Working Principle of Fresh Water Generator on Board Ship

Fresh water generator(FWG) is one of the essential machineries on board ship, After-all a large amount of fresh water is utilized on ship every day. On board ship Fresh water is used for the most part by huge boilers having steam turbines as main propulsion or cargo pumps driven by turbines. They all in all record for 30+ Tons of fresh water every day separated from the day by day necessities of 10+ ton for crew consumption as drinking, cooking, washing,Tank cleaning and different utilities. Adequate consumable water might be taken up against the cargo load capacity in the port for satisfying crew and machinery necessity yet isn't prescribed to utilize shore water for boilers because of their low quality, so Fresh water generator is unavoidable on board ship.

But why do we need the FWG on board in first place?

In the middle of good old days people used to bring across lots of water in their ship. It was good however it expands the load on the ship and furthermore water lack issues were always there. Be that as it may, the nature of shore water will be extremely (too much) bad to be used in water tube boiler and filling (expansion) tanks. The storage space that could have been used for fresh water can as a result be used for fuel or added/more space for payload and products (that are bought and sold) when fresh water generator is installed on a ship. As you may know the first (or most important) concern for running a ship or any transportation business is to make money. Further more Boiler needs demineralized water to reduce overall scale development and corrosion issues. It is also normally used to build the general efficiency of the running machinery, mostly it uses the engine warmth/heat by Cooling The Hot Jacket Cooling Water At Around 85 Deg Celsius To 65 Deg Celsius.

Working Principal Of FWG?

Extremely important rule of all low weight freshwater generator is that, boiling point of water can be decreased by lessening the pressure of the air surrounding it. By keeping up a low pressure, water can be bubbled at low temperatures say 55 degree Celsius. The source of warmth for the fresh water generator could be waste heat rejected by generators and main engine jacket cooling water. This decrease In Saturation Temp lead to early vaporisation of water due to vacuum created within the chamber. It Is Created By The Help Of An Air Ejector, Which Extracts The Air From That compartment/chamber. An Air Ejector Works On Bernoulli's Rule and being used side by side with a brine ejector used to suck salt water from the chamber. The vacuum help disappear the water leaving behind the salt or salt water to be sucked by salt water ejector. It is then passed through the dimmister (A sort of punctured plate with very minute gaps) which traps any water or salt particle traveling through it. The evaporated water is then condensed together with the help of ocean water and after that tested for sality with the help of salino-meter.

Regulations Regarding Production of sea water on board ship:

1. Ship must be 12 nautical miles away from the nearest coastline to start the FWG.
2. Engine must be running at full ahead sea speed during start of FWG.
3. Ensure main engine parameters are normal.
4. Ship is not in congested water.
5. Ship is not maneuvering.
6. There is no oil/chemical spill reported in the visinity of the ship.

Safety Equipments on A Typical FWG:

1. Vacuum Breaker For Releasing Vacuum when we shut down the FWG.

2. Relief Valve For Releasing The Excess Pressure.

3. High Salinity Alarm: It Is Fitted To The Salinometer As It Measures Higher Salt Content In The Water Produced.

4. Temperature Gauge.

Starting Procedures for Fresh water generator:

• First we need to ensure that suction, discharge and overboard valves for ejector pumps are under open condition. Now once been checked, start the ejector pump.
• Close the vacuum breaker valve.
• Make Sure the S.W pressure at ejector (air) is not less than 3 bar. Now wait for 10-15 minutes to build vacuum in the generation chamber of fresh water generator. Wait until it shows more than 90% vacuum.
• Now open the sea water feed to the evaporator. Check for the sea water level in the shell through the sight glass and ensure it is at optimum level controlling feed through feed valve. Once the heating coils are fully submerged by the sea water open the J.C.W valves to the evaporator slowly.
• Purge out any air in the system by opening air vent at the top of the evaporator.
• Check for evaporation from the sight glass and then start the salinometer.
• Divert the outlet back to the feed water until the salinity is under the limit.
• When the salinity level is as per the desired or set value, open the discharge valve of distillate pump which sends the water to the fresh water holding tank through flow meter.
• Increase the evaporation rate and start the discharge pump. Check for the sytem to be stable.

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Author Amit                                                          Article requested by: NIÑO GONZALES

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Ship side valve Functions, Definitions and Specification

The valves on the side of the ship / Ship-side valves on the top refer to valves that are connected to the hull, without having anything to medium with the valve on the side of the ship. During the dry dock, the valves are checked by the dry dock personnel, while the work of the ship's engineers is to check the internal valves. For total seaworthiness of the ship, the ship side valves must always be in proper condition, They must have local as well as remote control operation which must be permanently connected. Pipes of the inlet and the outlet to the sea must be provided with valves or taps attached directly to the outer coating or to the plating’s of fabricated water boxes attached to the shell plating. These accessories must be fixed with threaded bolts equipped with hazelnuts.

Heads or bolts screwed into heavy steel pads built into the plating. Screw holes must not penetrate into the plating. Valves for the Ship side Side Applications must be installed so that the pipe section can be located directly inside the valve without removing the sealed integrity of the hull. Taps and accessories of the ship, when made of steel or other approved material with low resistance to corrosion, must be adequately protected against wastage/rusting. In the visual inspection, the valves should not show any sign of defects on their body, their internals and the spindle. The Thread and other parts must be in good condition, which ensures freedom of movement in the operating conditions. Ship side valves are made and tested in accordance with the rules and regulations of the classification society in the presence of an expert.

Markings on the Ship Side valve of the Ship: The following data are marked on each side of the valve.

a) Nominal size of the drill (eg NB 80);

(b)Nominal pressure according to section 1.4.

c) Test pressure

d) Brand / seal of the manufacturer.

e) Marker / Stamp of Classification Surveyor.

f) Flow direction

g) The weight of the valve to be marked.

h) Metallic tag numbers provided with the table.

Why are they so important?

In a Ship, all that has been installed has a purpose, besides the valves on the side of the ship is controlled and supervised by the classification society. Maritime organizations (classification society and flag state) know a series of incidents of local flooding machinery space installations and averaging two reports of floods received annually. The side flaps ensure the sealed integrity of the shell and the internal working sea tube from the sea. Operation of the valves allows maintenance of pipeline equipment. They are used to prevent the ingress of water into the compartments after a failure in a pipeline or equipment. Therefore, the valves must provide a watertight barrier when closed. In normal commercial vessels, the ship is docked dry and the ship's valves are inspected to meet classification society standards. This inspection confirms the condition of the valve and closes it when closed. For installations, such as mobile drilling units of fleets or ships of intervention, the inspection may be performed by dry dock times or repair in the port, however, permanently anchored facilities these inspections are carried out. They become more complicated as the right holder must be able to demonstrate that the valve is sufficiently leak-proof and in good condition. This can be combined by a close visual inspection and on-site testing. After repairing or installing a new valve, the dry dock repair shop usually provides a 5-year warranty on these valves. However, if the valves are damaged during the warranty period, the workshop will bear the cost of the diver's time and expenses.

Listed below are few Ship-side valves that is seen on vessels.

