The process of extracting and processing uranium can present many challenges. Machinery and equipment are exposed to environments during production, which over time can cause damage and lead to shutdowns. During a planned upgrade, a uranium mine in Australia found internal linings in their exchange vessels to be suffering from corrosion underneath the existing rubber linings.
In previous blog posts such as “Process Vessel Corrosion Protection for 3rd Largest Oilfield”, we have highlighted the importance of corrosion protection to extend the service life of assets. If left untreated, corrosion can lead to major consequences for large assets, such as vessels. Both on a financial level as well as environmental.
AN UNNOTICED ISSUE
The uranium mine uses a unique extraction technology to produce high purity uranium. A planned upgrade revealed issues with the existing rubber lining of exchange vessels, critical to the extraction process. The lining failure had caused corrosion of the steel substrate (which had continued to go unnoticed behind the rubber) and now had the potential to severely impact production and ultimately shut them down completely.
The exchange vessels measure at around 2.5m (8.2ft) in diameter and 5m (16.4ft) in height and are considered the lifeblood of their business. The process conditions meant that there was a strong chemical presence and high operating temperatures further contributing to the corrosion of the lining.
A COMPLETE TURNKEY SOLUTION
Two of the vessels were able to be viewed, due to being out of service, in order to determine a brief overview of the process conditions. A solution had to be presented that could offer good chemical resistance and a resistance to high operating temperatures. Belzona 1391S, a spray-applied epoxy coating, was chosen as the most suitable material to replace the rubber lining due to its ease of application, chemical and corrosion resistance and high temperature resistance.
After further discussions with the team at the uranium mine, it was agreed that Belzona would provide a complete turnkey solution for the exchange vessels, including the internal linings, nozzles and manways. Belzona 1511 (Super HT-Metal) was selected for the installation of nozzle inserts. Stripe coats to welds and bracket details would be coated using Belzona 1391T.
The existing rubber internal lining had to be removed using a high temperature, ultra high pressure jet water operating at 150°C (302°F) and 40,000psi pressure to strip back the rubber lining, leaving a bare steel shell with only small amounts of rubber remaining. This was then whip blasted and any sharp angles, burrs and weld defects were identified and either removed or prepared to a minimum R5 radius suitable for coating.
Following on from the pre-surface preparation, the vessel was degreased using high-pressure water jetting at 6,000psi followed by a solvent wash using MEK before being blasted.
Nozzle Inserts Applied
Before the new internal linings were applied, nozzle inserts were fitted with a stripe coat of Belzona 1391T to the circumferential welds and bracket details. The nozzle inserts were checked, cleaned and then dry fitted into the appropriate nozzle where they were then marked and cut to size before being bonded in place using Belzona 1511. Small areas of pitting around the welds were filled at the same time and allowed to cure. After the required length of time and within the overcoat window of Belzona 1511, the stripe coat was applied to the welds and large nozzles.
Internal Linings Spray Applied
Spraying of the new internal linings began once the stripe coatings were cured. To provide a full turnkey solution without any delays, blasting of the second vessel began whilst the first vessel was being coated. The original coating was then left to cure overnight with a second coat to follow the next day. Heat was applied to the vessels to assist in providing a fast cure time.
Thanks to effective time management throughout, the overall application was able to be completed very quickly. With each vessel taking a few days to complete, including full inspection, the customer was very impressed with the turnaround. In fact, due to the success of this particular application, the asset owner requested the use of Belzona 1391S for elsewhere on the site, including the coating of large settlement tanks which were in a similar condition to the vessels.
BELZONA IN ACTION
Discover below how Belzona protected 40 new-build vessels against corrosion: