FUSIBLE PLUG
We have told you about a safety valve, we will now have something to say
of a safety plug. A safety, or fusible plug, is a hollow brass plug or
bolt, screwed into the top crown sheet. The hole through the plug being
filled with some soft metal that will fuse at a much less temperature
than is required to burn iron. The heat from the firebox will have no
effect on this fusible plug as long as the crown sheet is covered with
water, but the moment that the water level falls below the top of the
crown sheet, thereby exposing the plug, this soft metal is melted and
runs out, allows the steam to rush down through the opening in the lug,
putting out the fire and preventing any injury to the boiler. This all
sounds very nice, but I am free to confess that I am not an advocate of
a fusible plug. After telling you to never allow the water to get low,
and then to say there is something to even make this allowable, sounds
very much like the preacher who told his boy "never to go fishing on
Sunday, but if he did go, to be sure and bring home the fish.
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