Operation Manual

Diesel fuel flow sensor kit Installation and Operation Manual
23
NAVMAN
This section discusses fuel pipes terminology
and the fittings and tape used to join the pipes.
7-2-1 Pipe
Diesel fuel lines are often solid copper pipe.
Copper pipes are rated by their diameter:
Usually fuel lines will be called by their
outside diameter (OD) - this is also typical
of refrigeration pipe fittings.
However, domestic copper water pipe
is commonly measured by its inside
diameter (ID).
So ½ inch refrigeration pipe is a different size
from ½ inch water pipe - make sure you know
what size your boat fuel piping is before you
purchase fittings to install the sensors.
7-2-2 Flare Nuts
Flare nuts are often used to connect a sensor to
a solid copper fuel line. There are two different
systems of flare fittings:
45 degree flare: 45 degree fittings are
more common, and are in standard use
for refrigeration pipe work.
37½ degree flare: 37½ degree fittings
are more common for hydraulic systems.
JIC fittings are 37½ degree flare.
Fitting flare nuts
Push the flare nut along the pipe before
flaring the pipe!! Then flare the end of
the pipe using the flaring tool. Inspect the
inside face of the flared pipe - it must be
smooth and scratch-free. If it is not, cut it
off and try again.
7-2-3 Flexible Hoses.
Flexible hoses can make installation a lot
easier, but modern recommendations are that
only one short length of flexible hose should be
used - on the final link from the pipework fixed
to the boat to the engine, to allow for flexing
and vibration.
In many countries a boat licensed to carry
paying passengers has stringent codes of
installation practice to comply with - frequently
these require fixed, rigid fuel piping until the
last section. If your boat has to meet such
inspections, then check carefully before
attempting to use flexible hoses. At the very
least you may have to use metal braided flexible
hose to meet fire regulations.
There are also recommendations that the
fittings on the end of the flexible hose should
be professionally hydraulically crimped on.
Failing that, there are recommendations on
specific forms of field fitted hose fittings. Check
the use of flexible hoses against Coast Guard
recommendations, ABYC guidelines or with a
marine surveyor before deciding to use flexible
hose on your boat.
7-2-5 Threadseal tape or paste
Threadseal tape or paste is needed for all joints
where thread to thread sealing is required, for
example the adaptor fitting threads that are
screwed to the diesel fuel flow sensor.
Some manufacturers say to never use tape,
only use paste, while others say tape is OK.
Follow any requirements given by the engine
or boat manufacturer. The one thing you must
guard against with either type of threadseal is
bits of the thread sealer breaking off and getting
into the fuel.
Warning: Make sure pieces of the
threadseal tape or paste can not break off
and enter the fuel pipe.
7-2 Notes on pipes, fittings and installation
Only use fittings with the same flare in
your system. Do not mix fittings with
different flares.
If you don’t know how to use a flare
tool, then don’t fit a fuel flow sensor at
your first attempt. Ask to be shown how
to use the tool, then practice on some
scrap pipe before working on the pipes
on your boat!.
Warnings for flare nuts
Here are some comments and reminders:
Mark the pipe where you wish to cut it,
then cut it using a pipe cutter.
Do not cut the pipe with a hack saw - it
will leave small metal particles in the
pipes that will harm the sensor and other
items in the fuel line.