Safe Cleaning with Flammable Solvents

October 30th, 2015

Cleaning with flammable solvents creates a hazardous area

Cleaning with flammable solvents creates a hazardous area

Flammable solvents are often preferred for specific cleaning tasks, examples being cleaning newly manufactured surgical implants, medical and surgical instruments, printed circuit boards, inkjet cartridges and similar tasks where the absence of cleaning residues provides distinct advantages.  Popular solvents include acetone, IPA, MEK and toluene, all of which have the distinct disadvantage of being highly flammable and likely to cause an explosion unless precautions are taken.

An Ultrasonic Cleaner 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 proof ultrasonic cleaners are employed in the shop, and that the equipment be located in a properly designed location known as a hazardous area.

We’ll take a quick look at these two requirements.

Explosion-proof ultrasonic cleaners are exemplified by the Electrowave EXP units available from Tovatech in several tabletop and industrial tank capacities from approximately one gallon to 90 gallons.  The larger capacity models have remote ultrasonic frequency generators* as compared to self-contained units with integrated generators.

What distinguishes Electrowave EXP equipment is an internal design that keeps solvent liquids and vapors from being ignited by sparks that could be produced by the units’ internal electronics.  This is achieved by encasing all electronic components in high-density foam.   The design allows Electrowave explosion-proof ultrasonic cleaners to carry the NFPA Explosion Proof Apparatus label covering Class 1, 2 and 3; Divisions 1 & 2, and Groups A through G.  For more information on this see our post on NFPA safety ratings.

Hazardous Area Considerations

While the ultrasonic cleaner equipment is explosion proof by design, operating it creates what is noted above as a hazardous area due to cleaning solvent and solvent fumes.

This means that fumes must be vented using approved ventilation systems.  All electrical equipment, wiring, lighting fixtures, outlets and similar equipment must be rated as intrinsically safe by the National Electric Code, NFPA-70 Articles 500-503.  In short, all components and equipment must be listed by a nationally recognized testing lab such as Underwriters Laboratories or Factory Mutual.

A further precaution is prohibiting the use of cell phones and other personal electronic devices in the designated hazardous area, and that operators replace standard power plugs shipped with the cleaners with an explosion-proof plug. We suggest that you check our post on safety guidelines for explosion proof ultrasonic cleaners.

Explosion-Proof Ultrasonic Cleaner Specifications

Electrowave EXP explosion proof ultrasonic cleaners operate at an average 40 or 54 kHz ultrasonic frequency depending on models.  Other frequencies are available.

Units are fabricated of corrosion-resistant, cavitation resistant stainless steel for durability and cleanability.  A sweep function delivers homogenous distribution of cavitation action throughout the cleaning solvent to eliminate potentially damaging localized areas of intense ultrasonic energy.   A 30 minute timer is standard; a 60-minute timer is available on request.  Because of the volatility of solvents these explosion-proof cleaners do not have heaters.  Operating temperature is kept below 40 °C.

Safety note:  Because cleaning solvents evaporate quickly operators must continually monitor solvent levels in the tank.  It is strongly recommended that optional tank covers be used to reduce evaporation.  Optional cleaning baskets are also recommended to keep parts being cleaned from contact with the tank bottom.

Have questions?  Feel free to contact our scientists for answers to your questions on explosion-proof ultrasonic cleaners or for information on ultrasonic cleaning systems designed for water-based cleaning solutions.

*See our post on remote generators.