              Name of the Valve                                Side                          Type                        Specification

1  Sea water suction for low sea chest                   Starboard      Butterfly valve           10K 550A

2  Sea water suction for high sea chest                  Port               Butterfly valve           10K 550A         

3  Sea water suction F.W.G sea chest                     Starboard      Butterfly valve           10K 125A         

4  Main cooling S.W discharge overboard             Port               Butterfly valve           10K 300A               

5  O.W.S discharge overboard                                Port              SDNR                         10K 40A          

6  Fire & G.S pump discharge overboard               Starboard     SDNR                         10K 200A             

   (fire and ballast pump)                                                             (Screw Down Non-Return valve) 

7  Steam blow valve to high sea chest                    Port              SDNR                         16K 40A            

7a Air vent for high sea chest                                 Port              Ordinary Globe valve(SDGV)   10K 40A                         

8  Steam blow valve to low sea chest                     Starboard     SDNR                         16K 40A           

8a Air vent for low sea chest                                  Starboard     SDGV                         10K 40A              

9  Steam blow valve F.W.G sea chest                     Starboard     SDNR                         16K 40A      

9a Air vent for F.W.G sea chest                              Starboard     SDGV                         10K 40A                     

10 F.W.G discharge overboard                                Port             Butterfly valve            10K 125A                         

11 Boiler blow down direct overboard                    Port            SDNR                          16K 40A               

12 Soil/waste water discharge overboard                Starboard   Storm valve                  10K 100A                         

13 Stop valve for waste water overboard                Port            Storm valve                  10K 100A                  

14 Gally/provision refer drain overboard                Starboard   Storm valve                  10K 100A                       

15 I.G system scrubber cooling tower                     Starboard   Butterfly valve             10K 200A                             

   discharge overboard 

16 Draught gauge overboard valve                          Starboard   SDGV                         10K 50A                      

17 Weather deck scupper overboard                        Port                                                125A  

18 Weather deck scupper overboard                        Starboard                                       125A  

19 Main water ballast pump discharge overboard   Port            Butterfly valve            10K 550A             

20 ODME discharge overboard                               Starboard   Butterfly valve            10K 350A    

What does K and  A stand for in specifications?

 K : is the pressure.

 A : is the Nominal diameter of the pipeline.  

Click here to read the full Article from its Original Source

*Note: The Following Article is being Originally written by one of our co-Author (Arpit Singh) on his personal website and is being re-used with proper modifications, editing and due permission. If you have any problem with any part of the content please contact us, We will act ASAP.

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Author ARPIT SINGH and Amit

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How to do crude oil washing on ships in 10 easy steps

COW or Crude Oil Washing cleans cargo tanks with jets of high pressure oil when the ship is unloaded. The crude oil is pumped through the washing machines to the jets and serves as a cleaning agent which is then pumped to land with the load/Product Discharge. It has been found that crude oil is more reliable washing medium than water. The washing / dissolving effect results in heavy, waxy and asphaltic deposits on the sides and bottom of the Holding tank to convert back into the liquid so that they are easily discharge To the shore. The Crude Oil Washing (COW) techniques has several advantages over washing with water, using Cow as the washing medium reduces the Sludge deposition, thereby reduces the discharge (Stripping) time and increasing the load/cargo flow. There low deposition of mud at the bottom of the tank which reduces Ship constant and so increase its dead weight. On the other hand washing with water takes more time due to more deposition of mud at the bottom. They not only cause delay in washing but also release hydrocarbon gases which becomes a challenge to gas free the tank. There are three essential prerequisites for the washing of petroleum product:

A fully functional inert gas system for maintaining the tank atmosphere in an inert state during the whole wash cycle.
Fixed Piping Lines for Tank washing system
Means to ensure that the bottom of the tank is clean and dry at the end of the operation.

The vessel must be equipped with an inert gas system which can function properly and produce Inert Gas with a maximum oxygen content of 5%. This should be maintained during the COW to ensure that the oxygen content does not exceed this value. No COW operation to be performed if the Inert Gas installation of the ship is not working properly and the oxygen content is not within the desired limit. The oxygen content must not exceed 8% by volume. The IG pressure in the tank must not be less than 200 mm. wg. The vessel to be washed with oil must be equipped with a fixed tank wash system connected by permanent lines to the main load venting system or by separate laundry lines of the loading system. The crude oil washing of discharging tanks takes place in a single step or in several stages during the discharge of the charge.

One Step Washing:

As soon as the tank is almost emptied , Washing starts and the tank is dried under pressure during the last washing step using stripping. The machine adjusts to the vertical angle from 0 to 140 degrees. Since single-stage washing is performed only during the last tank discharge stage, it is necessary to use the ship's instructor to remove the pump or reduce the speed of the charge pump so that the vacuum pump is effective. This method is generally useful between discharges at two terminals or between ignition operations.

Multi-stage washing

This involves washing the interior areas of the tank in stages as the load is pumped out of the tank. The revolutions of the charge pump are not reduced. Depending on the back pressure in the distributor of the vessel, this process results in a very small time loss during the bulk discharge of the tank. The wax and sediment collected in the spacers and other structural elements above the bottom of the tank are removed and pumped with the load to the ground. Any wax or sediment on the underside of the tank remains as long as the soil is not washed and stripped as a separate step. This increases the total discharge time, but is required for sludge control.


The machines are pre-set in the first stage at a vertical angle of 120 ° to 60 °. In the second step, when the loading level is about two thirds of the tank depth, it is set at a vertical angle of 70 ° to 30 ° and during the third stage when it is set to about 1 meter of the residual charge in the tank to 40 ° to 0 ° is. Each step is superimposed by approximately 10 ° in the preceding step, and the cycle is normally 11/2, ie, in the first step, for example, the nozzle moves in the horizontal plane by slowly changing its angle from top to bottom or from 120 * to 60 * from top to bottom, or from 60 * to 120 *, and from top to bottom, or from 120 * to 60 *

The regulation requires that the cow jets cover at least 90% of the horizontal surface area of the floors, rods and structural elements and at least 85% of the vertical direct zone. Shaded areas should be covered with splashes or deformations.

List of oil washing equipment controls
In the case of unloading of raw materials, the master must notify the competent authority and the terminal (or any other ship in transit to the ship), at least 24 hours in advance or at the time of compliance with the regulations. The washing of crude oil should only be approved once each step of the COW operation must be specified in the oil wash operation plan. There must be an operational checklist for the use of the crew at each port of discharge. This includes the control and calibration of all instruments to be used during the operation of the cow.

Pre-Arrival Checks at Discharge Ports

1. Notification to the terminal of the operation of the cow.
2. Is the oxygen analyzer successfully tested and operated?
3. Is the water heater and the flushing system of the motor compartment insulated?
4. All Valves Marked washing is isolated from that of engine room pipe line.
5. Are all V/vs closed for stationary tank washing machines?
6. Are the tanks cleaning lines under pressure and tested for leakage?
7. Do you make portable drives for the M/C quick tank sink that will be tested?
8. Have gauges on the top line relief manifold has to be verified.
9. Should the trimming system control equipment cheked?
10. Has the communication system been reviewed and tested?
11. Has the organizational plan been set up and defined the duties and responsibilities of crew?

