marine engine simulation

Marine Engineering-Electrical-Fuses

2010-06-17T23:06:00.000-07:00

Fuses
High current flow through a thin fuse wire will raise its temperature causing it to melt and break the circuit before the current excess reaches a level sufficient to damage other, more substantial, parts of the system. Melting temperature depends on the material used (tinned copper in rewireable fuses melts at 1080ºC, the silver in cartridge fuses at 960ºC). The wire is sized so that the normal current is carried without overheating, but due to the resistance of the relatively small wire, that excess current will produce heat sufficient to melt it. Current rating gives the normal current that may be carried: minimum fusing current is the smallest current that will cause melting.
Avatar (Two-Disc Blu-ray/DVD Combo) [Blu-ray]
A fuse will melt much quicker with very large fault current than when the value of fault current is only just above the minimum fusing current. Time/current characteristics are found by testing six or more of the same type of fuse at different currents and plot ting the results. The bottom current for the test is not more than 1.05 X minimum fusing current, and the top current is one that will melt the wire in not more than 0.5 second. The other test currents are equally spaced between these. Fuses are rated for particular ac. and/or d.c. voltages
The Girl with the Dragon Tattoo

Cartridge Fuses
High Rupture Capacity (HRC) fuses have silver wire enclosed in a quartz powder filled ceramic tube with metal end caps (Fig. 9.1). Arcing when this type of fuse blows is buried in the powder, fusion of which in the arc path helps to extinguish it.
HRC fuses can be used for very high fault levels: deterioration is negligible; they have accurate time/current characteristics and reliability for discrimination; they are safer if accidentally inserted on a fault: there is no issue of smoke or flame; cartridges are sized to ensure that the correct value fuse is fitted.
Semi-enclosed Fuses
The rewireable fuse has an insulated carrier for safe handling and containment of the wire in an asbestos lined tube
The wire is easily replaced after operation, but the des is open to abuse as too heavy a wire can be used which could mask a fault and also cause severe arcing if it did operate. Another fault is that of premature failure if the wire is made thinner by oxidation or con tact with air, or by being stretched when fitted (a problem with wire made of lead, tin or an alloy of the two).
Fuses in Service
Fuses may be used as the only protection in a steady load circuit, such as for lighting. An ac. motor with its high starting current and varying load has fuses in each of the supply conductors, but fitted as a backup for the other forms of protection and to break the circuit in the event of a short-circuit current greater than that which the ordinary contact breakers are designed to interrupt without damage. Very accurate time/current characteristics are needed for fuses used in conjunction with other safety devices, to ensure that the overload trip is allowed time to operate for moderate over- current but that the fuse blows first if there is very high short-circuit current.
The Girl Who Kicked the Hornet's Nest
Live At The Troubadour [CD / DVD Combo]
Kindle Wireless Reading Device (6" Display, Global Wireless, Latest Generation)

marine Engineering-Electrical-D.C. Generators

2010-06-17T11:35:00.000-07:00

D.C. Generators

Operation of a d.c. generator relies (as with alternators) on the principle that when magnetic lines of force are cut by a conductor(Fig. 6.1) a voltage is induced in the conductor. Size of induced voltage and resulting current are dependent on magnetic field strength, length of conductor and speed of cutting.
The direction of current flow is dictated by the relationship between magnetic field and direction of movement of the conductor. Ii can be found from Fleming’s Right Hand Rule, which is applied to give direction of conventional current flow during generation,A simple generator can be constructed from a loop or coil of wire mounted on a spindle and arranged for rotation between opposite magnetic poles The field-cutting action of the straight sides will cause current flow as the result of induced voltage. Direction of flow is shown by the arrows (found from the Right Hand Rule) and can be seen to be continuous around the loop. The voltages generated are in series and therefore add to give twice the voltage produced in one side.
Direct current can be collected from the wire ends through the commutator which consists of two half-rings with brushes. Each brush takes current from one half-ring in turn, so that current flow is always in the same direction f or each collecting brush. The out put is not steady but has a wave form.
The Girl Who Kicked the Hornet's Nest Live At The Troubadour [CD / DVD Combo]Kindle Wireless Reading Device (6" Display, Global Wireless, Latest Generation)Avatar (Two-Disc Blu-ray/DVD Combo) [Blu-ray]The Girl with the Dragon Tattoo

