Alternating current motors

Supplying alternating current to a coil which is free to rotate in a magnetic field will not produce a motor effect since the current is constantly changing direction Use is therefore made in an induction or squirrel cage motor of a rotating magnetic field produced by three separately phased windings in the stator. The rotor has a series of copper conductors along its axis which are joined by rings at the ends to form a cage. When the motor is started the rotating magnetic field induces an...

Batteries

The battery is a convenient means of storing electricity. It is used on many ships as an instantly available emergency supply. It may also be used on a regular basis to provide a low-voltage d.c. supply to certain equipment. To provide these services the appropriate size and type of battery must be used and should be regularly serviced. Two main types of battery are used on board ship the lead-acid and the alkaline type, together with various circuits and control gear. The lead acid battery is...

Boiler operation

The procedure adopted for raising steam will vary from boiler to boiler and the manufacturers' instructions should always be followed. A number of aspects are common to all boilers and a general procedure might be as follows. The uptakes should be checked to ensure a clear path for the exhaust gases through the boiler any dampers should be operated and then correctly positioned. All vents, alarm, water and pressure gauge connections should be opened. The superheater circulating valves or drains...

Bow thruster

The bow thruster is a propulsion device fitted to certain types of ships to improve manoeuvrability. The thrust unit consists of a propeller mounted in an athwartships tunnel and provided with some auxiliary drive such as an electric or hydraulic motor. During operation water is forced through the tunnel to push the ship sideways either to port or starboard as required. The unit is normally bridge controlled and is most effective when the vessel is stationary. A controllable-pitch type thruster...

Centralised control

The automatic control concept, correctly developed, results in the centralising of control and supervisory functions. All ships have some degree of automation and instrumentation which is centred around a console. Modern installations have machinery control rooms where the monitoring of control functions takes place. The use of a separate room in the machinery space enables careful climate control of the space for the dual benefit of the instruments and the engineer. Control consoles are...

Combustion

Combustion is the burning of fuel in air in order to release heat energy. For complete and efficient combustion the correct quantities of fuel and air must be supplied to the furnace and ignited. About 14 times as much air as fuel is required for complete combustion. The air and fuel must be intimately mixed and a small percentage of excess air is usually supplied to ensure that all the fuel is burnt. When the air supply is insufficient the fuel is not completely burnt and black exhaust gases...

Common metals and alloys

Some of the more common metals met in engineering will now be briefly described. Most metals are alloyed in order to combine the better qualities of the constituents and sometimes to obtain properties that none of them alone possesses. The various properties, composition and uses of some common engineering materials are given in Table 16.1. Steel is an alloy of carbon and iron. Various other metals are alloyed to steel in order to improve the properties, reduce the heat treatment necessary and...

Common rail system

The common rail system has one high-pressure multiple plunger fuel pump (Figure 2.14). The fuel is discharged into a manifold or rail which is maintained at high pressure. From this common rail fuel is supplied to all the injectors in the various cylinders. Between the rail and the injector or injectors for a particular cylinder is a timing valve which determines the timing and extent of fuel delivery. Spill valves are connected to the manifold or rail to release excess pressure and accumulator...

Controllers

The controller may be located close to the variable measuring point and thus operate without the use of a transmitter. It may however be located in a remote control room and receive a signal from a transmitter and relay, as mentioned earlier. The controller is required to maintain some system variable at a desired value regardless of load changes. It may also indicate the system variable and enable the desired value to be changed. Over a short range about the desired value the controller will...

Correcting unit

The controller output signal is fed to the correcting unit which then alters some variable in order to return the system to its desired value This correcting unit may be a valve, a motor, a damper or louvre for a fan or an electric contactor. Most marine control applications will involve the actuation or operation of valves in order to regulate liquid flow. A typical pneumatic control valve is shown in Figure 15.34. It can be considered as made up of two parts the actuator and the valve. In the...

Corrosion

Corrosion is the wasting of metals by chemical or electrochemical reactions with their surroundings. A knowledge of the various processes or situations in which corrosion occurs will enable at least a slowing down of the material wastage. Iron and steel corrode in an attempt to return to their stable oxide form. This oxidising, or 'rusting' as it is called, will take place wherever steel is exposed to oxygen and moisture. Unfortunately the metal oxide formed permits the reaction to continue...

Cylinder lubrication

Large slow-speed diesel engines are provided with a separate lubrication system for the cylinder liners. Oil is injected between the liner and the piston by mechanical lubricators which supply their individual cylinder. A special type of oil is used which is not recovered. As well as lubricating, it assists in forming a gas seal and contains additives which clean the cylinder liner. Cooling of engines is achieved by circulating a cooling liquid around internal passages within the engine. The...

D

Turbo Diesel Diesel alternator alternator alternator Turbo Diesel Diesel alternator alternator alternator Figure 14.8 A.C. distribution system In the distribution system there will be circuit breakers and fuses, as mentioned previously for d.c. distribution systems. Equipment for a.c. systems is smaller and lighter because of the higher voltage and therefore lower currents. Miniature circuit breakers are used for currents up to about 100 A and act as a fuse and a circuit breaker. The device...

