Uranium mine upgrade

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The process of extracting and processing uranium can present many
challenges. Machinery and equipment are exposed to corrosive
environments during production, which 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. 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.
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.

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. This stripped 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 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.

STRIPE COAT 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. 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.

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 and return to service.
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. The vessels 
gained long-term protection against corrosion
 and a longer service life.

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