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If proposed evaporative emissions regulations in the United States come to pass, rotomolders could lose their substantial business supplying fuel tanks for marine use and small gasoline powered engines such as those in lawn mowers and leaf blowers.Legislation likely will take effect not later than 2007, and rotomolders are scrambling now to develop solutions. The boating regulations are being driven by the U.S.

Matt Defosse

October 1, 2003

7 Min Read
New regulations could push rotomolding from fuel tanks

If proposed evaporative emissions regulations in the United States come to pass, rotomolders could lose their substantial business supplying fuel tanks for marine use and small gasoline powered engines such as those in lawn mowers and leaf blowers.

Legislation likely will take effect not later than 2007, and rotomolders are scrambling now to develop solutions. The boating regulations are being driven by the U.S. Environmental Protection Agency (EPA), whereas the California Air Resources Board (CARB) is forcing the issue on small engines. The EPA also is eyeing the latter, say market insiders who expect federal regulation to follow California''s lead.

On small gasoline engines, rotomolders' loss could be blowmolders' gain or even injection molders' in high-volume projects. Officials at multilayer extrusion blowmolding equipment manufacturers including Graham Machinery Group (York, PA), Uniloy Milacron (Batavia, OH), Automa (Crespellano, Italy), and Bekum (Berlin, Germany), all say the proposed regulations have spurred interest in such machines. This year injection molder Kelch (Menomonee Falls, WI), which molds tanks for blue chip OEMs including Briggs & Stratton, the largest manufacturer of engines for outdoor power equipment, opened a fuel tank testing facility within its plant to help customers design fuel tanks and caps to meet stricter emissions standards.

Marine fuel tanks may be the hotter issue for rotomolders, as it is a business they control, but one in which regulators are intent on reducing fuel vapor emissions. In July 2002 the EPA proposed requiring up to an 80% reduction in evaporative emissions from these tanks. According to the Assn. of Rotational Molders (ARM), as many as 2500 rotomolding tools are in use for marine fuel tank processing. CARB is proposing even stricter regulations on these tanks, and a European standard will include reduction of carbon monoxide and noise emissions.

At ARM's national conference next month in Kansas City, MO, Bob White, president of testing facility Imanna Labs (Rockledge, FL), will speak on eliminating fuel vapors in marine tanks. Though the EPA has not yet set a start date for any regulation, White says the Agency is using the threat of a near-term mandatory date to drive change. "The bottom line is, the pressure is now on the processors and materials suppliers to come up with an adequate solution," he says. Imanna is developing economical screening tests to help processors and materials suppliers quickly determine not necessarily whether a material or tank meets the emissions limits, but whether one is better than another, giving processors and suppliers a quick indication of which avenue to pursue, explains White.

White predicts rotomolders will keep their hold on the marine tank market due to fire resistance requirements. Rotomolders use cross-linked polyethylene, which performs well in fire tests required by the U.S. Coast Guard. The tests are designed to determine if tanks explode in flames within a short period. Linear materials, such as those blowmolded, flow when heated, notes White, causing holes to form in tanks; the holes lead to explosions. Metal tanks are not a likely solution as corrosion of these eventually leads to leakage, considered an even larger problem than emissions, explains White.

X-PE and fluorination not enough for gas vapors

White and others say improvements in materials and tank designs may be enough to limit emissions in the diesel fuel tanks used on boats. The same is not true of gasoline fuel tanks, such as those fitted on most small yard tools: smaller gasoline molecules more easily escape. Off-road exhaust and evaporative emissions control regulations were the subject of a CARB public hearing late last month in Diamond Bar, CA, during which CARB officials were to meet with industry representatives to discuss points of the proposed legislation, and were expected to adopt mandatory evaporative emissions limits as of 2007-2008—with exemption for machinery sold in very low volumes in the state.

At lawn mower, yard tool, and snow- blower manufacturer Toro (Bloomington, MN), Ron Lloyd, consumer engineering department manager, says the firm favors rotomolded fuel tanks for their design flexibility and low piece and tooling costs. Toro has about 25 different rotomolded cross-linked polyethylene (X-PE) tanks in its vehicles, he says, designed to hold from 4 to about 7.5 gal. Toro tried curbing emissions with level five fluorination, but he says permeation was still about three times that of similarly treated HDPE blow- and injection molded tanks. If the legislation forces the firm to stop using rotomolded tanks, he reckons blowmolded tanks will be the second choice.

Still, he says, "The lowest-cost solution, we think, would be an improved rotomolded tank." Rotomolded tanks cost the firm $15 to $16 apiece. Based on bids from potential suppliers, he says that would increase to about $16.50 for multilayer blowmolded tanks, and jump to $52 to $70 for steel tanks. The piece price for multilayer blowmolded tanks is competitive, he says, but blowmolding tooling costs of $35,000 to $50,000 are much higher than the $8000 or so for rotomolding molds. Injection molds and tooling for steel tanks would be too costly at more than $150,000.

Development efforts on multilayer rotomolded tanks incorporating engineering thermoplastics to form a barrier layer are in high gear. Mark Kearns, molding research manager at Queen''s University of Belfast (QUB; Belfast, Northern Ireland), says QUB is working on both multilayer rotomolded tanks as well as incorporation of nanoclays into rotomolding materials to reduce emissions from rotomolded fuel tanks. Multilayer parts could include polyamide or other engineering thermoplastics, he says, including ethylene vinyl alcohol (EVOH), though "the jury''s still out" as to its compatibility with the process. Toro is working with one of its key tank suppliers, rotomolder Centro Inc. (North Liberty, IA), to design and make prototype multilayer rotomolded tanks.

Matthew Defosse [email protected]

Rotomolded tanks help trim costs at Finn

Rotomolded fuel tanks are valued for their low cost and variable design; often they can be made to fit where other tanks can not. Landscape and construction machinery maker Finn Corp. decided one cost-cutting measure worth pursuing was a transition from fabricated steel fuel tanks to thermoplastic ones. Rotomolder Meese Orbitron Dunne Co. (MOD; Saddle Brook, NJ) contacted Jeffrey Reichert, VP of operations at Finn, about the possibility of using plastics to complement the steel designs.

Bob Dunne, MOD's VP of sales, touted the design variation achievable with plastic tanks as well as their durability. MOD rotomolded a tank with a one-piece design shaped to fit a triangular pocket inside Finn''s Model T90 HydroSeeder. The tanks, shaped like a wedge of cheese, enabled Fairfield, OH-based Finn to cut costs without altering its machines and also ensure that units in the field could easily be retrofitted if necessary or desired. "We used the steel tank as our model, using the actual blueprints for designing the rotomold tank," Reichert says. "When a part gets damaged in the field, you can retrofit it with a plastic one."

The cross-linked polyethylene (X-PE) tanks cut tank manufacturing costs by 62%, says Reichert. Because the HydroSeeder runs on diesel fuel, the X-PE can likely meet any future emissions standards, according to Finn.

For parts such as gauges and vents, fittings are made and then welded into existing metal tanks. Rotomolding tanks allows insertion of pre-made fittings during the process, reducing assembly steps. MOD also molded-in inserts to secure a U-shaped channel along the entire length of the tank. These inserts permitted the tank and U-shaped channel to be slid into the machine and secured with only two bolts, eliminating entirely the need for welding. Metal tanks are typically hidden inside or underneath the unit because they are more easily dented and scraped, which can invite rust and then cause potentially damaging leaks and spills. "Plastic tanks can also be molded to permit the fuel level to be read directly from the tank," Dunne notes.

Greg Valero [email protected]

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