Direct current generators

A current is produced when a single coil of wire is rotated in a magnetic field. When the current is collected using a ring which is split into two halves (a commutator), a direct or single direction current is produced. The current produced may be increased by the use of many turns of wire and additional magnetic fields. With many coils connected to the commutator, sparking will occur as the current collecting brushes move across the insulated segments. Commutating poles or interpoles are used...

Electrical equipment

The complete electrical plant on board ship is made up of power generation equipment, a distribution system and the many power utilising devices. Electricity is used for the motor drive of many auxiliaries and also for deck machinery, lighting, ventilation and air conditioning equipment. A constant supply of electricity is essential for safe ship and machinery operation, and therefore standby or additional capacity is necessary together with emergency supply equipment. Emergency equipment may...

Electrical operation

Early installations used d.c. supply with resistances in series to provide speed control (see Chapter 14). This inefficient power-wasting method was one possibility with d.c., but a better method was the use of Ward Leonard control. The high cost of all the equipment involved in Ward Leonard control and its maintenance is, however, a considerable disadvantage. Machines operated on an a.c. supply require a means of speed control with either pole-changing or slip-ring motors being used. Slip-ring...

Emergency generator supply

In the event of a main generating system failure an emergency supply of electricity is required for essential services. This can be supplied by batteries, but most merchant ships have an emergency generator. The unit is diesel driven and located outside of the machinery space (see Chapter 10, Emergency equipment). The emergency generator must be rated to provide power for the driving motors of the emergency bilge pump, fire pumps, steering gear, watertight doors and possibly fire fighting...

Engineering drawing

Most engineering items defy description in words alone. To effectively communicate details of engineering equipment a drawing is usually used. Even the simplest of sketches must conform to certain rules or standards to ensure a 'language* that can be readily understood. Some of these basic rules will now be described with the intention of enabling the production of a simple drawing for manufacturing or explanation purposes. A drawing produced as a piece of information or communication should...

Engineering terms

The system of measurement has been outlined with an introduction to SI units. Some of the common terms used in engineering measurement will now be described. Mass is the quantity of matter in a body and is proportional to the product of volume and density. The unit is the kilogram and the abbreviation used is 'kg'. Large quantities are often expressed in tonnes (t) where 1 tonne 10s kg. Acceleration or retardation of a mass results from an applied force. When unit mass is given unit...

Fire fighting strategy

Fighting a fire on board ship may amount to a life or death struggle to enter into such a conflict unprepared and unarmed is to invite failure. The 'armaments' or equipment available have been described. Now comes the matter of being prepared. A basic strategy should be followed in all fire fighting situations. This will involve four distinct aspects, which are locating, informing, containing and finally extinguishing a fire. A fire may be located by detection devices fitted in the various...

H

Figure A.S Conventional representation seen are then drawn out, as shown in Figure A.5. View 1 is called the 'front elevation'. View 2 is the 'end elevation' and is located to the right of the front elevation. View 3 is the 'plan' and is positioned below the front elevation. Sections are used to show the internal details of a part or an assembly as full lines. Section lines or hatching are used to indicate the different items which have in effect been cut. Each different item will have section...

Hydraulic systems

The open-loop circuit takes oil from the tank and pumps it into the hydraulic motor. A control valve is positioned in parallel with the motor. When it is open the motor is stationary when it is throttled or closed the motor will operate. The exhaust oil returns to the tank. This method can provide stepless control, i.e. smooth changes in motor speed. The live-line circuit, on the contrary, maintains a high pressure from which the control valve draws pressurised oil to the hydraulic motor (in...

Instrumentation and control

All machinery must operate within certain desired parameters. Instrumentation enables the parameters pressure, temperature, and so on to be measured or displayed against a scale. A means of control is also required in order to change or alter the displayed readings to meet particular requirements. Control must be manual, the opening or closing of a valve, or automatic, where a change in the system parameter results in actions which return the value to that desired without human involvement. The...

Iron and steel production

Iron and steel are the most widely used materials and a knowledge of their manufacture and properties is very useful. Making iron is the first stage in the production of steel. Iron ores are first prepared by crushing, screening and roasting with limestone and coke. The ore is thus concentrated and prepared for the blast furnace. A mixture of ore, coke and limestone is used to fill the blast furnace. Within the furnace an intense heat is generated as a result of the coke burning. Blasts of air...

Joining metals

Many larger items of engineering equipment are the result of combining or joining together smaller, easily produced items. Various joining methods exist, ranging from mechanical devices, such as rivets or nuts and bolts, to fusion welding of the two parts. It is not proposed to discuss riveting, which no longer has any large scale marine engineering applications, nor will nuts and bolts be mentioned, since these are well known in their various forms. Brazing and soldering are a means of joining...

WlAUVt

The fitting must be selected according to the variation in system temperatures and installed to permit the expansion and contraction required in the system. Drains are provided in pipelines and usually have small cocks to open or close them. It is essential that certain pipelines are drained regularly, particularly in steam systems. When steam is admitted to a pipeline containing a reasonable surface of water it will condense and a partial vacuum occur the water...

