Tanker trucks transporting corrosive liquids and gases are a common sight on highways. Often made of steel, the cylindrical tanks are typically dedicated to one type of cargo. But thanks to a composite tanker configuration developed by Australian-based Omni Tanker Pty. Ltd., the next tanker you see rolling down the road could be lighter, enable a quicker turnaround between runs and deliver purer products. Plus, the tankers could be used to move bleach in one trip, then acid the next.
What sets Omni Tanker’s products apart from others is their thermoplastic liners, which absorb almost none of the transported goods, says Dr. Luke Djukic, chief technical officer of the company. It’s standard practice to line the inside of a tank transporting hazardous goods, both to protect the tank and the corrosive chemicals. Most of these nonstructural liners are made of materials such as rubber or thermoset polymer reinforced with glass chopped strand mat. In contrast, Omni Tanker uses a thermoplastic liner encapsulated by CFRP. The liner has high chemical resistance, ideal for transporting sodium hypochlorite, sulfuric acid and other dangerous chemicals.
The liner, which acts as an interior protective skin, works in tandem with an outer shell composed of the same CFRP. The outer section is custom molded to create a smooth exterior tank surface. The space between the interior and exterior skins contains a foam core. “The patented Omni Tanker liner technology overcomes the problems associated with bonding thermoplastics to thermoset composites,” says Djukic. “We have demonstrated bond strengths similar to epoxy-to-steel adhesion.”
Development of the liners began 10 years ago, when company founder Bill Rodgers noted that standard liners tended to degrade and require replacement every few years. The goal was to create a seamless, hollow vessel with high adhesion strength of inner-to-outer shells. Finite analysis helped nail down the design, and utilization of the directional strength of carbon fibers allowed tailoring of the material to create desired properties. The resulting tankers – which Omni Tanker markets as its A and AB tanks – have been in service in Australia since 2011. Each tank typically carries between 12,600 and 15,000 liters of goods, although higher volumes can be achieved based on customer requirements.
Another benefit of the liners is increased chemical resistance, which is achieved via several avenues. First, the manufacturing process and structural configuration minimize the tendency for stress cracks – and resulting weak points – to form during use. Second, the liner materials, including thermoplastics such as polyolefins and fluoropolymers, have very high chemical resistance compared to standard liners and minimal absorption of the chemical cargoes, says Djukic.