Specifying an Explosion-Proof Ultrasonic CleanerJune 25th, 2012
If you want to clean with low-flash-point volatile solvents such as alcohol, acetone and heptane in your ultrasonic cleaning system it is essential that you install an explosion-proof ultrasonic cleaner to safely handle the jobs. A reason to use such solvents is when no cleaning solution residue is permitted on cleaned items. Surgical implants are good examples.
Explosion-proof ultrasonic cleaners are not off-the-shelf products. They are specially designed to the job at hand and they must be installed by a qualified electrician. Their relatively high cost compared to conventional ultrasonic parts cleaners is more than justified when considering the devastation and possible loss of life that can occur due to a volatile solvent explosion.
Explosion-Proof Ultrasonic Cleaner Design
Here’s a general description of an explosion-proof ultrasonic cleaner installation. Specifics vary depending on your operations. Consult with Tovatech experts on the subject to establish specs for your particular needs.
- Establish a “hazardous area” in your facility to house the ultrasonic cleaning tank.*
- Equip the hazardous area with ventilation and fire suppression systems.
- Isolate the ultrasonic generator and its control box from the hazardous area.
- Pass coaxial cable from the ultrasonic generator through explosion-proof conduit to the ultrasonic transducers.
Tank Design Characteristics:
- Equip the tank with a cover and a fusible link to the cover support arm so the cover will automatically close in case of fire.
- Fit the tank with a sealed skirt and a low-pressure purge system to circulate nitrogen between the cleaning tank walls and the cabinet walls including the transducer area.
- Equip the purge system with a pressure safety switch and an over-temperature safety switch. These are designed to shut down the equipment in a no flow/low flow situation or if the sensed temperature reaches 80% of the solvent’s auto-ignition temperature.
- Consider a cooling water jacket to slow temperature buildup due to ultrasonic cavitation.
The sonic cleaner installation should be equipped with a timing device to prevent energizing the transducers until four volumes of purging gas (nitrogen) are circulated through the unit.
Establish detailed safe operating procedures for using volatile solvents in an ultrasonic cleaner and be certain that all employees are familiar with them.
There are less complex equipment options if you use solvents possessing relatively high flash points such as >55˚C (131˚F). Please see our post on cleaning with flammable solvents.
*If constructing a hazardous area is impractical generators and control panels must be placed in an explosion-proof enclosure. Again we suggest contacting the ultrasonic cleaning experts at Tovatech for sound advice.