Lining of a spent sulfuric acid storage tank required repairs to be completed on-site within 2 weeks to avert a plant shutdown. The plant engineers were provided with three options:
Research indicated an epoxy lining would not withstand the process chemistry. The time and money required to uninstall and ship the tank to be coated or lined at a contractor’s facility were deemed unacceptable to meet the 2 week schedule.
Field installation of a fluoropolymer PVDF lining was the choice to provide the quickest turnaround and longest life cycle. The client already had two other vessels in the same application performing very well with PVDF sheet linings so they were confident they would get the desired life cycle with the PVDF lining.
Within a few days of the initial phone call, Electro Chemical Manufacturing (ECM) was onsite with eight confined space-trained field technicians and the necessary equipment and materials to complete the job within 2 weeks. The vessel was stripped, repaired and grit-blasted to a white metal finish in preparation for the lining installation. Our crews then began working around the clock until the PVDF sheet was installed inside the vessel.
Upon completion of the interior blast the tank’s inner surface was primed and coated with an adhesive before installing the polyvinylidene fluoride (PVDF) sheet lining. The 90-mil-thick fabric backed sheet lining system was bonded in place using ECM’s proprietary elastomeric adhesive system which provides a flexible, tenacious bond capable of withstanding stresses from the differences in thermal expansion between the fluoropolymer lining and the carbon steel shell.
The lining was applied continuously to all wetted surfaces, including through the nozzles and out over the flange faces to provide a pinhole-free corrosion barrier. The bond between the PVDF fluoropolymer and the substrate surface was tested in accordance with ASTM D-903. We provided the client with documented installation procedures, plastic welders well-trained on American Welding Society (AWS) standards, and plastic welds tested in accordance with ASTM C-1147 to ensure a quality installation. Once the lining was installed, internal areas were visually inspected and tested for pinhole leaks using a dielectric spark test.
The installation was provided at the customer’s location which eliminated the need to decouple the tank pipe connections, hire a crane to remove the tank and shipping costs for the oversized load. The field installation was completed within 2 weeks working 24/7 which avoided shutting down the plant and the PVDF liner will provide a longer life cycle than traditional epoxy coatings.
