Process for pickling of articles of metal material, in particular barrels for foodstuffs

Description

[0001] The present invention relates to a process for pickling of articles of metal material, in particular barrels for foodstuffs and/or beverages, and the use of an acidic solution having a gel consistency for performing the process of claim 1.

[0002] The present invention deals with the industrial sector concerning chemical surface treatments, namely pickling, intended for removal of surface oxides from articles of metal material, such as cylindrical barrels for conservation of liquid foodstuffs such as beer or milk, and/or any other metal article requiring such a treatment.

[0003] It is known that after carrying out founding or welding operations or other treatments on metal materials the surface of same is covered with oxides, salts, different organic or mineral substances causing formation of scale during straightening out, drawing and similar operations, which will result in a dull finish, instead of a shiny one.

[0004] Cleaning my means of pickling can be carried out by chemical means and/or electrolytically.

[0005] With reference to the chemical surface treatments, processes are widespread that involve application of acidic solutions to the metal articles for the purpose of submitting them to a controlled surface deoxidation that is stopped by suitable washing operations carried out at the process end. In particular, it is a usual practice to arrange one or more holding vats capable of housing an important number of metal articles to be treated. These vats are usually provided with suitable delivery means ready to direct the appropriate acidic solution onto the metal articles housed therein. The acidic solution delivered goes on impinging on the metal articles under treatment causing surface deoxidation of same and removal of the previously formed oxidation. The acidic solution is accumulated and stored in the vats together with the removed oxide and is recovered and used again through suitable recycling systems.

[0006] Once application of the acidic solution has been completed, the treated metal articles are submitted to a high-pressure washing operation and/or operations for neutralising the acidic solution used.

[0007] This method has some drawbacks concerning both the quality of the obtained surface finish and the high bulkiness and costs of the installations for pickling.

[0008] In particular, the continuous recycling of the acidic solution causes a progressive decay of same since after each cycle it stores increasingly bigger amounts of removed oxide until reaching 60 ppm of iron. Pollution of the acidic solution inevitably impairs efficiency of same, which will result in an unsatisfactory surface finish. In addition, the surface finish of the treated articles has a tendency to become worse as the acidic solution is re-used. Therefore, in order to ensure a satisfactory finish, it is necessary to continuously replace the acidic solution used with a new acidic solution, which will have repercussions on the overall costs for putting the process into practice.

[0009] It is also to be pointed out that residence of the metal articles within the vats is particularly long and greatly affects the overall periods of time of the complete process. In order to reduce these periods and optimise the process, the solution is heated and the vats are such sized that they simultaneously house a plurality of metal articles to be treated. Obviously, if the metal articles have big sizes, as in the case of barrels for beverages, the vats designed to hold them must have an important bulkiness which will give rise to further problems connected with the sizes of the rooms where the installations are to be set.

[0010] It is also known from document GB2110196 a cleaning machine for hollow containers having a top opening, such as beer kegs, has a container-supporting rotor with a horizontal axis disposed so that the rotor dips into a pool of cleaning liquid. The kegs are loaded onto and unloaded from the rotor in a direction radially of the rotor with their top openings directed towards the centre of the rotor. The kegs are supported on the rotor in pronged self-centering carriers. A rinse facility is provided when the kegs are inverted. The rotor is arranged to move in small steps with periodic static intervals during which loading, filling, cleaning, draining, rinsing and unloading operations are carried out.
Furthermore, document GB2148862 discloses an apparatus for cleaning the interior surfaces of beer kegs. Cleaning liquid is forced into the keg through one path in the spier with another path either open to atmosphere with the keg upright or open to ambient with the keg inverted, in which case ambient may be cleaning liquid in a tank. The apparatus delivers kegs to an arrester where the keg is filled with cleaning fluid, moved sideways to a platform above an annular tank containing ultrasonic generators and filled with cleaning liquid, lowered into the tank, indexed round the tank using crank and index wheel, removed from the tank and emptied.

[0011] Alternatively, pickling processes are known in which the acidic solution has a gel consistency enabling application of same directly onto the surfaces of the metal articles to be treated without requiring the presence of possible holding vats. In particular, use of an acidic gel of known type enables direct application of same by means of a spreading and/or spraying action that is usually carried out through suitable automatic application means and/or manually by one or more operators.

