Accommodation

A number of fatal accommodation fires have been started by people falling asleep whilst smoking. The sprinkler system provides protection against this type of incident. The combination of structural fire protection and an installed sprinkler system which incorporates detection, alarm and fire-fighting capability, has proved very successful in combating the outbreak of fire in passenger ship accommodation. The structural fire protection is based on zones separated by fire proof bulkheads and...

Acknowledgements

The author and publishers would like to acknowledge the cooperation of the following who have assisted in the preparation of the book by supplying information and illustrations. Alfa-Laval Ltd. APE-Allen Ltd. ASEA. Bell & Howell Cons. Electrodynamics. IMI-Bailey Valves Ltd. IMO Industri. International Maritime Organisation. KaMeWa. Lister Blackstone Mirrlees Marine Ltd. Thos. Reid & Sons (Paisley) Ltd. Ruston Paxman Diesels Ltd. Simplex-Turbulo Marine Ltd. Serck Heat Exchangers Ltd....

Air compressors

A single stage compressor used to provide air at the high pressures required for diesel engine starting, would unfortunately generate compression temperatures of a level similar to those in a diesel. Such heat would be sufficient to ignite vaporized oil in the same way as in a compression-ignition engine. The heat produced in a single stage of compression would also be wasteful of energy. This heat of compression adds energy and produces a resultant rise in pressure apart from that pressure...

Air compressors and systems

Air at a pressure of 20 to 30 bar is required for starting main and auxiliary diesel engines in motorships and for the auxiliary diesels of steamships. Control air at a lower pressure is required for ships of both categories and whether derived from high pressure compressors through reducing valves or from special control air compressors, it must be clean, dry and oil free. A starting air system for main diesels (Figure 2.1) normally has two air compressors and two reservoirs with sufficient...

Anchor handling

The efficient working of the anchor windlass is essential to the safety of the ship. An anchor windlass can expect to fulfil the following I The windlass cablelifter brakes must be able to control the running anchor and cable when the cablelifter is disconnected from the gearing when 'letting go'. Average cable speeds vary between 5 and 7 m s during this operation. 2 The windlass must be able to heave a certain weight of cable at a specified speed. This full load duty of the windlass varies and...

Automatic operation

Before the general introduction of control equipment, air compressors were stopped and started by engine room staff, as necessary, to maintain air receiver pressure. In port or at sea, this usually meant operating one compressor for about half an hour daily unless air was being used for the whistle (during fog), for work on deck or for other purposes. Whilst manoeuvring, the compressors would be started and stopped very frequently unless they were steam driven, when demand could be met by...

Auxiliary power

Auxiliary medium- or high-speed diesel engines, are mainly used as the prime movers for generators but they may also be coupled up to provide a direct drive for large pumps, bow thrusters or other machinery. The steam turbine, used as the alternative independent method of driving a generator, can also be employed for driving cargo or feed pumps. Diesel driven generators can be expensive in terms of fuel cost and maintenance requirements. Continuous operation at sea and in port exacts a high...

Ballast arrangements

The ballasting of a vessel which is to proceed without cargo to the loading port is necessary for a safe voyage, sometimes in heavy weather conditions. On arrival at the port the large amount of ballast must be discharged rapidly in readiness for loading. Ballast pump capacity is governed by the volume of water that has to be discharged in a given time. The ballast pump is often also the stand-by sea-water circulating pump (Figure 3.1) but very large ballast discharge capacity is necessary for...

Batch and continuous lubricating systems

For small or medium units without a circulatory lubricating system, the oil can be treated on the batch system. As large a quantity of oil as possible is pumped from the engine or system to a heating tank. The heated oil is passed through the purifier and back to the sump. For removing soluble sludge, a system combining the batch and continuous systems is effective. The oil is pumped to a tank, where it is allowed to settle for 24 or 48 hours. The oil may be heated by steam coils and basic...

Biochemical oxygen demand

The bio-chemical oxygen demand (BOD) is determined by incubating at 20 C, a sample of sewage effluent which has been well-oxygenated. The amount of oxygen absorbed over a five-day period is then measured. The test is used in this context to evaluate the effectiveness of treatment as it measures the total amount of oxygen taken up as final and complete breakdown of organic matter by aerobic bacteria in the effluent occurs. The quantity of oxygen used equates to the amount of further breakdown...

Cascade trays

Three cascade trays are set one above the other in the lower part of the shell. The upper and lower of these trays have a raised lip on the outer periphery, have the central opening blanked and have a series of perforations arranged in rings towards the raised lip. The middle tray has a central opening with a raised lip and is perforated similarly. The falling spray collects on the upper tray and is again broken up as it passes through the perforations to the middle tray where the process is...

Cast iron

Cast iron has poor corrosion resistance in sea water, being especially vulnerable to graphitization. This form of attack gradually removes the iron from the surface in contact with sea water to leave soft, black graphite. The weakness of ordinary grey cast iron in tension and under shock loading limits its use to low pressure applications, and the brittle nature of ordinary grey cast iron excludes its use for side shell fittings where failure could result in flooding of the machinery space....

Chemical tankers

The enormous demand for crude oil and liquefied gas has meant that these cargoes are moved in very large quantities in ships that are dedicated to one cargo. Bulk chemicals are transported in smaller parcels and it is normal to find chemical tankers with almost as many different cargoes as there are tanks. With single cargo such as crude oil or one particular liquefied gas being carried continually, personnel become familiar with the risks. Dealing with a great variety of chemicals, each with...

