Improved Method of Attaching Tubes to Boiler Tube Plates.
Year: 1892

page_text: COMPLETE SPECIFICATION.
Improved Method of Attaching Tubes to Boiler Tube Plates.
THOMAS DANIEL BELFIELD 6 Waldegrave Park Twickenham Middlesex
Gentleman do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement :-
The present method of securing boiler tubes in the tube plates of fireboxes and
combustion chambers has shown itself to be unsatisfactory when they are exposed
to excessive heat. In such cases the ends of the tubes, which must have been
seriously strained when new and while being expanded to fill their respective holes
in the tube plate, tend to contract again, thus causing leakage at their circum-
ferences.
The object of my invention is to prevent this leakage by removing one of the
causes of contraction, and this is effected by compressing the circumference of the
back end of each tube before fitting it in place, and by securing the tubes in their
correct positions without expanding their back ends as at present.
One end of each tube is placed in a suitable press, and, while in a cold condition,
is subjected to a pressure of sufficient intensity to reduce its diameter about
three per cent. The moulds of the press should be so shaped, that when finished,
the tube ends should be perfectly circular and slightly conical. Perfection will
only be possible if the tube ends are turned smooth in a lathe, either before or
after they are compressed.
The holes in the back end tube plates, into which it is intended to fit these tubes,
should be carefully bored or rimered, so that they are all of the same diameter as
the compressed ends of the tubes and of the same taper. The holes in the front
end tube plates should be large enough to allow the tubes to be passed through
them.
The tubes should now be firmly driven into the holes in the back tube plate with
sufficient force to ensure that the joint will be a watertight one. These back ends
should not be expanded, but other means may be adopted to make them fit
perfectly such, such as cooling the ends before inserting them, or warming the tube
plate, or beading the ends when in place.
At their front ends the tubes may be expanded in accordance with the present
practice.
ን
Stay tubes can be treated in the same way as plain tubes, the threads at their
back ends being cut either before or after the cold compression. They, as well as
the tapped holes in the back tube plates, should be slightly taper. Expanders
should not be used, but the seams may be caulked, or other means adopted, to make
them watertight.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :
1. The use of boiler tubes whose back ends have been compressed circum-
ferencially while cold and without subsequent annealing.
2. The use of boiler tubes whose back ends have been conpressed circum-
ferencially while cold and without subsequent annealing, and whose back ends
have been turned circular or threaded and made taper either before or after
compression.