Today's cargo tanks available in variety of materials, including Lean Duplex

With the variety of products available for building cargo tanks today, window shopping may take on a whole new meaning for the tank truck industry, according to information presented at the National Tank Truck Carriers Maintenance Seminar November 12-14 in St Louis, Missouri.

Lean Duplex, as well as other types of steel, and fiberglass reinforced plastic (FRP) are but some of the options available to the tank truck industry. John Cannon of Brenner Tank LLC, Ralph Davison of TMR Stainless Inc, Peter Weis of Polar Tank Trailer LLC, and George Felix of Poly-Coat Systems Inc discussed the options at the seminar.

Brenner Tank has introduced a tank compliant with DOT407 regulations, using a duplex stainless steel that reduces the total cost of new bulk tank trailers, Cannon said.

Lean Duplex is a variant of a type of stainless steel that was developed more than 20 years ago for corrosive applications. This family of stainless steels generally has more chromium but less nickel than type 316L.

Cannon pointed out that one of the expenses related to stainless steel is its nickel content that cost about $4 per pound in 2003 compared to a 2007 price of $24 per pound, a situation that can raise the price of a tank trailer by $20,000.

Davison noted that Lean Duplex has good welding ability and is resistant to stress corrosion cracking. He also discussed austenitic stainless steels and said they have high ductility and low yield stress. They have relatively high ultimate tensile strength in comparison to carbon steel. Another type of steel, ferritic, is easily welded, but not typically very tough. They are corrosive resistant and immune to cracking, but expensive.

Weiss noted that new cargo tank designers are looking at new alloys for jacketing and framing, but with new steels entering the market, more technical sophistication is required, particularly in welding technique.

Turning to FRP tank trailers, Felix said that they are known for their light weight and resistance to corrosion. They can be used to haul various products, including bleach, acids, and general chemicals. He also pointed out that the tanks have a higher strength-to-weight ratio than steel tanks and have demonstrated resistance to rollover damage.

FRP tanks require an annual pressure test, which the manufacturer provides. The tanks are easily cleaned, typically by using warm water at 150° F, but the heat necessary varies according to ambient temperature, he said.

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