Chlorine sterilization and conditioning

Initial treatment (Figure 3.11) involves passing the distillate through a neutralite unit containing magnesium and calcium carbonate. Some absorption of carbon dioxide from the water and the neutralizing effect of these compounds, removes acidity. The addition of hardness salts also gives the water a better taste. The sterilizing agent chlorine, being a gas, is carried into the water as a constituent of sodium hypochlorite (a liquid) or in granules of calcium chloride dissolved in water. The...

Circulating systems for steamships

The main sea-water circulating system for a ship with main propulsion by steam turbine is similar to that of a motorship with a central cooling system. The difference is that the sea water passes through a large condenser and an oil cooler rather than central coolers and then to the overboard discharge. The main sea-water inlets, port and starboard, may be arranged as for the motorship example (Figure 1.1) with high and low suctions, orthodox double entry circulating pump (with emergency bilge...

Compressed air systems for steamships

A compressed air system is necessary to supply air for boiler soot-blower air motors, hose connections throughout the ship and possibly diesel generator starting. A general service air compressor would supply air at 8 bar but greater pressure (as for diesel ships) would be necessary for diesel starting. A general service air compressor can be shut down completely when air is not required but can be operated on either a stop start or load unload cycle, with the regulator controlling the pressure...

Condensate extraction pump

Removal of condensate from a condenser imposes very difficult suction conditions on the pump. The available net positive suction head (NPSH) is minimal because the condenser is situated low in the ship permitting a static suction head of only 450-700 mm and the condensate is at, or near its vapour pressure. It is necessary therefore to ensure that the pump's required NPSH is correspondingly low and to this end suction passages and inlets are given ample area. The pumps used for the duty, are...

Control air from starting air at 15 to 40 bar

A three stage filtration system (Figure 2.9) employing a pre-filter, a carbon absorber, and an after filter, may be installed to deliver good quality air. The pre-filter contains a medium grade porous ceramic element and removes the gross atmospheric impurities from the air. The absorber is packed with activated carbon and provides a deep bed producing an evenly distributed flow for the removal of vapours (it can also remove flavours or taints). The after filter contains a fine grade porous...

Control of temperature in heat exchangers

The three basic methods for controlling the temperature of the hot fluid in a heat exchanger when the cooling medium is sea-water, are 1 to bypass a proportion or all of the hot fluid flow, 2 to bypass or limit the sea-water flow 3 to control sea-water temperature by spilling part of the sea-water discharge back into the pump suction. The last of these methods could be used in conjunction with one of the other two and it was resorted to when sea water was used for direct cooling of diesei...

Control system air

Pneumatic control equipment is sensitive to contaminants which may be in the air. Viscous oil and water emulsions can cause moving parts to stick and produce general deterioration of diaphragms and other parts made of rubber. Water can cause rust build up which may also result in parts sticking or being damaged by rust particles. Metallic wear and other small particles can cause damage by abrasion. Any solids mixed with oil and water emulsions can conspire to block small orifices. Clean and dry...

Cooling

During compression much of the energy applied is converted into heat and any consequent rise in the air temperature will reduce the volumetric efficiency of Figure 2.2 Air compressor configurations Figure 2.2 Air compressor configurations Figure 2.3 Compressor indicator diagram (courtesy Hamworthy Engineering Ltd) Figure 2.3 Compressor indicator diagram (courtesy Hamworthy Engineering Ltd) the cycle. To minimize the temperature rise, heat must be removed. Although some can be removed through...

Cooling system

A variety of cooling systems may be adopted for marine auxiliary engines but the most commonly used is the simple closed circuit system (Figure 7.5). Sea water is passed through the intercooler, the oil cooler and then the jacket water cooler in series flow. Engine driven fresh-water circulating pumps are normally fitted, but the sea-water pump may be either an independent unit or engine driven in tandem with the fresh-water pump. The cooling system may be arranged so that in an emergency sea...

Cycle of operation

On the compression stroke (Figure 2.3) for a theoretical single cylinder compressor, the pressure rises to slightly above discharge pressure. A spring-loaded non-return discharge valve opens and the compressed air passes through at approximately constant pressure. At the end of the stroke the differential pressure across the valve, aided by the valve spring, closes the discharge valve, trapping a small amount of high pressure air in the clearance space between the piston and the cylinder head....

Deaerators

Mention has been made of the need for clean, neutral boiler feed, free from dissolved gases and of the consequent use of efficient de-aerators. Figure 1.26 shows one of several which liberate the dissolved gases from the feed and provide a measure of feed heating simultaneously. This type of de-aerator has a great range of capacity and given a temperature rise of at least 20 C, an oxygen content of 0.2 cc litre can be reduced to 0.005 cc litre, when working between one-half full load and full...

Detergent type or HD lubricating oils

The main function of detergent-dispersant additives in a lubricating oil is to pick up and hold solids in suspension. This capability can be applied to other additives such as the acid neutralizing alkaline compounds as well as solid contaminants. Thus detergent oils hold contaminants in suspension and prevent both their agglomeration and deposition in the engine. This function reduces ring sticking, wear of piston rings and cylinder liners, and generally improves the cleanliness of the engine....

