kochi).
2. The candidate is required to apply to the MMD for EXN-45.
3. The EXN-45 shall be issued to the candidate who will retain the same and will be presented to the Examiner of Engineers, after successful completion of embedded on-board ship training and further sea-service, to make him eligible for MEO Class IV Part A exemption and MEO Class IV Part B Examination.
4. The day the candidate completes his embedded on-board ship training (afloat training part of GME Course), the Master shall make an entry in candidate's CDC/logbook. In case the entry is made in the logbook, its copy duly signed by Master and Chief Engineer will be required to be handed over to the candidate.
5. The Master shall make an entry in candidate's CDC/logbook of the date of commencement of Sea Service by the candidate as Junior Engineer. In case the entry is made in logbook, its copy duly signed by Master and Chief Engineer will be required to be handed over to the candidate.
6. After completion of Sea Service as Junior Engineer, candidates will be required to apply for their assessment of eligibility to the Examiner of Engineers with copies of following documents ;
   1. Course completion certificate from the institute.
   2. CDC/logbook entry duly endorsed by Master/Chief Engineer indicating completion of embedded on-board ship training.
   3. CDC/logbook entry duly endorsed by Master/Chief Engineer indicating commencement of on board further sea service as Junior Engineer.
   4. TAR Book
   5. Passport
   6. INDoS Certificate
   7. Certificates of STCW-95 Modular Courses
   8. Sea service testimonials as required by META Manual
7. After assessment, and as required under Section M-III/1 of Chapter III of Maritime Education, Training and Assessment (META) Manual Volume I, the candidate will be eligible for MEO Class IV, Part A exemption. EXN-45 shall be endorsed and also allowing the candidate to sit for MEO Class IV Part B examination written and oral examination in all functions.
8. In case, the candidate approaches Examiner of Engineers only with embedded on board ship training, his application will be accepted for assessment for granting MEO Class IV Part A exemption.
9. For candidates having embedded on board ship training of minimum of four months in addition to further qualifying sea service, attending MEO Class IV preparatory course is optional.

Explain the working principle of an explosimeter and reasons for false readings?

An explosimeter is a device which is used to measure the amount of combustible gases present in a sample. When a percentage of thelower explosive limit (LEL) of an atmosphere is exceeded, an alarm signal on the instrument is activated.

The device, also called a combustible gas detector, operates on the principle of resistance proportional to heat—a wire is heated, and a sample of the gas is introduced to the hot wire. Combustible gases burn in the presence of the hot wire, thus increasing the resistance and disturbing a Wheatstone bridge, which gives the reading.

A flashback arrestor is installed in the device to avoid the explosimeter igniting the sample external to the device.

Note, that the detection readings of an explosimeter are only accurate if the gas being sampled has the same characteristics and response as the calibration gas. Most explosimeters are calibrated to methane or hydrogen.

What is meant by intrinsically safe?

The theory behind intrinsic safety is to ensure that the available electrical and thermal energy in the system is always low enough that ignition of the hazardous atmosphere cannot occur. This is achieved by ensuring that only low voltages and currents enter the hazardous area, and that all electric supply and signal wires are protected by Zener safety barriers. Sometimes an alternative type of barrier known as a galvanic isolation barrier may be used.

for example........

An intrinsically-safe walkie talkie radio, which has been designed and tested to not become an ignition source in a flammable atmosphere. Test standards may specify combinations of internal failures which may be present while still passing the ignition test.