Driven by customer demands and government regulations, storage tanks are becoming increasingly durable.

Geoff Clarkson, P.Eng., doesn’t fabricate composite storage tanks, but he knows a lot about what makes them last – and fail. Clarkson founded UTComp in 2008 to offer engineering and inspection services to the composites industry. Using the company’s UltraAnalytix non-destructive inspection system, he has assessed dozens of FRP tanks through the years. The outlook for most of these composite assets, he says, is extremely positive.

“Composite materials seem to significantly outlast predictions by the designers, manufacturers and constituent material suppliers,” says Clarkson. “That’s a really good result.” Consider the oldest tank that UTComp has inspected – a 62-year-old tank that stores a sulfuric acid solution in a metal processing plant in Quebec, Canada. The plant owner knew the tank wasn’t leaking, but was unsure if any other deterioration had occurred. So he called in UTComp for an ultrasound analysis, which revealed the tank “is still doing extremely well in a very corrosive environment,” says Clarkson.

The composites industry has changed dramatically since that tank was built and installed in the late 1950s. There have been tremendous advancements in materials and technology, in addition to rising customer expectations and the adoption of numerous standards and regulations surrounding the use of FRP in storage tanks. But the longevity of composites remains one of its strongest selling points.

“FRP is designed to stay in its original watertight, functional design from the day the tanks are delivered until the end of their service life, which in most cases is the life of the building or installation,” says Bruce Coe, regional sales manager for water applications in Canada and the U.S. for ZCL | Xerxes, a product line of storage tanks within the Composite Product Systems division of Shawcor Ltd. “That’s the value proposition of FRP products. It’s not the cost today: It’s the value proposition of a composite-built tank over the next 30 to 50 years.”

Factors that Influence Material Choice

While the long life of composites is appealing, it’s not the only decision-making factor that end users consider today when selecting tank materials. “The structure, the use and the budget dictate what the customer chooses,” says Coe. In the water and wastewater market he serves, most tanks are built from concrete, GFRP and high density polyethylene. HDPE is cheaper than GFRP, but doesn’t last as long.

“The above-ground tank market changed 20 years ago with the advancement of HDPE technology,” says Coe. “As the material became better and stronger, a segment of the market made an economic decision to buy a cheaper product that may need to be replaced in 10 or 12 years instead of a fiberglass tank.” For applications where the tank is small and easily accessible, some customers are willing to foot the replacement costs because an HDPE tank may be one-quarter to one-third the cost of a GFRP tank.