Eisan holding and recirculation zero discharge system

A retention or holding tank is required where no discharge of treated or untreated sewage is allowed in a port area. The sewage is pumped out to shore reception facilities or overboard when the vessel is proceeding on passage at sea, usually beyond the 12 nautical mile limit. Straight holding tanks for retention of sewage during the period of a ship's stay in port were of a size large enough to contain not only the actual sewage but also the flushing water. Each flush delivered perhaps 5 litres...

Electrokatadyn method of sterilization

The Electro-katadyn process (Figure 3.12) accepted as an alternative to chlorination (see Ml401) involves the use of a driven silver anode to inject silver ions (Ag+) into the distilled water product of the low temperature evaporator. Silver is toxic to the various risk organisms. Unlike the gas chlorine, it will not evaporate but remains suspended in the water. The sterilizer is placed close to the production equipment with the conditioning unit being installed after the sterilizer and before...

Erosion

Erosion of metal may be the result of abrasives or of high water speeds, entrained air, turbulence and cavitation. The latter are often caused by protuberances, tight bends or an abrupt change of pipe cross sectional area. Erosion from turbulent flow and cavitation also aids corrosion (corrosion erosion) by removing the oxide film that assists in the protection of metal surfaces. The exposed metal surfaces can form galvanic corrosion cells with adjacent areas where oxide film is still present....

Fire risk

Fire is an ever-present hazard with liquid fuel because the vapour from it can form a flammable explosive mixture with air. A hydrocarbon and air mixture containing between about 1 and 10 of hydrocarbon vapour, can be readily ignited by a naked flame or spark. Combustion will also occur if the flammable mixture is in contact with a hot surface which is at or above the ignition temperature of the mixture. Ignition temperature for a hydrocarbon mixture may be about 400 C or less. A crude oil will...

Flash evaporators

The evaporator described above, boils sea water at the saturation temperature corresponding to the uniform pressure through the evaporation and condensing chambers. With flash evaporators (Figure 3.13) the water is heated in one compartment before being released into a second chamber in which the pressure is substantially lower. The drop in pressure changes the saturation temperature below the actual temperature, so that some of the water instantly flashes off as vapour. Steam in the chamber at...

Fresh water

The fresh water is supplied to the system, by one of two pumps which are self-priming or situated at a lower level than the storage tanks. The pump starters are controlled by pressure switches which operate when pressure in the service tank varies within pre-determined limits as water is used. The pump discharges through filters to a rising main, branched to give cold and hot supplies, the latter through a calorifier. A circulating pump may be fitted in circuit with the steam or electrically...

Fuel blender for auxiliary diesels

Conventionally, the lower cost residual fuels are used for large slow speed diesel main engines and generators are operated on the lighter more expensive distillate fuel. The addition of a small amount of diesel oil to heavy fuel considerably reduces its viscosity and if heating is used to further bring the viscosity down then the blend can be used in generators with resultant savings. The in-line blender shown in Figure 2.28 takes fuels from heavy oil and light diesel tanks, mixes them and...

Fuel handling and treatment

Fuels and lubricating oils are obtained from crude primarily by heating the crude oil, so that vapours are boiled off and then condensed at different temperatures. The constituents or fractions are collected separately in a distillation process. Crude oil contains gaseous fuels, gasoline (petrol), kerosene (paraffin), gas oils, distillate diesel fuels and lubricating oils which can be collected from the fractionating tower (Figure 2.10) where they condense out at the different levels maintained...

Fuel heater

For burning heavy fuel oil in a boiler furnace, or a compression-ignition engine, it is necessary to pre-heat it. This may be done in a shell and tube unit either with plain tubes (Figure 2.22) or tubes with fins bonded to them (Figure 2.23) and the oil flowing on the outside of the tubes. The heating medium is normally steam but additional electric heaters are useful for start up from dead ship condition. The heating steam is used most effectively if it condenses during its passage through the...

Further reading

T. and Chamley, R. (1987) Drinking water from the sea-, reverse osmosis, the modern alternative, Trans I Mar , 88. Gilchrist, A. (1976) Sea Water Distillers, Trans I Mar , 88. Hill, E.C. (1987) Legionella and Ships' Water Systems, MER Merchant Shipping Notice No. M1214 Recommendations to Prevent Contamination of Ships' Fresh Water Storage and Distribution Systems. Merchant Shipping Notice No. Ml401 Disinfection of Ships' Domestic Fresh Water. The Merchant Shipping (Crew...

General pumping system characteristics

A pump divides its pipe system into two distinct parts, each with different characteristics. These are the suction and discharge sides. On the suction side the drop in pressure that can be produced by a pump is limited to that of an almost perfect vacuum. On the discharge side there is theoretically, no limit to the height through which a liquid can be raised. If a liquid to be pumped is in a tank which is open to atmosphere and it is also at a height above the pump (Figure 5.1) then the liquid...

Holding tanks

Simple holding tanks may be acceptable for ships which are in port for only a very brief period. The capacity would need to be excessively large for long stays because of the amount of flushing water. They require a vent, with the outlet suitably and safely positioned because of gas emissions. A flame trap reduces risk. Inhibiting internal corrosion implies some form of coating and, for washing through of the tank and pump after discharge of the contents at sea, a fresh water connection is...

Horizontal single element two stage air ejector

An air ejector which has been commonly used, is shown schematically in Figure 1.18. The unit comprises a stack of U-tubes contained in a fabricated mild steel condenser shell on which is mounted a single element two stage air ejector. The condensate from the main or auxiliary condenser is used as the cooling medium, the condensate circulating through the tubes whilst the air and vapour passes through the shell. The high velocity operating steam emerging from the first stage ejector nozzle...

