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Flammable Solvents and Ultrasonic Cleaners

There are many instances when flammable solvents such as IPA, acetone and toluene are used for cleaning parts that must be residue-free after the process. Extreme care must be taken under all circumstances but it is especially called for when using flammable solvents in ultrasonic cleaners.

That’s because spilled solvent and solvent vapors can be ignited by the cleaner’s electronics. Solvent and vapors can also be ignited by other sources as described later in this post.

Here are two options when using flammable solvents ultrasonic cleaners.

Cleaning solution maintenance is governed by what’s being cleaned.Store solvents in approved containers.

Option 1: Isolate Flammable Solvents from the Environment

This method is relatively simple and can be used to clean small parts in benchtop ultrasonic cleaners. A good example is the Elma E+ ultrasonic cleaner with the beaker kit option and operating it in observance of the safety measures noted below.

  • Fill the ultrasonic cleaner tank with water and a surfactant then activate the ultrasound for mixing and degassing.
  • Place parts in beakers and cover them with solvent. Or place parts in fine-mesh baskets then lower the baskets into the beakers. Loosely cap the beakers to reduce evaporation.
  • Lower the beakers into the water/surfactant solution. Place them in the cleaning basket, not on the bottom of the tank. Only one or two inches of the beakers need be immersed in the solution.
  • Activate the ultrasound. Cavitation passes through the beaker walls to the solvent and performs the cleaning operation with complete safety. At the end of the process first turn off the ultrasonic cleaner then remove the parts, which will dry residue free.

Option 2: Use an Explosion-Proof Ultrasonic Cleaner

If you frequently require volatile solvents for your work, the answer may be using an explosion proof ultrasonic cleaner.

Explosion-proof ultrasonic cleaners are designed to eliminate ignition points within the equipment itself that could ignite spilled solvent or fumes. Ask us about our SOLXP explosion-proof units. This equipment is designed for use in Class I Division 1 hazardous areas.

Common Safety Measures

Picking up on the above, ultrasonic cleaning with flammable solvents creates what is called a hazardous area due to the immediate presence of solvent and fumes. This means

  • Electrical apparatus that is not rated explosion proof should not be used in proximity to the cleaner.
  • Electrical wiring methods including explosion proof lighting enclosures, outlets, switches, plugs and conduit must be listed by a nationally recognized testing lab such as Underwriters Laboratories or Factory Mutual.
  • Wiring components and equipment must be installed and maintained as explosion proof.
  • Approved ventilation systems must be used to direct fumes outside the area. Fume generation is reduced when units are operated with a cover.
  • Avoid using personal electronic equipment in the area.
  • Always store fresh and used solvents in approved containers.

Call the ultrasonic cleaning experts at 973 440-2191 for more information on equipment and procedures to safely clean parts using volatile solvents or for answers to other ultrasonic cleaning challenges. 


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