Patent ID: 7159603

Claim:
In a method for hot tapping equipment composed of a structural material, said structural material having an inner surface that defines and encloses an interior volume of said equipment and an exterior surface exposed to an atmosphere that surrounds said equipment, said structural material having a finite thickness between its inner and outer surfaces, said interior volume containing a fluid that has a chemical composition that is at least one of decomposable and flammable, said equipment being surrounded at least in part by an exterior atmosphere that contains oxygen, the improvement comprising determining an area of said equipment for the removal of a coupon from the full thickness of said structural material by hot tapping thereby to expose said interior volume to said surrounding atmosphere by way of the area exposed by the removal of said coupon, based on the chemical composition of said fluid determining a target temperature which is the maximum temperature said structural material will reach during said hot tapping, drilling with a drill means carrying a drill bit a pilot hole in the area where said coupon is to be removed, said drill means carrying a coupon retaining means, said pilot hole drilling being accomplished without exceeding said target temperature by employing at least one of cyclic drilling composed of alternate periods of drilling and non-drilling and refrigeration, after said pilot hole is drilled and said drill bit extends through said structural material and said retaining means is in place to catch and support said coupon after severance of same from said equipment drilling said coupon out of said structural material, said coupon drilling being accomplished without exceeding said target temperature by employing said at least one cyclic drilling and refrigeration, and removing said coupon whereby said interior volume is exposed to said atmosphere.