Note: Descriptions are shown in the official language in which they were submitted.
CA 02269423 1999-04-15
GASOLINE VAPOUR RECOVERY
METHOD AND APPARATUS
BACKGROUND OF THE INVENTION
s This invention relates to an improved gasoline vapour
recovery method and apparatus used in association with
underground or inground gasoline storage tanks normally
vented to atmosphere.
Underground tanks typically used for gasoline storage
are vented to atmosphere to ensure that no positive or
negative pressure is created in the underground tank and
associated pumping equipment. The venting system
typically consists of a pipe connected to the underground
tank at one end which extends upwardly above ground to a
~s suitable and safe position thus permitting the underground
tank to breathe directly to atmosphere.
Simply, air enters the underground tank in response to
a negative pressure inside the underground tank
occasioned, for example, by the act of pumping gasoline out
ao of the underground tank into a motor vehicle. Conversely, a
positive pressure creating mixture of air and gasoline vapour
(air/gasoline mixture) exhausts directly to atmosphere
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through the venting system. One reason for pressure
being created within the underground tank is temperature
Zs changes and fluctuations.
The occasions and circumstances when a gas/air
mixture will exhaust to atmosphere through the venting
system, is not considered a problem from the point of view of
pollution, since most of the gas/air mixture consists of air
3o which is present in the system and overlays the gasoline in
the underground tank. Problems do arise, however, when a
significant volume of gasoline vapour is created during the
filling operation of the underground tank with product from a
gasoline delivery truck.
3s This filling operation creates an increased volume of
gasoline vapours which would normally escape or vent to
atmosphere in the absence of any method or device to
recapture the venting gases. The recapture of gasoline
vapour is, of course, desirable, since gasoline vapours
4o condense back to gasoline, which is a valuable commodity.
As well, recapture of the gasoline vapour prevents pollution
of the atmosphere.
The existing method of recapturing venting gasoline
vapours requires the delivery truck operator to connect a gas
4s vapour recovery hose between the venting system and the
gasoline delivery truck tank at a point below the above
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ground end of the vent pipe. Accordingly, the movement of
gasoline from the gasoline truck to the underground tank
creates a vacuum inside the gasoline truck tank which, in
so turn, acts on the venting gasoline vapours drawing them
back into the gasoline truck.
The problem with the existing method is that it is
inefficient. Notwithstanding the proper connection of the
recovery hose, most of the gasoline vapours nonetheless
ss exhaust to atmosphere due to the paramouncy of the
venting system over the recovery system. Quite simply, the
recovery system is crude and consists of connecting a 3 inch
hose between the venting system and the gasoline truck
tank. Since gasoline is delivered by means of a 4 inch
6o hose, the system is unbalanced and facilitates the escape of
gasoline vapour through the venting system. Another
reason for inefficiency is that the upwardly moving gasoline
vapours in the venting system do not sufficiently sense, or
react to, the vacuum in the gasoline truck tank and simply
6s continue their upward movement venting to atmosphere.
Another problem is that for whatever reasons, some
delivery truck operators neglect or forget to connect the
vapour recovery hose with the result that the gasoline
vapours escape silently and directly into the atmosphere with
obvious disadvantage.
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A need exists for improving the gasoline vapour
recovery system to ensure that most of the gasoline vapours
are recovered. As well, an automatic signaling means of
ensuring diligence on the part of the truck operator to
~s properly connect the gas vapour recovery hose is desirable.
SUMMARY OF THE INVENTION
It is an object of this invention to improve the gasoline
so vapour recovery system by adapting existing vapour
recovery systems and installations with an apparatus which
will assist in directing a larger proportion of venting gasoline
vapours back to the gasoline truck and thus improve the
recovery of the gasoline vapours. .
8s It is another object of this invention to provide an
apparatus which automatically signals the gasoline operator
to remind the operator in the event that he has not
connected the gas recovery system during the delivery of
gasoline.
9o According to one aspect of the invention there is
provided a gasoline vapour recovery apparatus comprising a
chamber, first valve means adapted to close in response to a
first pre-determined pressure within the chamber, and a
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second valve means adapted to open in response to a
9s second and higher pre-determined pressure in the chamber.
According to another aspect of the invention there is
provided a gasoline vapour recovery apparatus comprising a
chamber, first valve means adapted to close in response to a
first pre-determined pressure within the chamber, a second
valve means adapted to open in response to a second
higher pre-determined pressure in the chamber, and alarm
means operable in response to the opening of said second
valve means.
According to yet another aspect of the invention there
los is provided a method of recovering gasoline vapours from an
underground tank by means of a recovery hose connected
between a vent pipe and a gasoline truck, by means of
increasing pressure on the atmosphere side of the vent pipe
connection to the recovery hose.
ns BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings which form part of the
specification and are to be read in conjunction therewith and
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120
in which like reference numerals are used to indicate like
parts in the various views.
Figure 1 is a schematic showing the gasoline vapour
recovery circuit.
Figure 2 is a cross-sectional view of the gasoline
12s vapour recovery apparatus.
