4.6 PRUEBA DE CONCEPTO DEL MERCADO Y PRODUCTO
4.6.1 Entrevistas
Vanadium is a metallic element that chemically combines with sodium to produce very aggressive low melting point compounds responsible for accelerated deposit formation and high temperature corrosion of engine components. Vanadium itself is responsible for forming slag on exhaust valves and seats on 4-stroke engines, and piston crowns on both 2-stroke and 4-stroke engines, causing localized hot spot leading eventually to burning away of exhaust valve, seat and piston crown. As the vanadium content increases, so does the relative corrosion rate.
The ash contained in heavy oil includes the inorganic metallic content, other non-combustibles and solid contamination. Ash deposits can cause localized overheating of metal surfaces to which they adhere and lead to the corrosion of the exhaust valve. Excessive ash may also result in abrasive wear of cylinder liner, piston rings, valve seats, injection pumps and deposits which can clog fuel nozzles and injectors.
4. Question
State the circumstances which may lead to suspension or withdrawal of class explain the terms (i) period of class (ii) anniversary date (iii) survey time window (iv) memoranda (v) recommendations
ANSWER:-
The class may be suspended either automatically or following the decision of the Society under any of the following circumstances
a) The class of a vessel will be automatically suspended from the expiry date of the Certificate of Class if the special survey has not been completed by the due date and an extension has not been agreed to, or the vessel is not under attendance by the Surveyor with a view to complete the surveys prior to resuming service.
b) The class of a vessel will also be automatically suspended if the annual, intermediate survey become overdue.
c) When the surveys relating to specific additional notations of hull or equipment or machinery have not been complied with and thereby the ship is not entitled to retain that notation, then the specific notation will be suspended till the related surveys are completed.
d) The class of a vessel will be subject to a suspension procedure if an item of continuous survey is overdue at the time of annual survey, unless the item is dealt with or postponed by agreement.
e) The class of the vessel will also be subject to a suspension procedure if recommendations and/or conditions of class are not dealt with by the due date or postponed by agreement, by the due date.
f) The class of a ship is liable to be withheld or, if already granted, may be withdrawn in case of any non-payment of fees or expenses chargeable for the service rendered.
g) The class may be automatically suspended When it is found that a ship is being operated in a manner contrary to that agreed at the time of classification, or is being operated in conditions or in areas more onerous than those agreed.
h) The class may be automatically suspended when a ship proceeds to sea with less freeboard than that assigned, or has the freeboard marks placed on the sides in a position higher than that assigned, or, in cases of ships where freeboards are not assigned, the draught is greater than that assigned
i) The class may be automatically suspended when the Owner fails to inform the Society in order to submit the ship to a survey after defects or damages affecting the class have been detected
j) The class may be automatically suspended when repairs, alterations or conversions affecting the class are carried out either without requesting the attendance of the Society or not to the satisfaction of the Surveyor.
The Society will withdraw the class of a ship in the following cases: 6. at the request of the Owner
7. when the causes that have given rise to a suspension currently in effect have not been removed normally within six months after due notification of suspension to the Owner
8. when the ship is reported as a constructive total loss 9. when the ship is lost
10. when the ship is reported scrapped.
Anniversary date :-
Anniversary date means the day and month of each year corresponding to the expiry date of the classification certificate.
Condition of class.
Possible deficiencies shall normally be rectified before the renewal survey is regarded as completed.
The Society may accept that minor deficiencies, recorded as condition of class, are rectified within a specified time limit, normally not exceeding 3 months after the survey completion date.
The Society may accept that minor deficiencies, recorded as condition of class, are rectified within a specified time limit, normally not exceeding 3 months after the survey completion date.
Window period for survey.
The survey time window is the fixed period during which the annual and intermediate surveys are to be carried out.
Memoranda.
Other information of assistance to the surveyor and owners may be recorded as ‘memoranda’ or a similar term. They may, for example, include notes concerning materials and other constructional information. A memorandum may also define a condition which, though deviating from the technical standard, does not affect the class (e.g. slight indents in the shell which do not have an effect upon the overall strength of the hull or minor deficiencies, which do not affect the operational safety of the machinery).