Material forming

In the production of engineering equipment various different processes are used to produce the assortment of component parts. These forming or shaping processes can be grouped as follows Casting is the use of molten metal poured into a mould of the desired shape. A wooden pattern, slightly larger in dimensions than the desired item, to allow for shrinkage, may be used to form a mould in sand. Entry and exit holes, the gate and riser, are provided for the metal in the sand mould. Alternatively a...

Material properties

The behaviour of a metal under various conditions of loading is often described by the use of certain terms Tensile strength. This is the main single criterion with reference to metals. It is a measure of the material's ability to withstand the loads upon it in service. Terms such as 'stress', 'strain', 'ultimate tensile strength', 'yield stress' and 'proof stress' are all different methods of quantifying the tensile strength of the material. Ductility. This is the ability of a material to...

Medium and slowspeed diesels

Medium-speed diesels, e.g. 250 to 750 rev min, and slow-speed diesels, e.g. 100 to 120 rev min, each have their various advantages and disadvantages for various duties on board ship. The slow-speed two-stroke cycle diesel is used for main propulsion units since it can be directly coupled to the propeller and shafting. It provides high powers, can burn low-grade fuels and has a high thermal efficiency. The cylinders and crankcase are isolated, which reduces contamination and permits the use of...

Mooring equipment

Winches with various arrangements of barrels are the usual mooring equipment used on board ships. A mooring winch is shown in Figure 10.1 where the various parts can be identified. The winch barrel or drum is used for hauling in or letting out the wires or ropes which will fasten the ship to the shore. The warp end is used when moving the ship using ropes or wires fastened to bollards ashore and wrapped around the warp end of the winch. The construction of a mooring winch will now be examined,...

Navigation lights

The supply to the navigation lights circuit must be maintained under all circumstances and special provisions are therefore made. To avoid any possibility of accidental open circuits the distribution board for the navigation lights supplies no other circuit. A changeover switch provides an alternative source of supply should the main supply fail. If the navigation lights fail, a visual or audible indication must be given. A navigation lights circuit is shown in Figure 14.15. Two sources ol...

Operating procedures

Medium- and slow-speed diesel engines will follow a fairly similar procedure for starting and manoeuvring. Where reversing gearboxes or controllable-pitch propellers are used then engine reversing is not necessary. A general procedure is now given for engine operation which details the main points in their correct sequence. Where a manufacturer's instruction book is available this should be consulted and used. 1. Before a large diesel is started it must be warmed through by circulating hot...

Periodic safety routines

In addition to watchkeeping and maintenance duties, various safety and emergency equipment must be periodically checked. As an example, the following inspections should take place at least weekly 1. Emergency generator should be started and run for a reasonable period. Fuel oil, lubricating oil and cooling water supplies and tank levels should be checked. 2. Emergency fire pump should be run and the deck fire mam operated for a reasonable period. All operating parameters should be checked. 3....

Preface to second edition

Progress has been made in many areas of marine engineering since the first edition of this book was published. A greater emphasis is now being placed on the cost-effective operation of ships. This has meant more fuel-efficient engines, less time in port and the need for greater equipment reliability, fewer engineers and more use of automatically operated machinery. The marine engineer is still, however, required to understand the working principles, construction and operation of all the...

Purity of boiler feedwater

Modern high-pressure, high-temperature boilers with their large steam output require very pure feedwater. Most 'pure' water will contain some dissolved salts which come out of solution on boiling. These salts then adhere to the heating surfaces as a scale and reduce heat transfer, which can result in local overheating and failure of the tubes. Other salts remain in solution and may produce acids which will attack the metal of the boiler. An excess of alkaline salts in a boiler, together with...

SI units

The metric system of units, which is intended to provide international unification of physical measurements and quantities, is referred to as SI units. There are three classes of units base, supplementary and derived. There are seven base units length metre (m) mass kilogram (kg) time sound (s) electric current ampere (A) temperature kelvin (K) luminous intensity candela (cd) and amount of substance mole (mol). There are two supplementary units plane angle radian (rad) solid angle steradian...

Starting air system

Diesel engines are started by supplying compressed air into the cylinders in the appropriate sequence for the required direction. A supply of compressed air is stored in air reservoirs or 'bottles' ready for immediate use. Up to 12 starts are possible with the stored quantity of compressed air. The starting air system usually has interlocks to prevent starting if everything is not in order. A starting air system is shown in Figure 2.21. Compressed air is supplied by air compressors to the air...

Steam turbines and gearing

The steam turbine has until recently been the first choice for very large power main propulsion units. Its advantages of little or no vibration, low weight, minimal space requirements and low maintenance costs are considerable. Furthermore a turbine can be provided for any power rating likely to be required for marine propulsion. However, the higher specific fuel consumption when compared with a diesel engine offsets these advantages, although refinements such as reheat have narrowed the gap....

Steering gear

The steering gear provides a movement of the rudder in response to a signal from the bridge. The total system may be considered made up of three parts, control equipment, a power unit and a transmission to the rudder stock. The control equipment conveys a signal of desired rudder angle from the bridge and activates the power unit and transmission system until the desired angle is reached. The power unit provides the force, when required and with immediate effect, to move the rudder to the...

