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.”
Adds Sundby, “Furthermore, if the epoxy coating isn’t cured right, it could lead to failure of a soak test. When a brand new tank comes in, fuel is stored in the tank for a period of time required by the fuel provider. After that period of time, a sample of the fuel is taken to a lab and tested — that’s the soak test. If the results come back out of specification, the fuel fails the test and the fuel and tank could need to be cleaned.”
Regarding the life of the coating, says Sundby, it all comes back to the quality of the application of the product.
Thickstun agrees. “The lifespan of the initial epoxy application depends on conditions; I have liners in tanks that have been in use for 20 years and they are fine,” says Thickstun.
The reapplication of epoxy for a typical 12,000-gallon fuel tank takes usually a week or two and could cost some $15,000 per tank, says Sundby. The cost varies depending on the size of the tank.
Tank Tech provides a full range of storage tank services including video inspections, physical inspections, repairs, secondary containment, upgrading, and linings of both above and below ground storage tanks. Company senior analyst Duane Kelley says if a previously lined tank coating fails inspection, Tank Tech removes the existing coating and relines the tank. If required, it will also supply the tank owner with a new ten-year guarantee.
“Tanks typically have a ten-year warranty; I have seen linings that have lasted 20-some years,” says Kelley.
“How long the coating lasts depends directly upon the quality of the initial application, the quality of the product, and the method with which it was applied.”
According to Kelley, the cost for reapplication depends on the size of the tank, whether the customer wants the entire tank coated (or just the bottom third), and whether the tank is vertical or horizontal.
David Harris of ConVault Inc., manufacturer of protected above ground storage tanks, says the company also offers its customers a ten-year warranty to start, with inspections every five years.
The stainless solution
The benefits of the stainless steel inner lining over the standard epoxy-coated lining are three-fold, says Mittleman. “First, the customer doesn’t have to worry about the initial start-up of the tank or any problems with the epoxy coating.
“Second, the customer doesn’t have to keep checking the coating periodically for a breakdown of the epoxy material.
“And third, the cost of reapplying the coating and the cost of being down during the reapplication process is eliminated with the stainless steel inner lining.”
Due to Garsite’s sister company Walker Stainless Equipment, a large manufacturer of stainless steel products and solutions, it was very cost-effective for the company to implement stainless steel construction into its AST products, relates Sundby.
“Walker rolls, shears, and welds stainless steel; they told us they could manufacture these stainless steel inner linings for virtually the same price as their standard epoxy-coated tanks, he says.
Garsite’s biggest selling point? “We are selling these tanks at the same exact price as the epoxy-coated tanks,” says Sundby.
In addition to that, remarks Mittleman, “Garsite is so confident about the lifespan of the stainless steel inner tank that we are including a 30-year warranty with each tank at no additional cost.”
Feedback on the product, according to Sundby, has been very positive thus far. “We just received an order from Texas, and the differentiating factor was that the tank had a stainless steel inner lining.”
Going to market
“We feel we have good relationships with the major fuel providers and fuel marketers,” says Sundby. “They assist FBOs and airports in choosing the best fueling system for their location; and their fuel marketers gather data on the product to give to local FBOs. Garsite also plans on marketing the product to engineering firms.
Stainless steel tanks and piping has been an excepted practice for aviation fuel storage and the transferring of fuel for many years, relates Sundby. The concept for storage, he adds, has finally arrived and will become the industry standard as we move forward.
“The use of stainless steel in the tank has always been talked about,” says Sundby, “and everybody would’ve liked to have done it, but it was always cost prohibitive.
“It wasn’t until we teamed up with Walker Stainless that we were able to realize this: the tradeoff for stainless steel as opposed to epoxy coating is a home run for the customer.
“It’s a great example of leveraging the capabilities we have within our company to build new solutions.”
Industry standards, measures, and regulations related to aviation fuel quality control:
- API (American Petroleum Institute) 1500 — Storage and handling of aviation fuel at airports.
- API 1581 — Specifications and qualification procedures for aviation jet fuel filter/ separators.
- ASTM (American Society for Testing and Materials) MNL5 — Manual of aviation fuel quality control procedures.
- ASTM D 1655 — Specification for aviation turbine fuels.
- ATA (Air Transport Association) 103 — Standards for jet fuel quality control at airports.
- IATA (International Air Transport Association) — Guidance material for aviation turbine fuels.
- NATA (National Air Transportation Association) — Refueling and quality control procedures for airport service and support operations.
Source: Jet Fuel Quality: Flying Clean and Dry, by John Bagnall, P.E.