METHOD FOR MANUFACTURING A FIRE-RESISTANT PART OF AN AIR CONDITIONING SYSTEM AND PART PRODUCED BY SUCH A METHOD

Abstract

Method for manufacturing a fire-resistant part of an air conditioning system for an air or rail transport vehicle, characterized in that it includes at least the following steps: a step of obtaining a part including at least one aluminum alloy surface portion, and a step of treating the aluminum alloy surface portion by use of micro-arc oxidation in order to produce a ceramic coating on the surface portion.

Claims

1. Method for manufacturing a fire-resistant part of an air conditioning system for an air or rail transport vehicle, the method comprising at least the following steps: a step of obtaining a part comprising at least one aluminum alloy surface portion, a step of treating said aluminum alloy surface portion with micro-arc oxidation in order to obtain a ceramic coating on said surface portion, a step of sandblasting the surface portion treated with said micro-arc oxidation treatment step.

2. The method for manufacturing a part according to claim 1, wherein said step of treating said aluminum alloy surface portion comprises at least the following steps: a step of immersing said aluminum alloy surface portion in an electrolytic bath comprising an aqueous solution of sodium silicate, a step of applying a pulsed bipolar current at a current density passing through said aluminum alloy surface portion of between 20 A/dm.sup.2 and 60 A/dm.sup.2 for a period of more than 20 minutes.

3. The method for manufacturing a part according to claim 2, wherein said step of applying a pulsed bipolar current is carried out at a current density of the order of 40 A/dm.sup.2.

4. The method for manufacturing a part according to claim 1, further comprising a step of thermal spraying on the surface portion treated with said micro-arc oxidation treatment step.

5. The method for manufacturing a part according to claim 4, wherein the thermal spraying is chosen from amongst atmospheric plasma spraying, suspension plasma spraying and solution precursor plasma spraying.

6. The method for manufacturing a part according to claim 1, further comprising a step of applying a sol-gel coating onto the surface portion treated with said micro-arc oxidation treatment step.

7. Part of an air conditioning system for an air or rail transport vehicle comprising at least one aluminum alloy surface portion, wherein said part is obtained by a manufacturing method according to claim 1 to make the part resistant to fire.

8. The part according to claim 7, wherein said part is a valve comprising an aluminum alloy butterfly valve forming said surface portion treated with micro-arc oxidation.

9. Air conditioning system for an air or rail transport vehicle, comprising at least one part according to claim 7.

10. Air or rail transport vehicle comprising at least one propulsion engine, a cabin and at least one air conditioning system for said cabin, wherein the air conditioning system for the cabin is the air conditioning system according to claim 9.

11. The method of claim 2, wherein the step of applying a pulsed bipolar current is performed for a period of between 30 and 90 minutes.

12. The method for manufacturing a part according to claim 2, further comprising a step of thermal spraying on the surface portion treated with said micro-arc oxidation treatment step.

13. The method for manufacturing a part according to claim 3, further comprising a step of thermal spraying on the surface portion treated with said micro-arc oxidation treatment step.

14. The method for manufacturing a part according to claim 2, further comprising a step of applying a sol-gel coating onto the surface portion treated with said micro-arc oxidation treatment step.

15. The method for manufacturing a part according to claim 3, further comprising a step of applying a sol-gel coating onto the surface portion treated with said micro-arc oxidation treatment step.

16. The method for manufacturing a part according to claim 4, further comprising a step of applying a sol-gel coating onto the surface portion treated with said micro-arc oxidation treatment step.

17. The method for manufacturing a part according to claim 5, further comprising a step of applying a sol-gel coating onto the surface portion treated with said micro-arc oxidation treatment step.

18. Part of an air conditioning system for an air or rail transport vehicle comprising at least one aluminum alloy surface portion, wherein said part is obtained by a manufacturing method according to claim 2 to make the part resistant to fire.

19. Part of an air conditioning system for an air or rail transport vehicle comprising at least one aluminum alloy surface portion, wherein said part is obtained by a manufacturing method according to claim 3 to make the part resistant to fire.

20. Part of an air conditioning system for an air or rail transport vehicle comprising at least one aluminum alloy surface portion, wherein said part is obtained by a manufacturing method according to claim 4 to make the part resistant to fire.

Description

LIST OF FIGURES

[0074] Further aims, features and advantages of the invention can be found in the following description, which is provided solely as a non-limiting example, and which refers to the accompanying figures, in which:

[0075] FIG. 1 is a schematic view of a manufacturing method for a fire-resistant valve according to an embodiment of the invention;

[0076] FIG. 2 shows a graph of the evolution of the temperature of the rear face of a butterfly valve which has undergone the manufacturing method by micro-arc oxidation as a function of the exposure time to a flame of 1,100° C.; and

[0077] FIG. 3 is a schematic perspective view of an aircraft, in accordance with an embodiment according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

[0078] The method described below enables the manufacture of a fire-resistant air flow control valve (butterfly style) for an air conditioning system. Thus, the aluminum alloy surface portion corresponds to the obturator element of the butterfly valve, that is to say, the butterfly itself.

