Abstract
It is a common practice to install DC decoupling devices at pipeline joints where isolation flanges are installed. The decoupling device protects the isolation gasket from damage as a result of lightening or AC ground faults, including the possibility of fire. Historically, it has been less common to verify the operation of the decoupling devices deployed at isolation flange locations. This is likely due to several factors. First, decoupling devices are very reliable and the failure rate, even in extreme conditions, is very low. Second, the locations at which these devices are too numerous and widespread to physically inspect these devices at two month frequencies. Third, and most important in regards to this paper, there is a misconception that annual survey readings on these devices are sufficient to ensure operational integrity. Decoupling devices may utilize diodes and as such are subject to PHMSA1 regulations that require readings to be taken six times a year on rectifiers, critical bonds, reverse current switches and diodes.
This paper is a case study of multiple sites employing the use of monitoring equipment for the purpose of evaluating the operational integrity of decoupling devices at isolation flanges. Methods, best practices, and challenges will be addressed, providing the necessary information to successfully implement this solution at similar locations.