Hydraulic balance mechanism

To control the axial movement of the rotating assembly, a balance piston (Figure 1.33) is arranged to counteract the effect of the thrust of the turbine and impellers. The arrangement keeps the rotating assembly in its correct position under all conditions of loading. Water at the approximate pressure of the pump discharge passes from the last stage of the pump between the impeller hub and the balance restriction bush C into the annular space B dropping in pressure as it does so. The pressure...

Info

All air compressors and receivers to be fitted with suitable safety valves and drain valves Figure 2.1 Starting air system for main diesels components is limited as excess lubrication could cause the air start valves to be stuck by grease which has become hardened by the heat, and oil could accumulate in the pipes from this source. The draining of compressor coolers and air receivers is important. Drains on air start systems are also checked. Flame traps or bursting caps are fitted at each air...

Installation serving the accommodation aft

The deck officers', engineer officers' and crew accommodation is served by two air conditioning units, with a direct expansion refrigerating plant of the Freon 22 type, capable of maintaining an inside condition of 26.7 C (d.b.) and 20.0 C (w.b.) (55 relative humidity) when the outside condition is 32.2 C (d.b.) and 28.9 C (w.b.) (78 relative humidity). Finned tube type steam heating coils are fitted to maintain 21 C in the space when the outside temperature is 20.5 C. The schedule in Table...

Installation serving the cargo pump room

The cargo pump room is ventilated by two axial flow exhaust fans each to extract 1.4 m3 s against 3.1 mbar static, requiring a total of 2.25 kW. The fans should be of split case bevel gear driven type enabling the fan motor to be mounted in the adjacent engine room. Motor and controller spare gear must be provided. Air is extracted from two low level points through wire mesh grids fitted on galvanized steel ducting. The shipbuilder must supply and fit air outlet jalousies with hinged water...

Iv

Leading edge Moderate pressure drop Leading edge Moderate pressure drop Figure 5.22 Hydrofoil and supercavitating blades of pump for specialized rather than general duties. Contact between elements in some screw pumps (Figure 5.23) is made unnecessary by gear drives. When used for lubricating oil and hydraulic systems, rotary displacement pumps benefit from the sealing effect and provision of lubrication between parts. For a rotary positive displacement pump operating at zero pressure the...

L

Figure 11.19 Direct expansion battery with air circulation (R. C. Dean) Figure 11.20 Dual temperature brine system Figure 11.20 Dual temperature brine system non-corrosive, and may be used at much lower working temperatures than brine. Trichlorethylene has also been used as a secondary refrigerant, but has the disadvantages of being toxic and a solvent of many of the synthetic rubbers and other materials normally used as jointing. The design of an air circulating system is dictated principally...

Lubricating oil and treatment

Mineral oils for lubrication are, like fuel, derived from crude during refinery processes. Basic stocks are blended to make lubricants with the desired properties and correct viscosity for particular duties. Additives are used to enhance the general properties of the oil and these include oxidation and corrosion inhibitors, anti-corrosion and rust prevention additives, foam inhibitors and viscosity index (VI) improvers. The latter lowers the rate of change of viscosity with temperature. Basic...

Machinery service systems and equipment

Service systems are necessary for the main machinery and for generators in addition to the circulating systems described in the previous chapter. The supply of compressed air for starting and control systems requires the provision of compressors and air receivers. Modern residual fuels need a handling system with settling tanks, centrifuges, heating, filtration, and sometimes with homogenization and blending equipment. Lubricating oil also benefits from being centrifuged as well as being...

Machinery service systems and equipment 65 High density fuel treatment Alcap System

The density of a fuel tested at 15 C may approach, be equal to or greater than that of water. With high density fuels, the reduction in density differential between fuel and water can cause a problem with separation but not with the usual solid impurities. Heating of the fuel (Figure 2.19) will reduce the density and this may be sufficient in itself to obviate the problem of water separation. The change in density of water with temperature (dotted line) is not so pronounced, as can be seen from...

Main propulsion services and heat exchangers

The heat produced by running machinery, must be removed to ensure the satisfactory functioning of the equipment. Cooling is achieved primarily through circulation of water, oil and air but the abundant supply of sea water is normally reserved for use as an indirect coolant because the dissolved salts have a great potential for depositing scale and assisting in the setting up of galvanic corrosion cells. Pollution of coastal areas by industrial and other wastes has added to the problems of using...

Maintenance of heat exchangers

The only attention that heat exchangers should require is to ensure that the heat transfer surfaces remain substantially clean and flow passages generally clear of obstruction. Indication that fouling has occurred, is given by a progressive increase in the temperature difference between the two fluids, and change of pressure. Fouling on the sea-water side is the most usual cause of deterioration in performance. The method of cleaning the sea-water side surfaces depends on the type of deposit...

Manually operated expansion valves

These were used for C02 refrigeration installations where the compressor was started and stopped by a watchkeeper. The compressor was started with the expansion valve open. The valve was then closed in to bring up pressure on the condenser side until the saturation or condensing temperature for the pressure (shown on the gauge) was five or six degrees above that of the cooling sea water. After the manual expansion valve had been set in this way, the gauge on the compressor suction (or...