Steering gear testing

Prior to a ship's departure from any port the steering gear should be tested to ensure satisfactory operation. These tests should include 1. Operation of the main steering gear. 2. Operation of the auxiliary steering gear or use of the second pump which acts as the auxiliary. 3. Operation of the remote control (telemotor) system or systems from the main bridge steering positions. 4. Operation of the steering gear using the emergency power supply. 5. The rudder angle indicator reading with...

The fourstroke engine

A cross-section of a four-stroke cycle engine is shown in Figure 2.6. The engine is made up of a piston which moves up and down in a cylinder which is covered at the top by a cylinder head. The fuel injector, through which fuel enters the cylinder, is located in the cylinder head. The inlet and exhaust valves are also housed in the cylinder head and held shut by springs. The piston is joined to the connecting rod by a gudgeon pin. The bottom end or big end of the connecting rod is joined to the...

The fuel injector

A typical fuel injector is shown in Figure 2.16, It can be seen to be two basic parts, the nozzle and the nozzle holder or body. The high-pressure fuel enters and travels down a passage in the body and then into a passage in the nozzle, ending finally in a chamber surrounding the needle valve. The needle valve is held closed on a mitred seat by an intermediate spindle and a spring in the injector body. The spring pressure, and hence the injector opening pressure, can be set by a compression nut...

Turbine types

There are two main types of turbine, the 'impulse' and the 'reaction'. The names refer to the type of force which acts on the blades to turn the turbine wheel. The impulse arrangement is made up of a ring of nozzles followed by a ring of blades. The high-pressure, high-energy steam is expanded in the nozzle to a lower-pressure, high-velocity jet of steam. This jet of steam is directed into the impulse blades and leaves in a different direction (Figure 3.2). The changing direction and therefore...

Turning gear

The turning gear or turning engine is a reversible electric motor which drives a worm gear which can be connected with the toothed flywheel to turn a large diesel. A slow-speed drive is thus provided to enable positioning of the engine parts for overhaul purposes. The turning gear is also used to turn the engine one or two revolutions prior to starting. This is a safety check to ensure that the engine is free to turn and that no water has collected in the cylinders. The indicator cocks must...

Watertight doors

Watertight doors are provided where an opening in a watertight bulkhead is essential. On cargo ships with a shaft tunnel, the entrance would have a watertight door fitted. All doors fitted below the waterline must be of the sliding type, arranged horizontally or vertically. A horizontal sliding watertight door is shown in Figure 10.9. The robust frame fits into the bulkhead and provides the trackway along which the door slides. The door is moved by a hydraulic cylinder which may be power or...

Auxiliary feed system

The arrangements for steam recovery from auxiliaries and ship services may form separate open or closed feed sysems or be a part of the main feed system. Where, for instance, steam-driven deck auxiliaries are in use, a separate auxiliary condenser operating at about atmospheric pressure will condense the incoming steam (Figure 5.3). An extraction pump will supply the condensate to an air ejector which will return the feedwater to the main system at a point between the gland steam condenser and...

Feed systems

The feed system completes the cycle between boiler and turbine to enable the exhausted steam to return to the boiler as feedwater. The feed system is made up of four basic items the boiler, the turbine, the condenser and the feed pump. The boiler produces steam which is supplied to the turbine and finally exhausted as low-energy steam to the condenser. The condenser condenses the steam to water (condensate) which is then pumped into the boiler by the feed pump. Other items are incorporated into...

Valvecontrolled pump

In the variable injection timing (VIT) pump used in MAN B& W engines the governor output shaft is the controlling parameter. Two linkages are actuated by the regulating shaft of the governor. The upper control linkage changes the injection timing by raising or lowering the plunger in relation to the cam. The lower linkage rotates the pump plunger and thus the helix in order to vary the pump output (Figure 2.13). In the Sulzer variable injection timing system the governor output is connected...

Helixtype injector pump

The injector pump is operated by a cam which drives the plunger up and down. The timing of the injection can be altered by raising or lowering the pump plunger in relation to the cam. The pump has a constant stroke and the amount of fuel delivered is regulated by rotating the pump plunger which has a specially arranged helical groove cut into it. The fuel is supplied to the pump through ports or openings at B (Figure 2.12). As the plunger moves down, fuel enters the cylinder. As the plunger...

Other boiler arrangements

Apart from straightforward watertube and firetube boilers, other steam raising equipment is in use, e.g. the steam-to-steam generator, the double evaporation boiler and various exhaust gas boiler arrangements. Steam-to-steam generators produce low-pressure saturated steam for domestic and other services. They are used in conjunction with watertube boilers to provide a secondary steam circuit which avoids any possible contamination of the primary-circuit feedwater. The arrangement may be...

Control and safety devices

The principal control device on any engine is the governor. It governs or controls the engine speed at some fixed value while power output changes to meet demand. This is achieved by the governor automatically adjusting the engine fuel pump settings to meet the desired load at the set speed. Governors for diesel engines are usually made up of two systems a speed sensing arrangement and a hydraulic unit which operates on the fuel pumps to change the engine power output. A flyweight assembly is...

Control theory

To control a device or system is to be able to adjust or vary the parameters which affect it. This can be achieved manually or automatically, depending upon the arrangements made in the system. All forms of control can be considered to act in a loop. The basic elements present in the loop are a detector, a comparator controller and a correcting unit, all of which surround the process and form the loop (Figure 15.24). This arrangement is an automatic closed loop if the elements are directly...

