SAFETY CONSIDERATIONS
FUEL SYSTEMS
Why are there so many
requirements for fuel systems.?
Gasoline is extremely dangerous and volatile. It
can go boom at the worst moments ruining your whole day! But it's no joke.
Fuel system regulations have been developed over
many years, mainly by the Society of Automotive Engineers (SAE) and the
National Fire Protection Association (NFPA). These have been
incorporated into the ABYC standards and the US Coast Guard regulations.
Most fuel leaks occur at a fitting. So
standards were developed to prevent this. Things such as double clamping a
hose and using swaged fittings were made primarily to prevent leaking
connections.
Hoses that were used in autos were found to be
inadequate in boats. Fuel in cars does not stay in the hose very long, but
in boats it can sit for months at a time. This gives the additives
and the components of the gasoline itself time to attack the compound of
the hose. So hoses have to be able to resist this. Alcohol in
the fuel leaches out the parafins that make the hose pliable and flexible.
So hose was developed that was alcohol resistant. Even so, hose should be
checked periodically for cracks, stiffening, becoming very soft and mushy,
and replaced.
Hoses that are exposed to sunlight have to be UV
resistant as well. Hoses used for outboard engines in particular
have to be UV resistant because they often are outside exposed to the sun.
Hoses used in some areas on the boat also need to
be fire resistant. If a fire gets started the last thing you need is a
fuel hose burning through and dumping fuel into the boat, feeding the
fire. So hoses have to resist a fire for 2 1/2 minutes. Why 2
1/2 minutes? Because if your fire fighting system doesn't put out the fire
in that amount of time, you probably won't put it out. It gives you time
to get off the boat.
Fuel hose clamps are usually metal, although
plastic ones are being used occasionally. The metal has to be
corrosion resistant. So stainless clamps should be used, but all
stainless! Many supposed stainless clamps are not. The little screw
that tightens them is not always SS. The clamps corrode and lose their
tension, loosening the connection. One of the most common causes of fires
is fuel dumped in the boat when fueling up. This is because the clamps on
the fuel fill hose have loosened and fuel leaks at the fitting, or the
hose falls off.
Metal fuel lines also have problems. Copper in a
marine environment deteriorates rather rapidly. Plus that it is subject to
galvanic corrosion. So metal fuel lines have to be certain materials such
as copper-nickel or nickel copper. Steel lines are also allowed. A big
problem with metal fuel lines is vibration. Vibration loosens fittings,
and fatigues the metal, resulting in cracks, usually at the fittings. So
metal fuel lines are usually kept short, and there are short flexible
lines between the metal fuel line and the engine inlet.
Other fuel system components have the same sorts
of problems. Fuel pumps and filters have to be fire resistant and not
leak. Fuel filters used in cars don't meet these requirements. If you get
a fuel leak in a car the gas goes on the ground. In a boat it goes into
the bilge. So components have to meet the same requirements as hoses and
tanks.
Fuel tanks need to be of a material that doesn't
easily corrode, is fire resistant, and strong enough to last with all the
forces that they are subjected to. Tern plate (a lead tin compound) used to be common on cars. Unfortunately, it corrodes rapidly
on boats. So tern plate is not allowed. Steel needs to be properly
prepared and coated to resist corrosion. Aluminum corrodes if it is
constantly wet. It also is subject to corrosion from the inside of the
tank due to phase separation of the gasoline and alcohol, and alcohol's
tendency to attract water. So it needs to be mounted properly to avoid
corrosion. The same goes for any metal tanks. Stainless is a special
problem. It too will corrode if wet, so it needs to be mounted where it
can be kept dry. It is also subject to crevice corrosion, particularly at
the welds. So welds need to be kept to a minimum. All of these materials
have to be able to resist shock and vibration, sloshing of fuel in the
tanks, and sudden accelerations in all three directions.
One question that comes up often is "why can't I
put the fuel pump in or on the tank"?. This is commonly done with fuel
injected systems on cars . It helps to eliminate vapor lock and
insures a steady supply of fuel. However, this means that the fuel
line running from the tank to the engine is under pressure. In some fuel
injected systems this can be as much as 30 psi. Think what would happen if
a leak developed! In a pressurized system this would result in all of the
fuel in the system being sprayed into the boat. I mean all! It would
empty the tank. This is one of the basic laws of physics. So, the
fuel pump on a boat is required to be on or within twelve inches of the
engine. That way the only line under pressure is the one from the fuel
pump to the carburetor or fuel injection system. This line is usually very
short, generally about a foot or maybe two on larger engines. The fuel
from the tank is sucked to the engine rather than pushed. If a leak
develops, the fuel just stops flowing and the engine quits.
Pressurized lines and fuel systems are not allowed on boats, except for
that one short line.
Why not a closed fuel system? Why does it
have to be vented to the atmosphere? Doesn't this add to air pollution?
Yes it does. But for the reasons cited above you don't want a pressurized
system. A leak would dump all the fuel into the boat.
However, the new EPA Fuel system rules do allow for up to 1 psi in the
tank, fill and vent.
So the main purpose behind fuel system regulations
is to prevent leaks, thereby preventing fires and explosions.
To add a complication, the US Environmental
Protection Agency (EPA) and the California Air Resources Board (CARB) have
recently (since about 2001) proposed a series of regulations that would
control evaporative emissions from permanently installed fuel systems, and
exhaust emissions from inboard gasoline engines. The
regulations would limit evaporative emissions to 15 grams per square meter
of surface per 24 hour period. This is far less than the current 100 for
A1 or B1 hose and 300 for A2 and B2 hose. The same requirement would
apply to tanks and vent systems which have always been open to the
atmosphere. Because of the safety issues surrounding pressurized systems,
the EPA and CARB have agreed not to require closed systems, as are used on
cars, but to require a charcoal canister in the vent that would not create
back pressure and would absorb fuel vapors. Plastic tanks would also
have to limit the amount of vapor permeated through the tank wall.
The engine exhaust will have a catalytic converter, similar to cars but
much smaller in size. Some of these regulations go into effect in 2009,
and all go fully into effect in 2010. As of July 2012 all of these
EPA regulations are in effect. See
https://newboatbuilders.com/pages/environment.html
Revised 03/04/2022 © newboatbuilders.com 2007
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