Marine Engine Q & A -Electrical-Static Automatic Voltage Regulator

2010-06-16T07:52:00.000-07:00

Static Automatic Voltage Regulator
The carbon pile regulator uses a magnetic coil powered from the alternator output Strength of the field vanes with alternator voltage and this strength is tested against springs which are the voltage reference. The moving contact regulator employs a similar matching of alternator output effect through a magnetic coil against springs.
The availability of a small transformed, rectified and smoothed power supply from the alternator output makes possible the matching or it directly against an electronic reference in the static automatic voltage regulator. The direct current derived from the alternator output is applied to a bridge which has fixed resistances on two arms and variable resistances (zener diode voltage references) on the other two. The zeners operate in the reverse breakdown mode having been manufactured with a zener breakdown voltage of very low value. As can be seen from the earlier description of zener diodes, voltage remains constant once breakdown has occurred despite change in current. This implies, however, that changes in applied voltage while not affecting voltage across the diode will cause a change in resistance which permits change in current. .As with a Wheatstone bridge, imbalance of the resistances changes the flow pattern and produces in the voltage measuring bridge an error signal
The error signal can be amplified and used to control alternator excitation in a number of different ways. Thus it can control the firing angle of Thyristors (Fig. 3.14) through a triggering circuit to give the desired voltage in the brushless alternator described. It can be used in the statically excited alternator to correct small errors through a magnetic amplifier arrangement-The error signal has also been amplified through transistors in series, for Excitation control.
The Girl Who Kicked the Hornet's Nest
Live At The Troubadour [CD / DVD Combo]
Kindle Wireless Reading Device (6" Display, Global Wireless, Latest Generation)
Avatar (Two-Disc Blu-ray/DVD Combo) [Blu-ray]
The Girl with the Dragon Tattoo

Exile on Main Street
Apple iPod touch 32 GB, Case, and Charger Bundle
True Blood: The Complete Second Season (HBO Series)
Glee: The Music, Volume 3 Showstoppers (Deluxe)

Marine Engine Q & A- Electrical-Three-Phase Systems/

2010-06-13T09:14:00.000-07:00

Three-Phase Systems
Outputs from the three sets of conductors in the alternator are delivered to three separate bus-bars in the switchboard. This is necessary because of the voltage and current disparity between them at any instant.
Three-phase, four systems use a single return wire which is connected to the neutral point of the star windings. Current in the turn wire is the sum of currents in the individual phases. If loads on each phase are balanced with voltages equal and at .1 20 apart, the three currents will sum to zero and the return wire will carry no current The fourth (return) wire will carry a small current it there is imbalance.
Three-phase, three-wire systems have no return wire. This is acceptable for snips where, direct from the main switchboard, three-phase motors make up much of the load and unless there is a fault they take current equally from the phases. Also some imbalance is acceptable with a three-phase, three-wire system provided load is connected in delta Supplies for lighting, heating, single-phase motors and other loads are taken through delta-star or delta-delta transformers.
The Neutral Point
The majority of British ships use three-phase, three-wire distribution with the neutral points of alternators insulated (Fig. Very little current will flow through an earth fault on one phase, because there is no easy path for it back to the electrical system. With such a system, an essential electric motor with an earth fault can be kept running until stoppage for repair is convenient This would be as soon as possible to avoid a full-phase fault that would result if an earth occurred on another phase as well.
Although fault current is negligible with an insulated/unearthed neutral point, over voltages are high. The transient likely is 2.5 X line voltage. Such a voltage surge is within the capability of the main insulation of marine electrical equipment which is tested to 2 X line voltage + 1000 volts.

A few British vessels have electrical distribution systems with an earthed neutral . This is a connection of the system, via the neutral point of the alternator, to the hull steel. The result of not isolating the electrical system from the hull is that current flow from an earth fault on any phase has a path through the hull steel and earthed neutral back to the system. The availability of the path encourages higher fault current flow than is the case where the neutral is insulated or connected by resistance. Equipment with an earth fault, where-the system is earthed, must be disconnected immediately if a fault develops. This can be effected automatically with an earthed neutral system because the level of fault current is ugh enough to operate a trip.
Earth fault current is high with earthed neutral systems, but over- voltages due specifically to earth faults are lower. The earthed system is chosen to limit over voltages and to give automatic earth fault location and disconnection.
Over voltages due to switching are not affected by choice of earthing or insulating the neutral. These high surges, and the possibility of others from failure of the voltage regulator, means that the same standard of equipment insulation is required for both arrangements.
Mass Transfer with Chemical Reaction in Multiphase Systems - I & II: Volume I - Two-Phase Systems Volume II - Three-Phase Systems (NATO Science Series E: (closed)) (v. 1)

Marine Engine Q & A- Electrical-Alternator

2010-06-12T20:14:00.000-07:00

Alternators

The operation of generators relies on the principle that whenever, there is mutual cutting between a conductor and a magnetic field, a voltage and resulting current will be induced in the, conductor. The flow of induced current is not random: it is governed: by the directions of cutting and of the field and can be found from Fleming’s Right Hand Rule (Fig.).

