NZ212773A - Lpg tank with interior safety compartment of predetermined volume - Google Patents

Description

W /■ q 2 12773 7 \ ,. to-U> ......

Priority Date(s): . • /■ • • * • iSil Complete Specification Filed: Class- cqc 9...

Publication Date P.O. Journal, No: • • • • ■ " 1 * * . ....MMM. i: 9 Patents Form No. 5 PATENTS ACT 1953 COMPLETE SPECIFICATION TANK Number Dated fci-A. ?^TS5fi■ ' 1 /'MJIJ935 , . ; T I/^ex ANTONIO BOEMO, of 245 Johnston Street, Abbotsford, Victoria, Australia, an Australian citizen: . do hereby declare the invention for which I/sce pray that a Patent may be granted to meina, and the method by which it is to be performed, to be particularly described in and by the following statement: : - I' - ■; /''1! .-v ■ •••/ O G '. •:,) This invention relates to storage vessels and, in particular, to storage vessels for containing liquid petroleum gas (LPG) and the like.

LPG is used in a wide variety of fields. It is used as a source of thermal energy for heating and cooking and finds use as a vehicle fuel. In recent years LPG has replaced liquid hydro-carbon fuels such as petrol as a fuel source for internal combustion engines. This is in part due to the lower overall cost of LPG and its ready availability.

Storage of LPG and related low boiling point liquids presents its own particular problems. Because of its low boiling point, LPG has to be stored 10 under pressure, thus placing certain requirements on the storage vessel used. Thus the storage vessel has to contain safely the enclosed liquified gas under pressure and in all possible enviromental conditions the enclosing vessel is likely to encounter.

One factor that has to be considered in relation to the safety of a tank or container containing LPG is the effect of temperature on the enclosed contents. Liquids are virtually incompressible. Thus when a liquid is heated, it expands, and the resultant hydro-static pressure against any enclosing surface reaches a point where the enclosing container ruptures with the result that the liquid escapes and vaporises into the atmosphere, creating a potentially dangerous situation.

To overcome this problem it is usual to only fill LPG cylinders to a certain level such that a pre-determined volume of the enclosing vessel is occupied by LPG in the liquid phase and the remaining volume is occupied by the gaseous phase. Thus if the tank or container is subjected to an increase in temperature, although the pressure of the enclosed contents increases, its Boemo/44/Apri185 degree of increase is well within the stress limits that can be accommodated by the surrounding steel vessel.

Conventional LPG tanks and containers rely on a level indicator of the floating type to indicate the level of gas in the liquid phase in the container. This device comprises a float adapted to float on the surface of the liquid LPG which float is connected to an elongate member having at the opposed end, a counter balance. This float mechanism is adapted to indicate the contents of the tank by visually representing such on the outside of the container, on a dial for example. It is further adapted to close off the inlet valve so that further LPG is not admitted into the tank when the prescribed level of LPG in the liquid phase has been reached.

One disadvantage of this prior art means of controlling and monitoring the amount of liquified LPG in the tank or container is that if the limiting mechanism of the float device is tampered with in some way and/or the gauge indicator outside the tank is tampered with, or either mechanism malfunctions, then as there is no precise indication of the degree of filling of the tank, it is possible that over filling may occur with the consequent risk of rupturing of the tank when used in normal running conditions. This is particularly the case with containing vessels which are fixed or too large to allow weighing of the vessel to determine its contents.

An object of the present invention is to provide a tank with an automatic fill limiter which overcomes or mitigates the above described disadvantages of the prior art. It is a further object of the invention to provide a limiting device which allows speedy and rapid filling of the tank or container.

Boemo/44/Apri185 ■5 a s '".<) 7/ 11 0 ■■:<£, (J {J &0 ***■ T\ t»$r In its broadest sense the present invention comprises a tank or cylinder having interiorally thereof a compartment of pre-determined volume separated from the main volume of the tank and having first communicating means between the compartment and the main volume of the tank allowing restricted flow of fluid into the compartment from the main volume and second communicating means between the compartment and the main volume of the tank adapted to allow rapid discharge from the compartment into the main body of the tank when there is a pressure differential between the main body and the contents enclosed in the compartment.

M r tT "-s y The invention further provides a valve for use in the tank or cylinder referred to above which valve comprises an enlarged bore having a seating arrangement within the bore and substantially spherical means located interiorally of the bore and a capillary opening communicating with said enlarged bore.

It is to be understood that the present invention finds use in other areas where there is a requirement to store and contain liquified gasses, for example nitrogen and oxygen, and is therefore not solely limited to the storage and containment of LPG.

