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Classification & Types of Boilers. Rajan Bhandari Singapore Maritime Academy. Introduction. Know the need for steam on a motor vessel. Know the principles involved in heat transfer and in generating steam in a boiler. Know the various ways the boilers can be classified.
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Classification & Types of Boilers Rajan Bhandari Singapore Maritime Academy
Introduction • Know the need for steam on a motor vessel. • Know the principles involved in heat transfer and in generating steam in a boiler. • Know the various ways the boilers can be classified. • Know the basic constructional features of some of the popular boilers used.
Overview This is a introductory lecture and explains • the use of steam and • application of various types of boilers for use on a motor vessel.
Vocabulary • Smoke tube, • Fire tube, • Tank Type, • Drum Type • Carnot efficiency
Use of Steam • Heating duties: ME Fuel oil heater, Purifier heater, Oil tank heating, Cargo heating, Air conditioning & heating plant, Calorifier, Galley supply, sea‑chests, tracer lines for pipeline heating etc. • Run Turbine Generators • Run Cargo pump turbines in Tankers • Drive steam driven deck machinery like winches etc. • Operate bilge, stripping and other steam driven pumps • Drive boiler feed pump turbines • Evaporator/Fresh water generator heating media
Use of Steam • Tank washing in tanker ships and general cleaning • For boiler Soot blowing and for the steam atomised burners • Fire fighting as used in steam smothering system • Main engine Jacket F.W. preheater and Lub oil sump and drain tanks • Use in the waste oil, incinerator, slop tanks • Use as a steam ejector media for ejector pumps and • vacuum deviceswater generator heating media
Types of boilers • Main Boiler- Propulsion of the vessel • Auxiliary Boiler-Heating of heavy fuel oil using a steam heater, necessary for propulsion would qualify the supplying boiler to be referred to as an auxiliary boiler. • Tank Boiler-A boiler with large water carrying capacity where the shell is being used as the pressure vessel. Most low pressure auxiliary boilers will come into this category. • Exhaust Gas Boiler- Boiler operated by hot gas from engine or other exhaust gas sources. • Drum Type Boiler-Water tube boilers employing steam and water drums. They are also known as bent tube type boilers. • Package Boiler -Fully automatic, low capacity boilers packaged inside a box type casing, capable of quick steam production and flexible in being positioned anywhere; could be coil type or fire tube type.
Fire tube concept Shell with fire tubes inside Tank type boiler Water tube concept Drum with fire tubes Smoke tube & Water tube boilers
Fire tube concept Shell with fire tubes inside Tank type boiler Water tube concept Drum with fire tubes Tank type & Drum type boilers
Principle of heat transfer in boilers • Radiation • Conduction • Convection
Limiting the stress • Longitudinal stress = Pressure x diameter 4 x thickness of wall
Limiting the stress • Circumferential stress = Pressure x diameter 2 x thickness of wall
Fire tube concept Shell with fire tubes inside Tank type boiler Water tube concept Drum with fire tubes Maximum working pressure • Max working press. = Max stress x 2 x wall thickness diameter • Therefore Tank type boiler max press limited to 17.5 bar
Water and steam flow diagram • Blue: the downcomers lead the water from the steam drum to the water drum and the waterwalls headers. • Red and blue: the evaporation tubes and the water walls lead the water and steam emulsion back to the steam drum. • Red: the steam passes through the superheater before it leaves the boiler for the consumers.
Boiler with integral super heater Keep superheater vent open and maintain flow to prevent overheating
Carnot efficiency • Carnot's Eff iciency % = (T1 ‑ T2 ) x 100 (T1) • Turbo alternator • T2 at condenser T1 T2
Efficient heat exchange • Thickness of the tube material reduces its conductivity but it is an important factor in limiting stresses in the material • Heat conducted = Difference in temp x area x time thickness of material T1 T2
Summary • Need for steam on a motor vessel. • Principles involved in heat transfer and in generating steam in a boiler. • Various ways the boilers can be classified. • Basic constructional features of some of the popular boilers used.
Where to Get More Information • Morton, Thomas D, Steam Engineering Knowledge for Marine Engineers (1994), Thomas Reed Publications • Flanagan, G T H, Marine Boilers Question & Answers (1995) • Operation Manuals, Aalborg Boilers • Operation Manuals, Miura Boilers • Milton, J H and Leach, Roy M, Marine Steam Boilers (1995)
