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Ecodur 201: Apache Tank Repairs (Ranger Field Services)

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Forty 300-barrel tanks in the north-west Texas panhandle were in urgent need of internal bottom coating to protect against highly saline and corrosive chemicals in production water coming from the fracking process. The state they were in required near white SP-10 Nace 2 metal preparation of the bottoms. While there were some with considerable rusting and flaking, most had failed epoxy coating that was removed none were so bad that they needed any metal replacement or major plugging of holes.

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Problem
Conventional epoxy coating treatment of tanks generally results in micro-cracking within a few months due to the movement of the steel from large temperature fluctuations, especially on weld lines because of the lack of retained elasticity. The cracks themselves start off being very small but are sufficient to allow in minute traces of bottom water which contains corrosive chemicals that hasten penetration. VOC-free Ecodur starts with elasticity well in excess of conventional epoxies and retains it for the lifetime of the coating.

Notably all tanks had problems. The bottom was damaged from the use of a plumb bob that was dropped into the tank to measure contents. It impacted on the bottom to the point where it exacerbated the corrosion. The water inlet on the tanks had caused heavier than normal erosion to the existing coating and the tank bottom in all cases extra remedial action with PVC plates installed over-coated with Ecodur.

Solution
The client required a long term solution for protecting the 40 tanks which, despite significant bottom corrosion, showed that with a long lasting, cost-effective coating that would meet the challenges of changing production water contents, they would still have years of productive service ahead.

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With the performance limitations of conventional epoxies and the requirement for an application environment that would avoid the exposure to VOCs and solvents, Ecodur was chosen. It was manually applied as the size of these particular tanks made manual application a good option, whereas much large tanks, with an abundance of vertical surface to be coated, are generally better suited to Castagra’s unique spray technology.

Being VOC-free and with no solvents used either in the contents, application process or clean-up, the applicators were only required to have basic protection and there was no expensive, toxic waste clean-up as would have been required had solvents been used. Ecodur, which has an ANSI/NSF 61 potable water rating, is non-toxic.

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All but two of the tanks were required to be coated up to three feet from the bottom. The remaining two were specified to be coated up the entire wall as they had extended corrosion and thus required additional protection.

Application Results
The tanks had been coated in moderate temperatures for the area and generally dry conditions. Only two or three days experienced higher than average humidity levels. At all times strict adherence was made to the basic requirement of spraying at 5 degrees Fahrenheit above the Dew Point as a safety margin against potential bubbling from trapped moisture. The client reported satisfactory results and tanks were released back into service within 24 hours of coating completion. In most cases, the freshly coated surfaces were tack free within 30 minutes. Ecodur, with its unique and time-unlimited ability to re-bond to itself, made touch ups effective as the original coat. The coating contract was performed by Ranger Field Services.