Abstract: A plug for sealing the open end of a tube located in an opening in a tube sheet of a heat exchanger is described along with a method of installing the plug. The plug is comprised of a generally cylindrical metallic body of ductile material that is inserted into the open end of the tube at the tube sheet. The body carries one or more resilient seal rings and has a longitudinally extending blind central opening in the body. A body of pressure transmitting material, such as polyethylene is located in the body and an explosive charge is located in a longitudinally extending central opening in the body of pressure transmitting material. The explosive charge, when detonated, expands the metallic body of the plug and the resilient seal ring into sealing engagement with the tube.

Abstract: A method of and apparatus for severing multiple concentric casing strings in an abandoned oil or gas well allowing the upper portion of the casing strings to be removed comprising positioning a container holding a sealed cylinder full of air at atmospheric pressure that is surrounded by a high velocity explosive in the casing at the location of the desired cut. Igniting the explosive at one end of the container so that the mixture detonates producing a shock wave and gas bubbles that travel downwardly progressively, collapsing the sealed cylinder and increasing the pressure of the air in the cylinder until the cylinder fails whereby pressurized air forced from the cylinder causes the shock wave and gas bubbles from the TNT, RDX, and aluminum mixture to move laterally and sever the casing strings.