Medium speed auxiliary diesel engines

Over recent years, many owners have elected to burn low grade residual fuels in medium-speed auxiliary engines, sometimes with disastrous results. Fuels bunkered for slow-speed main engines may be of too poor a quality for use in auxiliaries even where the engines have been designed for heavy fuel operation. Major problems have been experienced on large slow-speed engines with some of the poor quality bunkers such as those containing catalytic fines. Fuel should conform to the specification...

Mooring equipment

Fuil load duties of warping capstans and mooring winches vary between 3-30 tonnes at 0.3 to 0.6 m s and twice full load speed is normally provided for recovering slack lines. The size of wire rope used on mooring winch barrels is governed by the weight of wire manageable by the crew this is currently accepted as 140 mm circumference maximum. The basic problems associated with the use of wire ropes is that they are difficult to handle, do not float and when used in multi-layers, due to...

Nash rotary liquid ring pumps

Nash rotary liquid ring pumps, in association with atmospheric air ejectors, may be used instead of diffuser-type steam ejectors and are arranged as shown in Figure 1.21. The pump, discharging to a separator, draws from the condenser MR INLET CASING VflCtAJM GAUGE CONKCTKxT THfRMOMFfER BCHT Figure 1.20 First and second stage ejectors Figure 1.20 First and second stage ejectors AIR JET MOTIVE AIR INLET FROM SEPARATOR through the atmospheric air ejector, creating a partial vacuum of about 600 mm...

Nonferrous alloys

Basically, brass is an alloy of copper and zinc bronze an alloy of copper and tin. In both cases there may be additions of other metals and there is some confusion of nomenclature some high-tensile brasses are called 'bronze' and the practice has prevailed for so long as to be accepted. Aluminium brass and other non-ferrous pipelines, are considered very-resistant to corrosion in sea water, but concentrated galvanic corrosion can occur if some part of the pipe system has a different make up. A...

Oil content monitoring

In the past, an inspection glass, fitted in the overboard discharge pipe of the oil water separator permitted sighting of the flow. The discharge was illuminated by a light bulb fitted on the outside of the glass port opposite the viewer. The separator was shut down if there was any evidence of oil carry over, but problems with observation occurred due to poor light and accumulation of oily deposits on the inside of the glasses. Present-day monitors are based on the same principle. However,...

Oilwater separators

Oil water separators are necessary aboard vessels to prevent the discharge of oil overboard mainly when pumping out bilges. They also find service when deballasting or when cleaning oil tanks. The requirement to fit such devices is the result of international legislation. Legislation was needed because free oil and oily emulsions discharged in a waterway can interfere with natural processes such as photosynthesis and re-aeration, and induce the destruction of the algae and plankton so essential...

Operation and maintenance

Compressors must always be started in the unloaded condition otherwise pressures build up rapidly producing very high starting torques (Figure 2.7). During running there is an accumulation of oil carried over from the cylinders and water from moisture, precipitated in the coolers. The emulsion is collected in separators at cooler outlets and these must be drained off regularly, to reduce carry over. This is extremely important, first to prevent any large quantity of water and oil emulsion...

Pretreatment and posttreatment

Sea-water feed for reverse osmosis plant, is pretreated before being passed through. The chemical sodium hexametaphosphate is added to assist the wash through of salt deposit on the surface of the elements and the sea water is sterilized to remove bacteria which would otherwise become resident in the filter. Chlorine is reduced by the compressed carbon filter while solids are removed by the other filters. Treatment is also necessary to make the water product of reverse osmosis potable. The...

Principle of operation

The main principle of separation by which commercially available oil water separators function, is the gravity differential between oil and water. In oily water mixtures, the oil exists as a collection of globules of various sizes. The force acting on such a globule, causing it to move in the water is proportional to the difference in weight between the oil particle and a particle of water of equal volume. This can be expressed as Fs separating force p density of water po density of oil D...

Pumping considerations

A faster rate of separation is obtained with large size oil globules or slugs and any break up of oil globules in the oily feed to the separator should be avoided. This factor can be seriously affected by the type and rating of the pump used. Tests were carried out by a British government research establishment some years ago on the suitability of various pumps for separator feed duties and the results are shown in Table 3.1. It follows that equal care must be taken with pipe design and...

Pumps and pumping

The centrifugal pump is now used for most applications and systems on ships. In the machinery space it provides a much more reliable service than the steam reciprocating pumps that were still being installed in the 'fifties as auxiliary boiler feed and fuel pumps for example. These reciprocating pumps required regular maintenance and, if neglected, they needed constant attention to keep them functioning. The general use of the centrifugal pump helped to make the unmanned machinery space viable.

Reason for distillate treatment

The low operating temperature of the evaporator described, is not sufficient to sterilize the product. Despite precautions near the coast, harmful organisms may enter with the sea water and pass through to the domestic water tank and system. Additionally there is a likelihood that while in the domestic tank, water may become infested with bacteria, due to a build up of a colony of organisms from some initial contamination. Sterilization by the addition of chlorine, is recommended in Merchant...

Reverse osmosis

Osmosis is the term used to describe the natural migration of water from one side of a semi-permeable membrane into a solution on the other side. The f* JL H -1 _ _ _ ____________STEAM 200Kg Hr DISTIILEO WATER TO TANKS 3200Kg Hr 50 C CONDENSATE DRAINS TO MAIN CONDENSER 1910 Kg Hr 85 90 C Figure 3.13 Flow diagrams - cascade evaporator (Caird & Rayner Ltd) DISTIILEO WATER TO TANKS 3200Kg Hr 50 C CONDENSATE DRAINS TO MAIN CONDENSER 1910 Kg Hr 85 90 C Figure 3.13 Flow diagrams - cascade...