Furthermore the invention finds application in various types of containers used to contain LPG for different purposes. For example the fuel limiter of the invention may be used in all LPG cylinders and storage vessels including those used in automotive fork lift trucks, domestic gas cylinders, industrial storage cylinders, barbeque cylinders.

In order that the invention may be readily understood I shall describe one Boemo/44/Apr i185 . - 7 NOV 1986 rfp.fjvep i emodiment of the invention involving a tank or cylinder adapted to contain LPG.

BRIEF DESCRIPTION OF DRAWINGS : Fig. 1. shows a cutaway side view of the apparatus of the invention. Fig. 2. is a cross-section view of the apparatus of the invention. Fig. 3. shows a detailed section of one form of valve means which may be used in the apparatus of the invention.

Fig. 4. shows a conventional cyclinder having a float value as the level indicator.

One form of the invention is shown in Fig 1. The tank (1) has incorporated therein a safety container (2). The container shown has on its exterior the conventional protective guard (4) and various plates (4), (36) and (37) which may have indicia punched or written thereon.

It is a requirement with LPG cylinders or tanks that they be filled with at most 80% of their volume with LPG in liquified form, the remaining 20% or more of the capacity of the tank being occupied by gaseous (vapour) LPG. The latter volume is often referred to as the safety volume of the tank. This safety volume exists to ensure the safety of the container and its enclosed contents.

First, referring to Fig.l, I achieve this safety volume by arranging a limiting device within the LPG tank (1). This limiting device comprises a closed cylindrical container (2) having a volume capacity not less than 20% of the total volume of the tank itself, preferably equal to 20% of the total volume of the tank. This cylinder may be placed at any position in the tank, however I prefer to position the cylinder at an upper portion of the tank such that its main axis is parallel to the longitudinal axis of the containing tank.

Connection between the safety volume and the useable volume of the tank is provided by valve means (3) a detail of which is shown in Fig. 3. This valve means includes a restrictive gauged opening (30) of 0.6mm in diameter. This opening allows restricted flow of fluid from the main volume of the tank to the safety volume enclosed within the cylinder.

The valve means also allows rapid discharge through a gauged hole (35) of 3mm in diameter. This hole has a necked seat portion having a bore of narrower diameter on the safety volume side of the valve. Within the larger diameter opening there is positioned a sphere (33), made of resilient material, which, when subjected to a greater pressure on the main volume side, is forced against the neck portion of the hole so as to close off the opening into the interior of the safety cylinder.

I shall now describe the invention in relation to the actual filling of the tank with LPG. When the tank (1) is filled with LPG the effective volume of the tank is the total volume of the tank less the volume of the safety cylinder or automatic fill limiter. This is because the ball (33) in the valve connecting the volume of the main tank with the safety volume is forced up against the seat of the enlarged opening (35) of the valve (3), during filling of the tank, so as to effectively close off that entrance into the safety volume. The capillary opening (30) of diameter 0.6mm is not sufficient to allow any significant flow of fluid into the container enclosing safety volume (2). Thus the volume of the tank with the enclosed automatic fill limiter is equivalent to a volume of 80% of the total tank volume.

Boemo/4 4/Ap r i18 5 The tank or cylinder of the invention may also incorporate a conventional float type indicator as shown in Fig. 4 of the drawings. This float indicator has a float (5) at one end of an extension (6) and at the other end, a counterbalance (7). The movement of the float (5) on the liquid surface is transmitted to a dial on the exterior of the tank by a cog wheel mechanism (8). The phantom lines show the position of the float mechanism when the tank is full with LPG.

Once the filling of the useful volume has been completed, the float (5) having closed off the inlet valve, the filling pump encounters a notable increase in pressure due to the restriction of the inlet gas by the narrowing of the inlet nozzle by the float mechanism. In such conditions the pressure of the pump rapidly reaches 16/Kg per square cm. causing the electromechanical valve of the by-pass of the column of the pump to release and the flow of LPG to return in a circle to the pump itself.

Further filling of the tank beyond 80% of the total volume therefore becomes practically impossible. Once the tank has been filled to the 80% level there is equilibration between the pressure of the main volume of the tank and the safety volume through the capillary opening (30) so that the pressure of the LPG in the tank and the gas in the safety chamber equalises rapidly. From experimentation it has been found that this equilibration occurs in about five minutes. Whilst the diameter of the capillary effectively limits the filling of the tank to 80% of its volume, it does not impede the slow thermal expansion of the fluid held within the main body of the tank into the safety volume until equilibration has occurred.

