Preperforated coiled tubing

Preperforated pipe milling machine is produced by forming a perforation in flat strip of raw material, forming a hollow, cylindrical tube from the flat strip, and placing a removable plug into the perforation, so as to form a fluid-tight seal. A sealing element may be placed into the perforation. The perforation may comprise a hole, into which first and second countersinks may be formed. The sealing element may be placed into the first countersink, and the plug may be placed through the countersinks and the hole, such that the plug's body fills the hole and the plug's head fits within the second countersink.
The invention provides preperforated steel pipe machine in which quick, easy, low-cost perforation of the tubing material is possible. The invention, in the preferred form, is used in conjunction with coiled tubing. However, it is within the scope of the invention to provide preperforated steel pipe machine, such as that which may be retrofitted to an end of a length of coiled tubing or connected between two lengths of coiled tubing. The invention also provides preperforated coiled tubing in which the perforation plugs can withstand repeated coiling and uncoiling stresses without leaking.
In another aspect of the invention, a method of perforating steel pipe making machine comprises the steps of forming a substantially circular hole in a section of tubing material; forming about the hole a first countersink having a first diameter and a first depth, the first countersink being substantially concentric with the hole; forming about the hole a second countersink having a second diameter and a second depth, the second countersink being substantially concentric with the first countersink and the hole, the second diameter being larger than the first diameter, and the second depth being smaller than the first depth; placing a sealing element substantially within the first countersink; and inserting a plug through the first and second countersinks and the hole; wherein a body of the plug substantially fills the hole and a head of the plug fits substantially within the second countersink, and wherein the sealing element and the plug cooperatively form a fluid-tight seal between an inner surface and an outer surface of the tubing material. In another aspect, the tubing material comprises a section of hollow cylindrical tubing. In still another aspect, the tubing material comprises a section of flat strip, and the method further comprises the step of forming a tube from the flat strip.