Atlanta — Kautex Maschinenbau GmbH — already the leader in blow molding machines for making automotive gasoline tanks — now is building complete automated production lines for filament-wound composite tanks for compressed natural gas and hydrogen-powered vehicles.
“We came up with not only the product design, but also the manufacturing line to come to your final product,” said Chuck Flammer, vice president of sales in North America for the German machinery company.
Flammer, who spoke at the Annual Blow Molding Conference, acknowledged that $2 gas is slowing consumer interest in the alternative technologies. But automakers are moving forward.
“We have done some projects with fuel cell vehicles, especially with Mercedes Benz. We actually built fuel cell vehicles which use composite tanks,” he said.
Flammer said there are several types of tank constructions to hold compressed natural gas, or CNG, which requires a pressure vessel. Tanks can be all-steel, or a steel liner that is wrapped with a composite liner.
But Kautex is pushing tanks with a blow molded liner, of polyethylene or nylon, that is then filament-wound with carbon fiber, usually epoxy coated.
The tanks are more expensive than steel ones, mainly because of the carbon fiber. But they give big weight savings — a key demand of automakers, as they try to boost gas mileage.
Just like trying to compete with low-priced gasoline is a challenge, Flammer said that making a composite tank presents tough technological issues, as well.
“The challenge for fuel tanks using any kind of [compressed] gas is the fuel density,” Flammer said. “Gasoline is very, very good — it has very high fuel density. So the same amount of fuel necessary for a natural gas [vehicle] would have to be many more tanks, bigger volume to go the same distance.”
Flammer showed videos depicting the fully automated tank production, at a customer's plant in China that makes water softener tanks. First, the liner gets blow molded. Flammer said the liner is fairly basic, but it must have a precise, uniform wall dimension. “It's very important because the winding equipment actually does put a lot of pressure on the rank during the winding,” he said.
Six-axis robots move the tanks through the preparation, automatic winding and curing. The winding machine can do multiple tanks at a time.
Kautex, based in Bonn, Germany, puts together the complete line for customers. Flammer is based at Kautex Machines Inc. in North Branch, N.J.
Kautex has done extensive testing, including for permeation, pressure, rupture, and even bonfire testing to simulate a car fire. The composite tanks will slowly melt and evenly release the gas, which burns up, he said. Flammer said steel tanks can explode.
The boss, where hoses go into the tank, is very important, and an area covered by patents, Flammer said, adding that Kautex has its own patents covering its process.
The boss cannot leak.
“The other challenges are permeation of gases through liners. The biggest challenge in any composite tank is how you put your boss — which is the connection point — to your tank, to whatever hoses you put on there,” he said.