In addition, memoranda could define recurring survey requirements, such as annual survey of specified spaces, or retrofit requirements, which have the de- facto effect of conditions of class.
Addition note.
Each of the Classification Societies has developed a series of notations that may be granted to a vessel to indicate that it is in compliance with some additional voluntary criteria that may be either specific to that vessel type or that are in excess of the standard classification requirements.
Class notations are assigned to vessels in order to determine applicable rule requirements for assignment and retention of class.
5. Question
What are P&I clubs? How P&I clubs collect funds from ships what are the risks covered under P&I. What is the minimum a ship owner / shipping company has to do for its ship to get coverage under P&I club.
ANSWER:-
1. A Protection and Indemnity or P&I club is a nongovernmental, non profitable mutual or co operative association of marine insurance providers to its members which consists of ship owners, operators, charterers and seafarers under the member companies for the purpose of mutual insurance against third party liabilities arising in connection with ship operation.
2. P&I mean Protection and Indemnity. The protection refers to ship owner‘s protection from risks which involve personnel injury, collision liability which is not covered by H&M policy and indemnity refers to the clubs indemnity or compensation for liability to cargo under a contract of carriage.
3. The P & I club membership is comprised of common interest group who wish to pool their risks together in order to obtain “ at cost” insurance cover. 4. It is governed by a board of directors (a committee elected). It has managers
for underwriting and claim sections and has correspondents, lawyers and surveyors at various ports of the world. There are 13 major P&I clubs world wide which covers almost 90% of the world fleet. Some of them are SKULD, GARD, BRITANIA, AMERICAN CLUB, STEAM SHIP MUTUAL, NORTH OF ENGLAND, WEST OF ENGLAND Etc.
5. Each P&I club sets a premium rating for an individual owner reflecting the risk against which he requires cover on the basis of his fleet‘s gross tonnage, his fleet‘s exposure to risk, type of ships, etc.
6. The member is advised of his total estimated call (premium) for next 12 months. This comprises of an advanced call and a supplementary call. Advance call is levied from all the members at the start of the P&I year. 7. Later in the year if the claims have been heavier than expected, the managers
will ask the members for a supplementary call.
8. The clubs aim to be as much accurate in their prediction for future claims, so that they do not burden ship owners with supplementary calls. Surplus refunds are made if income (call + investments) exceeds outgoings (claims + expenditure).
The protection and indemnity covers the following risks of an ―Entered Ship‖
Crew related
Injury/ hospitalization
Deviation
Death, repatriation of body
Repatriation of injured crew and for his reliever
Personal effects, in case of fire
Crew wages, if the vessel lost and passenger saved.
Passenger claims Third party people
Injury to Supplier, Agents, stevedores etc. Cargo related
Damage to cargo( Wet)
Collapsing of twin deck
Cargo shifting and damaging the hull- In this case the H&M insurance will pay first but later they will charge from the ship owner as it may be due to lack of lashing arrangement or improper lashings. That will be paid by the ship owner
Damage to fixed and floating objects/ installations
S.P.M, Buoys, shore crane etc. Wreck removal
Sometimes ship wrecks has to be removed, marked or destroyed if it is in a channel.
Pollution of any nature
Sometimes the claims will be so high and the individual clubs have limitations. Those cases it will be paid by clubs, pools and reinsurance. Reinsurance is available up to 2030B$
Fine
Customs, immigration cordaband etc. Piracy
For Crew and cargo. Stoways
Fines and cost for repatriation. Deserter
Fines and cost for repatriation. Salvage
Which is not a part of GA(Salvage for oil pollution) GA unrecoverable for cargo.
GA unrecoverable for H&M.
9. If a ship owner or charterer requires P&I insurance in connection with the operation of a vessel, he may contact a P&I association.
