Fuel tanks are often forgotten by
those fitting out until the boats are nearly finished. By that time, your
initial enthusiasm for the work is wearing pretty thin, and the tank can
easily be thrown in as an afterthought. Petrol(gasoline) is obviously the
most dangerous fuel used on craft, and if it is at all possible, I would
always prefer a diesel installation, but given the right conditions, even
diesel fuel can catch fire very easily.
In a new installation, the first
consideration must be the siting of the tank. Very often the designer of
the hull will be able to advise you. Weight distribution can be very
important, and the performance of a boat may be marred by a fuel tank in
the wrong place. If you are fitting out a standard hull it would be well
to follow the practice of the builders.
Many boats have tanks installed
where it is virtually impossible to inspect them. It is important to be
able to examine fuel outlets and breathers, and check for corrosion at
very regular intervals. A tank failure at sea will mean a bilge-full of
foul smelling highly inflammable liquid, If it is at all possible, site
your tank below an easy to open hatch, or where it can be examined
through, say a locker.
To maintain the centre of gravity
as low as possible, it is preferable to place tanks low in the boat. This
will enable a fire-retarding bulkhead to be placed on either side. Often,
the bilge will have to run through the tank compartment, and in the event
of failure, fuel will rush through the bilge into the engine compartment,
battery or galley.
In high speed planing craft, where
tanks are subjected to the most severe conditions, it might be advisable
to fabricate plates that can blank off the bilge run. These should be
easily fitted, and used only during rough or high speed passages, and
removed once in port to allow for ventilation. In this way, fuel spilt
after a tank failure will be contained for the most part in the tank
Choice of material for
constructing the tank is very important. I am very suspicious of steel
tanks, even when. galvanized. Steel tanks are quite often used for
gas-oil, but must not be galvanised if so. On any steel tank constant
scrutiny is required for signs of rust. In particular beware of straps and
braces, that might rub against the tank and wear off any galvanizing.
Often, heavy corrosion is found under retaining straps.
Much better to install a stainless
steel or marine alloy tank, supplied by a reputable maker. Such companies
will be able to construct a special tank for your requirements. that will
fit the space you have available, allowing the maximum fuel capacity.
Always be sure to tell the manufacturers exactly what you intend to do
with the boat. If you are keen on power-boat racing, then the tank will
have to be much stronger and contain more baffles. Always insist that the
tank is pressure tested before delivery, and if possible obtain a signed
note to that effect.
Often forgotten, is the correct
location of the tank filler. Should fuel be spilt, where will it run to?
If it should find its way into a locker, then you have an explosive
situation on your hands. Some builders favour placing the filler at the
bottom of a self-draining cockpit, but fuel vapour could remain on the
cockpit floor or in the drain pipes for quite some time. All you have to
do is to light one cigarette, and ...
In my opinion the ideal location on most boats is
on deck, outside the coamings. in a position where excess fuel will run
directly to the scuppers.
The choice of pipe from the filler
to the tank can be difficult. many yachts use reinforced plastic, such as
that found on toilet installations. Over a period of time, such plastic
may become brittle, and in any case they are not totally resistant to
fuel, so get expert advice.
Care must be taken to ensure that
the tank is adequately vented. If this is not the case. blowback will
occur when filling, throwing fuel all over the place. The vent pipe should
have a minimum of 1/4ins. ID. be of fuel resistant materials, such as
nylon hose, and be led out through the side of the hull in a flame proof
The fuel outlet should leave the
tank at the top, or high on the tank side. This will prevent fuel spillage
should the piping fracture. All outlets that enable fuel to run out under
gravity or siphon, must be fitted with an on/off tap, directly on the
tank. Often, fuel outlets block, usually at the most embarrassing moment.
It is not a bad idea to have a second outlet plumbed to the fuel line with
a change-over tap.
Fuel gauge sender units are a
source of leaks. Every care must be taken to ensure that this does not
occur. some tanks are fitted with a drain plug below, to remove sediment.
This is another source of failure, and if possible should be omitted.
Consider fitting an in-line fuel computer instead.
Fitting the tank into the hull can
cause problems. Remember, it will be extremely heavy when filled. Under no
circumstances can a tank be able to break loose in heavy weather. Fixings
should not be absolutely rigid. When in a seaway, the hull of a boat is
constantly working, and if the tank was rigidly fixed, this might cause
undue stress, resulting in a fracture. For the same reason, all plumbing
to and from the tank must be capable of flexing. The filler pipe must not
put strain on the tank filter flange, and if metal fuel piping is used,
bend in a coil close by.
Some tanks are provided with
fixing flanges that are bolted to the hull. I am against such designs, as
too much strain will be taken on only a small part of the unit. It is far
better to spread the fixing load over as great an area as possible. Metal
straps wrapping around the tank and bolted to the hull are often the ideal
arrangement. Always make sure that a rubber packing is placed between the
tank and the strap. On craft capable of planing at high speed, the tank
must be better insulated from shock. One effective method is to house the
tank in a compartment lined with several inches of closed cell fuel
resistant foam. This method will spread load evenly over the tank.
The United States Coastguard and several European countries have laid
down strict requirements for tank installations. Having studied them, I.
am doubtful whether all the requirements are possible to include in most
boat designs, in fact in many cases they are virtually impossible.
However, there is no question that much more effort should be made to
ensure maximum safety of small craft. Check that your boat is fitted out
safely. It could be your last chance!