Ultrasonic Cleaners for Flammable Solvents

Ultrasonic cleaners are widely recognized as providing outstanding cleaning action thanks to the cavitation produced by the equipment’s generator powered ultrasonic transducers.  But when cleaning with flammable solvents it is imperative that explosion resistant ultrasonic cleaners are employed in the shop, and that the equipment be located in an area equipped with an adequate exhaust system to vent fumes to an exterior location.
Flammable solvents are often preferred for tough cleaning jobs such as degreasing and removing tenacious contaminants like paint and adhesive residues.  Special care must be exercised when cleaning with flammable solvents under any circumstance, but especially when using an ultrasonic cleaner to both speed the process and improve cleaning results.   Unless they are specially constructed, ultrasonic cleaners present two risks:  sparks from internal electronics igniting spilled solvents and fumes, and vapors from solvent evaporation creating a hazardous area in the vicinity of the unit.   
Flammable liquids have different flashpoints. The lower the flashpoint the more flammable they are, which an important consideration when specifying an ultrasonic cleaner.  An example is the Elmasonic X-tra LSM series 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 cleaners can also be used with aqueous solutions, a feature that greatly increases their usefulness in the shop.
A Close Look at Flammable Solvent Ultrasonic Cleaners 
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.  But as noted above these ultrasonic cleaners should also be operated in areas with adequate ventilation, ideally equipped with code approved exhaust systems and fire suppression systems.   Lids also assist in reducing fume generation, reducing solvent evaporation and serving as a sound barrier.
Two models are available: 28 liters (21 liter service volume) and 60 liters (50 liter service volume).
An ergonomic, programmable control panel clearly displays operational parameters.

  • Cleaning time in increments to 15 minutes or continuous. Because solvents evaporate faster than aqueous cleaning solutions there is a level indicator caution lamp and a built-in safety shut-down if the solution reaches the minimum level.
  • Dual ultrasonic frequency. Set to 25 kHz for coarse cleaning or 45 kHz for fine cleaning.
  • A degas mode to drive off cavitation-inhibiting trapped air in fresh cleaning solutions. Activating the degas mode reduces the time required to initiate cleaning cycles.
  • Ultrasonic power from 10% to 100%. This feature together with the dual-frequency capability allows users to tailor cleaning cycles to the products being cleaned and the severity of contamination.
  • Cleaning basket oscillation (specify on ordering) provides a ± 2cm vertical oscillation that can increase cleaning speed as much as 20%.
  • On-off heater; digital thermostat allows operators to quickly bring the cleaning solution to the optimum temperature. The indicator shows actual and set temperatures. Note well the flash point criterion for this ultrasonic cleaner when using a volatile solvent.
  • Status indicator lamps show at a glance what is going on: green = ready, amber = solution level alert, reds = ventilation air flow and solution temperature alerts.

 Built-in Safety Factors for Elma X-tra LSM Ultrasonic Cleaners
The X-tra LSM explosion-resistant units have built-in protection against the formation of explosive atmospheres and as noted earlier are available with an optional solvent cooling system to retard the generation of vapors.  There is an automatic shut-off

  1. If the unit exceeds the manufacturers’ set temperature limit based well below the flash point of the solvent used in the unit. Note:  Purchaser must provide SDS for the lowest flash point  of  solvents to be used in the unit.
  2. If there is a malfunction of the internal ventilation system
  3. If the solvent level sinks below the minimum acceptable limit

We remind you again that these units are NOT for use when cleaning with low flash point highly volatile solvents such as alcohol, acetone, and saturated hydrocarbons like heptane, and ether.  These cases require the use of specially designed explosion-proof ultrasonic cleaning equipment. Contact Tovatech for information.  Flash points of commonly used organic volatile cleaning solvents are available on the web.
Continue at: https://www.tovatech.com/blog/26061/explosion-proof-ultrasonic-cleaners/ultrasonic-cleaners-flammable-solvents
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