Rf

Cross connection with multispray drencher and sprinkler systems Main machinery Tunnel room Ford machinery room P - Fire and bilge P P, Figure 14.2 Ferry fire main (R C. Dean) (Figure 14.3) The first stage below the waterline is driven by a hydraulic motor. The second stage and the hydraulic power unit are driven by a prime mover (or electric motor from the emergency supply) which can be positioned at more than the normal distance from the waterline. If the fire pump is driven by a water-cooled...

Safety overspeed trip

The 'Bolt' type overspeed trip (Figure 1.31) consists essentially of a spring-loaded stainless steel bolt which, due to its special design, is heavier at one end than the other. The rotary motion of the turbine shaft tends to move the bolt outwards, while the spring retains it in its normal position until the turbine speed reaches a pre-determined safety level. At this speed the centrifugal force exerted by the heavier end of the bolt overcomes the spring opposing it and the bolt moves outwards...

Sanitary water

The sanitary system operates on the same Pneupress principle as that described for fresh water. Pumps, if supplying sea water, are protected by filters on the suction side which require regular cleaning. A few sanitary systems use fresh or distilled water to reduce corrosion in pipes and flushing valves, particularly in vacuum systems where water consumption is minimal. Treated liquid effluent is recirculated in the chemical sewage treatment system described later in the chapter (p. 108) this...

Scoop arrangement for a motor ship

A scoop (Figure 1.11) designed to supply sea-water circulation through the central coolers while the vessel is underway, may be installed instead of a conventional sea-water circulating pump. The scoop imposes some extra drag on the hull so that the power for sea-water circulation is supplied from the main propulsion instead of from the generators and electrical system. Economic advantages are claimed for a correctly designed scoop but the arrangement is viable only for a simple straight...

Sewage systems

The exact amount of sewage and waste water flow generated on board ship is difficult to quantify. European designers tend to work on the basis of 70 litres person day of toilet waste (including flushing water) and about 130-150 litres person day of washing water (including baths, laundries, etc.). US authorities suggest that the flow from toilet discharges is as high as 114 litres person day with twice this amount of washing water. The breakdown of raw sewage in water is effected by aerobic...

Steamjet air ejector

A steam-jet ejector may be used to withdraw air and dissolved gases from the condenser. In each stage of the steam-jet ejector, high pressure steam is expanded in a convergent divergent nozzle. The steam leaves the nozzle at a very high velocity in the order of 1220 m s and a proportion of the kinetic energy in the steam jet transferred, by interchange of momentum, to the body of air which is entrained and passes along with the operating steam through a diffuser in which the kinetic energy of...

Steel

Steel being subject not only to galvanic corrosion but also to rusting, appears to be a poor material to select for sea water pipes or for installation in tank top or deck areas. Mild steel pipes for sea water are protected by being galvanized or rubber lined. Welding and pipe bending should be completed before galvanizing or application of a lining, so that weld spatter and deposits from manufacture can be removed. The mild steel, electric resistance welded (ERW) or hot rolled pipes are...

Surface feed heaters

These are shell and tube heat exchangers, made with materials and scantlings appropriate to their working temperatures and pressures. It can be shown that the minimum economic terminal difference (i.e. the temperature difference Figure 1.23(b) Extraction pump cavitation control curves Figure 1.23(b) Extraction pump cavitation control curves space and pipe connections can often be achieved and there is a movement in that direction in practice. Many parts of the feed system are now installed as...

System design

Careful system design and contamination control are required during manufacture and installation of equipment. The number of joints and pipes are kept to a minimum to reduce the possibility of leakage. Materials are selected that will produce the least quantity of contaminating particles in the system. Filters capable of taking out particles down to a specified size are necessary. Shaft glands or seals must prevent leakage of oil from the machinery and they must also keep contamination out...

Tanker and gas carrier cargo pumps and systems

The nominal time for complete discharge of cargo from a tanker is 24 hours and this is th figure that is normally written into the cargo pumping warranty. The form of the warranty in the tanker charter may be 'owners warrant the vessel is capable of discharging the entire cargo within twenty four hours or pumps are capable of maintaining 7 bar (sometimes 100 lb in2) at the ships rail'. The last part is important if cargo cannot be accepted ashore at the required rate for a 24 hour discharge or...

Tanker ballast

Sampling and monitoring equipment fitted in the pump room of a tanker can be made safe by using fibre optics to transmit light to and from the sampling chamber (Figure 3.6). The light source and photo-cell can be situated in the cargo control room together with the control, recording and alarm console. The sampling pump can be fitted in the pumproom to keep the sampling pipe short and so minimize time delay. For safety the drive motor is fitted in the machinery space, with the shaft passing...

The condenser

A condenser is a vessel in which a vapour is deprived of its latent heat of vaporization and so is changed to its liquid state, usually by cooling at constant pressure. In surface condensers, steam enters at an upper level, passes over tubes in which cold sea water circulates, falls as water to the bottom and is removed by a pump (or flows to a feed tank). The construction of condensers is similar to that of other tubular heat exchangers, with size variation extending up to the very large...

