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Showing posts from June, 2020

Timing diagram and Power card of 4 stroke cycle

The timing diagram shows the closing and opening of the valves. The working cycle is illustrated as a ‘P - V’ diagram (pressure-volume). The line ‘l – l’ represents atmospheric line. The piston is considered to have just moved over the ‘top dead centre’ and is on its way down. The air inlet is already open and because of the partial vacuum created when the piston moves towards its bottom position, fresh air is sucked into the cylinder. This process is represented in the 'p-v' diagram by the line ‘1-2’ which is termed suction line. This movement of the piston is called 'Suction Stroke". After the piston has moved over bottom dead centre, the suction valve closes and the volume of air in the cylinder is compressed during the course of the up stroke of the piston. This is represented by the line ‘2-3’ in the above diagram and termed as compression line. This movement of piston is compression stroke. The ignition takes place at point 3 and combustion continues for th

Slide Valves : Simple things that mean a lot

Exhaust valve Materials and Treatments

Material Requirements. The material should retain its greatest strength at high temperatures. No tendencies to air harden. Critical temperature above 800*C. No tendency of high temperature scaling. Hot and cold corrosion resistant. Able to be forged and machined easily. Capable of consistent and reliable heat treatment. Most diesel engines use an Austenitic heat-resisting alloy steel. The seating surface can be stellited. Typical heat treatment:  Heat up to 950*C and cool in air to give a Brinnel Hardness of 269. Surface Treatment: Surface treatment is frequently used to improve or modify valve steel characteristics. Chrome-cobalt-tungsten alloy available in various grades of hardness is widely used. The hardness when deposited is in the order of 375 to 425 Brinnel. The valve head is treated to more than 430*C to reduce contraction stresses. The value face is now sweated by an oxyacetylene flame and the alloy deposited continually by welding (1.02 mm to 1.52 mm).

Construction and Working Principle of Indicator

An engine indicator consists of a small bore cylinder containing a short stroke piston which is subjected to the same varying pressure that takes place inside the engine cylinder during one cycle of operations.  This is done by connecting the indicator cylinder to the top of the engine cylinder in the case of single-acting engines, or through change over cocks and pipes leading to the top and bottom ends of the engine cylinder in the case of double-acting engines. The gas pressure pushes the indicator piston up against the resistance of a spring, a choice of specially scaled springs of different stiffness being available to suit the operating pressures within the cylinder and a reasonable height of diagram. A spindle connects the indicator piston to a system of small levers designed to produce a vertical straight-line motion at the pencil on the end of the pencil lever, parallel (but magnified about six times) to the motion of the indicator piston. The “pencil” is often a brass

Procedure for opening Main Engine Liner

Following Procedure has to be followed when opening Liner Inform company and take permission.Take immobilisation certificate from port state control. Read the manual and have a tool box meeting with everyone involved in the job. Discuss the complete procedure. Prepare important tools and spares required for overhauling liner as given in the manual Prepare risk assessment and make sure all personal safety equipment are used Shut starting air for Main Engine and display placards Engage turning gear Open indicator cocks for all the cylinders Stop main lube oil pump and switch off the breaker Once the engine jacket temperature comes down, shut the inlet water valve for the unit to be overhauled Keep other units in Jacket preheating system to maintain the jacket temperature Drain the jacket water of the concerned unit from exhaust v/v and liner. Shut the fuel oil to the particular unit whose liner is to be removed Dismount the cylinder head using dedicated lifting tools Dis

Refrigeration Compressor Starting Unloader

At a star-delta start of electric motors it is often considered necessary to limit the compression work of the machine at the starting moment in order to reduce the starting torque of the electric motor.  Usually, a solenoid valve is used in a by-pass arrangement which in the starting up phase short circuits the discharge side to the suction side of the compressor.  At the same time, a non-return valve must be fitted in the discharge line to the condenser preventing the return flow of discharge gas to the compressor. When the electric motor has reached its max. number of revolutions per minute, a switch takes place from star to delta start.  The solenoid valve is closed and the compressor now works under normal conditions.