Preferably filters (32) are provided within the valve so as to prevent blocking of the capillary or the larger bore discharge hole so that a free Boemo/44/Apri185 n. i 160 170 passage is available to fluid passing between the main body of the tank and the safety volume. The valve (3) also has a pinstop (34).

When gas is taken off the container for use, for example, to power a vehicle or for heating purposes the liquid contained in the safety volume gradually flows back into the main volume via the enlarged bore (35) of the valve, as the pressure in the main volume falls below that in the safety cylinder. This is because the pressure on the safety volume side of the valve becomes greater relative to the main tank pressure causing the ball (33) to be pushed away from the seat so that fluid can pass from the safety volume to the main volume of the tank. When all the contained gas is removed from the tank the valve mechanism (3) of the safety cylinder is such that, it too, is emptied.

Thus the embodiment described above provides an effective limiting device which allows rapid filling of an LPG container or tank and ensures that it is practically impossible to fill the tank to a liquid level greater than 80% of the total volume of the tank whilst at the same time allowing any fluid contained in the safety cylinder to be drawn off as LPG is drawn off the tank.

As indicated above, the tank with the automatic fill limiter of the invention may be incorporated in a tank together with the conventional level indicator shown in Fig.4 of the floating type and may also include a safety valve and non-return valves. The automatic fill limiter of the invention automatically interrupts the entry of the liquid into the tank and is totally independent of the other mechanisms used to control ingress of fluid into the tank. It is less susceptible to tampering or to malfunction and allows for the rapid filling of the tank as compared to the conventional Bo emo/4 4/Ap r i 1 8 5 sS/' ■ ■ ' ■ 212773 180 W o 190 method. Most importantly it provides greater safety in the use and operation of such LPG cylinders and tanks.

In describing the emodiment I have indicated the use of a cylindrical safety vessel within the tank. However the safety vessel may be of any shape as long as it contains a volume equal to that specified for the particular liquified gas being stored, in the case of LPG that it hold a volume equivalent to at least 20% of the volume of the main tank.

Also in the description of the emodiment I have indicated that the rapid release means and the restricted opening be incorporated in the one valve means whereas it will be clear to those skilled in the art that they could be separate. Furthermore I have described the means for allowing rapid exhaust of the fluid contained in the safety volume to the main volume of the tank as a resilient ball valve device, whereas it will again be clear to any one skilled in the art that other valve means could be used.

It will be clear from what has been described above that further variations and modifications may be made to the particular embodiment described without departing from the scope and spirit of the present invention.as defined in the appended, claims.

N.Z. PATENT OFFICE -7 NOV 1986 received Boemo/4 4/Apr i185

Claims (11)

21277 WHAT I CLAIM IS:

1. A tank or cylinder having interiorally thereof a compartment of. predetermined volume, separated from the main volume of the tank and having first communicating means between said compartment and the main volume of the tank for,allowing restricted flow of fluid: into the compartment from the said main volume, and second communicating means/between the compartment and, the main volume of the tank, adapted to allow rapid flow from the compartment into the main body of the tank when the pressure ' of the fluid in the compartment: is greater than that in the main volume of the tank.

2. The tank or cylinder defined in claim 1 wherein the : first communication means is a capillary opening.

3. The tank or cylinder defined in claim 1 wherein the, second communication means is a valve means.

4. . The tank or cylinder, defined in claim 3 wherein the valve means includes a resilient sphere which closes off the opening into the compartment.

5. The tank or cylinder as defined in any one of the preceding claims wherein the said first and second communicating means are located in the. one valve means. /"-■"N 212773

6. A tank or cylinder according to any one of the.preceding claims wherein the volume of the compartment is 20 percent of the total volume of the tank or cylinder.

7. A tank or cylinder according to any one of the preceding claims also including a float valve.

8. A tank or cylinder according to claim 3 or claim 4,wherein the valve means comprises an enlarged bore, having a seating arrangement within the bore, a substantially. ' spherical shaped means located within the bore, and a capillary opening c.ommunicating with said enlarged bore.

9. A tank or cylinder according to any one of claims 1 to 7 which is adapted to be used with liquid petroleum gas.

10. A tank or cylinder , according to any one of the preceding claims 1 to 7 or claim 9 substantially as hereinbefore described with reference to the accompanying drawings.

11. A tank or cylinder according to claim 8 substantially as hereinbefore described with reference to, the accompanying drawings. ' WEST-WALKER, McCABE P°r: ATTORNEYS FOR^THE APPLICANT -11- N.Z. PATENT OFFI6E -7 NOV 1986 RECEIVE ..