It is estimated that 40 to 60 percent of pipe maintenance costs are due to corrosion under insulation (CUI). In order for corrosion to occur you need moisture, metal and an electron acceptor, such as oxygen. Prevention is often focused on the removal of one of these key ingredients. While, using a metal that is resistant to corrosion, such as a stainless steel, is an option, it can end up being very costly and lead to its own set of deterioration issues. As such, owners will often turn towards eliminating or minimizing either the moisture or the oxygen from the equation.
Oxygen can be minimized by coating the pipe, however that is often not enough to stave off corrosive activity in the presence of moisture. Or for practical reasons, the ideal pipe material and coating material combination may not be available. As such, it is recommended to minimize the moisture that gets to the pipe as well, particularly when the pipe is insulated. Once moisture gets under the insulation, the phenomena of crevice corrosion, a type of accelerated corrosion, occurs.
A regular inspection schedule is an integral part of an asset integrity plan for insulated piping. An easy way of being able to do these ultrasonic thickness testing (UTT) inspections in consistent locations to see potential wall thickness loss over time is to install an insulation inspection plug. However, cutting a hole in the insulation introduces a potential water intrusion site.
This is why the fit of your plug is vitally important to preventing corrosion.
Whereas some systems utilize a metal sleeve to go against the metallic insulation jacket, providing a poor fit up, NDT Seals’ sleeves are made of EPDM rubber or silicone in order to better fit the contours of the hole in the insulation and to keep water out. The metal fittings and cap that go on top protect these seal materials from UV exposure to help ensure the longevity of the inspection plug and ultimately the pipe. We designed our plugs with your asset integrity life cycle costs in mind.