 Checklist before cow Operation

1. All checks and conditions are in order prior to arrival.
2. Unloading/operating the raw oil wash has been discussed with ship and shore staff and is readily available the agreed plan for a simple reference?
3. Was the communication link between the control and control stations and the monitoring/shore station repaired and functioning properly?
5. Has the fixed and portable oxygen analyzer been verified and calibrated?
6. Is the inert gas generator functioning properly and the oxygen content of the inert gas is delivered below 5% of the volume?
7. Is the oxygen of the tank washed about below 8% in volume?
8. Is the gas pressure is positive for the entire cargo tank?
9. Keep person responsible for checking all the lines for leaks as soon as the operation starts?
10. Are stationary machines for the necessary washing and portable motor units, if installed, mounted and repaired?
11. Have valves and lines both in pump-room and deck been checked?

Checklist-During the operation of the cow

1. Is the quality of the inert gases supplied often controlled and recorded?
2. Are all deck and machine lines often tested for leaks?
3. Is the current tank only available for COW?
4. Is the pressure on the appropriate tank wash line indicated?
5. Is the processing time of the tank disk indicated?
6. Is the washing machine, which works with the propeller groups, often properly controlled and working?
7. is a responsible person constantly stationed on the bridge?
8. Will trim be satisfactory when bottom washing is in progress as specified in the COW manual?
9. Is the level in the reservoir for tank washing often checked to avoid overflow?
The cow should be abandoned immediately if:There is an error in the inert gas system or oxygen exceeds the permissible limit, or The pressure in the tank falls below the air pressure or a minimum required (usually 200 mm water gauge).

D Checklist-After cow operation

1. Are all the valves between the discharge and the washing line of the tank closed?
2. Has the laundry been drained of oil from the crude tank?
3. Are all valves closed to the washing machine?
4. Are the cargo pumps, tanks and pipes properly drained as indicated?

Sludge and sediment control

Under certain circumstances, substantial sludge may also form in the containers, even in the case of crude oils which are not normally associated with such accumulations. Studies of incidents of large sludge accumulation show that there are specific critical temperatures at which crude oil begins to precipitate hydrocarbon species that form mud. This temperature, cloud point, is the temperature at which the crude waxes change from their liquid phase to suspended, nearly solid particles with associated oil components. These particles separated by phases are installed at the bottom of the reservoir and form mud. Sludge from paraffinic crude oil, once formed, is extremely difficult to return to a liquid phase by heating alone. Even an effective COVER program, which eliminates them from boats, has only managed to solve the problem in shore-based containers.

Electrostatic risks
The oil used for COWing must be free of suspended water to minimize the formation of electrostatic charges by high pressure jets. To ensure that the oil supply to the VAE is dry, the cargo tank to be used must be discharged to the ground before the start of the COW. At least one meter of load must be discharged. This removes all bottoms from the tank before the mold starts. VACA procedures that remove the flushing fluid from the discharge current or use a sliding container that is then filled with clean oil will avoid this problem.

Image credit: Wikimedia

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Author ARPIT SINGH and Amit

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How inert gas is produced on board ship?

The Inert gas is produced in the IGG by the combustion of fuel with air. Marine diesel oil (MDO) or MGO is drawn from the storage tank and pumped through a filter to the main burners. A blower delivers the air necessary for combustion.
Oil and air is mixed in the correct proportion in an air-atomizing burner, which is ignited by the pilot burner. The fuel-air ratio and the oxygen content of the IG can be regulated by a valve in the fuel supply line to the main burner. Purple-blue to rose-purple flame indicates good combustion whereas yellow flame means too much fuel oil or too low delivery air pressure causing low atomizing pressure and risk of soot formation.

The inert gas thus generated consists of mainly Nitrogen and carbon dioxide. It is first cooled in the combustion chamber by means of a sea water jacket, which surrounds the combustion chamber. The gas then comes in direct contact with a water spray. The resultant IG comprises of:

Oxygen  :            2% by volume
Carbon dioxide: 13% by volume
Nitrogen   :        85% by volume

Due to perfect combustion, there is a complete absence of soot. The temperature of the gas leaving the generator is about 5-10* above the cooling water temperature.
During the operation, should there be a reduction in demand for the IG, the excess gas is vented to the atmosphere. The operation is continuously monitored for flame, water or control air failure and excessive cooling water level. Should any emergency condition arise, the IGG automatically shuts off and sounds an audible alarm.
This is a costly installation, which is usually found in product or chemical tanker. With some clean cargo tainting could be a problem, if flue gas from boiler is used.

Chemical tankers & Product tankers are normally FRAMO tankers hence IGG is fitted on these ships, secondly the quality of IG plays a very important role in maintaining the quality of chemicals being transported.
Conventional tankers with turbine driven COP will always have a large water tube boiler and thus Inert gas on these ships will be produced from boiler flue gas. Boiler will be used continuously during cargo discharge for running the cargo oil pump turbines (COPT).
On Framo tankers, the cargo discharge system consists of each cargo tank having a fixed submersible cargo pump, this pump is coupled to a hydraulic motor. The hydraulic motor is driven by high pressure hydraulic oil (220 bar), this high pressure hydraulic oil is delivered by hydraulic power-packs located in the engine room, these power packs are normally driven by diesel engines. Thus these ships use an IGG for production of inert gas. They do not have large boilers as no turbines are present, hence IG from boiler uptake is not possible.
Carbon Molecular Sieve type Nitrogen Generator

The molecular sieve nitrogen generating plant is usually installed on ships such as chemical carriers where oxygen critical cargoes may be carried and purity of the inert gas is of utmost importance.
The system uses the pressure swing absorption method using a carbon molecular sieve which has the unique property of absorbing oxygen in preference to and at a faster rate than nitrogen. When air passes through the molecular sieve, oxygen is absorbed. Nitrogen gets across and is collected. However the sieve gets saturated with oxygen after sometime and needs to be changed over.
The system uses two vessels packed with the carbon molecular sieve. The vessels are alternatively on line or in the process of regeneration. As one reaches saturation, the system switches to the second. Change over time is appox. 1 minute.

The oxygen from the saturated sieve is removed by applying a reduced pressure to the vessel and then venting to the atmosphere. The nitrogen gas thus generated is fed to a buffer vessel from where it is distributed to the inert gas line. The purity of the nitrogen depends on the flow rate and can be as high as 99.5%. The lower the flow rate, the higher the purity and vice versa.

Image credit: Ankit Raj (Facebook)

*Note: The cover image is taken from the facebook page of "Ankit raj" after taking his permission, if anyone has any problem with the picture, please contact us we will act ASAP!

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Author ARPIT SINGH

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How to apply for marine engineering | Admission

A Naval/Marine engineer has too many tasks and duties to take over. A marine engineer has all the functions and marine engines to check. In short, a naval engineer is a person who deals with everything related to the ship, from small things to big issues. Now the responsibility of ship engineers is not only related to ships, but also must ensure the safety of the crew and sailors.

Being A marine engineer is a lucrative job offer. A marine engineer acquires considerable knowledge and the ability to work under pressure and difficult conditions at sea. They are the true saints with jack of all trades and an ace of diesel engines. Working in  the transport company makes them meet and see many universal things as well as exposure to the outside world. They know how the configurations of the nations of the world are the same. They know how to get at different places in the world "Things Done". They look like the experts end their work quietly making the wheels of the global economic race.  


