Re: Case Boiler Explosion

Smitty;
A couple of months ago an operator lost two soft plugs the same day. In fact within a little over
an hour.
In both instances he had 2/3 to 3/4 glass of water showing.
Soft plugs are filled with 95/5 tin lead mixture that melts at about 450 degrees. There is no mistake that an operator can make that will change the melting point of that mixture.
This operator called me and I went over to check.
He was sure that there was something wrong with the soft plugs because he had water showing in the glass. Investigation showed that the opening in the top glass cock was plugged. These openings are small so as to reduce the amount of steam freed when a gauge glass breaks. Steam condensing above the water in the glass created a vacuum that pulled water up into the glass. IOW,
the glass was lying to him. The soft plugs did what they were supposed to do, they melted. and as I told him he is just damned lucky they did.
From reports that I have read it appears that there was a deteoriated crown sheet in the Case
and that probally had a bearing on the accident.
But, just because you saw water in the glass doesn't mean that there couldn't have been low water.
Jim