Suizer

The RTA72U is a single-acting, low-speed, two-stroke reversible marine diesel engine manufactured by New Suizer Diesel Ltd. It is one of the RTA series engines which were introduced in 1981 and in addition to a Geared camshaft drive from crankshaft through intermediate wheels Lost motion clutch Figure 2.27 Reversing arrangements Geared camshaft drive from crankshaft through intermediate wheels Lost motion clutch Figure 2.27 Reversing arrangements longer stroke than the earlier RL series, it has...

Gearing

Steam turbines operate at speeds up to 6000rev min. Medium-speed diesel engines operate up to about 750rev min. The best propeller speed for efficient operation is in the region of 80 to lOOrev min. The turbine or engine shaft speed is reduced to that of the propeller by the use of a system of gearing. Helical gears have been used for many years and remain a part of most systems of gearing. Epicyclic gears with their compact, lightweight, construction are being increasingly used in marine...

Temperature measurement

Temperature measurement by instruments will give a value in degrees Celsius ( C). This scale of measurement is normally used for all readings and temperature values required except when dealing with theoretical calculations involving the gas laws, when absolute values are required (see Appendix). Various liquids are used in this type of instrument, depending upon the temperature range, e.g. mercury 35 C to +350 C, alcohol 80 C to + 70 C. An increase in temperature causes the liquid to rise up...

Steam turbine

Twin cross-compounded steam turbines are used in the machinery layout of the container ship, shown in Figure 1.4. Only part plans and sections are given since there is a considerable degree of symmetry in the layout. Each turbine set drives, through a double reduction gearbox with separate thrust block, its own fixed-pitch propeller. The condensers are located beneath each low-pressure turbine and are arranged for scoop circulation at full power operation and axial pump circulation when...

Direct current motors

When a current is supplied to a single coil of wire in a magnetic field a force is created which rotates the coil. This is a similar situation to the generation of current by a coil moving in a magnetic field. In fact generators and motors are almost interchangeable, depending upon which two of magnetic field, current and motion are provided. Additional coils of wire and more magnetic fields produce a more efficient motor. Interpoles are fitted to reduce sparking but now have opposite polarity...

Open feed system

An open feed system for an auxiliary boiler is shown in Figure 5.1. The exhaust steam from the various services is condensed in the condenser. The condenser is circulated by sea water and may operate at atmospheric pressure or under a small amount of vacuum. The condensate then drains under the action of gravity to the hotwell and feed Filter tank. Where the condenser is under an amount of vacuum, extraction pumps will be used to transfer the condensate to the hotwell. The hotwell will also...

Jerk pump system

In the jerk pump system of fuel injection a separate injector pump exists for each cylinder. The injector pump is usually operated once every cycle by a cam on the camshaft. The barrel and plunger of the injector pump are dimensioned to suit the engine fuel requirements. Ports in the barrel and slots in the plunger or adjustable spill valves serve to regulate the fuel delivery (a more detailed explanation follows). Each injector pump supplies the injector or injectors for one cylinder. The...

Alternating current generators

A coil of wire rotating in a magnetic field produces a current. The current can be brought out to two sliprings which are insulated from the shaft. Carbon bushes rest on these rings as they rotate and collect the current for use in an external circuit. Current collected in this way will be alternating, that is, changing in direction and rising and falling in value. To increase the current produced, additional sets of poles may be introduced. The magnetic field is provided by electromagnets so...

Operation and maintenance

The responsibilities of the marine engineer are rarely confined to the machinery space. Different companies have different practices, but usually all shipboard machinery, with the exception of radio equipment, is maintained by the marine engineer. Electrical engineers may be carried on very large ships, but if not, the electrical equipment is also maintained by the engineer. A broad-based theoretical and practical training is therefore necessary for a marine engineer. He must be a mechanical,...

Allelectric steering

Steering gears which comprise electric control, electric power unit and electrical transmission, are of two types, the Ward-Leonard system and the Direct Single Motor system. Both types have a geared-down motor drive via a pinion to a toothed quadrant. A Ward-Leonard arrangement is shown diagrammatically in Figure 12.10. A continuously running motor-generator set has a directly coupled exciter to provide the field current of the generator. The Figure 12.9(a) Rotary vane steering gear Figure...

Air conditioning

Ships travel the world and are therefore subject to various climatic conditions. The crew of the ship must be provided with reasonable conditions in which to work regardless of the weather. Temperature alone is not a sufficient measure of conditions acceptable to the human body. Relative humidity in conjunction with temperature more truly determines the environment for human comfort. Relative humidity, expressed as a percentage, is the ratio of the water vapour pressure in the air tested, to...

Ships and machinery

As an introduction to marine engineering, we might reasonably begin by taking an overall look at the ship. The various duties of a marine engineer all relate to the operation of the ship in a safe, reliable, efficient and economic manner. The main propulsion machinery installed will influence the machinery layout and determine the equipment and auxiliaries installed. This will further determine the operational and maintenance requirements for the ship and thus the knowledge required and the...