[0012] The metal articles strewn with the acidic gel are temporarily placed in a waiting region to enable the acidic gel to act on the surfaces thereof. Subsequently, the metal articles are submitted to one or more high-pressure washing operations and further treatments for neutralisation of the acidic substances.

[0013] While use of the acidic gels of the above described type ensures removal of oxide from the treated metal articles and avoids the drawbacks connected with traditional processes, the Applicant has found that application of the above mentioned gel is not devoid of some drawbacks, mainly in relation to the quality of the obtained surface finish, the modalities and times for application of said gel onto the metal articles and the overall costs for the pickling process.

[0014] In particular, the main drawback is given by the difficulty in controlling the waiting time after application of the acidic gels, which time varies depending on the distribution of the acidic substance on the surfaces of each article under treatment.

[0015] It is also to be pointed out that for manual application of said acidic gel an important operating time is in any case required and it affects the overall costs of the pickling process.

[0016] Accordingly, it is an aim of the present invention to solve the problems encountered in the known art by proposing a process, ensuring an optimal surface finish of the metal articles under treatment.

[0017] It is a further aim of the present invention to improve the pickling process while at the same time reducing the overall costs of same.

[0018] The foregoing and further aims that will become more apparent in the course of the following description are substantially achieved by a process, for pickling of articles of metal material, in particular barrels for foodstuffs in accordance with the features herein described and claimed.

[0019] Further features and advantages will be best understood from the detailed description of a preferred but not exclusive embodiment of a process, for picking of articles of metal material, in particular barrels for foodstuffs, in accordance with the present invention. This description will be set out hereinafter with reference to the accompanying drawings, given by way of non-limiting example, in which:

• Fig. 1 is a diagrammatic representation of a step of a pickling process for articles of metal material in accordance with the present invention;
• Fig. 2 is a diagrammatic representation of a step of the pickling process which is subsequent to the step shown in Fig. 1;
• Fig. 3 is a diagrammatic representation of a step of the pickling process which is subsequent to the step shown in Fig. 2; and
• Fig. 4 is a diagrammatic representation of a step of the pickling process which is subsequent to the step shown in Fig. 3.

[0020] In accordance with the present invention it is disclosed a pickling process for articles 1 of metal material, in particular barrels 1a of substantially cylindrical shape for conservation of liquid foodstuffs and/or beverages. Preferably, this process deals with pickling of metal barrels 1a used for conservation of beer and usually made up of three parts welded together by respective weld beads 1b. In detail, barrels 1a are made up of a bottom 1c, a cylindrical central portion 1d and an upper cap 1e provided with a suitable aperture 1f for introduction and extraction of the product to be contained.

[0021] The metal articles 1 to be treated are first submitted to a step of applying an acidic solution 2 (Figures 1 - 4) which advantageously has a jelly consistency the kinematic viscosity of which measured at a temperature of 20°C following the ASTM D 446 method, is preferably included between 5.5 mm²/s and 7.5 mm²/s. This acidic jelly solution or acidic gel, for example, further has a surface tension measured at 25°C following the Du Nouy ring method, included between 75mN/m and 85mN/m, preferably equal to 81.2mN/m, and a density included between 1100kg/m³ and 1400kg/m³, preferably equal to 1280kg/m³.

[0022] In more detail, the acidic gel solution 2 comprises a solvent and a solute, including at least one inorganic acid such as sulphuric, nitric, phosphoric, hydrofluoric acids, and so on.

[0023] The step of applying the acidic gel solution 2 comprises a step of at least partly dipping at least one of the articles 1 to be treated. Preferably, the dipping step involves full immersion of each article 1 into the acidic gel solution 2.

[0024] As shown in Figs. 1 and 2, each barrel 1 is dipped in such a manner that its aperture 1f faces upwardly, said aperture being brought under the surface 2a of the acidic gel solution 2 so that the solution also enters barrel 1 and flows therein.

