Fluid handling – Systems – Plural tanks or compartments connected for serial flow
Reexamination Certificate
1999-11-16
2001-05-01
Rivell, John (Department: 3753)
Fluid handling
Systems
Plural tanks or compartments connected for serial flow
C062S050200, C141S018000, C141S095000, C141S198000
Reexamination Certificate
active
06223771
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to safety devices for gas tanks and, more specifically, to an overfill prevention device for liquefied gas tanks.
BACKGROUND ART
Liquefied gas tanks generally are used to store liquefied petroleum gases such as propane, propylene, butanes and butylenes for use in a plurality of applications including cooking, heating, drying and liquefied petroleum gas fueled engines. More than 18 billion gallons of liquefied petroleum gas are consumed each year in the United States alone. Since these highly flammable gases/liquids are under pressure in liquefied gas tanks, and since an enormous number of liquefied gas tanks are sold every year for use in both industrial and residential applications, there is an essential need for a design of these tanks that reduces the risk of bodily injury caused by tank overfill.
Storage tanks are typically filled to approximately 80-85% of the liquid capacity to allow for the expansion of liquefied petroleum gases and thus proper operation. Regulations and safety requirements have been implemented requiring that liquefied petroleum gas tanks not be filled to 100% capacity but preferably limited to approximately 80% capacity. As a result, a multitude of designs have been proposed to ensure compliance with these requirements. Many of the designs use a float-type system with a flapper portion, similar to a toilet flapper, that acts to close the fill input line when the volume in the tank reaches a specified amount. However, this type of design is disadvantageous, as flapper float mechanisms frequently get dislodged or hung, thereby resulting in an unreliable and less accurate means for preventing the overfilling of liquefied gas tanks.
It is readily apparent that a new and improved overfill prevention device for liquefied gas tanks is needed that is reliable, cost effective and under compliance with the user's local regulations and safety requirements. It is to the provision of such an improvement that the present invention is primarily directed.
BRIEF SUMMARY OF THE INVENTION
Briefly described, in a preferred embodiment, the present invention overcomes the above-mentioned disadvantages by providing a liquefied gas tank having a sealing partition positioned internally at less than one hundred percent (100%) and preferably, but not necessarily, at approximately the eighty percent (80%) of its liquid volume level as measured from the bottom of the tank. The sealing partition thus creates a vapor space in the upper portion of the tank of preferably, but not necessarily, approximately twenty percent (20%) of the liquid volume of the tank. An excess flow valve is positioned generally perpendicular to the partition in an upward direction such that any flow through the excess valve will be released into the vapor space of the tank. Attached to the top of the tank is a fill valve, preferably a multi-function valve, well known within the art, that allows input and output of liquefied and vapor gases. A fill tube extends from the fill valve through the partition and into the liquid space wherein liquefied gas is pumped into the liquid space of the tank.
In a preferred embodiment, the excess flow valve is rated at approximately one gallon per minute (1 gal/min), while the fill rate for the tank is greater than 1 gal/min, generally 3-4 gal/min. As such, when the liquid space is filled, the excess flow valve will open thereby allowing approximately 1 gal/min to flow into the vapor space. At the same time, the lower excess flow rate as compared to the fill rate will create a back pressure at the fill source and a stress on the fill source pump. The stress on the fill source pump will ordinarily cause an audible checking noise from the pump, thus indicating to the operator that the tank is adequately filled. In an alternate embodiment, a gauge may be added at the multi-function valve to indicate a back pressure and thus that the tank is filled to the desired liquid volume of less than 100%. In another embodiment, a pressure relief valve is carried by the partition and is generally vertical to allow pressure to be released from the liquid space to ensure that unsafe or unnecessary pressure does not buildup in the liquid space.
A feature and advantage of the present invention is to provide a new and improved liquefied gas tank that indicates to the user that the tank is filled to the desired liquid volume of less than 100% of the tank, preferably approximately 80% of its liquid volume capacity.
Another feature and advantage of the present invention is to provide a new and improved liquefied gas tank that incorporates an excess flow valve having a flow rate lower than the fill rate, thus creating a back pressure at the fill source when the tank is adequately filled.
Another feature and advantage of the present invention is to provide a new and improved liquefied gas tank having a sealing partition positioned internally at less than 100% of the liquid volume of the tank, preferably approximately 80% of its volume as measured from the bottom of the tank upward.
Another feature and advantage of the present invention is to provide a new and improved liquefied gas tank having a pressure relief valve positioned on a partition to allow pressure to be transferred from the lower partitioned area to the upper partition area.
REFERENCES:
patent: 2140559 (1938-12-01), Scully et al.
patent: 3684127 (1972-08-01), Kruse, Jr.
patent: 5829491 (1998-11-01), Bennett
Deveau Todd
Rivell John
Schneider Ryan A.
Troutman Sanders LLP
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