This document discusses fire-tube boilers and water-tube boilers. It begins by explaining that steam generators produce steam at desired rates and pressures by burning fuel in a furnace. It then describes that fire-tube boilers have combustion gases pass through tubes surrounded by water, while water-tube boilers have water pass through tubes with combustion gases on the outside. Key differences are that fire-tube boilers can only produce saturated steam up to 18 bars pressure, while water-tube boilers can reach much higher pressures and produce drier steam.

1. SUMITTED TO: SUBMITTED BY:
Prof. (Dr.) K. V. S. Rao Shiv Shanker
Prof. & Head 15/947
DEPARTMENT OF RENEWABLE ENERGY
RAJASTHAN TECHNICAL UNIVERSITY, KOTA

2.  Introduction
 Types
 Fire-Tube boilers
 Water-Tube boilers
 Diff b/w fire-tube boiler &water-tube boiler
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3.  A Steam Generator generate steam at desired rate at the desired pressure and
temperature.
 The steam generation is done by burning fuel in the furnace .
 A steam generator is a complex integration of furnance, superheater, reheater,
boiler or evaporator, economiser and air preheater along with various
auxiliaries such as pulverizers, burners, fans, stokers, dust collectors and
precipitators, ash-handing equipment, and chimney or stack.
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4. 1. On the basis of flows of fuel gases and water:
 Fire-Tube Boilers(P=18bar)
 Water-Tube Boilers(P=180bar)
2. From the point of view of applications:
 Utility steam generators (P=130-180bar)
 Industrial steam generators (P=5-105bar)
 Marine steam generators(P=60-65bar)
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5.  In this boiler, the product of combustion pass
through its tubes, which are surrounded by water.
 Fire tube boiler is one of the most basic types of boiler
and the design is also very old. It was popular in 18th
century. It was mainly used for steam locomotive engines.
 It produce saturated steam at the upper limit of about 18
bar pressure and 6.2 kg/s steaming capacity.
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6. External Fired:
6Fig.1: A typical fire-tube boiler

7. Working
 In fire tube boiler, the coal is burnt inside a furnace. The hot gases
produced in the furnace then passes through the fire tubes.
 The fire tubes are immersed in water inside the main vessel of the
boiler. As the hot gases are passed through these tubes, the heat
energy of the gasses is transferred to the water surrounds them.
 As a result steam is generated in the water and naturally comes up
and is stored upon the water in the same vessel of fire tube boiler.
This steam is then taken out from the steam outlet for utilizing for
required purpose. The water is fed into the boiler through the feed
water inlet.
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8. Internal Fire Tube:
8Fig.2:An oil-fired package boiler

9. Working
 An oil-fired package boiler is an internally fired fire-tube boiler, since the
furnace is within the cylindrical shell. Oil is filtered, sufficiently heated either
by electricity or steam, and is then fed through the burner.
 Air is supplied by an FD fan. Excess oil is returned to the main fed line
 Combustion occurs in a horizontal corrugated flue, and the combustion gases
flow through the tubes in two passes till they are let out through a chimney to
atmosphere.
 The corrugations of the flue increase strength and help in allowing thermal
expansion and contraction, also in cracking and removing the carbon deposited.
 The gases get cooled as they flow through the tubes and water is heated to form
steam.
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10. Advantages:
 Low installation cost
 Reliability in operation
 Need of only unskilled labour
 Quick response to load changes
Disadvantages
 As the water required for operation of the boiler is quite large, it requires
long time for rising steam at desired pressure.
 As the water and steam are in same vessel the very high pressure of steam
is not possible.
 The steam received from fire tube boiler is not very dry.
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11.  Water-tube boilers were developed to permit increases in
boiler pressure and capacity with reasonable metal
stresses.
 In water tube boilers, water flows through the tubes and
flue gases flow outside them. Puts the pressure in the
tubes and the relatively small diameter drums, which are
capable of withstanding extreme pressures of the modern
steam generator.
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12. 12Fig.3: Early water-tube boiler

13.  Straight-TUBE Boiler can be made, installed and replaced easily. The
tubes were of 75-100 mm O.D., inclined upward of about 15 degree to the
horizontal.
 Nearly Saturated water leaving the drum flowed through downcomer, into
the tubes. While flowing upward in the tubes some the water on being
heated by flue gases flowing outside gate transformed to vapour. Water-
Steam mixture went back to the drum through riser.
 Because of density difference, natural convection takes place. The drum
was arranged either parallel or perpendicular to the tubes
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14. 14Fig.4:A four-drum bent tube boiler

15.  Bent-Tube Boilers is being greater accessibility for inspection
, cleaning and maintenance and ability to operate at higher
streaming rates and to deliver drier steam.
 In a bent-tube boiler, the tube where so bent that they entered
and left the drum rapidly.
 The combustion gases flowed upward from the furnace
through the first bank of tubes connecting the front steam
drum and the mud drum and then second and third tubes banks
coonecting to the second and rear steam drum.
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16. 16
Table 1 : Difference B/W Fire-tube Boiler & Water-tube Boiler

17. THANK YOU
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