[0025] Application of the acidic gel solution 2 further comprises, subsequently to the dipping step, a step of drawing the immersed article 1 out (Fig. 3). The drawing step is carried out immediately after the dipping step so that the time required for application of the acidic gel solution 2 substantially corresponds to the time required for fully dipping article 1 and subsequently drawing it out, typically few ten seconds, preferably thirty seconds. In other words, for application of the acidic gel solution 2 article 1 is not required to stand in said solution because due to its intrinsic properties, the solution remains on all surfaces of the drawn out article 1, forming a thin covering gel layer (Figs. 3 and 4).

[0026] Advantageously, the density, viscosity and surface tension features of the acidic gel substance 2 must be of such a nature that, after article 1 has been drawn out, the acidic gel solution 2 remains on the article itself in an amount for square metre of covered surface included between 200g/m² and 300g/m².

[0027] In more detail, if a flat plate is dipped into and drawn out of the solution 2 being maintained in a vertical position, the amount of acidic gel solution 2 remaining on the flat plate 1 per square metre of covered surface is included between 225g/m² and 275g/m², being preferably equal to 250g/m², with a thickness of about 0.2mm.

[0028] Obviously, said application of acidic gel substance 2 can be carried out at the same time on two or more articles 1 that are dipped into and immediately drawn out simultaneously from the acidic gel solution 2.

[0029] Once the acidic gel solution 2 has been applied, each article 1 is laid in a waiting region (Fig. 4) where the treated articles stand for predetermined waiting times, to enable the acidic gel solution 2 to act and deoxidise the surfaces of same.

[0030] In accordance with the drawings, barrels 1 are first overturned (Fig. 3), to draw out the solution contained therein, and subsequently laid in the waiting region. The required waiting time is few minutes or few ten minutes, typically included between 10 and 30 minutes.

[0031] Then, articles 1 are submitted to a low- and/or high-pressure washing step with at least one aqueous solution or detergent and possibly also with neutralising agents for the acidic substances used. The washing step is adapted to take away the covering gel layer 3 together with the oxide and impurities removed by the acidic gel substance 2.

[0032] Possibly, in accordance with a process known by itself, the articles can be submitted to a further cleaning step involving introduction of same into a water-containing vat and bombarding with ultrasonic waves.

[0033] The above-mentioned process is carried out by means of an installation (diagrammatically shown only partly in Figs. 1 to 4) providing at least one application station 4 set for application of the above mentioned acidic gel solution onto the metal articles 1. As diagrammatically shown in Figs. 1 to 4, the application station 4 is provided with at least one vat 4a designed to receive at least one of the metal articles 1 to be treated. The vat 4a is at least partly, preferably almost completely, filled with the above mentioned acidic gel solution 2.

[0034] The application station 4 comprises suitable dipping/drawing means, such as mechanical arms not shown, capable of introducing at least one metal article 1 into the vat 4a and immediately drawing it out as soon as the whole inner and outer surfaces of said article have been wetted with the acidic gel substance 2. The mechanical arms are also able to overturn the containers to enable emptying of same.

[0035] The application station 4 is further preferably provided with detecting and feeding means (not shown) set to monitor the level of the acidic gel solution 2 that gradually decreases as the metal articles 1 are dipped and drawn out. The detecting and feeding means is further set to introduce further amounts of acidic gel solution 2 into the vat 4a in order to restore the correct level of same.

[0036] The installation further contemplates the presence of at least one waiting station 5 or similar stand-by warehouse, at which the treated metal articles 1, i.e. the metal articles covered with the acidic gel solution 2, are laid after they have been drawn out of vat 4a.

[0037] Preferably, this waiting station is defined by a conveyor belt or other suitable means, through which articles 2 are brought to one or more low- and/or high-pressure washing stations (not shown). The acid action advantageously takes place during transportation and therefore the advancing speed of the belt establishes the above mentioned waiting time of the barrels 1 covered with gel.

[0038] In the washing stations the metal articles 1 are set free from the covering gel layer 3 and the oxides removed by the acidic substances.

[0039] The present invention solves the problems encountered in the known art and achieves the intended purposes.

[0040] First of all, the process, enable achievement of a homogeneous surface finish of high quality. In detail, the particular intrinsic properties (viscosity, density and surface tension) of the acidic gel solution being the object of the present invention ensure an optimal deoxidising treatment of the surfaces of the treated article.

