EP0015193A1 - Improved liquid tank - Google Patents

Abstract

This tank (1) contains a filtering element (20) forming a chamber inside the tank, from which chamber the said liquid is sampled by means of the extraction pipe (3). The wall of the said chamber consists at least in part of a material suitable for retaining the particles of solid materials suspended in the said liquid and thus forms a filtering surface. The chamber formed by the filtering element has a height such that at least a part of the filtering surface is located above the zone (25) in which the precipitated constituents are concentrated. <IMAGE>

Description

The present invention relates to an improved liquid reservoir intended in particular to equip liquid fuel supply systems for engines or burners.

Liquid supply systems for a wide variety of apparatuses using said liquid generally include a reservoir in which the liquid is stored before use.

This is the case for devices operating thanks to the combustion of said liquid, for example, the engines of motor vehicles, or heating installations. The feeding systems also include several filters intended to stop the particles of solid matter suspended in the liquid and troublesome during its use.

This is the case, in particular, for diesel engines where the particles of solid matter suspended in diesel fuel could clog the injectors.

An example of a supply system already known will be described immediately below, for clarity, with reference to Figure 1 of the accompanying drawings.

Figure 2, which will be described later, shows an embodiment of a tank according to the invention. FIG. 1 schematically represents the supply circuit of an automobile diesel engine operating on diesel fuel.

The supply circuit includes a tank 1, containing diesel 2. In the diesel 2, plunges a withdrawal line 3. The line is equipped at its end with a first filter 4 called "strainer". This strainer 4 is constituted by a metallic fabric, the mesh size of which can vary according to the installations, but which can be close to 500 microns.

The diesel fuel is withdrawn from the tank 1 by means of a feed pump 5. Prior to its entry through the line 7 into the pump 5, the diesel fuel passes through a second filter 6, called a "pre-filter". This prefilter can be constituted by a metal screen or by a felt fabric, for example. The size of the particles stopped by the prefilter varies depending on the installation, but it can range from 50 to 150 microns approximately.

At the outlet of the pump 5, the diesel fuel is led by the line 8 in a third filter 9, called "main filter". This main filter can be made of felt or special paper elements. The size of the particles stopped by the main filter varies depending on the installation, but it can range from 3 to 5 microns. Some types of main filter stop particles of one micron.

At the outlet of the main filter 9, part of the diesel is returned to the tank by lines 10 and 11.

The other part is sent to the injection pump 13 via line 12. Part of the diesel entering the pump 13 feeds the injectors 14, the other part being recycled to the tank by lines 15 and 11.

Liquid tanks are generally not equipped thermal insulation, and the liquid they contain therefore undergoes variations in the outside temperature. This is the case, in particular, for the tanks of motor vehicles, such as that described above, and for certain heating installation tanks.

The liquid is therefore likely to be brought to relatively low temperatures. It happens that certain constituents of the liquid solidify and collect in suspension in the bottom of the tank. This is the case for paraffinic hydrocarbons contained in diesel oils used for the operation of diesel engines. When the fuel is withdrawn from the tank, the solidified constituents may clog after a certain time the strainer and / or the prefilter and / or the main filter; the racking is interrupted and the appliance stops.

It is possible to lower the filterability limit temperature at which it is possible to filter the liquid (for short, below, TFL). Certain additives added to the liquid, for example to a fuel, in fact lower the TFL. But this reduction is not always sufficient.

The Applicant has developed an improved tank which makes it possible to further lower the temperature at which a liquid can be drawn off from a tank.

The object of the present invention is to avoid the drawbacks caused by clogging of the filters present in a liquid supply system from a reservoir, clogging occurring during the precipitation of certain constituents of said liquid, when the latter is brought to a sufficiently low temperature.

To this end, the invention relates to an improved liquid reservoir, capable of being at a temperature such that certain constituents of said liquid precipitate at said temperature, the precipitated constituents then concentrating in an area located in the lower part of the reservoir, said reservoir containing a filtering element forming a chamber inside the reservoir, chamber from which said liquid is withdrawn, by means of a pipe withdrawal, the wall of said chamber being constituted at least in part by a material capable of retaining the particles of solid matter suspended in said liquid and thus forming a filtering surface, said tank being characterized in that the chamber formed by filter element at a height such that at least part of the filter surface is located above the area in which the precipitated constituents are concentrated.