Magnitude of the induced voltage depends on the strength of ‘the magnetic field, rate of cutting and conductor.
Simple Alternator
The arrangement used in the majority of alternators to exploit the principle of generation is shown simply in the sketch. Mutual cutting between conductors and magnetic fields is produced by rotating poles, the magnetic’ fields of which move through fixed conductors.
The rotor shown has a pair of poles so that output is generated simultaneously in two conductors. Reference to the Fleming Right Hand Rule will confirm the instantaneous direction of conventional current indicated by the arrows. The two conductors (R and R1) are connected in series so that the voltages generated in them add together to deliver current to the switchboard. The rotating fields, although moving at constant speed, will cut the conductors at a changing rate because of the circular movement Voltage induced at any instant is proportional to the sine of the angle of the rotating vector. The pattern of build-up and decline, and also reversal in the voltage induced, is shown by the sine wave R.
Powermaster 17294 Alternators - PowerMaster 100 Amp AlternatorDelcochrome ,Quality-Built 14129 Premium Alternator - Remanufactured ,Powermaster 17127 Alternators - PowerMaster 65 Amp AlternatorChevychrome,MasterQuality 23156 Premium Remanufactured Alternator,Transformers Hasbro Alternators Optimus Prime Dodge Ram SRT-10

Voltage and current are generated in each of the pairs of conductors in turn—first in one direction and then in the other—to produce three-phase alternating current. The effect in conductors Y and B is also shown.

Marine Engine Q &A-Electrical Emergency Electrical power

2010-06-12T19:51:00.000-07:00

Emergency Electrical Power Cobra CPI 1575 1500 Watt 12 Volt DC to 120 Volt AC Power Inverterfor Passenger and General cargo Vessel.

General cargo Vessel

In all Passenger and cargo vessels a number of essential services must be able to be maintained under emergency conditions. The requirements vary with type of ship and length of voyage. Self- contained emergency sources- of -electrical power must be installed in positions such that they are unlikely to be damaged or affected by any incident which has caused the loss of main power. The emergency generator with its Switchboard is thus located in a compartment which is outside of and away from main and auxiliary machinery spaces above the uppermost continuous deck and not forward of the collision bulkhead The same ruling a lies to batteries with the exception that accumulator batteries must not be fitted in the same space as any emergency Switchboard.

An emergency source of power should be capable of operating with a list of up to 22½º and a trim of up to 10°. The compartment should be accessible from the open deck

Passenger Vessels

Emergency generators for passenger vessels are now required to be automatically started and connected within 45 seconds. A set of automatically connected emergency batteries capable of carrying certain essential items for thirty minutes. is also required. Alternatively, batteries are permitted as the main emergency source of power.

Regulations specify the supply of emergency power to essential services on passenger ships for a period of up to36 hours. A shorter period is allowed in vessels such as ferries. Some of the essential services may be .operated by other than electrical means (such as hydraulically controlled watertight doors), others may have their own electrical power. If the batteries are the only source of power the must sup the emergency load without recharging or excessive voltage drop (12% limit) or the required length of time. Because the specified period is up to 36 hours, batteries are used normally as a temporary power source with the emergency generator taking over essential supplies when it starts.Ship Passenger Lists: National and New England (1600-1825)

Batteries fitted to provide temporary or transitional power supply emergency lights, navigation lights, and watertight door circuits including alarms and indicators, and internal communication systems. In addition they could Supply fire detection and alarm installations, manual fire alarms, fire door release, gear, internal signals, ships whistle and daylight signalling lamp. But some of these will have their own power or take it from a low-pressure D.C. system. Sequential watertight door closure by transitional batteries is acceptable.

The emergency generator when started supplies essential services through its own switchboard including the load taken initially by the transitional batteries. Additionally it would provide power for the-emergency bilge pump; fire pump, sprinkler pump steering gear .and other items if they were fed through the emergency switchboard-

Arrangements are required to enable lifts to be brought to deck level in an emergency. Also, emergency lighting from transitional batteries is required in all alleyways, stairs, exits, boat stations (deck and over side), control stations (bridge, radio room. engine control room, etc), machinery spaces and emergency machinery spaces.

Cargo Vessels

Emergency power for cargo ships is provided by accumulator battery or generator. Battery systems are automatically connected upon loss of the main supply, and in installations where the generator is not started and. connected within. 15 seconds automatically, are required as a transitional power source for at least 30 minutes.

Transactions, vol 32, 1924 (includes long article Cargo Vessels in the Great Lakes, as well as other items)The Port Montrea Cargo Vessel, September 2965 Framed Art Poster Print by Mirrorpix, 31x25 Deadly Cargo ,The Life of a Ship,Altamont The Vessel Board Short,Shorts for Men, 30,Black Acid Wash

Power available for emergencies must be sufficient to operate certain essential services simultaneously for up to18 hours. These are :emergency lights , navigation lights, internal communication equipment, daylight signalling lamp, ship’s whistle fire detection alarm installations, manual fire alarms; other internal emergency signals, the emergency fire pump, steering gear, navigation aids and other equipment Some essential services have their own power or are supplied from a low-pressure d.c. system. .

Transitional batteries are required to supply for 30 minutes power for emergency lighting, general alarm, fire detection and alarm system; communication equipment and navigation lights.

