Process for repairing small leaks in metallic vessels
BACKGROUND AND OBJECTS OF THE INVENTION 
     Porosity or other-type small leaks in metallic vessels (castings) usually intended to hold fluids under high positive or negative pressure, are a serious economic problem in the metal-vessel (especially casting) art. Attempts to seal such leaks by electric or flame welding have proven generally unsatisfactory, especially if the vessel is an aluminum-alloy casting because the worked-on areas would be made rough and discolored by the attempted repair. It is accordingly the principal object of this invention to provide a metallic-vessel-leak-repair method that economically produces a structurally sound repair job and which leaves the repair area unblemished. Other objects and advantages will become apparent as the following description proceeds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a largely schematic elevational view showing the leak-locating step of the invention 
     FIG. 2 is a similar view illustrating the leak-area-cleaning step. 
     FIG. 3 is a like view showing the cement-applying step. 
     FIG. 4 is a similar view illustrating electric-induction-heating of the repair area. 
    
    
     DETAILED DESCRIPTION 
     With reference now to the drawings, the numeral 11 generally designates a hollow metallic (e.g. aluminum-alloy) vessel, usually a casting, having an open top sealingly closed by a plate 13 fixed thereto as by machine screws 15. At least one wall of the casting may have at least one later-useful outlet aperture 17, which is herein shown being temporarily used to introduce a gas under high pressure (e.g. 300 psi) through a hose 21 connected to a reversible variable-delivery pump 23. 
     In FIG. 1 the sealed vessel 11 is shown immersed in a water-bath 25. The gas bubbles B locate the leak 27 which is then marked, as by a crayon-applied circle 29. Then the vessel 11 is removed from the water-bath 25, and with high pressure maintained therein, the leak area is mechanically (abrasively) cleaned. 
     Next the pressure is released, a high partial vacuum is produced and cleaning liquid 30 (FIG. 2), as from a conventional spray-bottle 31, is applied to be sucked into and through the small leak 27. With the high partial-vacuum (e.g. minus 14 psi gage) maintained, a drop 33 of powdered-metal-filled epoxy or other volumetrically stable cement is applied (as by a tube or rod 35) to the leak 27 and is suction-drawn thereinto. 
     Simultaneously with or immediately after the cement application, the area is moderately heated e.g. to 300° F. by suitable means (e.g. an electric-induction-heating coil 37) to somewhat expand the leak hole for better filling and to accelerate (catalytic) setting of the cement. The heating could also be produced by a laser, by a maser or by infrared radiation focused onto the area by an ellipsoidal or other-type reflector in known manner. 
     The epoxy cement preferably will be filled with sufficient powdered metal (which is of the same composition as the casting metal or is a fully compatible one) to make the repair practically undetectable to the naked eye after the repair area is lightly abrasively cleaned to remove any excess cement.