Bund before application.
Case-study: Composites for Bund Repair
In February 2016, a worldwide chemical company was looking for a solution to protect a bund at a chemical plant in Scotland. The client had a 450 tonne, steel methanol tank currently housed within an open-air, concrete bund. The bund was porous and unlike adjacent bunds onsite, it did not hold rain water. To ensure that the bund was compliant with the Scottish Environment Protection Agency (SEPA), the client wanted to put in place a protective chemical containment coating that was liquid tight to protect against the environmental release of methanol if the tank failed.
The total bund surface area to be coated was around 460m2, which included a 0.5m vertical band around the concrete plinth B, walls A, B, C, D and E, and a 1m band up onto the concrete plinth A. Previous attempts to repair cracks and fillets around the base of the plinth and surrounding walls had resulted in failures, leaving several areas of the bund vulnerable. As well as needing to restore these, a 25m, linear, mastic, expansion joint also needed to be replaced. To cope with the level of concrete movement, the asset owner required a protective coating which could move in sympathy with the large concrete pad and cope with stresses if any further cracks developed. A 0.4m drainage channel, previously coated with Belzona 3121 (MR7), was removed during preparation.
Every day, the plant receives three truck-loads of methanol, which takes up to one hour to completely unload. During this time, onsite work must stand down, therefore any solution had to be applied within this timeframe.
The client was offered a combination of solutions to address each problem within the bund, providing a complete repair and protection solution.
Before the application, the area was cleaned using a combination of detergent and antifungal washing, alongside high-pressure water to remove any contamination. Blasting wasn’t permitted due to the tank containing methanol, so any loose concrete was removed to ensure a firm substrate. The surface was then abraded to expose the aggregate by mechanical scarification.
First, Belzona 4911 (Magma TX Conditioner) was used on all the surfaces where Belzona repair and protection solutions were to be applied. Once the surfaces had dried, any cracks in the substrate were filled with Belzona 4131 (Magma screed). This material was also used to create fillets to reinforce the joints between the walls, floors and tank base where required. Belzona 4361 was then chosen to coat the entire bund area, including walls, concrete plinths and drainage channel due to its excellent chemical resistance against methanol, flexibility and good adhesion, facilitating long-term sealing between the wall and the floor.
The second coat of which was directly applied within 24 hours of the first. Belzona 9211 (Supergrip Aggregate) was sprinkled on top of the curing Belzona 4361 to create 1m wide non-slip walkway (80m linear) to key areas within the bund where regular access is required.
In addition, the 25m2 expansion joint was removed, cleaned, masked off and conditioned with Belzona 4911. A foam backing rod was subsequently inserted, before Belzona 4521 (Magma-Flex Fluid) was then mixed and poured into the void.
Appropriate secondary containment has long been a legal requirement in many countries, particularly around tanks, storage vessels and other plant equipment containing hazardous liquids. Regulations (such as the Control of Pollution Regulations 2001 in England) are enacted to establish preventative measures. By not complying with these regulations, companies run the risk of being heavily fined, sometimes to the extent of incurring criminal proceedings.