If the boiler is to be worked at 50 lbs., I watch the steam
gauge through a telescope until 100 lbs. is recorded, then draw the lamp
away. After passing the test, the boiler, when pressure has fallen, say, 20
lbs., may safely be inspected at close quarters for leaks.
This test is the only quite satisfactory one, as it includes the influence
of high temperature, which has effects on the metal not shown by "cold"
tests, such as the hydraulic.
Do not increase your working pressure without first re-testing the boiler
to double the new pressure to be used.
Fuels.--For very small stationary boilers the methylated spirit lamp is
best suited, as it is smell-less, and safe if the reservoir be kept well
apart from the burner and the supply is controllable by a tap or valve.
(See Fig. 104.)
[Illustration: FIG. 95.-Paraffin burner for vertical boiler.]
For medium-sized model boilers, and for small launch boilers, benzoline or
petrol blow-lamps and paraffin stoves have become very popular, as they do
away with stoking, and the amount of heat is easily regulated by governing
the fuel supply.
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