About the course: -

Marine Engineering is a 4 year regular course in various colleges in India specially situated in coastal areas. For four years of maritime engineering, B.Tech has been a course of proficiency in naval/Marine engineer officer class IV, issued by the Directorate-General for Shipping, Government of India, after six months of maritime service, the cadets will sail marine engineers worldwide on board Trade. This course is strictly residential.

Eligibility criteria to apply for marine engineering:

The Eligibility criteria for admission to B.Tech (Marine Engineering) :

Academic Qualifications: The candidate must have successfully completed the Senior Secondary Examination (10+2) or its equivalent with :
i)  At least 60% marks in Physics, Chemistry and Mathematics (PCM) and
ii) At least 50% marks in English either in Class X or Class XII.

Age: Candidates  less than 25 years of age as on 1st of August in the year of admission will be eligible to apply. The date of birth as recorded on the applicants School Leaving Certificate will be considered for this purpose.
* The Upper age limit for admission relaxed for SC/ST candidates by 5 Years.

Marital Status: Only Unmarried candidates will be considered.

Physical and Medical Standards : Medically fit as per the standards set by Merchant Shipping Medical Examination Rules, 2000 as
amended from time to time.

Eye-sight : Distance vision (unaided) 0.5 (values given in Snellen Decimal Notation) (6/12) in each eye or 0.67 (values given in Snellen Decimal Notation). (6/9) in better eye and 0.33 (Values given in Snellen Decimal Notation) and (6/18) in other eye. Normal colour vision.

Admission Procedure:

Through online / off-line examination, Interviews, Psychometric Test, And Medical Test.

The Entrance test format is multiple choice type. Candidates can be asked questions related to their 10-12th education, general English, etc. Selected applicants will be invited to a personal interview and later to psychometric test to assess their psychology including their suitability for a career In the sea. The selected candidates will be sent for medical examination. The final selection is obtained based on the ratio after the medical examination.

#Click To know how to crack the Entrance Exam? 

Some best Marine Engineering Colleges in the Country:

India is home to some of the oldest and at the same time the best institutes for studying nautical architecture, Marine engineering and science. Affiliates to the respective universities, colleges and courses, which are approved by the National Accreditation Board (NBA) and the Technical Education Council of India (AICTE).

A few of the best are:

1. Tolani Maritime Institute (TMI),Mumbai.
2. International Maritime Institute, Noida.
3. Vels Academy of Maritime studies, Chennai.
4. Maharashtra Academy of Naval Education and Training (MANET), Pune.
5. International Maritime Institute (IMI), Delhi.
6. International Maritime Academy (IMA), Chennai.
7. Institute of Technology and Marine Engineering (ITME), Kolkata.
8. Coimbatore Marine College (CMC).
9. Samundra Institute of Marine studies, Mumbai.
10. Academy of Maritime Education and Training (AMET).

Other best international college:

• South Tyneside College
• Webb Institute
• United States Merchant Marine Academy
• State University of New York Maritime College 
• Australian Maritime College
• Korea Maritime University 

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Hard to get a job as TME or Deck Cadet ? | Getting started on job hunt

For the past few years, I have been noticing how difficult it has been to get a job as trainee marine engineer or deck cadet on ship after completing marine engineering or nautical science course even from a well recognised maritime institute. The main reason behind this would be the approval of so many substandard institutions by the government in recent years, because of which the number of students graduating every year is far more than the number of job openings that we have. Along with this, a lot of job agents, mostly fraud ones have come up offering jobs in known and unknown companies taking a huge amount of money and you would wonder that the average agent fee they are charging has been above 3.5 to 4 lakh INR for a normal company and 5 to 6 lakh INR for a well known highly paying company which is one third of actual engineering course fee itself. The funniest part in fact is that the agents get only 10 to 15 % of the fee and the rest goes to the people who are sitting on top of crewing department in these companies, even the best shipping companies I would say.Though it is rare that the companies take freshers from outside without reference, there are few companies that do recruit cadets on regular or non-regular basis. Some of them are below.

1. Shipping Corporation of India, SCI ( www.shipindia.com )

2. Wallem Ship management ( www.wallem.com )

3. Nortrans Maritime ( www.nortrans.com )

4. United Ocean Ship management ( www.uosm.com )

5. Seastar Ship management ( https://www.seastargrp.com/shipping )

6. V-Ships ( www.vships.com )

Links of mumbai located companies are below ( in case if you guys want to do job hunt ).

Shipping Companies in Andheri West - https://www.justdial.com/Mumbai/Shipping-Companies-in-Andheri-West/nct-10432101

Shipping Companies in Andheri East -
https://www.justdial.com/Mumbai/Shipping-Companies-in-Andheri-East/nct-10432101

Shipping Companies in Nariman Point -
https://www.justdial.com/Mumbai/Shipping-Companies-in-Nariman-Point/nct-10432101

Shipping Companies in CBD Belapur -
https://www.justdial.com/Mumbai/Shipping-Companies-in-Cbd-Belapur/nct-10432101

I wouldn't say not to approach agents for a job because the fact is that 70% percentage of the students graduating from most of the maritime colleges don't get their placement and to get one, they should either have very good contacts in shipping or they should look for a genuine agent. Over the years, I have seen many trainee engineers and deck cadets coming to mumbai to find an agent, some of them get a job after long waiting, some of them don't and the rest of them get cheated by fraud recruiters. If you are a fresher and you are paying money to an agent, make sure the company they recruit you to is approved by DG Shipping of India and has an RPSL ( Recruitment & Placement Services License ) number which is not expired. 

Never ever pay the agent before your contract letter is signed !!!!

Use the link below to see DG Shipping approved manning companies in India -

http://www.dgshipping.gov.in/Content/RPSAgencies.aspx

I wish Indian government would take some actions against..........

To read the full article click here

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Guest Author Name: Jishnu Varakoth
Social Profiles: ?

Website link: 

1. http://traineemarineengineer.blogspot.in 

2. http://marinejobsforfresher.blogspot.in

Short Bio: Marine engineer with good sailing experience. He is also a blogger and writer.

Post Source: http://traineemarineengineer.blogspot.in/2017/07/vacancy-for-trainee-marine-engineers.html

* The following article is originally written by the guest author and is partly produced as it is taken from original source for the help of maritime society with better understanding the new challenges. Proper permission is being taken from guest author prior to using the post and all care is being taken to avoid copyright issues but in no cases the blog owner or other permanent authors are responsible for any copyright claims. Inform us if you have any problem with the content.

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How is Marine Engineering as a career? | Explained

Transport and transportation are the backbone of modern global economic outlooks and global prosperity. Ships are what the world traffic is based on, which  account for 90% of the total movement of fresh products in the world than any other transport accounts.  It Transmits solutions, food, medical care and living conditions, chemicals, oil, fuel and other loads that are necessary to ensure the viability of each country. Therefore, as an important aspect, a marine engineer plays an important role in international transportation of goods around the world in some form or another in shore, oil rigs, offshore and shipbuilding.