10. When a ship owner requires P&I insurance for a ship, the club underwriter will ask for information which the ship owner has to furnish. Information he will require is:
The tonnage of the ship in GT,
Year of build, Number of crew members,
Type of vessel (tanker, dry bulk, reefer, heavy-lift, container, passenger, ro-ro etc),
Type of cargoes to be carried (if a tanker is clean or dirty), Areas of trading,
Liner trade or tramp,
Classification society,
Management expertise,
Compliance with national and international legal requirements,
How many ships in the company,
Previous P&I history.
k) The club will often make a company audit with the management company of
the ship.
l) In addition, the club will often require a survey of one or more ships in the new fleet to ensure the quality and technical standard of the ships. Entry into the club is often dependent upon the ship being found satisfactory on inspection.
6. Question
What are the principal reasons responsible for compounding of machinery vibration in connection with operation of a long stroke diesel engines and associated machinery arrangements? What are the key factors for excitations generated by the engines?
ANSWER:-
Excitations generated by the engine can be divided into two categories:
1. Primary excitations:
Forces and moments originating from the combustion pressure and the inertia forces of the rotating and reciprocating masses. These are characteristics of the
T S S P N P/2 P/2 MAIN BEARING FORCE N α COMBUSTION PRESSURE GUIDE FORCE P/2 P/2 P
given engine, which can be calculated in advance and stated as part of the engine specification with reference to certain speed and power.
2. Secondary excitations:
Forces and moments stemming from a forced vibratory response in a ship sub- structure. The vibration characteristics of sub-structures are almost independent of the remaining ship structure.
Examples of secondary excitation sources from sub-structures could be anything from transverse vibration of the engine structure to longitudinal vibration of a radar or light mast on top of the deckhouse. Such sub-structures of the complete ship might have resonance or be close to resonance conditions, resulting in considerable dynamically magnified reaction forces at their interface with the rest of the ship. Secondary excitation sources cannot be directly quantified for a certain engine type but must be calculated at the design stage of the specific propulsion plant.
The vibration characteristics of low-speed two-stroke engines, for practical purposes, can be split into four categories that may influence the hull 1. External unbalanced moments
2. Guide force moments.
3. Axial vibrations in the shaft system. 4. Torsional vibrations in the shaft system.
External unbalanced moments:
e. These can be classified as unbalanced first- and second-order external moments, which need to be considered only for engines with certain cylinder numbers.
f. The inertia forces originating from the unbalanced rotating and reciprocating masses of the engine create unbalanced external moments although the external forces are zero.
g. Of these moments, only the first order (producing one cycle per
h. revolution) and the second order (two cycles per revolution) need to be considered, and then only for engines with a low number of cylinders.
The inertia forces on engines with more than six cylinders tend, more or less, to neutralize themselves.
First-order moments
These moments act in both vertical and horizontal directions and are of the same magnitude. Resonance with a first-order moment may occur for hull vibrations with two and/or three nodes. A resonance with the vertical moment for the two-node hull vibration can often be critical, whereas the resonance with the horizontal moment occurs at a higher speed than the nominal because of the higher natural frequency of the horizontal hull vibrations.
Remedy for first order moment is provided by compensator which comprises two counter-rotating masses rotating at the same speed as the crankshaft.
Second-order moments
The second-order moment acts only in the vertical direction and precautions need to be considered only for four-, five- and six-cylinder engines. Resonance with the second-order moment may occur at hull vibrations with more than
three nodes. A second-order moment compensator comprises two counter- rotating masses running at twice the engine speed.
Several solutions are available to cope with the second-order moment (Figure below) from which the most efficient can be selected for the individual case:
No compensators, if considered unnecessary on the basis of natural frequency, nodal point and size of second-order moment
A compensator mounted on the aft end of the engine, driven by the main chain drive
A compensator mounted on the fore end, driven from the crankshaft through a separate chain drive
Compensators on both aft and fore end, completely eliminating the external second-order moment.
Guide Force Moments
The so-called guide force moments are caused by the transverse reaction forces acting on the crossheads due to the connecting rod/crankshaft mechanism.