[0041] In addition, the consistency of the acidic gel solution is able to ensure adhesion of same to the treated articles. This ability allows arrangement of a system involving application of the solution by dipping and immediate drawing out, thereby greatly reducing the times for carrying out the application step, which times greatly affect the overall costs of the process.

[0042] In addition, since the amount of the acidic gel solution acting on the impurities is drawn out of the vat together with the articles under treatment, the bath remaining in the vat is not polluted and contains less than 10 ppm of iron.

[0043] It will be also recognised that the rapidity of the application step further allows vats of reduced bulkiness to be used. In fact, even in the presence of bulky metal articles such as barrels for beverages, it is possible to carry out application of the acidic gel solution consecutively and quickly on small amounts of articles treated simultaneously. The rapidity of the dipping steps and the immediately subsequent drawing steps therefore enables application of the acidic gel solution to high amounts of metal articles in the time unit, which will bring about important practical and economic benefits.

[0044] Finally, since the reaction of the acids with oxides mainly takes place out of the vat, the device being the object of the invention does not require thermoregulating devices adapted to heat the solution and is therefore of simpler structure.

Claims

1. A process for pickling articles (1) of metal material comprising the steps of:

- applying an acidic solution (2) onto an article (1) of metal material;

- washing said article (1) with at least one aqueous solution,

wherein the step of applying said acidic solution (2) onto said article (1) comprises the steps of:

- dipping said article (1) at least partly into said acidic solution (2);

- subsequently drawing said article (1) out of said acidic solution (2);

characterised in that said acidic solution (2) has a gel consistency, in that said drawing operation is carried out immediately after the dipping step, so that the time required for application of the acidic gel solution (2) substantially corresponds to the time required for fully dipping article (1) and subsequently drawing it out, typically few ten seconds, and in that the process further comprises a waiting step, subsequent to the drawing step and preceding the washing step, to enable treatment of the surface of said article (1) by said acidic gel solution (2).

2. A process as claimed in claim 1, characterised in that dipping of said article (1) takes place in an acidic gel solution (2) the viscosity of which is included between 5.5 mm²/s and 7.5mm²/s.

3. A process as claimed in claim 1 or 2, characterised in that dipping of said article (1) is carried out in an acidic gel solution (2) the surface tension of which is included between 75mN/m and 85mN/m.

4. A process as claimed in claim 1 or 2, characterised in that dipping of said article (1) is carried out in an acidic gel solution (2) the surface tension of which is of 81.2mN/m.

5. A process as claimed in claim 1 or 2, characterised in that dipping of said article (1), is carried out in an acidic gel solution (2) the density of which is included between 1100kg/m³ and 1400kg/m³.

6. A process as claimed in claim 1 or 2, characterised in that dipping of said article (1) is carried out in an acidic gel solution (2) the density of which is equal to 1280kg/m³.

7. A process as claimed in claim 1, characterised in that the waiting step has a waiting time included between 10 minutes and 30 minutes.

8. A process as claimed in claim 1, characterised in that the article (1) of metal material is a barrel (1a) for foodstuff.

9. Use of an acidic solution (2) having a gel consistency for performing the process of claim 1.

Ansprüche

1. Verfahren zum Beizen von metallischen Artikeln (1), umfassend die Schritte:

- Anwenden einer sauren Lösung (2) an einem metallischen Artikel;

- Waschen des Artikels (1) mit mindestens einer wässrigen Lösung,

bei dem der Schritt des Anwendens einer sauren Lösung (2) am metallischen Artikel (1) die Schritte umfasst:

- Eintauchen, mindestens teilweise, des metallischen Artikels (1) in die saure Lösung(2);

- darauf folgend Ausziehen des Artikels (1) aus der sauren Lösung (2),

dadurch gekennzeichnet, dass die saure Lösung (2) eine gallertartige Beschaffenheit hat, dass der Vorgang des Ausziehens unverzüglich nach dem Schritt des Eintauchens derart erfolgt, dass die für das Anwenden der sauren, gallertartigen Lösung (2) geforderte Zeit im wesentlichen der Zeit entspricht, der erforderlich ist, um den Artikel (2) vollständig einzutauchen und nachfolgend auszuziehen, auf typischer Weise um einige Zehntel von Sekunden, und dadurch, dass das Verfahren überdies einen Warteschritt umfasst, der dem Schritt des Ausziehens folgt und vor dem Schritt des Waschens liegt, um die Behandlung der Oberfläche des Artikels (1) durch die saure, gallertartige Lösung (2) zu erlauben.

