Inspection of corrosion under pipe supports (CUPS)

S F Burch and H R Peramatzis
ESR Technology, Milton Park, Oxfordshire OX14 4SA, UK 

Corrosion under pipe supports (CUPS) is a widespread issue within the oil & gas and other industries that has caused in-service leaks and ruptures. In-situ visual inspection can provide an indication of corrosion (product build-up, rust staining) but it is significantly hampered by the lack of access to the critical areas. Removal of a potentially corroded pipe from its support for direct examination is hazardous on live process lines. There is therefore interest in the use of advanced NDT methods that can provide information on the severity of the CUPS without removal of the supports and hence the need for a shutdown. Given the large numbers of supports on typical plants, there can be a need for a combination of rapid NDT methods for initial screening to identify a smaller number for follow up with more quantitative methods.

Blind trials of NDT methods for CUPS inspection have been conducted within the HOIS joint industry project, to assess inspection performance and sizing accuracy. The performance of different NDT methods was found to depend on parameters such as the pipe diameter and wall thickness. The results from these blind trials have informed the development of a HOIS CUPS inspection guidance document.