The Capital associated drive the demand in international trade and shipping, So the ships should be advanced and technically sophisticated. The ships are to be maintained with massive engines and factories of electricity for the propulsion and auxiliary on the ship with a specific end goal to Maintain Seaworthiness. All technical aspects of the Ship holds extreme operational efficiency and so  considered and maintained by ship engineers.

A naval engineer is a lucrative job offer. A marine engineer acquires considerable knowledge and the ability to work under pressure and difficult conditions at sea. It is self-confident research all aspects of the machines to work. The first and most important reason is the danger contains. Work on the vessel is carried out in coastal offices, as well as power stations, shipyards, etc. In all cases, the coast of jobs, they are not paying as much as they can on boats considering the fact that an office on the coast is the same Hard conditions, a boat facing.

Marine engineers are the true saints with jack of all trades and an ace of diesel engines. Working in  the transport company makes them meet and see many universal things as well as exposure to the outside world. They know how the configurations of the nations of the world are the same. They know how to get at different places in the world "Things Done". They look like the experts end their work quietly making the wheels of the global economic race.

There are usually six engineers on a Ship *:

Junior Engineer - Unlicensed Member Engineering Department, which helps senior engineers.

4th. Official supervision responsible engineer for air compressors, fuel oil cleaners and lubrication and auxiliary diesel generators.

Electrical Officer- Shares Equal Rank with Fourth Engineer, responsible for Electrical Aspects of Ship.

3rd. Engineer watch, responsible for the production of Fresh water, Sewage channel discharge, maintenance equipments, Air Conditioning, Refrigeration and various pumps.

2nd. Engineer responsible for the administration, responsible for the main motor and drive, boiler aux and steam generator. The Incharge of team management on ship, steering mechanism, ship cranes and engines, rescue boats and engines

Overall, chief engineer - by the actions of the department motors equal with the captain.

* This is based on the classification system of British engineers on the ship.

Economic Outlook Marine Engineer and Scopes:

According to the US Government’s Bureau of Labor Statistics, Marine Engineers and Naval Architects earn an average annual salary of $84,850. However, the top 10% of the career field pulls in a healthy $145,790 annually.

The need for marine engineers was expected to grow by 9% from 2014-2024, according to the U.S. Bureau of Labor Statistics (BLS). The demand for new Marine engineers will rise due to a no of factors, First many ships are to be modified and installed with latest machineries to comply with latest regulations drawn by IMO and flag states. Second, As the demand for oil is growing world wide, more and more shipment are chartered and so new ships will be bought to cope up with the rise in demand with additional crews and marine engineers hired to work on them. Third, there seems to be a sudden boom in the shipping field just after 10-15 years as the years of looms are to be end very soon, Leading to sudden high demands for fresh and experienced marine engineers.

The level of financial stability is high start from the beginning which allows great deal of money to spent and for savings. There is a whole new world out there to be explored and to feel and see the glim's of the world you watch or read in T.V and magazines.

Work of Marine engineers (Expectation vs Reality):

When i first join this field i had many expectations, crazy one to be precise, like i will be traveling all across the world have some very great times at ports, have a office inside the ship not much work, all time party, Lots of alcohol etc..etc.
            If you too have such ideas in mind thats totally rubbish. All I can tell you that there are quite less port time you get as the time for loading and discharging are reducing day by day, There no alcohol policy in many of the ships these days with lots and lots of hard work and maintenance to do just to catch up with the daily planed schedules.

Followings are the real work space and work of the marine engineers on board ship in reality:

Engine Room

The main propulsion plant, diesel generator boilers for power generation to produce steam, the fresh water generator, the electrical equipment to the various motors and are in the engine room.
The atmosphere is usually hot and loud in the engine room. The temperature can even rise up to 55 degrees Celsius. Marine engineers perform regular inspections and repairs and maintenance work at the time. Ensure a safe operation of all equipment and follow all safety precautions to prevent marine pollution complies with the strict international regulations.

ECR(Engine Control Room)

All parameters, conditions and the propulsion of the main motor and the connection between the bridge are remote from the engine control room is controlled. Engineers are placed on the watch during the peak day of unmanned ships. In the old ships are usually monitored 24 hours a day rotation 4 hours.

Life on board a Ship

In addition to machine operation, maintenance supervision and regular maintenance, ship engineers spend a lot of time on leisure activities such as sports, games, entertainment and fitness activities. The food served on board is good and healthy, there is plenty of time to relax. Watch the sunset, music, photography, fishing and sports are important activities that are usually done on a boat.

Sea- Merchant naval ship, the time is very important. The load must arrive on time. Communication between the bridge and the space navigation motor control is required to maneuver the ship. Total control with the engineers stopped when a fault monitoring device occurs in bridge. Steering device testing is necessary for the navigation of a ship. The machine must be addressed as required. Always observed always essential solution for the drive safely. The climate is another thing that affects the ship at sea, which affects people on board must be able to withstand tough conditions. All environmental policy and regulations oil pollution must be strictly adhered to. While the ship at sea, profound experience, practical skill and lower attachment is needed to overcome all unwanted situations. The ability to make decisions and take action is required in every ship engineer. The risk of fire and explosion is always high to minimize these risks, we must be well trained and competent.

Ship in harbor

While the ship is in the port, repairs, maintenance and additional checks are carried out by the port authorities. Dock can be at the port, which requires safety. Inventory store Engines and spare parts will be ordered as required. The charging process should go smoothly and the energy production is observed every time.

Apart from this, there is ample time to leave the port and explore new places. You can go and send entertainment. Seafarers can go the country of origin Seaman Club or hotels to sign up to its flight the ship.

Close of Contract

After the end of his contract, returns to his country of origin leaves the earth. There are few companies that pay wages a year. However, wages are usually high compared to other technical disciples on Earth. Full salary savings for us because the boat house and home for the return of the boat are born by the company. They are entitled to be on board in safety and are also exempt from the tax obligations. This point is very important because he / she stays away from home and the family for extended periods of a few weeks to several months.

Class Competency tests

Marine engineers must pass suitability tests to grow at a higher rank. These tests are carried out by the Ministry of Shipping and take most of the time you spend on Earth. Apart from this, they must be regularly updated with security and updating courses.

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Author AMIT

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Properties And Working System Of Marine Fuel Oil

Properties Of Marine Fuel

Density:

• This Is Described As The Weight Of A Unit Volume Of A Liquid.
• The Unit Is Kg/ M3.
• The Density Is Measured At A Standard Temp., Of 150c As It Varies With The Temp.
• If Density Is Taken At Different Temp., A Correction Factor Is Applied To Ascertain Correct Density At That Temp.
• Reciprocal Of Density Is Specific Volume.
• This Is Important Property For Estimation Of Bunker Capacity.

