Fluent material handling – with receiver or receiver coacting mea – Processes – Gas or variation of gaseous condition in receiver
Reexamination Certificate
1997-11-28
2001-05-22
Maust, Timothy L. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Processes
Gas or variation of gaseous condition in receiver
C141S005000, C141S044000, C141S049000, C141S285000, C141S372000, C137S588000, C137S592000
Reexamination Certificate
active
06234216
ABSTRACT:
This invention relates to the refilling of liquid storage tanks, in particular but not exclusively to the refilling of storage tanks with petroleum fuels or chemicals.
In the following, the discussion will relate to deliveries made to petrol storage tanks, although it is to be appreciated that the invention can be applied similarly to petroleum, chemical or other storage tanks.
Petrol storage tanks generally have a filling entry at the top of the tank, and have a direct fill point, or a remote (offset) fill point to which a delivery hose of a tanker delivery vehicle is connected for the delivery of liquid product to the tank. A permanent fixture in the form of a drop tube is supported at the filling entry. The liquid outlet of the drop tube is suspended a short distance above the base of the storage tank. This arrangement is intended to reduce disturbance of the incoming product when liquid is delivered into the tank. Rather than falling uncontrolled from the top of the tank on entering, the incoming product mixes directly with the contents remaining in the tank as it exits from the outlet at the end of the drop tube.
European patent application EP-A-0327518 relates to a method for recycling petrol vapors. The drop tube of a petrol storage tank is converted by drilling holes into the side of the drop tube at the top of the petrol tank, so that petrol vapor can enter the drop tube by those apertures. A substitute fill pipe is then inserted into the original drop tube, and the space between the substitute fill pipe and the original drop tube is used to convey vapors entering the original drop tube via the drilled holes from the body of the tank to a vapor recovery unit during filling of the tank. However, the substitute fill pipe functions in precisely the same manner as a conventional internal drop tube, by delivering incoming product directly at a liquid outlet which is immersed in the liquid contents of the tank.
British patent specification number 795,206, published on May 21, 1958, describes an arrangement for drawing seawater from the fuel oil tank of a ship. The seawater is used for ballasting purposes, and forms a non-misicle lower layer seated below an upper layer of fuel oil. When the seawater layer is to be drained, suction is applied to a drainage tube so that the seawater is drawn up through a bell mount. When sufficient seawater has been removed, air is discharged in to the suction pipe by means of an air pipe. When the amount of air entering the drainage tube balances the suction effect, no more seawater is drawn into the drainage tube. As the reader will appreciate, this patent does not describe a liquid storage tank with a filling conduit.
According to one aspect of the invention there is provided a method for refilling a liquid storage tank with a filling conduit having a liquid inlet and a liquid outlet, the liquid outlet being covered by the liquid contents of the tank and the filling conduit having gaseous contents between said liquid inlet and said liquid outlet, the method comprising the steps of removing at least part of the gaseous contents of the filling conduit without ejecting said at least part of the gaseous contents of the filling conduit into the liquid contents of the tank, and delivering liquid to the tank via the filling conduit.
According to a further aspect of the present invention, there is provided a liquid storage tank comprising a filling conduit defining a liquid flow path leading from a liquid inlet to a liquid outlet, said liquid outlet being arranged to be covered by the liquid contents of the tank when the tank is partially filled, and a separate gaseous outlet arranged to remove gaseous contents from said liquid flow path of the filling conduit when said liquid outlet is covered by the liquid contents of the tank and before said gaseous contents are forcibly expelled from the liquid outlet into the liquid contents of the tank.
According to a yet further aspect of the present invention there is provided apparatus for installation in a filling conduit of a liquid storage tank, said filling conduit defining a liquid flow path leading from a liquid inlet to a liquid outlet and said liquid outlet being arranged to be covered by the liquid contents of the tank when the tank is partially filled, said apparatus comprising means for forming a separate gaseous outlet in said filling conduit to remove gaseous contents from said liquid flow path of the filling conduit when said liquid outlet is covered by the liquid contents of the tank and before said gaseous contents are forcibly expelled from the liquid outlet into the liquid contents of the tank.
In the case of a petrol storage tank, the filling conduit, which may include the pipeline connecting the offset fill point (if present) to the top of the drop tube and the drop tube itself, normally contains a vapor/air mixture which is locked in the filling conduit between the inlet and the product inside the internal drop tube. On delivery of liquid into the filling conduit these gaseous contents are, in the conventional arrangement, forced downwards through the drop tube and forcibly expelled from the lower outlet of the drop tube. If, as is normally the case, the lower outlet of the drop tube is immersed in the liquid remaining in the tank, this gaseous mixture enters the remaining liquid.
Such expulsion of the gaseous contents of the drop tube causes turbulence which can cause damage to the tank and the fill pipe itself.
The arrival of the gaseous contents at the liquid surface can also cause an unnecessary amount of vapor emission from the tank during liquid delivery. In its ambient state, if the storage tank contains a volatile liquid product, for example, petrol, a shallow layer of saturated vapor forms above the product surface. The remainder of the tank is filled with unsaturated vapor. However, after a disturbance is caused as described above by the arrival of the gaseous contents at the liquid surface, the saturated vapor layer is destroyed and the remaining space in the tank receives a greater concentration of vapor. During delivery the pressure within the tank is balanced by venting gas from the top of the storage tank. The greater concentration of vapor at the top of the tank leads to a greater amount of emission from the tank during delivery. Increased vapor emissions lead to waste of product and, often more importantly, a environmental hazard insofar as the vapor may be poisonous or otherwise damaging to the environment.
By removing at least part of the gaseous contents of the filling conduit before that part is ejected into the liquid contents of the tank, damage to the tank and vapor emissions from the tank can be reduced.
REFERENCES:
patent: 1325991 (1919-12-01), King
patent: 3807465 (1974-04-01), Ginsburgh et al.
patent: 4513797 (1985-04-01), Tompkins, Jr.
patent: 6062274 (2000-05-01), Pettesch
Andrus Sceales Starke & Sawall LLP
Maust Timothy L.
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