Permanent Passenger: My Life on a Cruise Ship

Passenger Ship Technology

And the Ship sails On - Criterion Collection

Marine Engine Q &A-Electrical Emergency Generator

2010-06-11T12:14:00.000-07:00

Emergency Generator
There a number of ways in .which emergency power Black & Decker SS50B Storm Station With 50 Watt Power Inverter LED Flashlight And Digital AM/FM NOAA Weather Radio Duracell DPP-600HD Powerpack 600 Jump Starter & Emergency Power Source with Radio Black & Decker SS50B Storm Station With 50 Watt Power Inverter LED Flashlight And Digital AM/FM NOAA Weather Radio Duracell DPP-600HD Powerpack 600 Jump Starter & Emergency Power Source with Radio Wagan 400-Watt Power Dome EX Jumpstarter with Built-In Air Compressor can be supplied. The arrangement shown in Fig. 1.7 incorporates some common features.
The emergency switchboard has two sections, one operating at 440 volts and the other at 220 volts. The 440 volt supply, under circumstances, is taken from the main engine room switchboard through a circuit breaker A. Loss of main power this breaker to be tripped and the supply is taken over by the emergency generator when started through a An interlock prevents simultaneous closure of both breakers.
A special feeder is sometimes fitted so that in a dead- ship situation the emergency generator can be connected to the main switchboard. This special condition breaker would only be closed engine room board was cleared of all load. i.e. all distribution were open. Selected machinery within the capacity of the emergency generator could then be operated to restore power, at which stage the special breaker would be disconnected.
The essential services supplied from the 440 volt section of the emergency board depicted include the emergency bilge pump, the sprinkler pump and compressor, one of two steering gear circuits(the other being from the main board), and a 440/220 volt three-phase transformer through which the other section is fed.
Circuits supplied from the 220. volt section include those for navigation equipment, radio communication and the transformed and rectified supplies systems Separate sets of batteries are fitted for temporary emergency power and for a low pressure The former automatically supply emergency lights and other services not connected to the low-pressure tem Batteries for the radio are not shown.
The switchboard and generator for emergency power supply installed in one compartment which may be heated for starting in cold conditions. The independent and approved method of automatic starting (compressed air, batteries or hydraulic) should have the capacity for repeated attempts. And a secondary arrangement such that further attempts can be made within the 30 minute temporary battery lifetime.
The emergency generator is provided with an adequate and Independent supply of fuel with a flash point of not Less than 43ºC(110ºF).

Marine Engine Q & A-Electrical Battery Installations and Safety Measures

2010-06-11T09:46:00.000-07:00

Battery Installations and Safety Measures
The explosion risk in battery compartments is lessened by (1) ensuring good ventilation so that the hydrogen cannot accumulate, and (2) by taking precautions to ensure that there is source of ignition.
ventilation outlets are arranged at the top of any battery compartment where the lighter-than-air hydrogen tends to accumulate vent is other than direct to the outside an exhaust fan is required, and in any case would be used fore large installation The fan is in the air stream from the compartment and the blades must be a material which will not cause sparks from contact or electrostatic discharge. The motor must be outside of the ventilation passage with sea is to prevent entry of gas to its casting. The exhaust fan must be independent of other ventilation systems. All outlet vent ducts are of corrosion-resistant material or protected by suitable paint
Ventilation inlets should be below battery level with these and all openings, consideration should be given to weatherproofing.
The use of naked lights, and smoking, are prohibited in battery rooms and notices are required to this effect The notices should ed up by verbal warnings because the presence of dangerous gas is not obvious. Gas risk is highest during charging ventilation is reduced
Working on batteries there is always the risk of shorting ions and causing an arc by accidentally dropping metal tools across terminals. (Metals jugs are not used as distilled water containers for this reason.) Cables must be of adequate size and connections well made.
Emergency switchboards are not placed in the battery space because of the risk of arcing the precaution is extended to include any non-safe electrical equipment, battery testers, switches, fuses and cables other than those for the battery connections. Externally fitted lights and cables are recommended, with illumination of the space through glass ports in the sides or deck head. Alternately flameproof light fittings are permitted.
Ideal temperature conditions are in the range from 1 5°C to 25°C . Battery life is shortened by temperature rises above 50°C, and capacity is reduced by low temperaturesProfessional Car Battery Installation Tool - Terminal Spreader & Cleaner

Marine Engine Q &A-Electrical Standby Emergency Batteries

2010-06-11T09:40:00.000-07:00

Standby Emergency Batteries
Emergency power or temporary emergency power can be provided by automatic connection of a battery at loss of main power. A simple arrangement is shown (Fig. 1.6) for lead-acid batteries. This type of secondary cell loses charge gradually over a period of time. Rate of loss is kept to a minimum by maintaining the cells in a clean and it is necessary to make up the loss of charge: The system Shown has a trickle charge
In normal circumstances the batteries are on Standby with load switches (L) open and charging switches (C) closed. This position of the switches is held by the electromagnetic coil against pressure of the spring. Loss of main power has the effect of de-energizing the coil so that the switches are changed by spring pressure moving the operating rod. The batteries are disconnected from the mains as switch C opens, and connected to the emergency load by closing of L.
Black & Decker SS50B Storm Station With 50 Watt Power Inverter LED Flashlight And Digital AM/FM NOAA Weather Radio

