MARINE AUXILIARIES

The temperature rise of the fluid (air) depends on compression ratio; as given by expression ������������������( )˟ = ˟������������������ϒ (for adiabatic compression) ������������������ ������������������ = Where T1 = absolute temperature at inlet P1 = absolute pressure at inlet P2 = absolute pressure at outlet ������������ −1 X = ������������ = a constant = 0.286 for air Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Compressor Capacity Compressor capacity is determined as volume of the free air actually discharge by compressor in one hour, It is termed as F.A.D ( Free air delivery) in m³/hour Hence, Ƞv = ������������������������������������������������������������ ������������.������������.������������ ������������������������������������������������������������ ������������������������������������������������������������ ������������������������������������������������������������������������ ������������������������ Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Factors affecting Volumetric Efficiency. 1. Clearance volume (Bumping clearance) adversely affects volumetric efficiency. High pressure air remaining in below that the cylinder after compression and delivery will expand on the return stroke of the piston. This expanding air must fall to a pressure below that in the suction manifold before air charge can be drawn in. Hence, part of the return or suction stroke must be kept as small as possible in order to keep capacity to a maximum. 2. Sluggish opening and closing of valves. 3. Leaking past piston rings. 4. Insufficient cooling water. 5. Cooling water temperature high. 6. Air inlet temperature high. 7. Throttling of air intake, (Due to dirty intake filter, insufficient or excess suction valve lift, suction valve spring too strong) Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

The Unloader Valve Example of unloader valve at compressor The air compressor unloader valve is a small, but important, Marine Auxiliaries / WAS / Jan 2021 part of the reciprocating piston compressor. It blows off the pressure inside the discharge pipe when the compressor stops Malaysian Institute of Marine Engineering Technology (MIMET)

Cont’ Marine Auxiliaries / WAS / Jan 2021 The output of the piston compressor is connected through a pipe to the air receiver. When the compressor stops, the pressure in this pipe is blown off to 0 bar (atmosphere). This is the ssssssshhh sound you will here when the compressor stops. At the same time, a check-valve makes sure that not the whole air receiver (tank) flows empty, but only this small pipe. Why? When the compressor starts up again, and this pipe would still be under pressure, the electric motor will not be strong enough to turn the compressor. Malaysian Institute of Marine Engineering Technology (MIMET)

Automatic Drain Valve Marine Auxiliaries / WAS / Jan 2021 Drain valves are a crucial part of the compressed air system. Condensate drain valves remove condensate from the air system without losing excessive compressed air and without shutting down the system. Condensate can have harmful effects on a system when not removed. For instance, moisture can wash lubrication from air tools and production equipment causing downtime and maintenance; an inconsistent supply of dry air can cause production quality problems; and excessive rust and scale can form in the air distribution system. Also, water can back up into the compressor and wreck the machinery, air dryers can become overloaded, and in-line filters can be destroyed. Malaysian Institute of Marine Engineering Technology (MIMET)

Cont’ These drains incorporate a solenoid valve and an electric timer. The timer usually has two settings: time between valve openings (usually in minutes) and amount of time the valve stays open (usually in seconds). The drain comes with an electrical cord that can be plugged into a wall outlet. By matching these two settings to the amount of condensate a system produces the condensate can be removed from the compressed air system. The goal is to set the timer long enough to empty all of the condensate but not so long that compressed air is wasted Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021



Cooling System For Air Compressor Example of cooling system for compressor − In order to restrict the rise of air temperature during compression, Marine Auxiliaries / WAS / Jan 2021 − The air is cooled by circulating water around the cylinder − Cooling water will be circulated by cooling water pump attached from the compressor shaft. Malaysian Institute of Marine Engineering Technology (MIMET)

