An emerging technology for Department of Transportation (DOT) tanker trailer transportation applications and oil field operations is to poly coat steel vessels. This proven technology, known as PolyGard™, offers the longevity of steel vessels and offers cost advantages over other expensive coating options such as teflon and haylar.
Let’s explore this process and why it is ideal for DOT and oil/gas fracking operations where chemical transport is required.
How does poly coated steel work?
To coat a steel vessel in polyethylene, the customer first provides the steel vessel to Poly Processing. There are some limitations to the weight and size of the vessel as it must be able to fit in our ovens. The process of joining the polyethylene to the steel is to rotationally mold and ionically bond a 1/4-inch poly layer onto the inner surface of the steel vessel. This coating prevents highly-oxidizing chemicals such as sulfuric acid, hydrochloric acid, ammonia, and other chemical compounds from attacking the steel surface of the tanker trailer or vessel. As a result the life of the vessel is extended. After the polyethylene material is ionically bonded to the steel, a spark test is performed to ensure no pinholes or voids exist on the coating.
For pressured tanker trailer vessels such as transport of ammonia, the strength of steel is required. The polyethylene application extends the life of the steel. Larger vessels requiring steel where non-traditional polyethylene tank sizes and shapes are limited can also receive the application, as long as the vessel fits into the oven for processing.
DOT tanker trailer transporters of low flash point materials require steel for grounding, yet look to coating the steel vessel for longer life and durability. Inexpensive spray on applications such as phenolic and tnemec coatings lack durability. Teflon and haylar coatings are more durable, yet quite expensive. Polyethylene offers the perfect balance of durability and cost effectiveness for coating steel vessels, pressure vessels, and DOT tanker trailers.
In addition, with the protection of the polyethylene coating, a less expensive carbon steel tank can be used rather than an expensive stainless steel tank. This offers a more durable, less expensive option in the steel material. Another consideration is protection when transporting sulfuric acid that varies in concentrations. Sulfuric acid under a 93% concentration will corrode the steel tank and trailer.
For more information on polyethylene lined steel vessles, download our PolyGard™ brochure.