Marine Engine Q & A- Electrical-Nickel-Cadmium Battery charging-From DC Main & From AC main

2010-06-11T02:49:00.000-07:00

Nickel-hydrogen battery state of charge during low rate trickle charging (SuDoc NAS 1.26:201115)Nickel-hydrogen battery state of charge during low rate trickle charging (SuDoc NAS 1.26:201115)

Battery Charging

From DC Mains

The circuit for charging from D.C. mains includes a resistance connected in series, to reduce the current flow from the higher mains voltage A simple charging circuit is shown in Fig. 1.4. Feedback from the battery on charge is prevented, at mains failure, by the relay (is de-energized) and spring, arranged to automatically disconnect the battery. The contacts are spring operated; gravity opening is not acceptable for marine installations.

Charging from AC Mains

Mains ac. voltage is reduced by transformer to a suitable figure and then rectified to give a direct current for charging. The supply current may be taken from the 230 volt section and changed to say 30 volts for charging 24 volt battery Various transformer/rectifier circuits are described in Chapter 2 and any of these could be used (i.e. a single diode and half-wave rectification, two or four diodes or full-wave rectification, or a three-phase six diode circuit). Smoothing is not essential battery incorporated for power supplies to low-pressure D.C. systems with standby batteries for systems with batteries on float.

Marine Engine Q & A- Electrical-sealed Nickel-Cadmium Batterries

2010-06-11T02:32:00.000-07:00

Sealed Nickel-Cadmium Batteries
Gassing occurs as a conventional battery approaches full charge, and increases during any overcharge due to electrolysis of water in the electrolyte by the current supplied but no longer being used in charging. The gas is released through the vent to prevent pressure build-up and this loss together with loss from evaporation makes topping UP necessary. While on charge, the active material of the plates is being changed, but when the change is complete and no further convertible material remains, the electrical charging energy starts to break down the electrolyte. Oxygen is evolved at the positive plates and hydrogen at the negative
Sealed batteries (Fig. 1.3) are designed to be maintenance-free and although developed from and having a similar chemical reaction to the open type, will not lose water through gassing or evaporation. The seal stops loss by evaporation and gassing is inhabited by modification of the plates.
Sealed cells are made with surplus cadmium hydroxide in the negative plate so that it is only partially charged when the positive plate is fully charged. Oxygen is produced by the charging current at the positive plate (40H ˉ2Hˉ2O+4eˉ+O2) but no hydrogen is generated at the negative because some active material remains available for conversion. Further, the oxygen from the positive side is reduced with water at the negative plate (2Hˉ2O+4eˉ+O2 40H ˉ) so replacing the hydroxyl ions used in the previous action. The process leaves the electrolyte quantity unaffected. The hydroxyl ions acting as current carriers within the cell travel to the positive electrode.
Sealed batteries will accept overcharge at a limited rate indefinitely without pressure rise. Charging equipment is therefore matched for continuous charging at low current or fast charging used with automatic cut-out to prevent excessive rise of pressure and temperature. Rise of pressure temp and voltage all occur as batteries reach the overcharge area but the last two are most used as signals terminate the full charge.

Determination of copper, cadmium and lead in seawater and mineral water by flame atomic absorption spectrometry after coprecipitation with aluminum hydroxide [An article from: Analytica Chimica Acta]

Marine Engine Q & A- Electrical-Nickel-Cadmium Battery Plates

2010-06-11T02:29:00.000-07:00

Plates
The active materials for nickel-cadmium cells are improved by additions of other substances. Positive plates carry a paste made up initially of nickel hydroxide with a small percentage of other hydroxides to improve capacity and 20% graphite for better conductivity. The material is brought to the charged state by passing a current through it, which changes the nickel hydroxide to hydrated nickel oxide NiO(OH). Performance of cadmium in the negative plates is improved by addition of 25% iron plus small quantities of nickel and graphite.
Active materials may be held in pocket or sintered plates former are made up from nickel plated mild steel strip shaped to form an enclosing pocket The pockets are interlocked at their crimped edges and held in a frame. Electrolyte reaches the active materials through perforations in the pockets.
Sintered plates are produced by heating (to 900°C) powdered nickel which has been mixed with a gas-forming powder and pressed into a grid or perforated plate. The process forms a plate which is 75% porous. Active materials are introduced into these voids

