Fire tube boiler and Water tube boiler

Water tube boilers are better suited for the high pressures and temperatures requirements. Higher pressures require greater wall thickness, but this reduces heat transfer. The practical limit is about 16bar pressure.

Fire / smoke tube boilers are also more prone to catastrophic failure. The water - and energy - in a Scotch boiler, say at a modest pressure of 10 bar, is enough to launch the boiler through bulkheads and accident in the boiler room.

Fire tube boilers have limitation of pressure & temperature as only saturated steam can be obtained, for power generation high pressure superheated steam is needed for turbine which is possible in water tube boilers with integral super heaters. Water tube boilers are good for cyclic loads as the steam drum has holding capacity more than fire tube design steam space. Fire tube boilers have a constraint of fuel selection such as oil / gas. There are integral furnaces fire tube boilers for solid fuels too but the overall efficiency of this design is poor. The water tube boilers can be fired with any fuel and has a varied scope of fuel selection. With very efficient modes of firing such as FBC, CFBC etc. water tube boilers are safer to operate than fire tube boilers.

All designs have their respective limitations, Fire Tube design is limited to low pressure, low capacity output only since it is design and constructed that much only.

Water tube boilers lend themselves to modern modular construction techniques more than fire tube boilers. Even in field-erected water-tube boilers, most of the fabrication - for instance, water-wall panels - can be done in a workshop under controlled conditions or using automated equipment. This improves quality and reduces construction time and costs

Fire tube boilers are due to their big shell diameter not suitable for high pressure and temperature.

Water tube boiler is the fast steam generation and low water holding capacity boiler so we can design compact type boiler than fire tube boiler and water tube boiler has more heating surface than fire tube boiler.

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Comparison between fire tube boiler and water tube boiler.