Steam

With a steam powering and control system the steam pipelines are run along the deck to the various machines. Steam is admitted first to a directional valve and then to the steam admission valve. Double-acting steam engines, usually with two cylinders, are used to drive the machinery. Additional back pressure valves are used with mooring winches to control tension when the machine is stalled or brought to a stop by the load. Arrangements must also be made, often associated with the back pressure...

Anchor handling equipment

The windlass is the usual anchor handling device where one machine may be used to handle both anchors. A more recent development, particularly on larger vessels, is the split windlass where one machine is used for each anchor. One unit of a split windlass is shown in Figure 10.2. The rotating units consist of a cable lifter with shaped snugs to grip the anchor cable, a mooring drum for paying out or letting go of mooring wires and a warp end for warping duties. Each of these units may be...

Ward Leonard speed control system

As a very flexible, reliable means of motor speed control the Ward-Leonard system is unmatched. The system is made up of a driving motor which runs at almost constant speed and powers a d.c. generator (Figure 14.14). The generator output is fed to a d.c. motor. By varying the generator field current its output voltage will change. The speed of the controlled motor can thus be varied smoothly from zero to full speed. Since control Figure 14.14 Ward-Leonard speed control is achieved through the...

The twostroke engine

A cross-section of a two-stroke cycle engine is shown in Figure 2.7. The piston is solidly connected to a piston rod which is attached to a crosshead bearing at the other end. The top end of the connecting rod is Figure 2.7 Cross-section of a two-stroke diesel engine Figure 2.7 Cross-section of a two-stroke diesel engine also joined to the crosshead bearing. Ports are arranged in the cylinder liner for air inlet and a valve in the cylinder head enables the release of exhaust gases. The incoming...

Wplv t Thram

The control signal to a correcting unit may be pneumatic, electric or hydraulic. The actuating power may also be any one of these three and not necessarily the same as the control medium. Electrical control signals are usually of small voltage or current values which are unable to effect actuator movement. Pneumatic or hydraulic power would then be used for actuator operation. A separate pneumatic power supply may be used even when the control signal is pneumatic, as described in the previous...

The engine indicator

An engine indicator is shown in Figure 2.8. It is made up of a small piston of known size which operates in a cylinder against a specially Linkage to provide straight line movement of stylus Linkage to provide straight line movement of stylus Coupling nut to fasten onto indicator calibrated spring. A magnifying linkage transfers the piston movement to a drum on which is mounted a piece of paper or card. The drum oscillates (moves backwards and forwards) under the pull of the cord. The cord is...

Auxiliaries

Two Stage Air Compressor

Machinery, other than the main propulsion unit, is usually called 'auxiliary' even though without some auxiliaries the main machinery-would not operate for long. The items considered are air compressors, heat exchangers, distillation equipment, oil water separators, sewage treatment plants and incinerators. Compressed air has many uses on board ship, ranging from diesel engine starting to the cleaning of machinery during maintenance. The air pressures of 25 bar or more are usually provided in...

Nonmetallic materials

Many non-metallic materials are in general use. Their improved properties have resulted in their replacing conventional metals for many applications. The majority are organic, being produced either synthetically or from naturally occurring material. Ceramics are being increasingly considered for marine use particularly where galvanic corrosion is a problem. Sintered alpha silicon carbide and other silicon-based ceramics have good strength properties and are inert in sea water. The general term...

Testing of materials

Various tests are performed on materials in order to quantify their properties and determine their suitability for various engineering applications. For measurement purposes a number of terms are used, with 'stress' and 'strain' being the most common. Stress, or more correctly 'intensity of stress', is the force acting on a unit area of the material. Strain is the deforming of a material due to stress. When a force is applied to a material which tends to shorten or compress it, the stress is...

Twin system steering gears

Marine Rotary Vane Steering Gear System

To meet the automatic changeover within the 45 seconds required for tankers of 10 000 ton gross tonnage and above, a number of designs are available. Two will be described, one for a ram type steering gear and one for a rotary vane type steering gear. In each case two independent systems provide the power source to move the tiller, the failure of one resulting in a changeover to the other. The changeover is automatic and is achieved within 45 seconds. The ram type steering gear arrangement is...

Bunkering

The loading of fuel oil into a ship's tanks from a shoreside installation or bunker barge takes place about once a trip. The penalties for oil spills are large, the damage to the environment is considerable, and the ship may well be delayed or even arrested if this job is not properly carried out. Bunkering is traditionally the fourth engineer's job. He will usually be assisted by at least one other engineer and one or more ratings. Most ships will have a set procedure which is to be followed...

Pressure measurement

The measurement of pressure may take place from one of two possible datums, depending upon the type of instrument used. Absolute pressure is a total measurement using zero pressure as datum. Gauge pressure is a measurement above the atmospheric pressure which is used as a datum. To express gauge pressure as an absolute value it is therefore necessary to add the atmospheric pressure. A U-tube manometer is shown in Figure 15.1. One end is connected to the pressure source the other is open to...

Boiler mountings

Certain fittings are necessary on a boiler to ensure its safe operation. They are usually referred to as boiler mountings. The mountings usually found on a boiler are Safety valves. These are mounted in pairs to protect the boiler against overpressure. Once the valve lifting pressure is set in the presence of a Surveyor it is locked and cannot be changed. The valve is arranged to open automatically at the pre-set blow-off pressure. Main stqam stop valve. This valve is fitted in the main steam...