Marine Engine Q & A- Electrical-Nickel-Cadmium Battery Gassing, Topping up,

2010-06-11T02:26:00.000-07:00

Gassing
The gases evolved during charging are oxygen (at the positive plates; and hydrogen (at the negative plates). Rate of production of gas increases in periods of overcharge. When hydrogen reaches a proportion of about 4% and up to 74% it constitutes an explosive mixture. Good ventilation of battery compartments is therefore necessary to remove gas. Equipment likely to cause sparking or arcing must not be located or introduced into battery spaces. Vent caps are non-return valves, as shown diagrammatically (Fig. 1.2) so that gas is released but contact by the electrolyte with the atmosphere is prevented. The electrolyte readily absorbs carbon dioxide from the atmosphere and deterioration results because of the formation of potassium carbonate. For this reason, cell vent caps must be kept closed
Topping Up
Gassing is a consequence of the breakdown of water in the electrolyte. This together with a certain amount of evaporation means that topping up with distilled water will be necessary from time to time. High consumption of distilled water would suggest overcharging.
Electrolyte
Potassium hydroxide solution is strongly alkaline and the physical and chemical properties of potassium hydroxide closely resemble those of caustic soda (sodium hydroxide). It is corrosive, so care is essential when topping up batteries or handling the electrolyte. In the event at skin or eye contact the remedy is to wash with plenty of clean water (for 15 minutes) to dilute and remove the solution quickly. Speed is vital to prevent burn damage; and water, which is the best flushing agent, must be readily available. Neutralizing compounds (usually weak acids) cannot always be located easily, although they should be available in battery compartments.
Specific of electrolyte in a Ni-Cd cell is about 1.210 and this does not change with charge and discharge as in lead-acid cells. However, over a period of time the strength f. the solution will gradually drop and renewal is necessary at about a specific gravity of 1.170

Containers
The electrolyte slowly attacks glass and various other materials. Containers are therefore of welded sheet t which is then nickel plated or moulded in high-impact polystyrene casings are preferred when batteries are subject to shock and vibration. Hardwood crates are used to keep the cells separate from each 2t and from the support beneath. Separation is necessary cause the positive plate assembly is connected to the steel casing.

Marine Engine Q & A- Electrical-Nickel Battery Discharging & charging action

2010-06-10T06:29:00.001-07:00

Discharge Action.

During discharge the complicated but uncertain action at the positive plates (hydrated oxide of nickel) cause’s hydroxyl ions (OHˉ) to be introduced into the electrolyte. As the action progresses the nickel hydrate is changed to nickel hydroxide. .Simultaneously, hydroxyl ions (OHˉ) from the electrolyte form cadmium hydroxide with the cadmium of the negative plates. Effectively, the hydroxyl ions (OHˉ) move from one set of plates to the other, leaving the electrolyte unchanged. There is no significant change in specific gravity through the discharge/charge cycle and the state of charge be found sing a hydrometer

Charging

A direct current supply for charging is obtained from ac. mains, through the transformer and rectifier in the battery charger. The positive of the charging supply is connected to the positive at the cell, and negative to the negative terminal. Flow of current from the charging source reverses the discharge action. The reactions are complicated but can be summarized by the simplified equation:

Marine Engine Q & A- Electrical-Nickel-Cadmium Storage Batteries

2010-06-10T06:05:00.000-07:00

Nickel-Cadmium Storage Batteries
The active materials of positive and negative plates In each cell of a charged nickel-cadmium battery (Fig 1.2) are nickel hydrate and cadmium, respectively. The chemicals are retained in the supporting structure of perforated metal plates and the design is such as to give maximum contact between active compounds and the electrolyte.

The strong alkaline electrolyte is a solution of potassium hydroxide in distilled water (with an addition of lithium). The ions produced in the formation of the potassium hydroxide solution (K+ and OHˉ) act as current carriers and take part in an ion transfer.

Marine Engine Q & A- Electrical-Plate Construction,Electrolyte

2010-06-10T05:55:00.000-07:00

Describe the plate construction of lead-acid battery.
Describe the eletrolyte reaction of lead-acid battery.

Plate Construction
A lead-acid battery is made up of a number of cells each with a nominal voltage of 2 volts Thus three cells separated by divisions ii common casing and connected in series make up a 6 volt battery, and six cells arranged in the same way make a 12 volt battery. Each cell has, say, seven positive and eight negative plates which are interleaved and arranged alternately positive and negative. Common practice is to have both end plates negative. Plates are prevented from touching by porous separators of insulating plastic; the design of the plates is such as to give the greatest possible surface area, adequate strength and good conductivity. The porous paste active material extends plate area to give maxi mum contact between active material and the electrolyte, and therefore good capacity. The oxide paste has little strength and is a poor conductor of so the deficiencies are made by a lead-antimony grid into which the taste is pressed.

Electrolyte
Sulphuric acid used to make .electrolyte for lead-acid batteries is, in its concentrated form. a non-conductor of electricity. In solution with water it becomes an electrolyte because of the break down of the H molecules into hydrogen (H+) ions and sulphate (SOˉ ˉ) ions as current carriers in the liquid.
Concentrated sulphuric acid has a great affinity for water and this, together with the heat evolved when they-come Into contact makes the production of electrolyte hazardous. A violent reaction results if water is added to concentrated sulphuric acid. Successful safe mixing is only possible if the acid is very slowly added to pure water while stirring .Normal the electrolyte is supplied ready for use in acid-resistant container.
Electrolyte is strongly corrosive and will damage the skin as well as materials such as paint wood, cloth, etc. on which it may spill it is recommended that electrolyte on the skin be removed by washing thoroughly (for 15 minutes) with water . Acid resisting paint must be used on battery room decks.

