The characteristics of electromagnetic waves propagating down steel piping are modified when these waves encounter corrosion on the external surface of pipe. This fact forms the basis for a new non-destructive testing technique that has been developed to provide a method of rapidly evaluating insulated or buried piping for external corrosion. Broad-band electromagnetic waves are introduced to excite the pipe. As these waves travel along the pipe they are altered in predictable ways when encountering corrosion. The waves can travel hundreds of feet down piping and provide full-body inspection without the need to access the pipe's surface. For this reason this new electromagnetic inspection of piping offers a unique advantage over conventional non-destructive inspection methods for evaluating the integrity of piping whose surface is not directly accessible.
There is an urgent need for an inspection method that can be used to rapidly, completely interrogate long runs of insulated or buried piping for external corrosion. Recent government regulations have focused on inspection of piping, while industry figures indicate that up to 94% of plant failures are caused by piping problems. Often, piping in arctic facilities are insulated to preserve process heat, as can be seen in this photograph on the left of a piping corridor in an arctic oil field. In these fields, many hundreds of miles of piping are carrying gas, oil, water and multiphase production in piping with diameters ranging ffi'om four to sixty inches (10 to 152 cm). The majority of the lines cannot accommodate inspection pigs, so other non-destructive techniques that do not offer complete inspection of the external surface have been used in the past on these lines. In another costly. situation often encountered, hundreds of miles of insulated piping are typically found in refmeries and petrochemical plants, with the majority of the piping difficult to access. The picture on the left of insulated piping in such a plant illustrates the problems encountered when faced with the task of verifying the integrity of these complex piping systems. Finally, inspection of buried piping poses a large problem. If the buried piping cannot be inspected with internal devises, they must be dug up and exposed as seen in this photograph on the right. This, of course, can be very
Conventional methods of non destructive testing do not offer a cost effective way to locate corrosion under insulation (CUI) or in buried piping since they do not provide techniques to examine the entire piping system without expensive preparation and full access to the pipe's surface. The established non-destructive testing methods for locating corrosion damage in insulated piping either require removal of the insulation or inspect only a small area of piping. Removal of insulation as required for visual inspection is very costly and since areas of corrosion are generally a relatively small percentage of the pipe surface, this represents a large, unnecessary expense. Methods available to locate CUI without removing insulation, such as radiography ~) and neutron backscatter 2), only provide information where the pipe can be accessed and then only at discrete points. The need to access each area of buried pipe to be inspected can again present a costly problem, as in the case where below-grade piping must be dug up to gain access to the surface.
Electromagnetic wave inspection offers an ideal solution to rapid location of corrosion damage in insulated or buried piping. After nearly a decade of research, a company has developed patented technology which can be utilized to globally evaluate the condition of piping segments. Electromagnetic waves are i