The feed system and feed heating

Non-condensable gases and some vapour are removed from the main condenser (Figure 1.13) by an air ejector, cooled by the main condensate and released in the ejector condenser. The condensed ejector steam passes with other clean drains (gland steam condenser, low pressure feed heater, evaporator) to a drains tank from which a pump draws, to discharge, with the mains condensate, to the de-aerator. It is common practice to reflux these drains, that is to return them to the main condenser in the...

The regenerative condenser

As it expands through a turbine, as much as possible of the available useful work is extracted from the steam by maintaining vacuum conditions in the condenser. Part of the function of the condenser is to condense the steam from the low pressure end of the turbine at as low a pressure as possible. The effective operation of a condenser requires that the sea water is colder than the saturation temperature of the exhaust steam and this means that undercooling will occur. Any undercooling must be...

The Simplex Turbulo oilwater separator

The Simplex-Turbulo oil water separator (Figure 3.2) consists of a vertical cylindrical pressure vessel containing a number of inverted conical plates. The oily water enters the separator in the upper half of the unit and is directed coalesce until the enlarged globules have sufficient rising velocity to travel along the plate surface and break away at the periphery. The oil rises, is caught underneath an annular baffle and is then led up through the turbulent inlet area by risers to collect in...

Treatment of water from shore sources

There is a risk that water supplied from ashore may contain harmful organisms which can multiply and infect drinking or washing water storage tanks. All water from ashore, whether for drinking or washing purposes, is to be sterilized. When chlorine is used, the dose must be such as to give a concentration of 0,2 ppm. The Department of Transport recommends in Merchant Shipping Notice number M1214 that because of the risk from legionella bacteria entering the respiratory system by way of fine...

Turbine driven oillubricated pump

Prior to the introduction of the water lubricated turbo-feed pumps an oil-lubricated pump with a relatively long horizontal shaft was commonly used. In this particular pump the overspeed trip (Figure 1.32) was of the ring type. The pump was mounted on a taper at the end of the turbine shaft adjacent to the trip gear and was secured by a mild steel set bolt tapped into the end of the shaft. This set bolt was locked in place by a copper lock washer. The overspeed mechanism consisted of a...

Ultraviolet sterilizer

A means for sterilizing potable water at the point of use, is provided on many offshore installations and ships, by an ultra-violet radiation unit which is positioned after the hydrophore tank and as close as possible to the tap supply points. The stainless steel irradiation chamber contains low pressure mercury-vapour tubes, housed in a quartz jacket. Tubes are wired in series with a transformer for safety. A wiper is fitted within the chamber to clean the jackets and lamp observation window....

Valves and pipelines

The various pipe systems for commercial ships must comply with any applicable rules of the responsible government department and those of the designated classification society. Guidance is provided in government and classification society publications and it is required that plans for principal systems are submitted for approval. The safety and reliability of critical individual fittings is ensured by a requirement that they are made to specification by an approved manufacturer. Materials are...

Venting and draining

It is important that any heat exchanger through which sea water flows should run full. In vertically-mounted single-pass heat exchangers of the shell-and-tube or plate types, venting will be automatic if the sea-water flow is upwards. This is also the case with heat exchangers mounted in the horizontal attitude, with single- or multi-pass tube arrangements, provided that the sea-water inlet branch faces downwards and the outlet branch upwards. With these arrangements, the water will drain...

Cargo access

Although not strictly a machinery item, the mechanical complexity of present-day cargo hatch covers - whose periodic maintenance may fall in the domain of the ship's Engineering Department - warrants some mention in this chapter. Many types of mechanically operated hatch covers can now be found at sea. The principal ones are listed in Table 13.1. The single pull hatch cover (Figure 13.12) consists of a number of transverse panels which span the hatchway and are linked together by chains. In the...

Low pressure evaporators

The main object of distillation is to produce water essentially free of salts. Potable water should contain less than 500 mg litre of suspended solids. Good quality boiler feed will contain less than 2.5 mg litre. Sea water has a total dissolved solids content in the range 30 000 42 000 mg litre, depending on its origin but the figure is usually given as 32 000 mg litre. Low pressure evaporators for the production of water can be adapted for steamships but operate to greatest advantage with...

Ship service systems

Some of the equipment in the machinery space is dedicated to servicing the ship in general and providing amenities for personnel or passengers. Thus the bilge system is available to clear oil water leakage and residues from machinery and other spaces as well as to provide an emergency pumping capability. The domestic water and sewage systems provide amenities for personnel. Bilge systems and oily water separators The essential purpose of a bilge system, is to clear water from the ship's 'dry'...

Alfa Laval intermittent discharge centrifuge

Figure 2.18 shows a centrifuge bowl capable of being programmed for periodic and regular dumping of the bowl contents to remove the sludge build-up. The sludge discharge takes place through a number of slots in the bowl wall. Between discharges these slots are closed by the sliding bowl bottom, which constitutes an inner, sliding bottom in the separating space. The sliding bowl bottom is forced upwards against a seal ring by the pressure of the operating liquid contained in the space below it....

Weir multi stage turbofeed pump

The water tube boiler, with its low storage capacity in relation to its steaming capability, demands a steady supply of pure feed water. The robust and reliable turbine driven centrifugal pump, is ideal for use as a water tube boiler feed pump. Additionally its uncontaminated exhaust can be used for feed heating and this improves cycle efficiency. The successful development of water lubricated bearings and their use in the Weir turbo-feed pump, permitted the turbine and pump to be close-coupled...

