Process for repairing small leaks in metallic vessels

Porosity or other types of small leaks in metallic vessels designed to hold fluids under pressure or partial vacuum are repaired by: (1) sealing the chamber of the vessel, (2) introducing (preferably inert) gas at high pressure into the chamber, (3) immersing the vessel in a liquid (water) bath to locate and mark the leak(s), (4) mechanically cleaning the leak areas(s) while the gas pressure is maintained, (5) releasing the gas pressure and drawing a high partial vacuum in the chamber, (6) applying solvent to the leak area(s) to be suction-drawn through, and to clean, the leak(s), (7) while maintaining the partial vacuum, applying a liquid epoxy cement filled with a powdered metal compatible with that of the vessel, and (8) promptly heating the repaired area(s) to a moderate temperature and then releasing the vacuum. The repair will set in a few minutes and cure in several hours. The repair area(s) can be lightly abrasion-cleaned to remove any excess cement.

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.

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.degree. 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.