How to Safely Use Flammable Solutions in an Ultrasonic Cleaner

June 19th, 2012

An Elma X-tra LSM Ultrasonic Cleaner for Flammable Solutions

An Elma X-tra LSM Ultrasonic Cleaner for Flammable Solutions

Using flammable solutions in an ultrasonic cleaner may be necessary if conventional biodegradable cleaning solution formulations are not up to the task.  But as the name indicates, flammable cleaning solutions give off vapors that are both unhealthy for personnel and may be explosive.   Vapor generation is greatly increased due to cavitation action in the ultrasonic cleaner tank.

Dealing with Flammable Solutions in an Ultrasonic Cleaner

There are two generally accepted procedures for using flammable solvents in an ultrasonic cleaning operation.   The simplest and least costly approach can be used to clean small parts in conventional benchtop ultrasonic cleaners available from Tovatech.  This approach, however, does not preclude careful handling of the solvents and using them in well-ventilated areas.

As a preparatory step fill the ultrasonic cleaner tank with water containing a surfactant to improve cavitation efficiency.  Activate the ultrasonic cleaner’s degas function to remove entrained air in the solution, otherwise operate it until air bubbles not longer rise to the surface.

Place parts to be cleaned in beakers or flasks.  Then add enough cleaning solvent to fully immerse the parts.  Loosely cap the container to slow the escape of solvent vapors. Do not tightly cap the containers.  

A tank lid with openings to snugly accommodate the containers is put in place.  Otherwise use a shallow-draft mesh basket. Lower the containers into the tank taking care that they are immersed 2 to 3 inches into the solution.  Containers should not contact the bottom the tank. 

Turn on the ultrasonic cleaner.  Cavitation action in the aqueous solution will penetrate the container walls to cavitate the solvent and clean the products. 

At the end of the cycle decant the solvent into a sealable container for reuse or for disposal according to local regulations.  Because most solvents rapidly evaporate there may be no need to rinse and dry the cleaned products unless your procedures call for it.

Large Scale Ultrasonic Cleaning with Flammable Solvents 

Specially designed and code-approved ultrasonic cleaners are required when cleaning large parts using flammable solvents in the tank itself.  An example is the Elmasonic X-tra LSM available from Tovatech.  This cleaner is designed for solvents with flash points at or above 55˚C (131˚F) such as such as NEP (N-ethyl-2-pyrrolidone) or NMP (N -Methyl-2-pyrrolidone). These ultrasonic cleaners should also be operated in areas with adequate ventilation, ideally equipped with exhaust systems and fire suppression systems.

The X-tra LSM units have built-in protection against the formation of explosive atmospheres and are available with an optional solvent cooling system to retard the generation of vapors.  They feature dual frequency (25 or 45 kHz) operation and stepless variable ultrasonic power regulation.  There is an automatic shut-off

  1. If the unit exceeds the manufacturers’ temperature limit
  2. If there is a malfunction of the internal ventilation system
  3. If the solvent level sinks below the minimum acceptable limit  

Note that the LSM unit is NOT for use when cleaning with low flash point highly volatile solvents such as alcohol, acetone, saturated hydrocarbons like heptane, and ether.  These cases require the use of specially designed explosion-proof ultrasonic cleaning equipment, also available from Tovatech. 

Contact the ultrasonic cleaning professionals at Tovatech for help in specifying the correct ultrasonic cleaner for your applications.


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