Marine Engine Q & A- Electrical-Gas Emission,Topping up

2010-06-10T05:49:00.000-07:00

Gas Emission
Towards the end of charging and during overcharge, the current wing into the cell causes a breakdown or electrolysis of water in electrolyte shown by bubbles at the surface. Both hydrogen and oxygen are evolved and released through cell vent caps into battery compartment. There is an explosion risk if hydrogen is allowed to accumulate (flammable range is 4% to 74% of hydrogen air). Thus regulations require good ventilation to remove gas and precautions against naked lights or sparks in enclosed battery compartments (see below)
Topping up
Batteries suffer water loss due to both gassing and evaporation, with consequent drop in liquid level There is no loss of sulphuric acid from the electrolyte (unless through spillage) checks are made to ensure that liquid level s above the top of the plates and distilled water is added as necessary. Overfilling will cause the electrolyte to bubble out of the vent.

Marine Engine Q & A- Electrical-Battery charging action

2010-06-10T05:46:00.000-07:00

Lead acid Battery Charging procedure-
To charge lead-acid batteries, the cell is disconnected from the load id connected to a D.C. charging supply of the correct voltage. The positive of the charging supply is connected to the positive side of cell, and the negative of the .charging supply to the negative of a cell. Flow of current from the charging source reverses the discharge action of the cell: thus lead sulphate on the plates is broken down. The sulphate goes back into Solution as sulphate ions (SO4ˉˉ) leaving the plates as pure lead. Water in the electrolyte breaks down returning hydrogen ions (H+) to the solution and allows the oxygen to recombine with the lead of the positive plate and form lead peroxide (PbO2).

Marine Engine Q & A- Electrical-Battery Discharge

2010-06-10T05:41:00.000-07:00

Discharge Action
During discharge, he hydrogen ions (H+) remove oxygen from the lead peroxide (PbO2) of the positive plates and combine with it to form water (H2O). Loss of oxygen from the lead peroxide reduces it grey lead (Pb). The water formed by the action c the electrolyte so that as the cell discharges, the specific gravity (relative density) decreases Measurement of the specific gravity change with a hydrometer will show the state of charge of the cell.
At the negative side of the cell, sulphate ions (SO4ˉˉ) combine with the pure lead of the negative plates to form a layer of white lead sulphate (PbSO4) The lead sulphate layer increases during discharge and finally covers the active material of the plate so that further reaction is stifled. Some sulphate also forms on the positive plates but this is not a direct part of the discharge reaction.
A fully charged cell will be capable of producing 1.95 volts ad and the relative density of the .electrolyte will be at a maximum (say 1.280) After a period of discharge the electrolyte will be weak due to formation of water and the plates will be sulphated, with the result that the voltage on load will .drop .Recharging is required when voltage on load drops to say 1.8 volts per cell and the relative density is reduced to about 1.1 20.

Marine Engine Q & A- Electrical

2010-06-10T05:32:00.000-07:00

Batteries and Emergency Systems

Lead-Acid Storage Batteries
Each cell of a lead-acid battery contains two interleaved sets of plates, immersed in electrolyte. Those connected to the positive terminal of a charged cell are of lead peroxide: those connected to the negative terminal are of lead The simple sketch used here to explain the discharge and recharge has only one plate of each type (Fig. 1.1).
The electrolyte in which the plates are immersed is a dilute .solution of sulphuric acid in distilled characteristic of electrolytes Is that they, contain ions of the compounds dissolved in them which can act as current carriers. In this solution, the ions are provided by sulphuric acid (H2SO4) molecules, which split into positively charged hydrogen ions (H+) and negatively charged sulphate ions (SO4ˉˉ). The separated parts of the molecule are electrically unbalanced because the split leaves sulphate ion with extra (negative) electrons, and hydrogen ions with an overall positive charge due to the loss of electrons.

MARINE ENGINE Q&A-MAIN ENGINE SAFETY GUIDE

2010-06-09T10:44:00.000-07:00

Q: The purpose of Safety guide which definitions are generally followed in Marine Ship(Tanker).

p-2
• Resuscitator: Equipment to assist or restore the breathing of a man overcome by gas or lack of oxygen.
• Spontaneous combustion: The ignition of materials brought about by a heat producing (exothermic ) chemical reaction within the material itself without exposure to an external source of ignition.
• Stripping : The final operation in pumping bulk liquid from a tank or pipe line.
• Reid vapour pressure: (RVP) The vapour pressure of a liquid determined in a standard manner in the Reid apparatus at a temperature of 37.8oc and with a ratio of gas to liquid volume of 4:1
• Insulating Flange: A flanged joint incorporating an insulating gasket, sleeves and washer to prevent electrical continuity between pipelines, hose strings or loading arms.
• Interface detector: An electrical instrument for detecting the boundary between oil and water.
• Petroleum: Crude oil and liquid hydrocarbon products derived from it.
• Petroleum gas: a gas evolved from petroleum. The main constituents of petroleum gases are hydrocarbons, but they may also contain other substances such as hydrogen sulphide or lead alkalies, as minor constituents.

