Tank vents

[robbio c]

Evening all is it nessesary to install diesel and water tank air vents through a fitting to outside or can you just install the vent and leave it inside attached to tank ?

[Alan de Enfield]

11 minutes ago, robbio c said:

Evening all is it nessesary to install diesel and water tank air vents through a fitting to outside or can you just install the vent and leave it inside attached to tank ?

It is convention to have them outside (would you want diesel fumes venting inside the boat ?)

 

Don't forget you need an anti flash gauze attaching / included in your fuel vent.

 

 

2.3 Fuel tank vents
2.3.1
Does every fuel tank have a vent facility? 
Check all fuel tanks for the provision of a vent facility.
A vent line must be fitted to each fuel tank, or a vent must be
fitted to either the filling cap or filling line.
NOTE – vents in filler caps, lines or tank tops must have their outlets at, or above the filling point level.
NOTE – multiple diesel fuel tank arrangements having a shared vent facility are acceptable provided the
arrangements comply with all other requirements at 2.3.

2.3.2
Does the fuel tank vent line have a minimum internal diameter of 9.5mm (⅜in)? R
Measure the outside diameter of fuel vent lines. The internal diameter of vent lines must be at least 9.5mm (⅜in).
NOTE – this may be verified by measuring the outside diameter and estimating wall thickness. The
following are approximate indications, copper 11.5mm (½in), steel 12.5mm (½in) and hose 15.5mm (⅝in).
NOTE – the small hole in the filler cap as provided by the original engine or fuel tank manufacturer, on tanks
of no more than 27 litres capacity, is deemed to meet this requirement. Examples are those found on Stuart
Turner petrol tanks, Yanmar engine close‐coupled tanks or diesel tanks supplying appliances.

2.3.3
Are the fuel tank vent line connections free of signs of leaks and in good condition, and are
all vent hose connections accessible for inspection?

Check for the presence of vent hose connections,
and the condition by sight and touch.
Check the condition of fuel tank vent pipe
connections where they can be seen or reached.
All vent hose connections must be accessible for
inspection, secure and free of signs of leaks or other
signs of damage and/or deterioration.
Vent pipe connections must be secure and free of signs
of leaks, signs of damage and/or deterioration.

2.3.4
Is the fuel tank vent line self‐draining so that fuel is not retained, and is it free of kinks or
other restrictions?

Check the fall of each vent line where it
can be seen or reached.
Check for any kinks or other obvious
restrictions in any vent lines where they
can be seen or reached.
Vent lines must be connected to the top of the tank and be ‘selfdraining’,
i.e. fall continuously from the vent outlet to the tank,
or, where a swan neck is installed, from the top of the swan neck
down to the vent outlet and the fuel tank connection.
Vent lines must not be kinked or restricted.
NOTE – vent lines must not have their internal bore diameter restricted to less than 9.5mm (¾ in).
NOTE – ‘top of the tank’ means the top plate of the fuel tank or the highest part of the side of the tank.

2.3.5
Is the material of the fuel tank vent line suitable and in good condition? R
Check the material and condition of vent
lines which can be seen or reached.
Check the markings on any vent hose.
Vent lines must not show signs of fuel leaks, damage or
deterioration.
Vent hose must be marked as suitable for the fuel in use or
supported by an appropriate declaration.
NOTE – diesel tank vent hose in good condition may be accepted without marking or declaration
provided it can be examined over its entire length.
NOTE – in cases where the vent hose is suitably marked, enough of the hose must be accessed in order that
the examiner can make a reasonable assessment as to its general condition.
NOTE – hoses marked with the correct type of fuel in use are acceptable. Hoses marked ISO 7840, or
equivalent, are recommended, and hoses marked to SAE J 1527, DIN 4798, RINA DIP/66/96 are equivalent to
ISO 7840.

2.4 Fuel tank vent outlets
2.4.1
Does the fuel tank vent outlet, or the vent line swan neck, rise at least as high as the filling
point?

Check the rise of each vent line.
Fuel tank vent outlets, or the vent line swan neck must rise to a
height at least that of the fuel filling point.
NOTE – where the filling point is mounted on a deck a swan neck in the vent line to the underside of the
deck meets this requirement.

2.4.2
Is the fuel tank vent outlet fitted with an effective flame arrester or flame‐arresting gauze? 
Check each vent outlet for the presence
of a flame arrester or flame arresting
gauze.
Vent outlets must be fitted with either a suitable proprietary
flame arrester or gauze of at least 11 wires per linear cm (28
wires per inch) mesh.
Where the flame arrester is not of a suitable proprietary type the
openings in the arrester’s body must be at least of the same area
as the cross‐sectional area of the vent line.
Flame arresters or gauze must be complete and free of damage
or restrictions.
NOTE – flame arresters not recognised as proprietary must be supported by satisfactory
documentation.
NOTE – the small hole in the filler cap as provided by the original engine or fuel tank manufacturer, on fuel
tanks of no more than 27 litres capacity, is deemed to meet this requirement.

2.4.3
Is the fuel tank vent outlet in a position where no danger will be incurred from leaking fuel
or escaping vapour?

Check the position of each vent outlet.
Vent outlets must be clear of any potential sources of ignition and
must be in a position where no danger will be incurred from
leaking fuel or escaping vapour into the interior of the vessel.
NOTE – the small hole in the filler cap as provided by the original engine or fuel tank manufacturer, of diesel
tanks of no more than 27 litres capacity meet this requirement.
NOTE – vent outlets located within open vessels such as RIBs having no accommodation and having a
continuous deck or sole which is fuel‐tight to the interior of the vessel, including bilge spaces, meet this
requirement.
NOTE – diesel vent outlets within self‐draining cockpits having a continuous deck or sole that are fuel‐ tight to
the interior of the vessel, including bilge spaces, meet this requirement.

 

 

Edited February 15, 2020 by Alan de Enfield

[WotEver]

10 minutes ago, robbio c said:

Evening all is it nessesary to install diesel and water tank air vents through a fitting to outside or can you just install the vent and leave it inside attached to tank ?

Water yes. Fuel no. From BSS:

NOTE – vents in filler caps, lines or tank tops must have their outlets at, or above the filling point level.

[robbio c]

Ok thanks for the replies guys answers my question ?

[PaulJ]

Although not a BSS fail its always a good idea to run your water tank vent to the outside-better surplus water goes outside than in when you are refilling your tank..