Two Stages Compressor The main difference between single- and two-stage Example of 2-stages compressor compressors is the number of times that air gets compressed between the inlet valve and the tool nozzle. In a single-stage Marine Auxiliaries / WAS / Jan 2021 compressor, the air is compressed one time; in a two-stage compressor, the air is compressed twice for double the pressure. The process within a two-stage compressor — alternately referred to as a dual-stage compressor — is similar to that of a single-stage, but with one variation: the compressed air isn’t sent to a storage tank; it’s instead sent to a smaller piston for a second stroke, this time at roughly 175 psi. From there, the double-pressurized air is cooled and delivered to a storage tank, where it serves as energy for vast arsenals of high- powered equipment Malaysian Institute of Marine Engineering Technology (MIMET)

Malaysian Institute of Marine Engineering Technology (MIMET) Figure 124 : 2-Stage Air Compressor Marine Auxiliaries / WAS / Jan 2021

Air Cooler in System Cooling is a crucial step in the compressed air process. The ideal gas law tells us when the pressure on any constant volume of gas increases, the temperature also increases. Compressed air is no exception; it can become as hot as 300 degrees F. Without cooling, this level of heat can damage equipment, hurt employees and compromise products. There are two main steps for cooling compressed air. The intercooler removes heat from the air between compressor stages while the aftercooler is used for cooling air discharged from a compressor. Two methods can be implemented in each of these stages: water cooling and air cooling. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Example of aftercooler in compress air system Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

INTERCOOLING Intercooling Advantages of Intercooling: To avoid excessive temperature rise • Compression work is reduced. associated with higher compression ratios, and to approach isothermal compression, • Volumetric efficiency and hence compressor capacity is intercooling is adopted after each stage of increased. compression in multistage compression. • It approximates isothermal compression. Usually, delivery temperature from final stage is limited to 93º C (Lloyd’s Rules) • The volume of air delivered is reduced, requiring reduced sizes of cylinder, piston and delivery pipes. • The temperature of the delivered is reduced, which gives less thermal loading onto material and better lubrication of piston and cylinder. • Due to less temperature, suction and delivery valves remain cleaner without being fouled with carbonized oil. • moisture separation is easier through intercooler drain. • Use of after cooler allows smaller receivers. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

COMPRESSOR LUBRICATION • The lube oil system (Figure 4) supplies oil to the compressor and driver bearings and to the gears and couplings. The lube oil is drawn from the reservoir by the pumps and is fed under pressure through coolers and filters to the bearings. Upon leaving the bearings, the oil drains back to the reservoir. • When in operation, the compressor lubricant oil is normally circulated by the main oil pump. An auxiliary pump serves as a standby. These two pumps generally have different types of drive or power sources. When both are driven electrically, they are connected to separate supply feeders. • Heat generated by friction in the bearings is transferred to the cooling medium in the oil coolers. Air-cooled oil coolers may be employed as an alternative to water-cooled oil coolers. The former have long been used in regions where water is in short supply. A pressure-regulating valve is controlled by the pressure downstream of the filters and maintains constant oil pressure by regulating the quantity of bypassed oil. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Compressor Lubricants The overwhelming majority of compressors are best served by premium-grade turbine oils with ISO viscosity grades of 32 or 46. However, there are many different types of compressors and each manufacturer is likely to recommend lubricants that have been used on a test stand and at controlled user facilities. Premium-grade ISO VG 32 turbine oils are used more often than the heavier viscosity grades. The typical viscosity index is 97, with a pour point around -37ºC (-35ºF). Oxidation stability (per ASTM D943) should exceed 5,000 hours and the flash point (per ASTM D92, COC) should below 206ºC, or 403ºF. These lubricants must provide the following: •Long life without need for changeout •Prevention of acidity, sludge, deposit formation •Excellent protection against rust and corrosion, even during shutdown •Good demulsibility to shed water that enters the lubrication system •Easy filterability without additive depletion •Good foam control Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021