[0079] Of course, the method according to the invention can also be applied to any other type of valve, in particular ball valves, flap valves, as well as to any type of parts with a surface portion made of aluminum alloy such as an actuator body or a regulator body.

[0080] The manufacturing method as shown in FIG. 1 comprises the following steps: [0081] a step 10, obtaining a butterfly valve comprising a butterfly made of aluminum alloy, [0082] a step 11, degreasing the aluminum alloy butterfly, [0083] a step 20, treating the butterfly valve with a micro-arc oxidation treatment comprising a step 21 of immersing the butterfly valve and a step 22 of applying a pulsed bipolar electric current to obtain the formation of the ceramic coating on said butterfly, [0084] a step 23, rinsing and drying the butterfly valve, and [0085] a step 30, sandblasting the butterfly valve.

[0086] According to this embodiment, step 10 of obtaining the butterfly valve to be treated consists in having a butterfly valve, the butterfly of which is made of aluminum alloy and forms the surface portion to be treated. In this case, the butterfly is isolated from the valve body in order to be treated on its own, and it is then reassembled onto the valve body after treatment.

[0087] Step 11 of degreasing the butterfly of the butterfly valve consists in removing the impurities that may be deposited over the aluminum alloy butterfly. Degreasing is carried out manually using acetone applied directly to the butterfly.

[0088] Step 20 of treating the butterfly by micro-arc oxidation comprises a step 21 of immersion in an electrolytic bath and a step 22 of applying a pulsed bipolar current to form the ceramic coating on the butterfly of the valve.

[0089] Immersion step 21 consists in putting the butterfly valve, only the aluminum alloy butterfly of which is in direct contact with an electrolyte, into an aqueous solution comprising sodium silicates (Na.sub.2SiO.sub.3) and potassium hydroxide (KOH).

[0090] Step 22 consists in applying a pulsed bipolar current to the electrodes using a specific generator applying a current density of the order of 40 A/dm.sup.2 for a period of between 30 and 90 minutes. At the end of step 22, a ceramic coating is formed on the butterfly.

[0091] The rinsing and drying step 23 is carried out using distilled water, making it possible to rinse the treated portion and to eliminate the electrolyte in which the butterfly valve was immersed. The butterfly valve is then dried with compressed air.

[0092] The butterfly undergoes step 30 of surface sandblasting of the coating in order to remove any surface defects in the coating caused by the micro-arcs. This step allows for a coating to be obtained on the butterfly that is smooth and free of imperfections, optimizing the flow passage.

[0093] According to this embodiment, the ceramic coating has a thickness of between 80 and 150 micrometers.

[0094] Tests were carried out on coated butterflies to demonstrate the effectiveness of such a treatment with micro-arc oxidation, in regard to fire resistance.

[0095] FIG. 2 shows a graph illustrating the change in the temperature of the rear face of a butterfly, in line with the time, when the front face of said butterfly is subjected to a flame of 1,100° C. for 15 minutes, according to the IS02685 standard.

[0096] Two aluminum alloy butterflies were treated using the method according to FIG. 1. The first butterfly has a 100 μm thick coating; it corresponds to the high curve “MAO 100 μm” on the graph. The second butterfly has a 120 μm thick coating; it corresponds to the low curve “MAO 120 μm” on the graph.

[0097] Each butterfly is subjected to the flame of an ISO 2685 kerosene burner for 15 minutes. The face exposed to the flame is referred to as the front face, and the unexposed face is referred to as the rear face. The burner is positioned at a distance of 10 cm from the butterfly and the burner flame is in direct contact with the surface of the front face of the butterfly. A surface thermocouple (type K, class 1) is positioned on the rear face in order to measure the temperature of the rear face throughout the flame test. The flame temperature was calibrated before the test and was recorded at 1,100° C.+/−100° C.

[0098] The graph shows the change in the temperature of the rear face during the flame test. It is noted that the coating allows the temperature perceived by the aluminum alloy to be reduced by about 500° C. for the thickest coating. When the flame is applied to the front face of the “MAO 120 μm” and “MAO 100 μm” butterflies, the rear face of each butterfly heats up to a value of approximately 600° C. and 700° C., respectively. The temperature measured on the rear face remains generally constant when a flame at 1,100° C. is maintained at the front face of each butterfly for 15 minutes.

[0099] This graph shows the fire- and flame-resistance of an aluminum alloy butterfly that has been treated according to the method shown in FIG. 1 with micro-arc oxidation.

[0100] The ceramic coating produced by the micro-arc oxidation method shown in FIG. 1 makes it possible to obtain butterfly valves coated with a fire-resistant aluminum alloy.

[0101] FIG. 3 illustrates an air transport vehicle 8 that comprises a propulsion engine 7, a cabin and at least one air conditioning system 9 for said cabin that comprises a butterfly valve obtained according to the method shown in FIG. 1. Thus, the butterfly valve can be fitted in ducts of the air conditioning system on-board an aircraft, in order to regulate the air flows, while being fire-resistant. If a fire breaks out in the engine environment, the control butterfly valve fitted in the ducts of the air conditioning system for an aircraft makes it possible to isolate the fire and prevent it from spreading through the air circulation ducts.