Insulation resistance measurement

Good insulation resistance is essential to the correct operation of electrical equipment. A means must be available therefore to measure insulation resistance. Readings taken regularly will give an indication as to when and where corrective action, maintenance, servicing, etc., is required. Insulation resistance may be measured between a conductor and earth or between conductors. Dirt or other deposits on surfaces can reduce insulation resistance and cause a leakage current or 'tracking' to...

The Engineering Department

The Chief Engineer is directly responsible to the Master for the satisfactory operation of all machinery and equipment. Apart from assuming all responsibility his role is mainly that of consultant and adviser. It is not usual for the Chief Engineer to keep a watch. The Second Engineer is responsible for the practical upkeep of machinery and the manning of the engine room he is in effect an executive officer. On some ships the Second Engineer may keep a watch. The Third and Fourth Engineers are...

Fourstroke cycle

Four Stroke Diagram

The four-stroke cycle is completed in four strokes of the piston, or two revolutions of the crankshaft. In order to operate this cycle the engine requires a mechanism to open and close the inlet and exhaust valves. Consider the piston at the top of its stroke, a position known as top dead centre (TDC). The inlet valve opens and fresh air is drawn in as the piston moves down (Figure 2.1(a)). At the bottom of the stroke, i.e. bottom dead centre (BDC), the inlet valve closes and the air in the...

Stabilising systems

There are two basic stabilising systems used on ships the fin and the tank. A stabilising system is fitted to a ship in order to reduce the rolling motion. This is achieved by providing an opposite force to that attempting to roll the ship. One or more pairs of fins are fitted on a ship, one on each side, see Figure 10.7. The size or area of the fins is governed by ship factors such as breadth, draught, displacement, and so on, but is very small compared with the size of the ship. The fins may...

Fire fighting and safety

It results in more total losses of ships than any other form of casualty. Almost all fires are the result of negligence or carelessness. Combustion occurs when the gases or vapours given off by a substance are ignited it is the gas given off that burns, not the substance. The temperature of the substance at which it gives off enough gas to continue burning is known as the 'flash point*. Fire is the result of a combination of three factors 3. A supply of oxygen,...

Pumps and pumping systems

At any one time in a ship's machinery space there will be a considerable variety of liquids on the move. The lengths of pipework will cover many kilometres, the systems are often interconnecting and most pumps are in pairs. The engineer must be familiar with each system from one end to the other, knowing the location and use of every single valve. The various systems perform functions such as cooling, heating, cleaning and lubricating of the various items of machinery. Each system can be...

Refrigeration air conditioning and ventilation

Air Conditioning Plant Marine Engineer

Refrigeration is a process in which the temperature of a space or its contents is reduced to below that of their surroundings. Air conditioning is the control of temperature and humidity in a space together with the circulation. Filtering and refreshing of the air. Ventilation is the circulation and refreshing of the air in a space without necessarily a change of temperature. With the exception of special processes, such as fish freezing, air is normally employed as the heat transfer medium. As...

Gauges In A Marine Biological Sewage Plant

Figure 7.6 Boiling process evaporator remainder constantly overflows a weir and carries away the extra salty water or brine. A combined brine and air ejector draws out the air and brine from the evaporator. Flash evaporation is the result of a liquid containing a reasonable amount of sensible heat at a particular pressure being admitted to a chamber at a lower pressure. The liquid immediately changes into steam, i.e. it flashes, without boiling taking place. The sensible heat content, water...

Fire fighting equipment

Water Extinguisher Diagram

There are four principal types of portable extinguisher usually found on board ship. These are the soda-acid, foam, dry powder and carbon dioxide extinguishers. The container of this extinguisher holds a sodium bicarbonate solution. The screw-on cap contains a plunger mechanism covered by a safety guard. Below the plunger is a glass phial containing sulphuric acid (Figure 13.4). When the plunger is struck the glass phial is broken and the acid and sodium bicarbonate mix. The resulting chemical...

Turbine construction

The construction of an impulse turbine is shown in Figure 3.5. The turbine rotor carries the various wheels around which are mounted the blades. The steam decreases in pressure as it passes along the shaft and increases in volume requiring progressively larger blades on the wheels. The astern turbine is mounted on one end of the rotor and is much shorter than the ahead turbine. The turbine rotor is supported by bearings at either end one bearing incorporates a thrust collar to resist any axial...

Power measurement

The burning of fuel in an engine cylinder will result in the production of power at the output shaft. Some of the power produced in the cylinder will be used to drive the rotating masses of the engine. The power produced in the cylinder can be measured by an engine indicator mechanism as described in Chapter 2. This power is often referred to as 'indicated power'. The power output of the engine is known as 'shaft' or brake power'. On smaller engines it could be measured bv applying a type of...