Sludge formation in Refer system

Acid content inside a system can emulsify with the compressor oil to form an aggressive oil sludge that reduces lubrication properties. This can lead to serious compressor damage. Sludge can also cause a variety of other problems in a system, such as blockages of strainers, expansion valves and other tiny passage

Corrosion in Refer system

Moisture can cause corrosion. However, moisture in combination with a HCFC refrigerant containing chlorine (like for example R-22 or R-409A) creates much more serious corrosion, as the chlorine hydrolyses with the water to form hydrochloric acid (HCl) which is aggressive to most metals. Heat adds significantly to the problem by accelerating the acid-forming process.  For HFC refrigerants (like R-404A or R-407C), it is the polyolester oils that are very hygroscopic and may decompose at high temperatures forming hydrofluoric acid with the moisture which could be introduced to the system through a sub-standard refrigerant.

York Antwerp Rule

There is a general average act when and only when, any extraordinary sacrifice or expenditure is intentionally and reasonably made or incurred for the common safety for preserving from peril the property involved in common maritime adventure

Certificate of Proficiency (COP) and Competency (COC)

Certificate of Proficiency (COP) refers to a certificate, other than a certificate of competency issued to a seafarer, stating that the relevant requirements of training, competencies or seagoing service in the Convention have been met. Able seafarer deck :Person qualified in accordance with the provisions of regulation II/5 of the STCW Convention Able seafarer engine :Person qualified in accordance with the provisions of regulation III/5 of the STCW ConventionAble seafarers whether deck or engine are given Certificate of Proficiency (COP) Competency (COC) refers to the possession and demonstration/application of the knowledge, understanding and proficiency required of seafarers under the Convention. Electro - technical officer : Person qualified in accordance with the provisions of regulation III/6 of the STCW ConventionETO is given Certificate of competency (COC).

Bill of Lading

Bill of Lading (B/L) The bill of lading is the declaration of the master of the vessel by which he acknowledges that he received the goods on board of his ship and assures that he will carry the goods to the place of destination for delivery, in the same condition as he received them, against handing of the original bill of lading. "Bill of lading means a document which evidences a contract of carriage by sea and the taking over of loading of the goods by the carrier, and by which the carrier undertakes to deliver the goods against surrender of the document. A provision in the document that the goods are to be delivered to the order of a named person, or to order, or to bearer, constitutes such an undertaking." The bill of lading (B/L) serves as: A receipt of the goods by the shipowner acknowledging that the goods of the stated species, quantity and condition, are shipped to a stated destination in a certain ship, or at least received in custody of the shipowner for t

Reversing of ME-C engine

Reversing of the engine is performed electronically and controlled by the Engine Control System,by changing the timing of the fuel injection, the exhaust valve activation and the starting valves.

Biochemical Oxygen Demand and Coliform Count

Biochemical Oxygen Demand (B.O.D) Amount of oxygen taken up by sewage sample in mg/l or ppm is termed as Biochemical Oxygen Demand. Measure of strength of sewage. Identifies biological decomposable substances and is a test on the activity of bacteria, Presence of oxygen feed on and consume organic matter. Test results are expressed as amount of oxygen taken by one litre sample (diluted with aerated water)when incubated at 20°C for five days. It gauges the effectiveness of sewage treatment process. B.O.D of raw sewage is 300 to 600 mg/litre. I.M.O recommends a B.O.D of 50 mg/litre after treatment. Coliform Count Coliform organisms are recognised as the indicator Organisms of sewage pollution. Numbers present in sewage are large. Each person contributes between 125 billion, in winter to 400 billion, in summer. Coliform are present in human intestine and presence in water is taken as an indication of the pathogen count. Responsible for Typhoid, Dysentery, Polimyelitis, Cho

How to prepare the IOPP Survey ?