Operation : Starting and Stopping the Air Compressor Checks before Starting the Air Compressor The following steps are to be followed before starting an air compressor on a ship. 1. Check the lube oil in the crankcase sump by means of dipstick or sight glass. 2. All the valves of compressor discharge must be in normally open condition. 3. If any manual valve is present in un-loader line, it must always be kept open. 4. All alarms and trips- Lube oil low pressure, water high temperature, over load trip etc. must be checked for operation. 5. All valves in cooling water line must be in normally open position. 6. Cocks for all the pressure gauges must be in open position. 7. Air intake filter should be clean. 8. If compressor has not been started from long time than it should be turned on manually with a tommy-bar to check for the free movement of its parts. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Checks during the Operation of Compressor 1. Check if all the pressure gauges are showing correct readings of lube oil pressure, water pressure etc. 2. Check for any abnormal sound like knocking etc. 3. Check for any lube oil or water leakages. 4. If cylinder lubrication is provided, check the supply from sight glass. 5. Check if the discharge pressure for all units is normal. 6. Check air temperature after the final stage is under limit. 7. Check the flow of cooling water from sight glass. 8. If attached cooling water pump is provided check for its free rotation. 9. Check the relief valve of all units for leakage. In some compressor, provision is given to check the relief valve with hand lever, if provided check all units. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021





























Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

A high-speed centrifuge is a type Example of fuel before and of separator which is used on a after purifier ship to remove contamination from liquids such as fuel and lube oils. Marine Auxiliaries / WAS / Jan 2021 It is imperative to carry out this treatment in order to remove solid impurities and water before they are supplied to the marine engine Malaysian Institute of Marine Engineering Technology (MIMET)

Oil treatment • Both fuel oils and lubricating oils require treatment before passing to the engine. This will involve storage and heating to allow separation of water present, coarse and fine filtering to remove solid particles and also centrifuging. • The centrifugal separator is used to separate two liquids, for example oil and water, or a liquid and solids as in contaminated oil. Separation is speeded up by the use of a centrifuge and can be arranged as a continuous process. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Cont’ • Where a centrifuge is arranged to separate two liquids, it is known as a 'purifier'. • Where a centrifuge is arranged to separate impurities and small amounts of water from oil it is known as a 'clarifier’. • The separation of impurities and water from fuel oil is essential for good combustion. The removal of contaminating impurities from lubricating oil will reduce engine wear and possible breakdowns. • The centrifuging of all but the most pure clean oils is therefore an absolute necessity. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Differences between purifier and clarifier ? Purifier 1.Remove water and suspended solids particles from oils 2.Two outlets water and clean oil 3.Gravity disc on top 4.Blind disc on the top of disc stack 5.Sealing water required Clarifier Marine Auxiliaries / WAS / Jan 2021 1.Remove finer and lighter particles from oil 2.One outlet for clean oil 3.No gravity disc only sealing ring 4.Blind disc at bottom. 5.Sealing water not required Malaysian Institute of Marine Engineering Technology (MIMET)

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Clarifier characteristic: 1. A clarifier bowl is design to separate solids from oil/liquid. 2. Only one outlet and no gravity disc, it’s mean no interface is formed. 3. Cleaning oil which contain little or no water is achieved in a clarifier bowl where the impurities/sludge and water collect at the bowl periphery. Purifier characteristic 1.The centrifugal separation of two liquid and solids, such as oil and water. 2.It’s design with two outlet . 3.Have a gravity disc to formed the interface cylindrical water seal between oil and water. 4.The setting of the interface is achieved by use dam ring or gravity disc at outlet of the centrifuge; various diameter rings are available for each machine when different densities fuel are used. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

So, how does the oil purifier/clarifier concept? If you have a bucket of a mixture of dirty oil and water and you leave it in a quiet place to settle, what will happen? You will find that after a long time, the oil will separate out from the water. And if the solid particles are heavy enough, they will also settle at the bottom of the bucket. Notice that the separation is due to gravity (or specific gravity). Heavy bunker fuel oil has an SG of about 0.95, diesel oil about 0.85 and fresh water has an SG of 1. Because of the difference in Specific Gravity, or SG, the oil will float on top of the water. The solid particles that is heavier than water will sink down. But the above method will take a long time. Furthermore, if the SG's of the mixture are very close, the oil and the water may not be able to separate very well. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021