MARINE ENGINE Q&A-MAIN ENGINE SAFETY GUIDE

2010-06-06T23:22:00.000-07:00

Q: The purpose of Safety guide which definitions are generally followed in Marine Ship(Tanker).

p-1

A: The following definitions are applied to Marine Ship (Oil & Chemical Tanker).

• Antistatic additive: A substance added to a petroleum product to raise its electrical conductivity above 100 pico siemens/metre to prevent accumulation of static electricity.
• Bonding: The connecting together of metal parts to ensure electrical continuity.
• Clingage: Oil remaining on the walls of a pipe or on the surfaces of tank interiors after the bulk of the oil has been removed.
• Cold Work: Work which can not create a source of ignition.
• Cathodic Protection: The prevention of corrosion by electro chemical techniques. On tankers it may be applied either externally to the hull or internally to the surfaces of tanks. At terminals, it is frequently applied to steel piles and fender panels.
• Entry permit:A document issued by a responsible officer permitting entry to a space or compartment during specific time interval.
• Flash Point: The lowest temperature at which a liquid gives off sufficient gas to form a flammable gas misture near the surface of the liquid.
• Inert Condition: A condition in which the oxygen content throughout the atmosphere of a tank has been reduced to 8 percent or less by volume by addition of inert gas.
• Inert Gas: A gas or a mixture of gases, such as flue gas, containing insufficient oxygen to support the combustion of hydrocarbon.
• Gas free: A tank, compartment or container is gas free when sufficient fresh air has been introduced into it to lower the level of any flammable, toxic, or inert gas to that required for a specific purpose, e.g. hot work,entry etc.
• Gas free certificate: A certificate issued by an authorized responsible officer confirming that at the time of testing a tank, compartment or container it was gas free for specific purpose.
• Pour point: The lowest temperature at which a petroleum oil will remain fluid.
• Toxic: Poisonous to human life.
• Topping off: The operation of completing the loading of a tank to a required ullage.
• Topping up: The introduction of inert gas into a tank which is already in the inert condition with the object of raising the tank pressure to prevent any ingress of air.

MARINE ENGINE Q&A-MAIN ENGINE EXHAUST VALVE

2010-06-05T21:56:00.000-07:00

Q: 1 Explain the operation of a main engine Exhaust valve which is operated hydraulically?

A: A hydraulic pump, operated by the exhaust cam supplies the hydraulic oil to operate the valve. A small permanent vent ensures that air is excluded fro the system. This leak off of oil returned to the air spring cylinder for lubrication and is then drained away. The hydraulic pump is supplied with a make up supply via a non return valve and a relief valve.
As the cam rotates in time with the crankshaft it lifts the plunger on the hydraulic pump. Oil displaced by the pump plunger displaces the exhaust valve operating piston, moving it and the exhaust valve spindle downwards against the air spring pressure and opening the exhaust valve.
The exhaust gas passes over the spinner, rotating the exhaust valve spindle, this reduces distortion due to uneven temperatures and helps remove deposits as the valve closes .when the cam passes its peak, the pump plunger moves downwards and the compressed air in the air spring closes the valve. As the operating piston enters the damping pin, the closing is slowed, thus preventing hammering of the valve.

MARINE ENGINE Q&A-BEARING

2010-06-05T21:20:00.000-07:00

Q:1 Explain how effective lubrication of the top end bearing is achieved.

A: The crosshead on a slow speed two stroke engine is very difficult to lubricate bearing effectively.The load is continually downward and because the connecting rod(con rod) swings about the pin, Changing direction each stroke, so true hydrodynamic lubrication cannot take place.Instead the lubrication starts as boundary and as the rubbing speed increases, a hydrodynamic film is built up.As the rubbing speed decreases the lubrication becomes boundary once again Oil supplied to the crosshead can be boosted in pressure to help with effective lubrication. A large pin diameter gives increased rubbing speeds, allowing the oil wedge to be built up as soon as possible.

Marine Engine-Q & A - Piston

2010-06-04T18:36:00.000-07:00

Q: What are the faults in Marine engine Piston?
A:
1. Cracking:Cracking in piston occur in piston crown and mainly in upper piston wall.
2. Burning: Burns in piston are found in piston crown to surface.
3. Scaling:   Scaling in piston is found in piston cooling chamber and passage.
4. Steeping : Steeping in piston occurs in edges of piston ring grooves.
5. Wear :   Wear occurs mainly in wear ring, piston skirt and side wall.
6. Hot Corrosion: Hot corrosion on piston occurs mainly in the crown and the acidic corrosion occurs mainly
under crown