Validity of the IOPP certificate checked. Proper entry of ORB and, sludge disposal receipts to shore facilities attached to ORB. Calculate the sludge formation, and compared with 1% of voyage fuel consumption. Incinerating time, incinerated waste oil amount, remainder of waste oil in waste oil tank should be reasonable. Incinerator kept ready for demonstration, such as heating of waste oil tank, alarms, control and functional test, done priorto survey. OWS in good order, it’s piping free from oil leaks, overboard valve from OWS locked in closed position. If possible, one section of discharge pipe removed and free from oil residues. ODM checked for 15-ppm alarm and automatic stopping. High-level alarms of sludge tank, waste oil tank and bilge holding tank checked. Spare filter for OWS must be kept onboard. USCG Notice posted near OWS and bilge pumping out station.

Stern tube leakage

Causes Misalignment of bushes  Poor material, design of liner and seals Contaminated oil supply with foreign materials Fishing net, rope and similar material entering into seal due to defective rope guard. Electro static pitting on shaft due to defective shaft earthing device. Prolonged low speed operation, in which hydrodynamic oil film could not attain. Remedies Keep good alignment of bushes.  Use good material and an improved seal design. Always maintain L.O level due to draught condition.  Keep sufficient aft peak tank water level. Use good design of rope guard.  Keep earthing device in good order. Action to be taken at sea to continue the voyage When stern tube seal leaks at sea, minimized as possible. To continue the voyage, following actions are to be taken. Correct the vessel trim, as possible as minimum astern, to certain allowable trim Use more viscous oil (e.g. Cylinder oil) Use lower header tank. If not possible, reduce the oil pressure-head by using

Steam boiler water tube leakage

How to know Excessive feed water consumption from cascade tank Continuously running boiler feed pump If large amount of leakage, boiler water level low, steam pressure drop & continuous firing of boiler Some water comes out from furnace cover White smoke escaping from boiler uptake Check Leakage For water tube boiler (Z boiler) Stop firing and open combustion chamber, leakage can be seen easily. For individually boiler water tube, fill up the boiler water level to full and check. If necessary, pressure test should be done. For smoke tube boiler Open the smoke side drain valve, water will come out if boiler tube is leaking. After opened up the fireside cover and fill up the boiler water level until all smoke tubes are flooded, we can easily check which one is leaking ligaments. Possible Sources of water leakage Leakage from tubes Distorted furnace crown plate. Furnace shell plate, opposite to burner opening due to flame impingement. Lower section plate of fur

Damage Stability

Oil tankers    Oil tankers shall be regarded as complying with the damage stability criteria if the following requirements are met: The final waterline, taking into account sinkage, heel and trim, shall be below the lower edge of any opening through which progressive flooding may take place. In the final stage of flooding, the angle of heel due to unsymmetrical flooding shall not exceed 25°, provided that this angle may be increased up to 30° if no deck edge immersion occurs. The stability in the final stage of flooding shall be investigated and may be regarded as sufficient if the righting lever curve has at least a range of 20° beyond the position of equilibrium in association with a maximum residual righting lever of at least 0.1 m within the 20° range; the area under the curve within this range shall not be less than 0.0175 m·rad. The Administration shall be satisfied that the stability is sufficient during intermediate stages of flooding Equalization arrangements requirin

Intact Stability criteria

In port The initial metacentric height GMo, corrected for the free surface measured at 0° heel, shall be not less than 0.15 m At sea The following criteria shall be applicable: A-area under curve up to 30 degrees to be not less than 0.055 metre-radian. B-area under curve up to x degrees to be not less than 0.09 metre-radian C-area between 30 degrees and x degrees to be not less than 0.03 metre-radian. x-40 degrees or any lesser angle at which the lower edges of any openings in the hull, Superstructure or deckhouses which lead below deck and cannot be closed weathertight, would be immersed E-maximum GZ to occur at angle not less than 30 degrees and to be at least 0.20 metre in height The maximum righting arm shall occur at an angle of heel preferably exceeding 30° but not less than 25° The initial metacentric height GMo, corrected for free surface measured at 0° heel, shall be not less than 0.15 m

