Understanding Polymeric Weld Morphologies

Polymer and polymer-lined equipment has become more common in the chemical process industries due to its cost-effective corrosion resistance to severe chemical service. Equipment in service can be damaged during an inspection, require a modification such as the installation of a new nozzle, or otherwise have need of a localized repair before the life of the liner is reached. However, performing weld repairs on equipment that has already been exposed to chemicals can be difficult, because chemicals permeate the polymers, and weld repairs can result in extensive bubbling and weak welds that don’t “stick” to the base material, requiring a complete vessel relining. This article describes a project that MTI has undertaken with Swerea KIMAB to study the morphological changes of welds on polymers that have been exposed to chemicals and determine corrective actions to reverse the effects and perform acceptable welds.