Viscosity:

• This Is Defined As The Resistance Of Fluids To Change Shape, Which Is Due To The Friction Between The Molecules Of A Fluid Producing A Frictional Drag.
• Absolute Dynamic Viscosity: This Is Defined As The Force Required To Shear A Plane Fluid Surface From Other Plane Surface, Over An Area Of 1sq. M. At The Rate Of 1m/Sec., When The Distance Between The Two Surfaces Is 1m. Absolute Viscosity Is Difficult To Ascertain And Therefore , Kinematic Viscosity Is Generally Used To Measure.
• Kinematic Viscosity: This Is The Ratio Of Absolute Viscosity To Density Of The Fluid At A Particular Tyemp. This Is Measured By Flow Of A Set Of Volume Of A Fluid At A Particular Temp., And Through A Specifically Calibrated Instrument. It Is Measured On The Basis I.E., Number Of Seconds For A Calibrated Instrument Like Redwood No.1, At 380c.
• Centistoke: This Is The Unit Used By International Standard And Measured At 500c. Higher Temperature At The Time Measurement Can Be Used For Viscous Fluids And Appropriate Corrections Can Be Made Later.
• Temperature Affects The Viscosity , Which Decreases With The Temperature Of The Liquid.
• Viscosity And Temp., Play A Vital Role While Selecting Oil For A Particular Service.
• For Best Results During Automisation Of Fuels Of High Viscosity, It Is Necessary To Heat The Fuel To Bring Down The Viscosity To About 30 Centistokes Or Still Lower At The Injector Point.
• Viscosity Of Diesel Oil Is 7centistoke At 380c.
• Viscosity Is Always Quoted At A Certain Temp., Without Which, It Has No Meaning.

Flash Point:

• This Is The Minimum Temperature At Which The Oil Begins To Give Out Flamable Vapours, Which Would Cause Momentary Ignition On Application Of Heat / Flame In A Specified Apparatus.
• The Test May Be Specified As ‘OPEN’ Or ‘CLOSED’ Depending On The Type Of Apparatus.

Fire Point:

• It Is The Minimum Temperature At Which The Vapours Given Out By The Heated Oil Are Sufficient To Ignite And Give Out More Vapours By The Heat So Produced, So That They Burn Continuosly.
• This Temp., Is Different From Flash Point And Is Higher By Anything Up To 400c.

Acidity (ALKALINITY):

• It Is Indicated By Neutralisation Number.
• The Number Is The Mass In Miligram Of An Alkali  Required For Neutralising The Acid Present In 1gm Of The Sample.Neutralsation Number Can Also Be Expressed As Parts Per Million Per Ml Of Sample Of Oil.
• Total Base Number (TBN) Is Often Used For Alkalinity Indication Of Lubricating Oils.

Ash:

• This Is Expressed As Percentage By Mass Of The Original Sample Of Oil, Which Is Evaporated And Ignited Until All The Traces Of Carbon Have Disappeared
• The Ash Left After Above Process Contains Hard And Abrasive Minerals Such As Quartz, Silicates, Iron, Aluminium Oxides, Sand Etc.

Preparation Of Heavy Fuel Oil:

• Present Days Modern Marine Diesel Engines Are Run Continuosly On Heavy Fuel Oil Only
• The Main Purpose / Object Of Preparing The Heavy Fuel Oil For Use In Two Stroke Diesel And Four Stroke  Engine Is To Remove The Impurities Like Water, Sludge, Catfines. Also To Heat The Fuel To  Get The Correct Injection Viscosity As Recommended By Engine Manufacturer.

Preparation:

• After Receipt On Board Fuel Oil Is Stored In Bunker Tanks. In These Storage Tanks Fuel Is Heated To Just The Required temp To Keep It Pumpable.
• The Fuel Is Transferred From The Storage Tanks To The Settling Tank By Using A Transfer Pump. The Settling Tanks Are Normally Two In Number Having Capacity Of  24 Hours Use.
• In The Settling Tank Fuel Is Further Heated And Retained For As Long As Possible. In The Settling Tank Some Of The Heavier Solid Impurities And Water Get Separated By Gravity And Collect At The Bottom Of Tank. These Have To Drained Out Regularly.
• Heavy Fuel Oil Is Then Purified Further By Centrifuges. Centrifuges I.E., Purifiers And Clarifier Are Connected In Series. In Centrifuges The Impurities Such As Solid, Liquid And Sludge Are Removed Completely.
• In case Of Alfa Laval Purifiers Then By Using Alcap System  The Oil Is Clarified And At Same Time Separated Water Is Removed From Bowl.
• Purified Oil Is Then Pumped To The Daily Service Tanks. From Daily Service Tank Oil Flows Through A Three Way Valve To A Mixing Tank. 
• A Flow Meter Is Fitted In The System To Indicate The Fuel Consumption.
• A Mixing Tank Installed In Fuel Oil System Of Engine, Is Designed To Operate On Heavy Fuel Oil. The Purpose Is To Produce A Gradual Variation Of Fuel Quantity During Transition Period From Diesel Oil To Heavy Oil Or Vice Versa. The Supply Oil Changes In Viscosity And Temp., Progressively With This System. Mixing Tanks Has Proved To Be Useful For De gasification And Entrainment Of Air From The System. Mixing Tank Can Also Be Used As A Metering Tank. This Is Used To Collect Recirculated Oil And Also Acts As A Buffer Tank As It Will Supply Fuel Oil When Daily Service Tank Is Empty.
• Booster Pump Draw Fuel From Mixing Tank, Raises It’s Pressure And Passes Through The Heater. Oil Is Heated Up With Curresponding Reduction In Viscosity In Accordance With The Temperature – Viscosity Relationship.
• Controled Temperature By Viscosity Regulator Ensures Fuel Have A Viscosity Of Combustion Quality.
• A Pressure Control Valve Provides Constant Supply To Engine Driven Fuel Pump Ensuring High-Pressure Injection Supply Pressure.
• Pre-Warming Bypass Valve / Line Is Used To Heat Up The Fuel Before Starting The Engine.
• Service Tank Diesel Oil Are Connected To System Through A Three-Way Valve. The Engine Can Be Started And Manevier On Diesel Oil Or Even A Mixture Of Diesel Oil And Heavy Oil.
• Further The Sestem Include Various Safety Devices Viz., Low Level Alarms And Remotely Operated Tank Outlet Valves Viz., Quick Closing Valves, Which Can Be Closed From Outside The Engine Room In The Event Of Fire.

Importance Of Viscocity In Fuel Oil:

• Steady Values Of Viscosity Is To Be Maintained For Proper Atomization. Atomization Is Breaking Down Of Fuel Oil To Fine Droplets So That A Large Surface Of Oil Is Exposed To Heat And Oxidation.
• Low Viscosity Cause Too Fine Atomization And Thus Droplets Will Not Penetrate Deep Enough. This Will Cause Burning Close To Nozzle Tip. Because Of This Poor Combustion Nozzle Operation May Be Troublesome.
• On The Other Hand High Viscosity Cause Too Large Droplets Of Oil And Have Enough Energy To Strike Metallic Surface. This Will Lead To Overheating. This Also Create Problems In Functioning Of Centrifuges