Hydrostatic Curves

A series of graphs drawn to a vertical scale of draught and a base of length, which gives values such as the centre of buoyancy, displacement, moment causing unit trim, and centre of flotation. In practice tables with hydrostatic parameters calculated for different draughts are used. However, only having traditional graphs it is possible to observe character of hydrostatic curves and understand ship behaviour

Bonjean Curves

Curve plotted on lines plan of ship is calls bonjean curve, here the longitudinal section of the vessel is divided in 10 stations. At each station transverse section and each draft, we calculate e area and moment of area., these moments then plotted on the lines plan.... Use: fo calculation of hydrostatics like displacement block coefficient centre of floatation TPC etc. Enable the users to calculate the displacement and the centre of buoyancy for a given waterline, in an upright condition curves of areas of transverse sections and their moments about the baseline of a ship used in making calculations (as to determine the force of buoyancy during launching) The Bonjean curve had as its ordinate the cross sectional area at that section, up to the waterline concerned. Each curve was usually plotted with its axis The vertical axis was traditionally at ship scale. Their main uses were for launching (end launching) and longitudinal strength. For launching, prior to stern lift,

KN cross curves of stability

Same as the GZ cross curves and also used to get the GZ values for making the curve of statical stability. The only difference being that here the KG is assumed to be ZERO. This solves the problem of a sometimes positive and sometimes negative correction, as now the correction is always subtracted. GZ = KN – KG Sine θ

In Water Survey

Hull survey while ship is afloat done by authorized diving company with surveillance of Class surveyor as the replacement of docking survey Requirements for IWS Age not greater than 15 years. ( Ships of age 15 years and over may be permitted as special consideration) All ships excluding Enhanced Survey Program (ESP) ships, such as Bulk carrier, Oil Tankers and Dangerous chemical bulk carrie rs of 15 years of age and over. Ship with class “IWS” notation. Need agreement of Flag administration. High quality paint coating for 7.5 years extended dry docking (EDD). Fitted effective anodes, fitted effective current corrosion protection (ECCP). Access arrangements for - sea valves, rudder bearing & pintle clearance. Stern tube wear down measurement, bow & stern thruster  -seal checking   Documents Survey plan, Location and date of IWS, Detail of hull marks and drawings. Preparations in dry dock for IWS notation Fitted approved Cathodic protection system. Ship hul

Cross curves of stability

The Cross Curves Of Stability are used to determine the length of the righting arm at any angle of inclination for a given displacement. To draw the curve of statical stability, we need GZ values for various angles of heel. For this we use the GZ cross curves of stability. These curves are provided for an assumed KG, tabulating GZ values for various displacements and angles of list. Called cross curves because the various curves actually ‘cross’ each other. Since the curves are plotted for an assumed KG, if the actual KG differs from this a correction (GG1Sineθ) needs to be applied. This correction is positive if the actual KG is less than the assumed KG and vice-versa. After obtaining the GZ values at various angles, the curve of statical stability is prepared

GZ curves of stability

Graph where GZ is plotted against the angle of heel. Drawn for each voyage condition by the ship’s officer. This curve is for a particular displacement and KG. From this curve it is possible to ascertain the following: Initial metacentric height – point of intersection of the tangent drawn to the curve at the initial point and a vertical through the angle of heel of 57.3° (1 radian) Angle of contra flexure – the angle of heel up to which the rate of increase of GZ with heel is increasing. Though the GZ may increase further, the rate of increase of GZ begins to decrease at this angle. The range of stability – where all GZ values are positive. The maximum GZ lever & the angle at which it occurs. The angle of vanishing stability – beyond which the vessel will capsize. The area of negative stability. The moment of statical stability at any given angle of heel (GZ x Displacement of the ship). The moment of dynamical stability – work done in heeling the ship to a particu

