When performing a repair application on a metallic surface with polymeric paste grade composites, it is always desirable to work on surfaces that have been dried, cleaned and specially prepared. These surfaces offer the best conditions for an optimum adhesion and bonding of the repair material. Having plenty of time to carry out the repair does not hurt either, but unfortunately these conditions are not always available.
Some machinery and equipment is simply too vital, or too expensive, to remove from its location or even remove from service, meaning that achieving ideal surface conditions can be a challenge. Wet or oily surfaces, surfaces that cannot be grit-blasted for safety reasons and other adverse conditions can also make it difficult to achieve an optimum surface preparation. On top of this, if the equipment in need of treatment is vital to the operation of a plant or facility, and if that facility does not have the capacity for extended periods of downtime, then the repairs must sometimes be effected within a very narrow timeframe.
Cold-curing and easy-to-apply composite materials are a versatile and effective option for the repair of metallic surfaces as they do not require hot work, minimising Health & Safety concerns.
The challenge
However, there are some condition sets that can pose a challenge for even the most innovative of materials. This was the case at a coastal hydrocarbon storage tank farm in Genoa, Italy, where a vital piece of equipment had sprung a leak. Belzona 1212, a recently developed polymeric repair material designed to deal with wet substrates and short working windows, was selected to tackle this problem.
One of the vertical seawater tanks at the tank farm had sprung a leak, with severe corrosion having made a through-wall defect which was leaking seawater. Three further tanks had suffered similar corrosion damage to a lesser extent, thinning the tank walls in certain spots, which threatened to develop into further leaks in eight places. This project posed a complex problem, as the damaged area could not be dried and the plant could not be shut down for longer than two hours. This tight time window meant that solutions with anything but the shortest of cure times were not an option for the client.
Cold-bond solution
The decision was made to use Belzona 1212 to cold-bond metal repair plates to the tanks, in order to reinforce the weakened spots and seal the through-wall defect.
The surface areas were rapidly prepared with a mechanical hand-held tool to remove the existing paint and achieve a more suitable working surface, and Belzona 1212 was then applied directly onto the leaking and damaged areas. Metal plates were then cold-bonded using the same material, sealing the leak and reinforcing the weakened areas of the tank walls. This application was carried out in-situ directly onto the tanks, meaning that downtime was reduced to a minimum. Within two hours, the repair material had cured to a satisfactory level, allowing the client to turn their attention back to business.
Combination of properties
The combination of fast curing and water-tolerant properties required for this repair was the main parameter when selecting the solution material. In order to minimise downtime, it is important that the repair material cures and develops its mechanical strength quickly. Belzona 1212 will cure rapidly after mixing of the two components, even in low temperatures, without compromising on durability or strength. At low ambient temperature, the system will exhibit the same robust, hard-wearing properties synonymous with Belzona’s epoxy technology.
Reduced downtime
The company chose this solution as it allowed them to bypass the wet surface issue without any wasteful downtime. Replacing the tanks outright would have required them to shut down the plant, drain the tanks, wait for and then install expensive replacements. In contrast, the Belzona application was completed within a matter of hours, requiring no downtime and at a cost of less than €1,200.
Where conventional repair composites would be ineffective and perform poorly, Belzona 1212 bonds tenaciously onto steel substrates, even when surface preparation is minimal or if the substrate is heavily contaminated with oil or water. It provides a cost-effective repair that can reinstate equipment for years of service.
Alternative repair
A UK oil supplier was faced with a major dilemma when a transformer oil storage tank began to leak in several places. As the tank was located in a confined space, it would be highly dangerous to repair the damage in-situ using hot work. If the tank was removed and repaired offsite, not only would this incur large amounts of downtime, but the cost of welding alone would be over £15,000.
The supplier required a bespoke in-situ repair solution that would safely repair and protect the steel tanks against corrosive attack for the long-term, whilst incurring minimum downtime. In addition to this, as the application area was highly contaminated with oil, the repair method needed to be compatible with this environment and provide a robust repair solution despite the contaminated surface.
Background Information
The supplier recycles millions of litres of transformer oil every year. This process works by extracting the moisture from recycled oil by shutting the tanks off from the atmosphere. The tanks are then connected to silica gel tanks to remove the moisture. As a result of this repeated process, several areas located at the seams of the steel tanks were beginning to corrode.
Application Specification
Belzona 1212 was chosen to bond steel plates to the damaged areas followed by a protective coating using Belzona 5831 (ST-Barrier). Launched earlier this year, Belzona 1212 represents a milestone for epoxy technology as not only does this material provide excellent, long-term corrosion resistance, but it achieves this even when applied to oil contaminated surfaces where grit blasting is not possible. Coupled with the rapid cure feature ensuring minimal downtime, Belzona 1212 is the ideal solution to repair the leaking tank. Belzona 5831 was chosen to coat the repaired area as this surface tolerant epoxy coating is specially designed for the protection of oil contaminated surfaces.
Fast and Simple
The application was carried out by Belzona. Once the leaks were stemmed, the area was then cleaned and roughened to prepare the surface for the Belzona systems. Belzona 1212 was used to bond pre-manufactured steel plates onto the damaged areas. This was done by firstly applying a thin film of the epoxy system onto the prepared substrate, pushing the material well into the profile. Further material was then applied to the steel patch forming a peak of material at the centre. The patch was then pushed into place allowing the excess material to exude from beneath ensuring minimal air entrapment. The excess material was then removed and the system was allowed to cure before coating the area with Belzona 5831, providing long-term corrosion protection.
Two-day repair
“If the oil supplier had chosen to use welding as the repair method, this could have taken weeks to complete, leading to big problems in terms of trying to stop moisture entering the tanks,” explains Osian Jones, Belzona Field Sales Engineer. “The Belzona application was completed in just over two days without the tanks being taken offline. This ensured moisture ingress would not occur and allowed the plant to continue as normal with minimal disruption. Furthermore, the supplier was able to avoid a significant amount of capital expenditure as the Belzona repair method could be carried out at a fraction of the cost of welding.”