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Ecodur 201: Pemex Tank Coating Project

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Produced water is the largest by volume source of waste coming out of the oil and gas industries and it has to be stored safely. Not surprisingly they contain a lot of toxins, corrosive chemicals and volatiles and hence need to be handled and disposed of in a safe and effective manner.

In the US, the water to oil/gas ratio (WOR) averages seven barrels of water to one barrel of oil and may go as high as 50 to one. Energy companies pay $3-12 on wastewater disposal. Traditionally, produced water is stored temporarily in containment ponds to allow volatile contents to evaporate into the atmosphere, but in this case study, the focus is on welded tank produced water storage in northern Mexico.

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Problem
As always, the prevailing problem with steel tanks is being able to coat them so they can withstand attack from a cocktail of chemicals contained in the produced water, which usually includes acids that can make short work of exposed metal. The other problem is that even with a traditional coating, temperature extremes can quickly trigger micro-cracking, due to the metal movement.

It is remarkable how quickly conventional epoxy coatings suffer in this way on dynamic steel surfaces that flex constantly, albeit with movements not visible to the naked eye that are induced by temperature changes.

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Solution
Ecodur 201M was deemed the most suitable coating for three Pemex tanks that have 50-foot diameters. Ecodur is a plasticized gypsum coating that is non-toxic, VOC and solvent free, and has the unique ability to retain a sufficient measure of flexibility throughout its lifetime to withstand the natural flexing of the steel walls. It is also ideal for coating remedial work as it bonds back onto original Ecodur surfaces in a perfect molecular bond, again for its lifetime. Normal NACE standard surface preparation was done prior to coating. The prevailing temperatures and dew points were well within guidelines. (It should be noted that Ecodur has outstanding winter weather application performance far exceeding most conventional epoxies.)

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Application Results
The Ecodur was hand applied – mop and buckets as a spray rig was not available – over the entire floor and five feet up the interior sides. Ecodur is ideal for spraying and this is the usual mode for applying it.

No solvents are contained in the product, used in the application process, or used in cleaning up afterwards, thus eliminating a costly aspect of conventional coatings which mostly contain solvents that require cleanup.

Being hand applied, the applicators were required to wear the same safety gear as for spraying as droplets can still become airborne during manual application, presenting a potential hazard to exposed skin and eyes. Being odorless and VOC-free, only particulate masks are needed. Independent air supplies are only needed for highly confined spaces or where air quality is questionable.

The Ecodur 201M was set up within 20-30 minutes and was fully cured within 24 hours when a final inspection was made and the tank was released for return to service. No product or application issues were encountered and Pemex, the Mexican state-owned petroleum company, expressed complete satisfaction.

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