Until now, typical above-ground storage tanks (ASTs) for commercial jet fuel at airports have been lined with epoxy coating. The epoxy application is critical in preventing interior tank corrosion which could ultimately compromise the integrity of the fuel quality. Many standard epoxy-lined tanks are guaranteed for ten years, and inspected periodically during this time. If an inspection fails due to breakdown of a tank’s epoxy lining, the costly process of reapplication is required. By leveraging the capabilities of sister company Walker Stainless, Garsite looks to revolutionize the AST market with a new solution: stainless steel inner linings.
According to a report authored by John Bagnell, chief mechanical engineer for Burns & McDonnell, the primary contaminants in jet fuel are water, surfactants, sediment or particulates, and microbial growth. These contaminants can cause complications ranging from fuel system corrosion to fouling or disarming fuel filtration components, ultimately leading to potential failure of aircraft fuel system instrumentation and possible shutdown of fuel supply to an aircraft’s engines, says Bagnell.
The report outlines fuel system design and states, “The fuel system must be arranged to minimize the potential for fuel contamination; current practice is to internally line or coat all system piping, storage tanks, and major equipment.” Bagnell says high solids epoxy paint, suitable for hydrocarbon immersion service, is the coating of choice because its slicker surface minimizes corrosion and sediment build-up on the vast majority of fuel-exposed surfaces.
Bagnell adds that the use of copper, brass, cadmium, or zinc (galvanizing) in fuel-exposed equipment is undesirable because these metals can affect the thermal properties of the fuel or damage engine parts.
The trouble with epoxy
Advanced Fuel Systems, Inc. of Columbus, OH designs and builds aviation fueling cabinets and fuel handling systems; the company is also experienced in the rebuild and repair of aviation fueling systems.
Vice president Steve Thickstun says the company inspects fuel tanks to let customers know how they are holding up against time. The company also applies the initial epoxy coating to the interior of new tanks; but does not reapply epoxy to used tanks.
Says Thickstun, the application of a 10,000-gallon tank’s initial epoxy lining could cost some $6,700. Of course, he explains, “It’s much more difficult to take the epoxy off and reapply it, which if I did that today, would probably cost some $10,000.”
Garsite’s Paul Sundby is responsible for the sales and marketing of the company’s above ground fueling systems (AST) division. Sundby, who coordinates the design, engineering, and installation of Garsite projects, says the epoxy coating process can be a huge expense; “And that’s one of the beauties of the new stainless product.”
Relates Sundby, “When you apply epoxy coating, the first thing you do is shot blast the tank down to a bright (clean) finish. The prep work for reapplying the coating is very important to make sure that the metal is absolutely clean in order to have the epoxy coating bonded to the metal and not have failure in the future.
“If the tank interior is not completely clean, the epoxy could fail in less than a year, or the life of the coating could be shortened.”
The epoxy also has to be painted on in a dark environment, says Sundby, which means someone has to apply the coating at a specific mill thickness.
“The process is really an art,” says Sundby, “because the application of the coating has to be done very well, or the chances for premature failure (flaking or scaling off of the coating and commingling with the fuel) is more likely.
“What you have to do is be very precise. You can’t perform this task on a high humidity day or a rainy day. There are a lot of factors that go into the coating process to make sure you get an effective finish. You have to have the right person at the right time; and having the right weather is crucial to the result of the finish.”