Re: Egg ended boiler

Peter Evans

The key is the presence or absence of any way of determining the water level
in the boiler. If there are no places to put a water gauge, it is an air
compressor receiver. (Compressed air in mines was introduced into Australia
I think in the late 1860s). Air receivers were commonly converted from old
boilers (a Babcock & Wilcox "Wrought-Iron-Front" steam and water drum was a
favourite choice), so even this test is not conclusive. And air receivers do
have safety valves too. My money is very heavily on a purpose-built air
receiver (on account of the non-flanged ends) but I would actually have to
see it to make sure.

Egg-ended boilers are very ancient devices. The Cornish boiler was invented
by Richard Trevithick in 1812, and quickly supplanted the egg-ended boiler
and its close cousin, the elephant boiler. The big problem with egg-ended
boilers was their lack of efficiency and the fact that the hottest gases
impinged on the part of the boiler where there was potentially the greatest
deposition of sediment. Mistaking air receivers for boilers is more common
than you may think - even in reputable journals like "Australasian
Historical Archaeology" published by ASHA. One has to laugh when confronted
by a proud archaeologist standing next to a "wood-fired steam engine" (yes,
that was actually the caption!) when its ever so clearly an air receiver!

Peter Evans

Production Management, Corporate Writing and Heritage Services

0407 537 837 <>

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