PubChem, an open chemistry database at the National Institutes of Health (NIH), defines acetone as a colorless, volatile, flammable organic solvent. It is also called dimethyl ketone, 2-propanone, and beta-ketopropane. As a low flash point solvent, acetone cleaner is widely used in manufacturing as a highly effective degreaser for residue-free removal of contaminants in an ultrasonic bath.
Key cautions or “red alerts” for using an acetone cleaner include low flash point, volatility and flammability. This is why special precautions are required to safely use acetone cleaner in an ultrasonic bath to avoid potential fire and an explosion. Here we describe equipment and procedures to follow when using acetone cleaner in an ultrasonic bath.
Why Care is Critical when using an Acetone Cleaner
What is a flash point?
Acetone cleaner, along with similar solvents such as toluene and IPA, are characterized by relatively low flash points.
A flash point is the temperature at which a particular organic compound such as an acetone cleaner gives off sufficient vapor to ignite in air when given an ignition source.
The American Chemical Society publishes a table of common organic solvents that includes flash points. Examples of low flash point volatile solvents are 1-propanol at 22⁰C (72⁰F), acetone at -20⁰C (-4⁰F) and toluene at 4⁰C (39⁰F). Solvents with higher flashpoints include NEP (N-Ethyl-2-pyrrolidone) or NMP (N -Methyl-2-pyrrolidone).
What is a hazardous location?
Because of its low flash point an acetone cleaner creates what is defined by OSHA as a hazardous location wherever it is used.
This is because fumes or spilled solvents can be ignited by extraneous sources. These include, among other sources, electrical equipment, associated wiring as well as an ultrasonic cleaner not certified as explosion proof.
Two Options for Using Acetone Cleaner in an Ultrasonic Machine
Here are two options offered by Tovatech for safely using an acetone cleaner with ultrasonic energy (along with recommended safety practices):
1. Isolate the Acetone Cleaner from the Environment
This may be the most practical solution if you use an acetone cleaner for relatively small parts on an occasional basis and are not prepared to invest in specially designed equipment. It uses conventional benchtop ultrasonic cleaners such as the Elmasonic E Plus, S and P series along with common safety precautions as described later in this post.
In this instance you can use tap water with a surfactant such as a few drops of dishwashing liquid in the ultrasonic cleaning tank. Before proceeding further remember to degas the solution by running the cleaner for about 10 minutes without a load.
Carefully place the parts in a flask or beaker and add just enough acetone cleaner or other flammable solvent to ensure they are fully immersed. You can also use small, fine mesh screen baskets containing the parts and set into the container. In this case the small baskets must be such that you can cover the container loosely to minimize the vapor escaping during the cleaning process.
Flasks can be fixed into position in a standard mesh basket using flask clamps, and beakers can be supported using a beaker cover instead of a basket. Ultrasonic beaker kits available from Tovatech are a great solution for this application.
In either case, the bottom 1-2 inches of the containers should be immersed in the water. The ultrasonic energy will penetrate the glass walls and cavitation action will occur in the acetone cleaning solvent.
At the conclusion of the process carefully remove the parts which, when dry, will be residue free.
Important Note: When cleaning using this option operations should be carried out with sufficient ventilation to prevent solvent vapor accumulation.
The ventilation system must ensure that the flammable vapor cannot reach an ignitable concentration near the ultrasonic tank. Always check local fire regulations for the maximum quantity of flammable solvent that may be treated in an open ultrasonic tank.
2. Use Specially Designed Explosion-Proof Ultrasonic Cleaners
For large scale operations the SOL XP explosion-proof ultrasonic cleaning systems in 4, 6, 9 and 33 gallon tank capacities are available from Tovatech. These are designed to be used with low flash point volatile cleaning solvents such as an acetone cleaner.
The 40 kHz ultrasonic frequency SOL XP equipment is compliant with all Class I, Division 1 (CID1) code and zone requirements.* Different only in tank dimensions and capacities they can be fitted with a cooling jacket around the upper tank perimeter to capture solvent vapor and reduce odor.
Also available is an optional air driven pump and purification system to reduce handling and improve product quality. This provides continuous solvent purification thereby extending its useful life.
The SOL XP explosion-proof ultrasonic cleaners have Intertek ETL Certification and are shipped with a remote electrical panel to be located outside the CID1 envelope. Units are nitrogen inerted for additional fire protection. Other included and optional features can be found on Tovatech’s SOL XP flammable liquid ultrasonic cleaning systems web page.
Common Sense Safety for an Acetone Cleaner or other Flammable Solvents
While we provide in this post two options for using acetone cleaner and other flammable solvents in an ultrasonic cleaner, operators must be sure that several safety precautions are in play regarding the use and placement of these cleaners.
This is because vapors and solvent are open to the immediate environment. Always check with plant safety personnel and local public safety officials. As a start follow these simple safety steps:
- Acetone cleaner evaporates quickly. When using the SOL XP be certain that the tank is at least half full as lower levels can damage the ultrasonic transducers.
- Do not clean plastic-containing parts unless they are acetone-resistant
- Provide code-approved ventilation such as a fume hood to draw off explosive vapors and protect personnel
- All electrical fixtures in proximity to the unit(s) must meet explosion-proof standards
- Operating personnel must not carry cell phones or other electronic devices that could cause a spark
- Use special precautions in the disposal of spent acetone cleaner solvent
- Bottom line: keep any source of ignition remote from the cleaning area
Please contact the professionals at Tovatech for assistance on selecting and using an ultrasonic cleaner for acetone or other volatile solvents.
*For details see these specifications on hazardous locations.