OPERATIONS MANAGEMENT
T
he process of extracting and processing uranium can present many challenges. Machinery and equipment are exposed to
environments during production that, over time, can cause damage and lead to shutdowns. If left untreated, corrosion can lead to major consequences for large assets, such as vessels – both on a financial level as well as environmental.
A uranium mine in Australia 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. Te 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. Te exchange vessels measure at around 8.2ft in diameter and 16.4ft in height and are considered the lifeblood of their business. Te process conditions meant that there was a strong chemical presence and high operating temperatures further contributing to the corrosion of the lining. Two of the vessels were able to be
viewed, due to being out of service, helping to understand the process conditions. A solution had to be presented that could offer good chemical resistance and withstand high operating temperatures. Te existing rubber internal lining had
to be removed using a high temperature, ultra-high-pressure jet water operating
The manway after coating
CLEVER COATINGS
Case study from uranium mine shows how internal linings were saved by corrosion-resistant coatings
at 150°C and 40,000psi pressure. Tis stripped back the rubber lining, leaving a bare steel shell with only small amounts of rubber remaining. Tis was then whip blasted and any sharp angles, burrs and weld defects were identified and 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.
Blasting in progress: the shell was whip blasted before being coated
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STRIPE COATING 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. Nozzle inserts manufactured using Belzona 1511 (Super HT-Metal) were initially dry fitted into the appropriate nozzle where they were then marked and cut to size
before being bonded in place using Belzona 1391T. 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 1391T, the stripe coat was applied to the welds and large nozzles. 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. Te 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 and return to service. Tanks to effective time management
throughout, the overall application was able to be completed very quickly, with each vessel taking a few days to complete. Te vessels gained long-term protection against corrosion and a longer service life.
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