Safety and safety equipment

Much that is written or promulgated with respect to safety at sea is concerned with the obvious sort of risks that threaten those who are careless in any work situation. The survival of seafarers is additionally jeopardized by special factors, many of which are not obvious and not always present. Thus entry to enclosed spaces whether they are ballast or cargo tanks, pumprooms, cofferdams or even dry cargo holds may be made hazardous by the presence of dangerous liquids, toxic or flammable gas...

Heating ventilation and air conditioning

Good ventilation is vital to the health and well-being of those on board ship and the general requirements for ventilation, formulated before the universal installation of air conditioning systems, still apply. Heating, always necessary for the colder areas of the world, has in the past been provided by local radiators or by heating coils incorporated with ventilation units. With extremes of low temperature, these primitive methods of heating increased the capacity of the air to absorb moisture...

Bosch type fuel pump

Line Sketch Jerk Type Fuel Pump

The most common fuel pump used on auxiliary diesel engines is the Bosch type. This is a cam operated jerk pump with a helical groove on the plunger to control the fuel cut-off and therefore the quantity of fuel delivered to the cylinder for combustion. These pumps can be arranged singly along the camshaft, with one at each cylinder position or they may be housed in a single block. Each pump unit contains a pump plunger and guide together with a spring loaded delivery valve and its seat....

Heat exchange theory

The rate of flow of heat through a heat exchanger tube or plate from the fluid at the higher temperature to the one at the lower (Figure 1.6) is related to the temperature difference between the two fluids, the ability of the material of the tube or plate to conduct and the area and thickness of the material. If neither fluid is moving, the conductivity of the fluids has also to be taken into account and the fact that with static conditions as one fluid loses heat and the other gains, the...

General construction based on the Allen S12 engine

The in-line S12 engine structure (Figure 7.1) is based on a deep section cast iron bedplate and a cast iron A-frame of monobloc construction which are flanged and bolted together. The bedplate carries thin wall, steel-backed, white-metal or aluminium-tin lined main bearings. An additional bearing is incorporated to carry the combined loads of the flywheel and part of the weight of the generator. Access doors are provided at the front and back. Those on the back of the engine are fitted with...

Bow thrusters

Flexible Inboard Shaft Coupler

The transverse thruster, installed in the bow and or the stem, has become an essential item of equipment on many vessels. It enables the normal process of docking to be managed without tug assistance because the vessel is made more manoeuvrable at low speeds. Safety is increased when berthing in adverse weather conditions provided that the required thruster capacity has been correctly estimated. Transverse thrusters are installed to facilitate the positioning of some types of workboats. Some...

Shell and tube coolers

Tube Coolers Diagram

Shell and tube heat exchangers for engine cooling water and lubricating oil cooling (Figure 1.2) have traditionally been circulated with sea water. The sea water is in contact with the inside of the tubes, tube plates and water boxes. A two-pass flow is shown in the diagram but straight flow is common in small coolers. The oil or water being cooled is in contact with the outside of the tubes and the shell of the cooler. Baffles direct the liquid across the tubes as it flows through the cooler....

Refrigeration

Refrigeration is used in the carriage of some liquefied gases and bulk chemicals (Chapter 6), in air conditioning systems (Chapter 12) to cool bulk C02 for fire fighting systems (Chapter 14) and to preserve perishable foodstuffs during transport or storage, as described in this chapter. The principles of refrigeration, briefly stated below, are the same for each of the applications. Details of the different types of plant are described in the relevant chapters. The main consideration with a...

Centrifuges

Liquids with a specific gravity or relative density difference can be separated in a settling tank by the effect of gravity and the process can be represented mathematically by Clearly in a standing vessel the acceleration cannot be altered to enhance the Figure 2.12 Centrifuges arranged in series (courtesy Alpha-Laval) Figure 2.12 Centrifuges arranged in series (courtesy Alpha-Laval) separation force Fs, but by subjecting the operation to centrifugal force the above expression can be replaced...

Plate type heat exchangers

The obvious feature of plate type heat exchangers, is that they are easily opened for cleaning. The major advantage over tube type coolers, is that their higher efficiency is reflected in a smaller size for the same cooling capacity. They are made up from an assembly of identical metal pressings (Figure 1.4a) with horizontal or chevron pattern corrugations each with a nitrile rubber joint. The plates, which are supported beneath and located at the top by parallel metal bars, are held together...

Circulating systems for motorships

Salt Water Recirculating System

The usual arrangement for motorships (Figure 1.1) has been to have sea-water circulation of coolers for lubricating oil, piston cooling, jacket water, charge air, turbo-charger oil (if there are sleeve type bearings) and fuel valve cooling, plus direct sea-water cooling for air compressors and evaporators. The supply for other auxiliaries and equipment may be derived from the main sea-water system also. There may be two sea-water circulating pumps installed as main and stand-by units, or there...

Bilge and ballast system layout

In the system shown, (Figure 3.1) the bilge main has suctions from the port and starboard sides of the engine room, from the tunnel well and from the different cargo holds. There are three pumps shown connected to the bilge main. These are the fire and bilge pump, the general service pump and the auxiliary bilge pump. These pumps also have direct bilge suctions to the engine room port side, starboard side and tunnel well respectively. The ballast pump (port side for'd) could be connected to the...