The reservoir according to the invention can be produced in many different ways. It suffices that the filter element which it contains conforms to the characteristic indicated above in the subject of the invention.

An exemplary embodiment of a tank according to the invention is shown without limitation in Figure 2 of the accompanying drawings. Like FIG. 1, this FIG. 2 represents the supply system of an automobile diesel engine operating on diesel. Elements identical to those shown in Figure 1 have been identified by the same numbers assigned to the index '.

In the tank 1 'according to the invention, the diesel withdrawal line 3' is devoid of a strainer. The tank is however equipped with a filter element 20. This filter element has the shape of a cylinder, but it could have another shape, the shape of a rectangular parallelepiped, a cone, a trunk of cone with the small base arranged at the bottom, for example.

The filter element forms a chamber inside the tank in which the end of the withdrawal line 3 'is situated. The opening of the pipeline back 11 'can also be located inside said chamber.

The wall of the element 20 is made of a material capable of stopping particles having a size equal to or greater than 5 microns, for example metallic fabric.

The bottom 21 and the roof 22 of the element 20 may be made of the same material as the vertical wall or of a waterproof material. The bottom 21 and the roof 22 can also be constituted by the bottom 23 and the roof 24 of the tank.

As shown in the figure, the element 20 is held by the pipe 3 ', but it can of course be made removable by any suitable support.

• 1. L'extrémité de la canalisation 3' doit être située de préférence aussi près que possible du fond du réservoir, ceci afin d'éviter des remplissages fréquents du réservoir ;
• 2. Lorsque le gazole se trouve ramené à une température suffisamment basse pour entraîner la précipitation de cristaux d'hydrocarbures paraffiniques, ceux-ci vont se concentrer dans la partie inférieure du réservoir, dans la zone désignée par la référence 25. Si l'on soutire alors du gazole, les hydrocarbures paraffiniques vont colmater la partie de l'élément 20 située dans la zone 25. Il est donc nécessaire que la hauteur de l'élément 20 soit telle qu'une partie de la paroi se trouve en dehors de la zone 25 pour permettre la poursuite du soutirage du gazole à travers l'élément 20 au-dessus de la zone 25 .

The height of the element 20 is determined by two factors

• 1. The end of the pipe 3 'should preferably be located as close as possible to the bottom of the tank, in order to avoid frequent filling of the tank;
• 2. When the diesel is brought to a temperature low enough to cause precipitation of paraffinic hydrocarbon crystals, these will concentrate in the lower part of the tank, in the area designated by the reference 25. If one then draws off the diesel fuel, the paraffinic hydrocarbons will clog the part of the element 20 located in the zone 25. It is therefore necessary for the height of the element 20 to be such that a part of the wall is outside the zone 25 to allow continued withdrawal of diesel fuel through element 20 above zone 25.

The section of the element 20 should preferably be such that the volume of the said element located in the zone 25 is low enough so that the paraffinic hydrocarbons precipitated inside the element 20 do not clog the prefilter and / or the main filter. In addition, this clogging is thwarted by the return of diesel preheated by the pipes 15 '. and 11 '. In fact, the diesel oil heats up when it passes near the engine, so that, after a certain time, the heated diesel oil dissolves the paraffin particles contained in the bottom of the tank.

The dimensions and the shape of the filter element contained in the tank according to the invention are to be adapted to the use considered, that is to say, in particular, the nature of the liquid to be filtered and the temperature of use considered. ; the temperature at which the first constituents of a liquid precipitate varies according to the liquid, the constituents being different.

It appears from FIG. 2 that, if maximum safety is to be obtained, the height of the filter element must be as close as possible to that of the tank, but this is absolutely not essential. The height of the filter element can be reduced according to the nature of the liquid contained in the tank and the quantity of the constituents likely to precipitate at the temperature of use.

The Applicant has found that, for a diesel or domestic fuel oil tank that can be used at temperatures below the limit filterability temperature, it is possible that the height of the filter element is at least equal to half of the height of the tank, so that, when the bottom of the filter element is close to the bottom of the tank, the top of the filter element is located above half the height of the tank.

If we compare Figures 1 and 2, we can notice that the filter surfaces of the strainer 4 and the element 20 are very different, that of element 20 being much larger. This much larger filtering surface of the element 20 makes it possible to reduce the size of the mesh of the wall of the element 20, without serious risk of seeing it rapidly clogged by the solid matter in suspension.

