CH692084A5 - Device for degreasing and drying mechanical components using ultrasound and non-halogen hydrocarbon solvent comprises airtight enclosure under controlled pressure and temperature - Google Patents

Abstract

A device for degreasing and drying mechanical components comprises an airtight enclosure containing a solvent, of non-halogen hydrocarbon-type with a flash point of 40-100 deg C, in which the components are immersed and a source of ultrasonic emissions greater than 15 kHz. The enclosure is maintained at at least 120 mbar and 60 deg C. Preferred Features: The device is such that the solvent can be changed and allows the components to be treated successively with several solvents with different chemical compositions adapted to the stains encountered on the components

Description

       

  



  Flammable solvents replacing chlorinated solvents are used in the engineering industry at a temperature not exceeding 15 DEG C below the flash point.



  The solvency qualities of the degreasing system presented above are significantly improved compared to the systems currently in operation.



  This improvement is due on the one hand to the high temperature which increases the solvency of oils and greases, on the other hand to the effect of the vacuum which allows better penetration of the solvent into the blind holes. In addition, the solvent is permanently under vacuum. It is therefore degassed, which significantly improves the efficiency of ultrasound. Current systems pump the flammable solvent into the working chamber at atmospheric pressure, which causes air to enter the solution. The ultrasound then has the effect of degassing the solution and not of cavitating on the parts. The degassing times are of the order of fifteen minutes while the washing times are generally less than five minutes.

   Measuring the power of ultrasound in a degassed solution at a temperature above 60 DEG C demonstrates the increase in ultrasonic power, compared to a non-degassed solution at less than 40 DEG C.



  The steam injection and drying phases which complete the degreasing-drying cycle of the system described above are identical to the systems currently in operation.



  Legislation (OPAIR) imposes industrial washing-drying machines recycling volatile organic compound (VOC) emissions in order to minimize these emissions.



  The present invention makes it possible to improve the efficiency of degreasing and drying by using solvents of non-halogenated hydrocarbon type whose flash point is located between 40 DEG C and 100 DEG C. For a few years, closed degreasing machines have been used using solvents of this type at 15 DEG C at least below the flash point.



  The present invention uses this type of solvent under vacuum, above the flash point. This process improves the quality of cleaning, due to better solvency of oils and greases and facilitates the drying of parts. The distillation of the solvent according to the usual techniques makes it possible to minimize the losses of solvent.



  The successive use of different solvents makes it possible to optimize the cleaning cycle by using non-polar or polar solvents.



  The invention also guarantees the safety of the installation, since the vacuum of less than 120 mbar practically prevents the formation of an explosive gas mixture. Furthermore, even in the event of the formation of an explosive mixture and of an explosion, the volume expansion of seven times the initial volume which results from the explosion makes it possible to remain at a pressure below 840 mbar, therefore below atmospheric pressure. This therefore eliminates any risk of damage to the installation and of risk for the operator.


    

Claims (2)

  1. Degreasing and drying device for mechanical parts, comprising a sealed enclosure, enclosure containing a solvent in which said parts are immersed, and ultrasonic emission means greater than 15 kHz, characterized in that said solvent is of the isoparaffin type or alkane, the flash point of which is located between 40 DEG C and 100 DEG C and in that said device comprises means for maintaining the pressure in the enclosure at less than 120 mbar and the temperature at more than 60 DEG C at l inside the enclosure. 2. Device according to claim 1, comprising means for changing the solvent and successively treating said parts with several solvents of isoparaffin or alkane type, of different chemical composition, suitable for the dirt encountered.