Angle of loll

Intial unstable ship will not be upright. While heeling one side, the angle at which the G & B coincides in neutral equilibrium. If GZ=0 then angle of Equilibrium = angle of loll How to Recognize Vessel will not remain upright and will assume a list to either port or starboard. Vessel "flops" to port or starboard. Vessel will have a very long, slow roll period about the angle of list. A small GM is known to exist, plus any of the above. Angle of Loll -ve GM Unstable Equilibrium. G on the Centreline. Corrected by lowering G below M CORRECTION OF ANGLE OF LOLL Moving cargo to a lower position; Jettisoning top-weight (in an emergency); Reducing FSE by pressing up/emptying tanks; Filling low ballast spaces such as DB tanks Top up tanks that are already slack. Start with the smallest tank on the LOW side first. (If a tank on the high side is filled first, the ship will start to right herself but will then tend to roll over suddenly in an uncontrolled

Tailshaft Survey

Tailshaft Condition Monitoring System: Complete tailshaft survey will be required if the last complete tailshaft survey was carried out more than five (5) years prior to the initial survey For vessels with TCM notation, tailshaft survey interval required by 7-2-1/13.1.3 will be extended up to 15 years provided: Annual surveys are carried out to the satisfaction of the attending Surveyor, and The following are carried out at each tailshaft survey due date required Bearing weardown measurement Verification that the propeller is free of damage which may cause the propeller to be out of balance Verification of effective inboard seal Renewal of outboard seal in accordance with manufacturer’s recommendation Complete tailshaft survey may be waived subject to satisfactory review of the following records for appropriate period as considered necessary Stern bearing oil analysis records Stern bearing oil consumption records Stern bearing temperature monitoring records Tailshaf

Derating of engine

A vessel’s engine and propeller are optimized and designed for a given operational and max. speed. If the operational speed of the vessel is generally lower than the one originally optimized for, it may be beneficial to consider derating of the main engine and propeller. Derating as a retrofit product offers reduction of the total fuel consumption by improving the match between the operational speed and optimization speed. Derating is usually an attractive option for fuel oil savings if a reduction of 10-15% of the max. speed at SMCR can be accepted. It is a techno-commercial concept done at the time where shipping industry is in bad shape Methods : Readjusting fuel timing Decreasing compression ratio Fuel nozzle size Turbocharger matching t/c, propeller and shaft matching Fuel saving originates from Optimisation of the engine and propeller layout to the actual operational speed Utilisation of the latest engine tuning methods Utilisation of state-of-the-art high ef

Continuous synopsis record (CSR)

Continuous synopsis record is a special measure under SOLAS for enhancing the maritime security at the sea. According to SOLAS chapter I, all passenger andcargo ships of 500 gross-tonnage and above must have a continuous synopsis record on board. The continuous synopsis record provides an onboard record of the history of the ship with respect to the information recorded therein Continuous synopsis record (CSR) is issued by the administration of the ship, which would fly its flag. Following details should be present in the continuous synopsis record (CSR) Name of the ship The port at which the ship is registered Ship’s identification number Date on which ship was registered with the state Name of the state whose flag the ship is flying Name of registered owner and the registered address Name of registered bareboat charterers and their registered addresses Name of the classification society with which the ship is classed Name of the company, its registered address and th

Load line survery preparation

The preparation for a load line survey will involve ensuring that the hull is watertight below the freeboard deck and weathertight above it The following checks should be conducted prior to survey: Check that all access openings at the ends of enclosed superstructures are in good condition. All dogs, clamps and hinges should be free and greased. Gaskets and other sealing arrangements should not show signs of perishing (cracked rubbers). Check all cargo hatches and accesses to holds for weathertightness. Securing devices such as clamps, cleats and wedges are to be all in place, well-greased and adjusted to provide optimum sealing between the hatch cover and compression bar on the coaming. Replace perished rubber seals as necessary. Hose test hatches to verify weathertightness. Check the efficiency and securing of portable beams. Inspect all machinery space openings on exposed decks Check that manhole covers on the freeboard deck are capable of being made watertight. Check that a