Fuel oils lubricating oils and their treatment

Diagram Lube Oil Clarifier

Crude oil is, at the present time, the source of most fuel oils for marine use. Synthetic fuels are being developed but will probably be too expensive for ship propulsion. Solid fuel, such as coal, is returning in a small way for certain specialised trade runs. The various refined products of crude oil seem likely to remain as the major forms of marine fuel. The refining process for crude oil separates by heating and distillation the various fractions of the oil. Paraffin fuel would be used in...

The gas exchange process

Loop Scavenging

A bask part of the cycle of an internal combustion engine is the supply of fresh air and removal of exhaust gases. This is the gas exchange process. Scavenging is the removal of exhaust gases by blowing in fresh air. Charging is the filling of the engine cylinder with a supply or charge of fresh air ready for compression. With supercharging a large mass of air is supplied to the cylinder by blowing it in under pressure. Older engines were 'naturally aspirated' taking fresh air only at...

Lubrication

The lubrication system of an engine provides a supply of lubricating oil to the various moving parts in the engine. Its main function is to enable the formation of a film of oil between the moving parts, which reduces friction and wear. The lubricating oil is also used as a cleaner and in some engines as a coolant. Lubricating oil for an engine is stored in the bottom of the crankcase, known as the sump, or in a drain tank located beneath the engine Figure 2.17 . The oil is drawn from this tank...

Explosion relief valve

Crankcase Explosion Relief Valve

As a practical safeguard against explosions which occur in a crankcase, explosion relief valves or doors are fitted. These valves serve to relieve excessive crankcase pressures and stop flames being emitted from the crankcase. They must also be self closing to stop the return of atmospheric air to the crankcase. Various designs and arrangements of these valves exist where, on large slow-speed diesels, two door type valves may be fitted to each crankcase or, on a medium-speed diesel, one valve...

Flow measurement

Centrifugal Force Tachometer

Flow measurement can be quantity measurement, where the amount of liquid which has passed in a particular time is given, or a flow velocity which, when multiplied by the pipe area, will give a rate of flow. A rotating pair of intermeshing vanes may be used which are physically displaced by the volume of liquid passing through Figure 15.11 a . The b rotating element Figure 15.11 Flow quantity measurement number of rotations will give a measure of the total quantity of liquid that has passed. The...

Man Bw

The L70MC is a single-acting, low-speed two-stroke reversible marine diesel engine manufactured by MAN B amp W. It is one of the MC series introduced in 1982, and has a longer stroke and increased maximum pressure when compared with the earlier L-GF and L-GB designs. The bedplate is made of welded longitudinal girders and welded cross girders with cast-steel bearing supports Figure 2.29 . The frame box is mounted on the bedplate and may be of cast or welded design. On the exhaust side of the...

Shafting and propellers

The transmission system on a ship transmits power from the engine to the propeller. It is made up of shafts, bearings, and finally the propeller itself. The thrust from the propeller is transferred to the ship through the transmission system. The different items in the system include the thrust shaft, one or more intermediate shafts and the tailshaft. These shafts are supported by the thrust block, intermediate bearings and the sterntube bearing. A sealing arrangement is provided at either end...

Unattended machinery spaces

Pitch Propeller Bridge

The sophistication of modern control systems and the reliability of the equipment used have resulted in machinery spaces remaining unattended for long periods. In order to ensure the safety of the ship and its equipment during UMS operation certain essential requirements must be met 1. Bridge control. A control system to operate the main machinery must be provided on the bridge. Instrumentation providing certain basic information must be provided. 2. Machinery control room. A centralised...

System components

Gland Vent Condenser Turbine Photo

The condenser is a heat exchanger which removes the latent heat from exhaust steam so that it condenses and can be pumped back into the boiler. This condensing should be achieved with the minimum of under-cooling, i.e. reduction of condensate temperature below the steam temperature. A condenser is also arranged so that gases and vapours from the condensing steam are removed. An auxiliary condenser is shown in Figure 5.5. The circular cross-section shell is provided with end covers which are...

Telemotor control

Crosshead Tiller Arm

Telemotor control is a hydraulic control system employing a transmitter, a receiver, pipes and a charging unit. The transmitter, which is built into the steering wheel console, is located on the bridge and the receiver is mounted on the steering gear. The charging unit is located near to the receiver and the system is charged with a non-freezing fluid. 9 Gland housing 10 Retracting plate The telemotor system is shown in Figure 12.4. Two rams are present in the transmitter which move in opposite...

Fuel oil supply for a twostroke diesel

A slow-speed two-stroke diesel is usually arranged to operate continuously on heavy fuel and have available a diesel oil supply for manoeuvring conditions. In the system shown in Figure 2.11, the oil is stored in tanks in the double bottom from which it is pumped to a settling tank and heated. After passing through centrifuges the cleaned, heated oil is pumped to a daily service tank. From the daily service tank the oil flows through a three-way valve to a mixing tank. A flow meter is fitted...

Fresh water cooling system

A water cooling system for a slow-speed diesel engine is shown in Figure 2.18. It is divided into two separate systems one for cooling the cylinder jackets, cylinder heads and turbo-blowers the other for piston cooling. Figure 2.18 Fresh water cooling system Figure 2.18 Fresh water cooling system The cylinder jacket cooling water after leaving the engine passes to a sea-water-circulated cooler and then into the jacket-water circulating pumps. It is then pumped around the cylinder jackets,...