In the case of a diesel tank, the mesh of the wall of the element 20 can be between 500 and 50 microns, and can even be as small as 5 microns.

This reduction in mesh eliminates the prefilter 6 shown in Figure 1, which is therefore yet another advantage provided by the invention.

As already indicated above, the tanks according to the invention can in particular be used for the storage of diesel oils intended for the supply of internal combustion engines (as defined by the norma NF M15 - 007) or of fuels oils domestic appliances intended for the supply of domestic heating appliances (as defined by standard NF M 15 - 008).

The invention is illustrated by the following example, which has no limiting character.

EXAMPLE

This example relates to clogging tests of the fuel system of a diesel engine running on diesel.

• a) un essai témoin T, avec le système d'alimentation représenté sur la figure 1, mais sans le préfiltre 6 et la pompe 5
• b) un essai A, avec le système d'alimentation représenté sur la figure 2, mais sans la pompe 5'.

We realized:

• a) a control test T, with the supply system shown in FIG. 1, but without the prefilter 6 and the pump 5
• b) a test A, with the supply system shown in FIG. 2, but without the pump 5 '.

• - masse volumique à 15°C: 0,840 ;
• - point de trouble : + 1°C ;
• - nature de l'additif abaissant la TLF : copolymère éthy-. lène-acétate de vinyle ;
• - TLF selon norme NF M 07-042 : -6°C.

The strainer 4 and the element 20 were successively placed in a tank containing a diesel fuel doped with an additive lowering the TLF, this diesel fuel having the following characteristics:

• - density at 15 ° C: 0.840;
• - cloud point: + 1 ° C;
• - nature of the TLF-lowering additive: ethyl copolymer. lene-vinyl acetate;
• - TLF according to standard NF M 07-042: -6 ° C.

The strainer 4 has the shape of a cylinder whose bottom and top are closed and whose vertical wall is constituted by a metallic fabric having a mesh size of approximately 500 microns. The height of the strainer is 4 cm and its diameter is equal to 1 cm.

The strainer 4 was placed in the tank so that its bottom is 1 cm from the bottom of the tank.

The element 20 has the shape of a cylinder whose bottom and top are closed and whose vertical wall is constituted by a metallic fabric having a mesh size of approximately 45 microns. The height of the tank is 35 cm. The height of the filter element is 30 cm and its diameter is 45 mm.

The element 20 has been placed in the tank so that its bottom is 1 cm from the bottom of the tank.

Filters 9 and 9 'consist of a paper filter stopping particles of around 5 µ.

The tank containing the diesel successively equipped with the strainer 4 and the element 20 was brought to -10 ° C. and the injection pump 13 or 13 ′ was put into operation.

• 1) pour l'essai témoin T, le colmatage du système d'alimentation était obtenu au bout de 10 mn (le colmatage est constaté quand la pompe d'injection s'arrête) ;
• 2) pour l'essai A, au bout de 1 h, le système d'alimentation n'était pas encore colmaté.

It has been found that:

• 1) for the control test T, the clogging of the supply system mentation was obtained after 10 min (clogging is noted when the injection pump stops);
• 2) for test A, after 1 hour, the supply system was not yet blocked.

This example clearly illustrates the advantages of the reservoir according to the invention.

Claims (3)

1. - Improved liquid reservoir, capable of being at a temperature such that certain constituents of said liquid precipitate at said temperature, the aforementioned constituents then concentrating in an area located in the lower part of the reservoir, said reservoir containing a filter element forming a chamber inside the tank, chamber from which said liquid is withdrawn by means of the draw-off pipe, the wall of said chamber being constituted at least in part by a material capable of retaining the particles of solid matter suspended in said liquid and forming thus a filtering surface, said tank being characterized in that the chamber formed by the filtering element has a height such that at least a part of the filtering surface is situated above the zone in which the precipitated constituents are concentrated. 2.- tank according to claim 1, characterized in that the tank is a diesel or domestic fuel oil tank that can be used at a temperature below the limit filterability temperature, in that the height of the filter element is at least equal to half the height of the tank and in that the bottom of the filter element is close to the bottom of the tank. 3.- tank according to claim 2, characterized in that the mesh of the filter element is between 5 and 500 microns.

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