Enclosed Space Entry

Preparation for enclosed space entry Competent person and a responsible officer to take charge of operation. Carried out risk assessments, identified potential hazards Space isolated and secured against ingress of dangerous substances by blanking off pipe-lines or other openings and by closing valves. Clean Sludge and deposits and ventilate space thoroughly Test oxygen deficiency, flammability and toxicity to confirm space is safe to entry. When space is safe for entry, "Enclosed space entry permit" has to be issued. The procedure and arrangement before entry Access to and within the space should be adequate and well illuminated. No source of ignition used. Rescue and resuscitation equipment should be available at the entrance to the space. Arrange means of hoisting physical inability person from the confined space. Select only working number of personnel entering the space to rescue the physical inability person in any accident. Lifelines should be long enoug

Differences between MC/MC-C and ME/ME-C engines

The electrohydraulic control mechanisms of the ME engine replace the following components of the conventional MC engine: Chain drive for camshaft Camshaft with fuel cams, exhaust cams and indicator cams Fuel pump actuating gear, including roller guides and reversing mechanism Conventional fuel pressure booster and VIT system Exhaust valve actuating gear and roller guides Engine driven starting air distributor Electronic governor with actuator Regulating shaft Engine side control console Mechanical cylinder lubricators. The Engine Control System of the ME engine comprises: Control units Hydraulic power supply unit Hydraulic cylinder units, including: Electronically controlled fuel injection, and Electronically controlled exhaust valve activation Electronically controlled starting air valves Electronically controlled auxiliary blowers Integrated electronic governor functions Tacho system Electronically controlled Alpha lubricators

Dampers, Detuners and Compensators

Every running machine has a tendency to vibrate because of several moving parts incorporated within it. When in motion, the machine will have an oscillatory motion around an equilibrium point. The natural frequency of vibration is always present in marine engines, but the effect can be dangerous when the vibration frequency reaches high levels. This happenswhen the natural frequency of vibration from an external source integrates with the engine vibration or when there are out-of-balance forces generated inside the engine which create 1st and 2nd order movements. Such effects can result in severe damage to the marine engine’s internal moving parts, cracks in the structure, loosening of bolts and securing and damage to bearings. Dampers : Dampers are used to damp or reduce the frequency of oscillation of the vibrating components of the machine by absorbing a part of energy evolved during vibration Axial vibrations : When the crankthrow is loaded by the gas force through the co

Green Engines

 The ‘G’ prefix before an engine means it has a design that follows the principles of the large-bore, Mark 9 engine series that MAN Diesel & Turbo introduced in 2006 with an ultra-long stroke that reduces engine speed, thereby paving the way for ship designs with unprecedented high-efficiency. Specification of G-80ME-C9             ▪    Power kW/cyl    : 4,450             ▪    Engine speed rpm    : 68             ▪    Stroke mm        : 3.720             ▪    MEP bar        : 21             ▪    Mean piston speed m/s    : 8.43             ▪    Length mm (7 cylinder)     : 12.500             ▪    Dry mass ton (7 cylinder)    : 960             ▪    SFOC, L1 (g/kWh)        : 167 The G-type achieves SFOC reductions through a combination of several factors, such as:             ▪    increased scavenge-air pressure             ▪    reduced compression ratio (twostroke Miller timing)             ▪    increased maximum combustion pressure             ▪    adjustments of co

Windlass requirements

Letting go anchor cable speed vary between 5 ~ 7 mtr/sec. Heaving up speed 0.125 ~ 0.25 mtr / sec or 3 ~ 5 rpm. Full loaded duty of windlass commonly 4 ~ 6 time of the weight of one anchor. Warpends for mooring purpose and light line speed up to 0.75 ~ 1.0 mtr /sec

What limit of elongation should be tighten the chain

1.5 % of original length . Slack chain: Symptoms: Excessive chain vibration and noise. Power loss in all units, indicated [by Power Card]. Late injection, low Pmax, [by Draw Card]. Late closing of Exhaust Valve, [by Light Spring Diagram]. High exhaust temperature and smoke. Effects: Impose heavy mechanical load, resulting fatigue failure. Damage to chain system and engine frame. Retardation of Fuel Pump and Exhaust Valve timings, resulting: Reduced Scavenge Efficiency due to late closing of exhaust valve. High exhaust temperature and smoke, due to after burning. Low Pmax, due to late injection. Reduced engine power