PREFERRED EMBODIMENT
130
Turning now to the drawings in greater detail, and
initially to Figure 1, the underground gasoline tank (1) is
vented at all times to atmosphere (2) by means of a vent
pipe or stack (3). In other words, any positive gasoline
13s vapour pressure created inside the underground gasoline
tank is released through the vent pipe by exhausting the
pressure creating gasoline vapour/air mixture to atmosphere.
Any negative pressure inside the underground gasoline tank
is equalized and corrected by an intake of fresh air through
14o the vent pipe. This arrangement represents the normal
state of affairs. The arrangement changes when gasoline is
being delivered to the underground tank and the operator
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hooks up the gasoline vapour recovery hose in order to
recapture the gasoline vapours.
~4s According to the existing method of recapturing
gasoline vapour during product delivery, there is provided
surface access (4) to the vent pipe to which the delivery
truck operator connects one end of a gasoline vapour
recovery hose (4A). The other end is connected to the
~so gasoline truck tank (5) at location (6). The connections at
locations (4) and (6) at either end are conventional.
Thus, during the filling operation of the underground
gasoline tank by means of a typical surface connection (7),
increased gasoline vapours and corresponding pressure is
lss created in the underground gasoline tank which conveys the
gasoline vapours upwardly through the vent pipe. Because
the filling operation also creates a vacuum (7A) in the
delivery truck tank, this vacuum acts on some of the
upwardly moving gasoline vapour and draws some of it back
into the gasoline truck tank by means of the vapour recovery
hose connected at location (4A). Thereafter, the gasoline
vapours are collected and stored inside the gasoline truck
tank.
The gasoline vapour recovery apparatus is shown in
~6s cross-section in Figure 2. An inlet pipe (8) leading directly
to a central chamber (9) is connected to the top of the vent
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pipe (3) by means of a suitable connection. First valve
means (10) is provided within the body of the apparatus in
the nature of a check valve. During normal operations, the
loo check valve permits the underground tank to breathe as
described above. In the event of closure of the first valve
means due to an increase of pressure inside the central
chamber, a second valve means is provided in the nature of
a pressure relief valve to permit the pressure creating
~~s gasoline vapour/air mixture to exhaust to atmosphere by
means also of passing through the whistle assembly (11 ).
In use, the gasoline vapour recovery apparatus is
mounted on top of the vent pipe (2) leading directly to the
underground tank. The rain cap normally present on top of
~so the vent pipe (not shown) is removed from the vent pipe and
re-installed on top of the whistle assembly (11 ) to prevent
the entry of rainwater into the underground tank.
The first valve means consists of a check valve
mounted in hanging relationship to orifice (12). The design
ass and location of the check valve is such that it offers no
restriction to the intake of air from atmosphere into the
central chamber for passage to the underground tank. Its
design, however, provides for the closure of the orifice (12)
when the pressure in the central chamber rises above
atmosphere by reason of the exhausting gas/air mixture.
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With the gasoline vapour recovery system connected
and delivery of fuel commenced, the increased volume of the
exhausting gasoline air mixture will create pressure in the
central chamber and close the check valve. Because the
~9s pressure required to close the check valve is less than the
pressure required to open the second valve means, the
central chamber is sealed. The second valve means remain
closed. This effect and action effectively closes and shuts
down the venting system with the result that a working
Zoo pressure will build inside the central chamber. The working
pressure will act downwardly in the vent pipe to force and
direct the venting gasoline vapour/air mixture through the
recovery hose and into the truck tank. In this way the
apparatus improves the efficiency of the gas vapour
Zos recovery.
Referring to the second valve means, the pressure
relief valve is set to open at an operating pressure of about 1
PSI gauge in the central chamber. This setting is considered
sufficient to permit the improved gasoline vapour recovery
Z~o method to take place for normal operations. It should be
noted that the second valve means will always open if the
pressure inside the central chamber exceeds 1 PSI gauge
which feature satisfies any safety concerns and requirement
to have the underground tank vented at all times.
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Zls In the event, however, that the gasoline truck operator
neglects or forgets to connect the gasoline vapour recovery
system as described, the pressure within the central
chamber will quickly exceed 1 PSI gauge, which will open
the pressure relief valve permitting the gasoline vapour/air
aao mixture to vent to atmosphere via the whistle conduit (11 ).
The action of the escaping gasoline vapour/air mixture will
sound a whistle causing an audible alarm and signal to the
truck driver reminding him that he has failed to hook up the
gasoline vapour recovery system. As well, given that the
a2s precise volume of gasoline vapour/air escaping through the
vapour relief valve can vary, the whistle is mounted in a
floating and seated relationship with reference to orifice (12)
such that air in excess of what is required for sounding of the
whistle will pass around the base of the whistle to
23o atmosphere.
From the foregoing, it will be seen that this invention is
one well adapted to attain all the ends and objects
hereinabove set forth together with other advantages which
a3s are obvious and which are inherent to the structure.
It will be understood that certain features and sub-
combinations are of utility and may be employed without
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reference to other features and subcombinations. This is
a4o contemplated by and is within the scope of the claims.
Since many possible embodiments may be made of
the invention without departing from the scope thereof, it is
to be understood that all matter herein set forth or shown in
24s the accompanying drawings is to be interpreted as
illustrative and not in a limiting sense.
