1. REPAIR OF LEAKY TUBES.
Leakages at the point of insertion of the tubes are still generally and exclusively repaired by means of roller apparatus for opening the tubes, and with which an endeavor is made to tighten the latter in the hole in the tube-plate.
The cones which were formerly employed injured the ends of the tubes by splitting them; if the workman was not very skillful, the holes in the plate became oval; and fractures likewise quite often occurred between the holes in the plate itself.
The best apparatus to open the tubes are those in which the wedge that separates the rollers is actuated by a screw; those in which the wedge is driven in by a hammer are scarcely better than the old cones.
When apparatus for opening tubes are used, care must be taken to begin with the external tubes, and to open these gradually. The same operation is afterward performed upon the neighboring ones, in approaching the center, and then the first ones are taken up. The tubes should never be opened at one operation, but each one should be subjected to several passes.
At the second pass, the rollers should be placed a little more deeply, and should then be half within the tube-plate. The tube thus opens behind the plate and forms a bearing against it, and this not only renders it tighter, but also increases its adhesion to the plate. Finally, the operation is finished by beating down the edge of the tube that has been raised a little by the preceding pass. If this edge is already somewhat deteriorated, or if it is not very thick, tightness may be had by means of rings. The use of rings should be avoided as much as possible, because they diminish the section of the tubes, and render the cleaning of their interior more difficult. They should only be employed as an exception, and should be considered as an unavoidable evil. Even in old boilers, in which the holes have become oval, they should be considered only as a means of rendering a small number of tubes tight.