   The homogenizer (Vickers Type: See figure above) provides an alternative solution to the problem of water in high-density fuels. It can be used to emulsify a small percentage for injection into the engine with the fuel. This is in contradiction to the normal aim of removing all water, which in the free state can cause gassing of fuel pumps, corrosion and other problems.  However, experiments in fuel economy have led to the installation of homogenizers on some ships to deal with a deliberate mixture of up to 10% water in fuel.  The homogenizer is fitted in the pipeline between service tank and engine so that the fuel is used immediately. It is suggested that the water in a high-density fuel could be emulsified so that the fuel could be used in the engine, without problems.  A homogenizer could not be used in place of a purifier for diesel fuel, as it does not remove abrasives such as aluminium and silicon, other metallic compounds or ash-forming sodium which damages exhaust v

Checks to Perform on Ship before Coming out of the Dry Dock

It is extremely important to maintain a checklist of things and procedure to be done before undocking and not to miss any vital point which will lead to delay in undocking. Following things must be checked by a responsible engineer and deck officers before water is filled up in the dock: All Departments in charge to confirm that repairs assigned under their departments are completed successful with tests and surveys are carried out Check rudder plug and vent and also check if anode are fitted back on rudder Check hull for proper coating of paint; make sure no TBT based paint is used. Check Impressed Current Cathodic Protection system (ICCP) anodes are fitted in position and cover removed Check Anodes are fitted properly on hull and cover removed (if ICCP is not installed) Check all double bottom tank plugs are secured Check all sea inlets and sea chests gratings are fitted Check echo sounder and logs are fitted and covers removed Check of propeller and rudder are clear from a

Name of refrigerant significance(R22,R134A)

The prefix describes what kinds of atoms are in a particular molecule, the next step is to calculate the number of each type of atom. The key to the code is to add 90 to the number; the result shows the number of C, H, and F atoms. For HCFC-141b: One more piece of information is needed to decipher the number of Cl atoms. All of these chemicals are saturated; that is, they contain only single bonds. The number of bonds available in a carbon-based molecule is 2C + 2. Thus, for HCFC-141b, which has 2 carbon atoms, there are 6 bonds. Cl atoms occupy bonds remaining after the F and H atoms. So HCFC-141b has 2C, 3H, 1F, and 2Cl: First, consider two-carbon molecules. For example, HCFC-141, HCFC-141a, and HCFC-141b all have the same atoms (2C, 3H, 1F, and 2Cl), but they are organized differently. To determine the letter, total the atomic weights of the atoms bonded to each of the carbon atoms. The arrangement that most evenly distributes atomic weights has no letter. The next most even

Comparison between Rapson Slide Type and Rotary Vane Type

Loadline ( Plimsoll ) Marking

Each vessel is required to hold a Loadline Certificate. Part of the requirements for this is the permanent marking of loadlines on either side of the hull arounf about midhsips. Permanent marking means that they have to be impressed or welded so that they cannot be removed by normal wear and tear. They should be white or yellow on a dark contrasting back ground. Regulations govern the number and size of these, the main ones are described below. Danish Load mark The Load Line Mark shall consist of a ring 300 millimeters (12 inches) in outside diameter and 25 millimeters (1 inch) wide which is intersected by a horizontal line 450 millimeters (18 inches) in length and 25 millimeters (1 inch) in breadth, the upper edge of which passes through the centre of the ring. The centre of the ring shall be placed amidships and at a distance equal to the assigned summer freeboard measured vertically below the upper edge of the deck line Deck Mark The deck line is a horizontal line 300 millimet