2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass das Eintauchen des Artikels (1) in eine saure, gallertartige Lösung (2) durchgeführt wird, deren Viskosität zwischen 5,5 mm²/s und 7,5 mm²/s liegt.

3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Eintauchen des Artikels (1) in eine saure, gallertartige Lösung (2) durchgeführt wird, deren Oberflächenspannung zwischen 75 mN/m und 85 mN/m.

4. Verfahren nach Anspruch 1 oder 3, dadurch gekennzeichnet, dass das Eintauchen des Artikels (1) in eine saure, gallertartige Lösung (2) durchgeführt wird, deren Oberflächenspannung gleich 81,2mN/m ist.

5. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Eintauchen des Artikels (1) in eine saure, gallertartige Lösung durchgeführt wird, deren Viskosität zwischen 1100 Kg/m³ und 1400 Kg/m³ liegt.

6. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Eintauchen des Artikels (1) in eine saure, gallertartige Lösung (2) durchgeführt wird, deren Viskosität gleich 1280 Kg/m³ ist.

7. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass der Warteschritt eine Wartezeit zwischen 10 Minuten und 30 Minuten aufweist.

8. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass der Metallartikel (1) ein Fass (1a) für Lebensmittel ist.

9. Verwendung einer sauren Lösung (2) mit einer gallertartigen Beschaffenheit zur Ausführung des Verfahrens des Anspruchs 1.

Revendications

1. Procédé pour le décapage d'articles (1) en métal comprenant les étapes de:

- appliquer une solution (2) acide sur un article (1) en métal;

- laver ledit article (1) avec au moins une solution aqueuse,

où l'étape d'appliquer ladite solution acide (2) sur ledit article (1) comprend les étapes de:

- plonger ledit article (1) au moins partiellement dans ladite solution acide (2);

- ensuite extraire ledit article (1) de ladite solution acide (2);

caractérisé en ce que ladite solution acide (2) a la consistance d'un gel, en ce que ladite opération d'extraction est effectuée immédiatement après l'étape de plongement, de telle sorte que le temps demandé pour l'application de la solution acide en gel (2) correspond essentiellement au temps demandé pour le plongement complet de l'article (1) et son extraction subséquente, typiquement quelques dizaines de secondes, et en ce que le procédé comprend en outre une étape d'attente, qui suit l'étape d'extraction et précède l'étape de lavage, pour permettre le traitement de la surface dudit article (1) par ladite solution acide en gel (2).

2. Procédé selon la revendication 1, caractérisé en ce que le plongement dudit article (1) a lieu dans une solution acide en gel (2) dont la viscosité est comprise entre 5,5 mm²/s et 7,5 mm²/s.

3. Procédé selon la revendication 1 ou 2, caractérisé en ce que le plongement dudit article (1) est effectué dans une solution acide en gel (2) dont la tension de surface est comprise entre 75 mN/m et 85 mN/m.

4. Procédé selon la revendication 1 ou 2, caractérisée en ce que le plongement dudit article (1) est effectué dans une solution acide en gel (2) dont la tension de surface est de 81,2 mN/m.

5. Procédé selon la revendication 1 ou 2, caractérisé en ce que le plongement dudit article (1) est effectué dans une solution acide en gel (2) dont la densité est comprise entre 1100 kg/m³ et 1400 kg/m³.

6. Procédé selon la revendication 1 ou 2, caractérisé en ce que le plongement dudit article (1) est effectué dans une solution acide en gel (2) dont la densité est égale à 1280 kg/m³.

7. Procédé selon la revendication 1, caractérisé en ce que l'étape d'attente a un temps d'attente compris entre 10 minutes et 30 minutes.

8. Procédé selon la revendication 1, caractérisé en ce que l'article (1) en métal est un baril (1a) pour des produits alimentaires.

9. Usage d'une solution acide (2) ayant la consistance d'un gel pour réaliser le procédé de la revendication 1.

Drawing