Package boiler

Typical gas-fired package boiler

A package boiler or packaged boiler[1] is a modern form of steam boiler. They are factory-made to a range of standard designs, according to the size and evaporative capacity required.[2] They are used as both hydronic boilers for heating and as steam generators for small power purposes. The advantages of a package boiler are that they are available 'off the shelf' without a lengthy design step and also that they are simpler to install. Package boilers are also cheaper to operate as they automatically manage their burner and water level, so not requiring the continual attention of a boilerman.[3]

Package boilers are not used for large-scale power purposes such as electrical power generation. These use more complex and more efficient custom-designed boilers, usually today water-tube boilers working at high pressure.

Internal arrangement

Internal layout

The internal arrangement of a package boiler is usually a one- or two-pass fire-tube boiler with an internal furnace tube. This is similar to the much earlier Scotch boiler.

Combustion

Package boilers are fired with fluid fuels, either liquids or gases. These use fuel-supplied burners that do not require manual stoking, as solid fuels would. They also burn cleanly, without requiring the grates and ashpan that a solid fuel furnace does.

Burners use built-in electric fans to provide draught through the burner. This encourages mixing with combustion air, thus good burner performance. Liquid fuels are often pressurised with a spray burner, supplied by either a fuel pump or a compressed air supply. Burner electronics is increasingly sophisticated, with auto-ignition and on-demand lighting as a common feature, leading up to flame monitoring and for the most sophisticated, closed-loop control of the fuel mixture based on monitoring the flame colour or exhaust gases.[4]

As well as flame monitoring, the water level is also maintained automatically.[3]

Draughting

A great cost-saving for package boilers is their simple need for draughting. The chimney may either use an existing masonry chimney, or else a simple steel tube stack is provided, just sufficient to clear the nuisance of the exhaust fumes. As the burner provides its own draught from a fan, they do not require the tall brick chimneys needed to provide the draught for a coal-fired boiler.

See also

References

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  1. ↑ Milton, J. H. (1961) [1953]. Marine Steam Boilers (2nd ed.). Newnes. pp. 205–215.
  2. ↑ "Package Boilers". Foster Wheeler.
  3. ↑ 3.0 3.1 Milton Marine Steam Boilers, pp. 214–215
  4. ↑ "Measurement of Oxygen Concentration in Package Boiler Flue Gases". Yokogawa Electric Corporation.