Emergency fire pump requirement: - SOLAS ch II-2 reg 10,

  Independent driven power operated pump  Capacity should not be less than 40%  of the total fire pump capacity required by regulation II-2 / and in any not less than 25 m3 /hr for cargo ships 200 Gt and above. (Each of the required fire pumps (other than any emergency pump required in paragraph for cargo ships) shall have a capacity not less than 80% of the total required capacity divided by the minimum number of required fire pumps but in any case not less than 25 m3/h and each such pump shall in any event be capable of delivering at least the two required jets of water. These fire pumps shall be capable of supplying the fire main system under the required conditions. Where more pumps than the minimum of required pumps are installed such additional pumps shall have a capacity of at least 25 m3/h and shall be capable of delivering at least the two jets of water required in paragraph Minimum pressure at any hydrant  not less 2.7 bar.( 4.0 bar for p

Hull repair

Cracked weld : Inform Class surveyor & seek his opinion. Trace the length ok crack by DPT. One inch from both sides  drill crack arresting holes. Gas free the tank from inside Guaging of Crack to be carried out by guaging electrode till bottom of the crack is reached Welding electrode, welder & procedure to be class approved. Low Hydrogen Electrodes are used. The affected portion to be heated to 200 deg C by flame torch & temp to be noted by IR sensor. Carry out welding from either side The weld is again to be heated by flame to rleive stress & covered with insulation tapes to reduce cooling rate. Weld to be inspected & arrest holes to be welded Radiography to be carried out. Hose test to be carried out. Primer & paint to be applied Severe indentation in way of frame  : It cannot be tolerated so has to be cropped off alongwith bend frame & renewed. Put 2 small size plates & weld it to frame (tag) with actual size plate. Heating &am

Stern Frame

  A stern frame may be cast or fabricated and its shape is influenced by the type of rudder being used and the profile of the stern. Sternframes also differ between twin and single screw ships, the single screw sternframe having a boss for the propeller shaft. Adequate clearance is essential between propeller blade tips and sternframe in order to minimise the risk of vibration. As blades rotate water immediately ahead of the blades is compressed and at the blade tips this compression can be transmitted to the hull in the form of a series of pulses which set up vibration. Adequate clearance is necessary or alternatively constant clearance, this being provided with ducted propellers such as the Kort nozzle. A rotating propeller exerts a varying force on the sternframe boss and this can result in the transmission of vibration. Rigid construction is necessary to avoid this. The stern post, of substantial section, is carried up inside the hull and opened into a palm end which connects to

Chain stopper

For anchoring operations the stopper bar is locked upright. When it is required to fix the position of the chain the stopper is lowered into the position shown. This allows the brake to be released and is typically used for stowing the anchor. chain stopper arrangements are not design to stop a runaway chain. Alternately an arrangement known as the 'devil's claw' may be used which has a forked locking piece. For smaller vessels, and where extra security is required bottle jacks with wire strops passed though the chain may be used

Water tight doors

Vertically mounted watertight door  To allow the passage for personnel water tight doors are fitted , openings must be cut only were essential and they should be as small as possible. 1.4m high, 0.7m wide being the usual. Doors should be of mild steel or cast steel, and they may be arranged to close vertically or horizontally. The closing action must be positive i.e. it must not rely on gravity. Hinged water tight doors may be allowed in passenger ships and in watertight bulkheads above decks which are placed 2.2m or more above the waterline. Similar doors may be fitted in weather decks openings in cargo ships. Hinged water tight door   Hinged water tight doors consist of a heavy section door which when closed seals on a resilient packing mounted in channel bar welded to the door frame. The door is held firmly in the door frame when closed by the dogging arrangements shown which allow the doors to be opened from either side.Normally six of these dogs are spread equally around t

Automatic water tight door operating gear

Automatic operating gear allows the remote operation of watertight doors. These are fitted on many vessels including passenger ships. In the event of fire or flooding, operation of switches from bridge/fire control area sends a signal to an oil diverter valve. Oil from a pressurised hydraulic system is sent to a ram moving the door. The door may also be operated locally by a manual diverter valve. In addition, in the event of loss of system pressure the door may be operated by a local manual hand pump remote door position indicators are fitted as well as were appropriate alarms to indicate operation.