These moments may excite engine vibrations, moving the engine top athwart ships and causing a rocking (excited by H moment) or twisting (excited by X- moment) movement of the engine.
Axial vibrations
d. The calculation of axial vibration characteristics is only necessary for low speed two-stroke engines.
e. When the crank throw is loaded by the gas pressure through the connecting rod mechanism, the arms of the crank throw deflect in the axial direction of the crankshaft, exciting axial vibrations. These vibrations may be transferred to the ship’s hull through the thrust bearing.
f. In order to counter the axial vibrations all engines are equipped with axial vibration dampers
Torsional vibrations
g. The varying gas pressure in the cylinders during the working cycle and the crankshaft/connecting rod mechanism create a varying torque in the crankshaft.
h. It is these variations that cause the excitation of torsional vibration of the shaft system.
i. Torsional excitation also comes from the propeller through its interaction with the non-uniform wake field.
j. Torsional vibration causes extra stresses, which may be detrimental to the shaft system. The stresses will show peak values at resonances: that is, where the number of revolutions multiplied by the order of excitation corresponds to the natural frequency.
k. Limiting torsional vibration is vitally important to avoid damage or even fracture of the crankshaft or other propulsion system elements.
l. Taking a shaftline of a certain length, it is possible to modify its natural frequency of torsional vibration by adjusting the diameter: a small diameter results in a low natural frequency, a larger diameter in a high natural frequency.
7. Question
Differentiate between static and dynamic stability? Can a ship, high on GM, be low on stability? Justify your answer with reasoning. Enlist the governing factors you will inspect, while taking over a new ship in shipyard as Chief Engineer for having optimum stability in both categories. Substantiate your answer with reasons.
ANSWER:-
STATIC STABILITY:-
1) It is defined as the ability of a ship to regain its upright equilibrium position, after the removal of external factor which caused the vessel to heel at an angle. 2) It gives the stability information of a vessel under the condition that the outside water is static.
3) It is expressed in terms of metacentric height. i.e. GM ( for angle of heel up to 10 degree) and righting lever GZ ( for angle of heel above 10 degree)
4) It’s unit is meter
DYNAMIC STABILITY:-
1) It is defined as the energy required heeling the ship from upright equilibrium till the angle of heel in question.
2) It gives the stability information of a vessel considering dynamic behavior of the sea.
3) It is expressed in terms of the area under righting moment curve. ( or GZ curve multiplied by displacement of the ship in tons)
4) It’s unit is ton-meter-radian
5) The dynamic stability at two different angle of heel cannot be the same
A value of metacentric height gives accurate measure of stability only for small disturbances i.e. angle not beyond 10 degree. For larger angle of heel, the righting lever GZ is used to measure stability. In any stability analysis, the value of GZ is plotted over the entire range of heel angles for which it is positive or restoring.
So, as a thumb rule we say that vessel stability is decided on its value of GM up to 10 degree of heel. But is it possible that a vessel high on GM can be low on stability?
Yes, a ship high on GM can be low on stability. Let us consider the vessels which are built with high forc’le and low working aft for e.g. offshore supply vessels. These vessels possess a large upright GM value due to generous beam to length ratio. But these boats tend to tolerate less heel angles than narrower boats. Also the vanishing stability of these vessels is relatively low.
The hull form of a vessel is an important factor in determining the characteristics of its stability. Increased beam will result in higher value of GM and righting lever(GZ). However the point of vanishing stability will be less. This is due to free trim effect. i.e. heeling of these vessels produces a trimming moment by astern.
While taking over a new ship in shipyard as chief engineer the following governing factors for having optimum stability in both the static and dynamic categories should be inspected:-
1) The new ship must fulfill six criteria of intact stability as follows –
a) The area under righting lever curve is not to be less than 0.055 m.rad up to 30 degree heel
b) Area under GZ curve not less than 0.09 m-rad up to 40 degree heel
c) Area under GZ curve between 30 degree and 40 degree heel should not be