Settling Tank

• The Fuel Is Transferred From Bunker Storage Tanks To The Settling Tanks Prior To Centrifuging, For Use In Diesel Engines And Also For Burning In Boilers.
• The Fuel Is Heated In Settling Tank And Retained There For As Long As Possible. The Settling Period Should Not Be Less Than 24 Hours For Optimum Separation Of Impurities.
• While The Fuel Is In Settling Tank Some Of The Solids, Sludge And Water Separates Out And Settle Down At The Bottom Of The Tank From Where They Can Be Drained Off Through The Drain Connections Which Must Be Of Self Closing Type.
• For Use In Diesel Engines, Only Purification By Settling Is Not Enough As Subsequent Centrifuging Is Carried Out To Separate The Impurities. Still Draining Of The Settling Tank Regularly Once In A Watch Is Recommended.
• High And Low Level Alarms Are Fitted On The Tanks.
• Fuel Oil Is Heated In The Settling Tank For Faster Separation Of Impurities, For This Reason Settling Tanks Are Provided With Heating Arrangement.
• The Rate Of Separation Of Impurities In Settling Tank Depends On Following Factors.
• Higher The Density Difference Between Oil And Other Impurities, Greater Will Be The Rate Of Separation.
• Bigger The Size Of The Impurity Particle Better Will Be The Rate Of Separation.
• Lower The Viscosity Of Oil, Better Will Be The Rate Of Separation.
• As Heating Results In Better Separation, The Fuel Is Generally Heated To A Minimum Temp., Of 500c Or To A Temp., About 700c.
• One Of The Solid Contaminats In The Fuel Oil Is A Cat (CATALYTIC) Fine, Having Density Of 2600 To 2800 Kg/M3 And Having Particle Size Of 10 To 50 Microns. These Compound Take Long Time To Settle Even When The Fuel Temp., Is Raised To 700c.
• An Ideal Settling Tank Should Have Inclined Bottom To Facilitate The Separation And Draining.

Safety Devices Fitted  On Settling Tank;

Fuel Outlet Valve: This Is Remotely Operated Quick Closing Valve Fitted On The Settling Tank.  It Is Arranged To Operate From Outside The Engine Room In Case Of Emergency.
Air Pipe: This Pipe Is Led To Above The Upper Deck Level And External To The Deck House. The Outlet Of This Pipe Is Fitted With Metallic Wire Gauge Screen Called Flame Trap To Prevent Fire Hazards.
Thermometer:This Is Used For Measuring The Temp., Of Oil
Sludge Valve / Cock: This Is Used For Draining Water And Sludge  Collected At The Bottom Of The Tank. This Valve Must Be Self-Closing Type.
Over Flow Pipe: It Is Fitted At The Top Of The Tank And Led To An Over Tank In The Double Bottom. An Alarm Activated By An Over Flow Condition Is Sometime Fitted To The Tank.
Alarms: These Are Fitted To Warn High Fuel Temp., And Low Fuel Level.
Dumping Valve: This Valve Is Used In The Event Of Fire, To Dump The Oil To The Double Bottom Tank.
Quick Closing Valve: In Case Of Emergency To Stop The Engine, This Valve Cuts The Supply Of Oil To The Engine. The Arrangement Provided Outside The Engine Room  To Close This Valve.
Sounding Valve: This Pipe Is Provided To Take Sounding Of The Tank For Checking Fuel Level.

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Author Amit                                                                 

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Basic concept on Ship stability and free surface area

Stability Of Ships

Two Principal Forces Which Act On A Ship Floating Freely Are – Weight  &  Buoyancy.

For The Ship To Float, It Must Displace It’s Own Weight Of Water.

Then To Be In Equilibrium Condition, The Centre Of Weight & The Centre Of Buoyancy Must Be Vertically In Line.

External Or Internal Forces Can Move The Ship In Either Transverse Direction Or Longitudinal Direction. But It’s Ability To Return To It’s Original Stable Position I.E., Equilibrium Condition Is Related To The Stability.

Upright Position Of Ship :  A Vessel Is Said To Upright If It Is Rolling Slightly About The Upright Position.
Statical Stability : This Is The Measure Of The Tendency Of A Ship To Return To The Upright Position If Inclined By An External Force.
Upright Position Of Ship : In The Upright Position, Weight Of The Ship Acts Vertically Down Through The Centre Of Gravity ‘G’. While The Upthrust Acts Through The Centre Of Buoyancy ‘B’.
Equilibrium Condition Of Ship : When Weight Of The Ship Is Equal To The Upthrust And The Centre Of Gravity And The Centre Of Buoyancy Are In The Same Vertical Line, The Ship Is Said To Be In Equilibrium Condition.

Consider A Ship Inclined By External Force To An Angle ‘Ǿ’.
               In This Case Centre Of Gravity Remains In The Same Position, But The Centre Of Buoyancy Moves From ‘B’ To ‘B1’.
    Therefore Buoyancy Acts Through ‘B1’  And The Weight Still Acts Through ‘G’, This Creates
    The Righting Moment = Δg X Gz -------------------(1)
    This Moment Tends To Turn The Ship To It’s Upright Position.
    Righting Lever = Gz = Gm Sinǿ
    Now

The Vertical Through New Centre Of Buoyancy -‘B1’ Intersects The Centreline At ‘M’ Which Is Called The Metacentre. The Height  Of ‘M’ From The Centre Of Gravity Is Called The Metacentric Height- ‘GM’

Stable Ship : ‘GM’ Is Said To Be Positive When ‘G’ Lies Below ‘M’. In Such Case Ship Will Roll Back To Original Upright Position When Disturbed By External Or Internal Force.

Tender Ship : A Stable Ship With Small Metacentric Height Will Have Small Righting Lever At Any Angle And Roll Easily. In Such Case Ship Is Said To Be Tender Ship.

Stiff Ship : A Stable Ship With Large Metacentric Height Will Have A Large Righting Lever At Any Angle And Will Have Considerable Resistance To Rolling. In Such Case It Is Called The Stiff Ship.

Unstable Ship : When Metacentre ‘M’ Lies Below The Centre Of Gravity ‘G’, Then ‘GM’ Is Said To Negetive, Which Increases The Angle Of Heel. In Such Case The Vessel Is Said To Be Unstable And Will Not Return To Upright Positon.

Neutral Equilibrium : When Centre Of Gravity And The Transverdse Metacentre ‘M’ Coinside, The Righting Lever Is Zero And There Is No Righting Moment Acting On The Ship. In Such Case Ship Will Remain In Inclined Position With An Angle ‘Ǿ’, And The Ship Is Said To Be In Neutral Equilibrium Condition.

Stability At Small Angle Of Heel
Transverse Metacentre :
The Height Of Transverse Metacentre Above The Keel ‘KM’ May Be Found Out, By Considering The Small Inclination Of The Ship About It’s Centre Line.
For Small Angle Of Heel
Upright And Inclined Water Line Intersects.
Volumes Of The Emerged And The Immersed Wedges Are Equal For Constant Displacement.
    Now
    The Distance Of The Transverse Metacentre Above The Keel Is Given By
    Km = Kb + Bm -------------------------------------------(1)
    Note : ‘KB’ Is The Distance Of The Centre Of Buoyancy Above The Keel. This Can Be Found Out From The Hydrostatic Curve.

