Aging fuel tanks may pose hazard

On the Outdoors

April 13, 1997|By Peter Baker | Peter Baker,SUN STAFF

If you are a boater -- racer, cruiser or fisherman -- by now several weekends have been spent puttering around the marina or storage area in the yard or drive, getting the boat ready for the season.

The hull has been inspected, washed and waxed, the bottom painted, the engine de-winterized and tuned.

Electrical systems have been checked, including navigation lights, radios, Loran or GPS units. Charts have been updated or replaced. Flares, fire extinguishers and safety kits have been checked and replaced or refilled.

Hoses from through-hull fittings to heads, sinks, showers, bilge pumps, live wells and cockpit drains have been inspected for wear and the hose clamps re-tightened or replaced.

And finally, it seems time to count passengers and life jackets and head out.

But according to the latest "Boating Safety Circular" from the Coast Guard, an alarming number of boaters whose crafts have gasoline engines are unaware of potentially explosive situations, all of which might stem from aging aluminum fuel tanks.

Coast Guard statistics indicate 83 percent of boats in use are powered by gasoline engines.

According to the circular, a study by Underwriters Laboratories found that 23 percent of the owners of gas-powered boats continued to operate their craft after a fuel-tank problem was detected.

Gasoline leaking into the bilge or fuel vapors accumulating near live ignition systems can ignite and explode. Fuel leaks are one of the major causes of boat fires across the country.

"Since the majority of respondents to this survey were members of major boating organizations which promote boating safety," the circular said, "the UL survey concluded that the proportion of uninformed boaters was probably higher in the general boating population."

In 1992, UL was awarded a grant to survey boat owners and determine how many had problems with leaking fuel tanks. And while the Coast Guard admits the survey of 164 respondents was not a statistically valid representation of the boating population, the data gathered showed that "aluminum fuel tanks failed in many different makes, types and models of recreational boats."

In the UL study, 92 percent of tank failures were caused by corrosion, and failure at baffle welds also seemed to be a significant problem area. But in general, anywhere an aluminum tank comes in contact with water -- especially saltwater -- over extended periods, there is a danger of corrosion and eventual failure.

The tank begins to weep fuel, the fuel drips to the bilge and the vapors are trapped below decks, accumulating until they are dense enough to explode when an electrical spark or an open flame is present.

Bilge blowers, which should be operated for several minutes prior to each starting of the engine, will clear the bilge of vapors. But a full inspection of the fuel system -- from tank to engine, including all fuel lines and connections -- should be a must each spring and periodically through the season.

A 20-year-old runabout I purchased for my wife and kids last fall has an aluminum fuel tank mounted above deck, but behind and under a jump seat. Its surface is corroded, and although there are no visible leaks and the smell of gasoline cannot be detected, it will be replaced this year before they are allowed to take the boat out. Simply, the chance of failure and explosion is too great.

According to the Coast Guard circular, a monthly publication listing manufacturers' defects and recalls and detailing potential problems with recreational boats, there are alternatives to old aluminum tanks -- but none include quick fixes such as puttying problem areas or encasing old tanks in foam.

Heavier-gauge aluminum tanks are one option, 0.125 inches rather than the standard 0.090 inches, for example. But UL tests showed that in some cases even the thicker aluminum failed at about the same rate as the thinner gauge.

Stainless steel tanks can be used to replace the aluminum tanks installed by manufacturers, but only 316L stainless with minimum wall thickness of 0.031 inches is acceptable. Under Coast Guard and American Boat and Yacht Council standards, they must be cylindrical with domed heads and less than 20 gallons in capacity.

Fiberglass (fiber-reinforced plastic or FRP) tanks built with fire-retardant resins are highly effective, but are expensive to build and best suited to custom installations on larger boats.

A workable alternative for many installations, the Coast Guard says, is polyethylene (PE) tanks, which have been widely used in smaller, outboard-powered boats for years.

Properly manufactured and installed PE tanks have withstood the Coast Guard's benchmark 2.5-minute fire test with acceptable results, and PE does not corrode.

According to the circular, PE tanks "properly manufactured and installed should last for the expected service life of the boat."

This spring, before the boat is slid off the trailer, launched by the yard or motored out of the slip, go through the fuel system step by step.

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