MARINE AUXILIARIES

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

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

Maintenance of evaporator plant. During the operation of evaporating plants, scale will form on the heating surfaces. The rate of scale formation will depend upon the operating temperature, the flow rate and density of the brine. Scale formation will result in greater requirements for heating to produce the rated quantities of distilled water or a fall-off in production for a fixed heating supply. Cold shocking, the alternate rapid heating and cooling of the tube surfaces, for a boiling process type, can reduce scale build-up.  The plant must be shut down and the scale is removed either by chemical treatment or manual cleaning. 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

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

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

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

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



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

• Air compressor is a device with vast application in almost all sorts of industries and household requirements. In the maritime industry as well, air compressors are used in essential equipment or the feeder equipment to different systems. They can be employed in a number of processes ranging from small process of cleaning of the filters to the bigger and crucial tasks such as starting main as well as secondary engines. • Air Compressor produces pressurized air by decreasing the volume of air and in turn increasing its pressure. Different types of air compressors are used according to the usage. • In a more technical language, an air compressor can be defined as a mechanical device in which electrical or mechanical energy is transformed into pressure energy in the form of pressurized air. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

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

Application Of Air Compressor On Ships • For Starting main and auxiliary engines • For Control air and service air application on board ship • For various automation and controls, general service application • Painting and spraying • To operate pneumatic hand tools such as rivets sets, drills • To blow air Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Working Principles of Air Compressor (Single Stage) • A reciprocating air compressor consists of a Left : Suction stroke piston, connecting rod, crankshaft, wrist pin, Right : Discharge Stroke suction valve and discharge valves. Marine Auxiliaries / WAS / Jan 2021 • The piston is connected to the low and high side of the suction line and discharge line. The crankshaft rotates which in turn rotates the piston. • The downward moving piston reduces the pressure in the main cylinder, the pressure difference will open the suction valve. Malaysian Institute of Marine Engineering Technology (MIMET)

• The piston is taken down by the rotating Example of air bottle crankshaft and the low-pressure air gets filled in on ship the cylinder. Now the piston reciprocates upward and this upward movement starts building up the Marine Auxiliaries / WAS / Jan 2021 pressure and closes the suction valve. • When the air gets pressurized to its specific value discharge valve gets opened and the pressurized air starts moving through the discharge line and gets stored in air bottle. • This pressurized air in air bottle can be used to run the main as well as auxiliary engines later on. There can be single acting and a double-acting reciprocating air compressor on the ship. Malaysian Institute of Marine Engineering Technology (MIMET)

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















Theory of Compressor Equation of state for perfect gas is: PV = mRT where, P = Absolute pressure (N/m²) V = Volume (m³) m = Mass (kg) R = Gas constant (Nm/kgK) T = Absolute Temperature (ºK) During compression, volume reduces, pressure and temperature increase; While mass remains same ������������������������ Thus : ������������ = mR = Constant Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Pressure DVC DVO Discharge Compression SVO Suction SVC Volume Suction Valve Piston Discharge Marine Auxiliaries / WAS / Jan 2021 Valve Malaysian Institute of Marine Engineering Technology (MIMET)

Process of compression increases the pressure by reducing the volume, but at related by the given equation, temperature also rises. Depending on the allowed rise of temperature the compression can be of following type. 1. Isothermal Compression: It is the compression at constant temperature. In practice, it means that the temperature by the gas ( air ) remains constant throughout the compression. It means that heat of compression is immediately taken away. This type of compression theoretically is most efficient compression, but difficult to achieves. Very slow moving piston in a well cooled small bore cylinder can approach Isothermal compression Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

2. Adiabatic (Isentropic) Compression It is the compression under constant enthalpy condition. i.e. on heat is given to or taken from the gas through the cylinder walls and all the work done in compressing the gas is stored within it. During this compression the temperature rises progressively causing increase in rate of pressure rise which calls for increased power input to piston. This gives it poor efficiency. Avery fast moving piston in totally insulated cylinder will give adiabatic compression. 3. Polytropic compression It is the compression process which lies in between two extremes of isothermal and adiabatic compression. Here, some parts of heat of compression is usually extracted by Jacket cooling and multistaging with inter cooling is used to reduce work of Compression Following figure show PV diagram of the various compression processes Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

P 3 2 The figure show P2 clearly the extra work adiabatic done by compressing polytropic adiabatically, hence it isothermal would be more sensible to compress 4 P1 1 isothermally. V However, this would required a very slow, long stroke piston running in a small bore perfectly cooled cylinder which would give very low air delivery Compressor work for various types of compression indicated in a P – V diagram Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

The figure show clearly the extra work done by compressing adiabatically, hence it would be more sensible to compress isothermally. However, this would required a very slow, long stroke piston running in a small bore perfectly cooled cylinder which would give very low air delivery Multistage Compression If we had an infinite number of stages of compression with coolers in between each stage returning the air to ambient temperature, then we would be able to compress over the desired range under near isothermal conditions. This of course is impracticable so two or three stage compression with interstage and cylinder cooling is generally used when relatively high pressure have to be reached Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

3 STAGE COMPRESSION P Shade area represents work saved due to multistage compression with interstage cooling 3rd stage Inter stage cooling reduces air volume and temperature 2nd stage Interstage cooling Isothermal Compression 1st stage Actual compression V Figure show clearly the work saved by using this method of air compression, but even with efficient cylinder cooling the compression curve is near the adiabatic than the isothermal and MatlhaeysfiaanstIensrttithuetedoefliMvearriyneraEtnegtinheeemrinogrTeecthhnisowlogilyl (bMeIMsoET) Marine Auxiliaries / WAS / Jan 2021

Clearance Volume To provide the thermal expansion and for machining tolerances, a small clearance, called, Bumping clearance, is left between cylinder head and the piston. This clearance must be as small as possible, as its increase will reduce the volumetric efficiency and hence capacity of the compressor P2 Bumping clearance P1 Vs Malaysian Institute of Marine Engineering TechnologyV(pMIMET) Marine Auxiliaries / WAS / Jan 2021

Volumetric Efficiency Volumetric efficiency is the ratio of the actual volume of air drawn in each suction stroke to the stroke volume. Referring to the adjacent figure; Volumetric efficiency = Ƞv = ������������������������ ������������������������ To standardise, volume of delivered air is taken at atmospheric pressure (1.013 bar) and 15º C temperature. This is termed as volume of “free air” Thus, Ƞv = ������������������������������������������������������������������������ ������������������������ ������������������������������������ ������������������������������������������������������������������������������������������������������������ ������������������������ \"������������������������������������������������ ������������������������������������������ ������������������������������������������������������������ ������������������������������������������������������������������������ ������������������������ ������������������������������������������������������������ ������������������������������������������������������������ The ratio of the absolute inlet pressure to the discharge pressure is called compression ration, and is donated by: ϒ ������������������ = ������������������ Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021