‘BM’ Can Be Found Out As Follows.
        Let Us Consider A Ship As Shown In Figure, Whose Volume Of Displacement Is ‘▼’, Lying Upright At Water Line ‘WL’. The Centre Of Buoyancy ‘B’ Being On The Centre Line Of The Ship.
        If The Ship Is Now Inclined By An Angle ‘Ǿ’, It Will Lie At The Water Line W1l1, Which Intersects The Original Water Line ‘WL’ At ‘S’. Since ‘Ǿ’ Is Small It May Be Assumed That ‘S’ Is Lying On The Centre Line.
        A Triangular Wedge Of Buoyancy ‘W1SW’ Has Been Moved Across The Ship To ‘L1SL’ Causing The Centre Of Buoyanmcy To Move From ‘B’ To ‘B1’
    Now
    Moment Of Shift Of Ship’s Buoyany From B To B1
    = Moment Due To Shift Of Buoyancy Wedge
Therefore
    ▼ X Bb1  =  V X Gg1
                                         V X Gg1                                        
                Bb1  =   ---------
                              ▼
                                   V X Gg1
             Bm Tanǿ = ---------- -----------------( As Bb1 = Bm Tanǿ )
                                      ▼
                     V X Gg1
        Bm = --------------  ----------------------------------(2)
                        ▼ X Tan∆

    Now To Determine The Value Of (v X Gg1) , Ship’s Length Is Devided In To Thin Strips Of Length
    Δx. The Half Width Of Original Water Line Is ‘Y’
    Therefore
    Immersed C/S Area Of Wedge = ½ Y X Y Tanǿ X Δx
                                                                   = ½ Y2tanǿ X Δx
    Volume Of Immersed Wedge  = Σ ½ Y2tanǿ X Δx

The Volume Of This Wedge Is Effectively Moved From One Side To The Other By A Distance Of (4Y/3)
    Therefore
    Total  Moment Of Shift Of Wedge
                        = Σ ½ Y2tanǿ X Δx  X (4Y/3)
                                                        = Tanǿ (2/3) Σ Y3 Δx
    We Know That,  (2/3) Σ Y3 Δx = Ixx
    (IXX = Second Moment Of Area Of Water Plane         About The Centre Line Of The Ship )
    Therefore
    Total  Moment Of Shift Of Wedge = Ixx X Tanǿ --(3)
    From Equation (2) And (3)
                                                                                     Ixx
    Height Of Metacentre From ‘B’  =  ------ ------------(4)
                                                                                      ▼
Metacentric Diagram
In This Diagram Kb (HEIGHT Of Centre Of Buoyancyfrom Keel ) & Bm ( Height Of Metacentre Above The Centre Of Buoyancy )  Are Plotted Against The Ship’s Draught As Shown In Figure.
As The Position Of Buoyancy-B & The Position Of Metacentre-M Depends Only Upon The Geometry Of The Ship & Draught Of The Ship At Which It Is Floating, Position Of ‘B’ & ‘M’ (HEIGHT Of Metacentre) Can Be Found Out Without The Knowledge Of Loading Of The Ship At Any Intermediate  Draught.

Stability At Large Angle Of Heel
Stability Discussed So Far Is For Small Angle Of Heel With Certain Assumptions ( Two Water Planes Intersect At The Centreline,Wedges Formed Are Right Angled Tringles) The Metacentric Height ‘GM’ Was Taken As The Measure Of Stabilty.
When Ship Heels To An Angle Greater Than 100, Above Assumptions Cannot Be Made & The Principle On Which Initial Stability Were Based Are No Longer True. Insteadthe Righting Lever ‘GZ’, Which Is The Peprendicular Distance Between Vertical Lines Through The Centre Of Gravity & The Inclined Centre Of Buoyancy, Is Used As Measure Of Stability.

Let Us Consider
A Ship Which Is Inclined To Some Angle ‘Ǿ’ From The Vertical.
‘WL’ Is The Initial Water Line And W1li New Water Line When Inclined.
The Volume Of Displacement In Each Case Is Same.
If The Side Of The Ship Were Vertical Along It’s Length, Then The Two Water Line Would Intersect At The Centreline At Point ‘P’
    Further,
Volume Wpw1 Which Has Emerged Will Be Equal To The Volume Which Has Been Immersed. Let This Volume Be ‘v’
The Centroid Of These Two Wedges ‘g’ And “g1’ Be Located At A Distance Of ‘d’

Now
    Moment Of Shift Of Ship’s Buoyancy
    = Moment Due To Shift Of Buoyancy Wedge
    Bc X ▼ = D X V
                       D X V
            Bc = -------  ------------------------------------------------(1)
                         ▼
    &   Gz = Bc – Bg Sinǿ
                       D X V
                 =  -------- - Bg Sinǿ          
                        ▼
                                                   D X V
     Righting Lever ‘GZ’ = -------- - Bg Sinǿ -------------(2)
                                                      ▼
    Note ;  This Is Called Atwood’s Formula. From This Formula If ‘v’ And ‘d’ Are Evaluated For A Range Of Angles Of Inclination ‘Ǿ’ , The Graph Of Righting Lever ‘GZ’ Verses The Angle Of Inclination ‘Ǿ’ Can Be Drawn. The Curve So Drawn Is Called ‘CURVE Of Statical Stability’

Curve Of Statical Stability

In This Curve Righting Lever Can Be Seen, Rising To A Maximum Value And Then Slowly Fall To Zero.
A Ship Inclined Beyond The Point Of Zero ‘GZ’ Will Be Unstable.
Angle Up To Zero ‘GZ’ Point Is The Range Of Ship Stability At That Particular Load Condition.
Ship Operator Should Know This For Safe Operation Of The Ship.

Free Surface Effect

If The Tank On A Ship Containing Liquid Is Not Fully Filled, The Liquid Moved Through The Tank In The Direction Same As The Heel. For This Reason, The Focus Of The Vessels Central Gravity Shifts Away From The Centre Reducing The Righting Lever "GZ" And Height Metacenter Which Results In Increase In Heel Angle. This Effect Is Known As The Effect Of The Free Surface.
We Consider A Full Tank Water In Ship Of Displacement "Δ" With Inclination To Any Angle Ǿ.
The Focus Of Vessel Moves From "G" To "G1", As Wedge Of Liquid Moves Through The Tank

Tank Divisions Use In Tankers:

Largest Ship With Free Surface Effect Must Be Left Space Of Oil Tank For Expansion.
Tanker Was Built Initially With Centeline Bulkhead And Expansion Tanks. Twin Length, Bulkhead Were Introduced Without Expansion Tanks And Successfully Proved Because It Deals With The Loss Of Metacentric Height Of Design Due To The Free Surface Effect.
It Is Not Possible To Design A Dry Cargo Ship In Same Way As C.G Position Varry With The Nature Of Deposition Of Cargo. Effect Of The Free Surface Is Dangerous For A Ship With Small Metacentric Height And Can Make The Ship Unstable.
In These Ship Tanks Required To Be Pressed Up. If The Ship Is Initially Unstable And Helling To Port, Then Any Attempt To Fill The Water Ballast Results In Reduction Of Stability.

# Various books, study material and other online sources has been refereed prior to writing this article but no part is copied or produced  from any of the source but explained same thing in better detailed way.

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Author Arpit Singh and Amit                                                                 Article requested by: Deepak Kumar

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