Industrial-scale ultrasonic cleaning involving flammable solvents with low flash points* requires special equipment as well as special procedures. The American Chemical Society publishes a table of common organic solvents that includes flash points. In terms of equipment specifications, you will need ultrasonic cleaners with remote generators to comply with NEC and NFPA as well as local codes to minimize dangers of fire or explosions.
Ultrasonic Cleaner Generators – What they Do
Benchtop ultrasonic cleaners and most floor-mounted industrial-sized units used with non-flammable aqueous cleaning chemicals have self-contained ultrasonic generators mounted in the unit casing along with the ultrasonic bath tank, transducers, control panel and, if so equipped, heaters.
These generators power the ultrasonic transducers that create billions of microscopic bubbles that implode on contact with items being cleaned to blast and carry away contaminants. For more on this see our post on how ultrasonic cleaners work.
In contrast, some large industrial cleaners (due to space restraints) and all those employing volatile solvents require remote generators, also called modular generators, either as a practical or required alternative.
An example of the latter case is the SOL XP explosion-proof ultrasonic cleaner series offered by Tovatech. These units are often called on to replace older configurations such as Electrowave or other brands that may not fully comply with NFPA, NEC and other regulations. The SOL XP models exemplify ultrasonic cleaners with remote generators.
How Ultrasonic Cleaner Remote Generators Work
In fact they work the same as internally mounted power generators with the exception that they are, as the name implies, remote from the cleaning tank and associated equipment.
Remote generators are contained in their own housing and connected to the tank-mounted ultrasonic transducers by means of coaxial cables. This provides some latitude in positioning the generator a safe distance away from the ultrasonic cleaning unit.
Specifying Explosion Proof Ultrasonic Cleaners
Explosion proof ultrasonic cleaners should have these features supporting safety regulations:
- Class I Division 1 Explosion Proof Electronics
- ETL/Intertek Certification
- All stainless steel construction to support long term operation
- Nitrogen auto purge system for additional fire protection
- Liquid level, over-temperature and nitrogen pressure interlocks
- Remote electrical panels outside the CID1 area
- An optional air driven pump and purification system to reduce handling and improve product quality
- An optional cooling jacket to reduce solvent loss and further control odor
- A 10-year warranty on ultrasonic transducers to protect your investment
- 120V operation
Application Examples Using Remote Generators
As noted in our summary below, where solvent cleaning is required for very small items, alternatives to explosion-proof ultrasonic cleaners are available. But for industrial operations where larger volumes of low flash point solvent are required, units such as the SOL XP models must be used.
Here are links to two case studies that highlight how the SOL XP system is employed:
- Removing machining oils and particulates from piece parts and brazed assemblies at various stages of the assembly process.
- Cleaning new and reconditioned stainless steel filters
Locating Explosion-Proof Ultrasonic Cleaners
When using volatile solvents to sonically clean products several considerations come into play.
Spilled volatile solvents and solvent fumes create what is defined as a hazardous location as defined by the National Electric Code (NEC). This is because fumes or spilled solvents could be ignited by extraneous sources such as electrical equipment, associated wiring as well as an ultrasonic cleaner not certified as explosion proof.
While the NEC, National Fire Preventive Association (NFPA), other regulatory authorities and your local fire regulations apply, here are points to keep in mind when locating an explosion-proof ultrasonic cleaner. (A good source is National Electric Code, NFPA-70 Articles 500-503 related to intrinsically safe apparatus and wiring.)
- Electrical apparatus 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 meet more stringent requirements than those used in other locations. All components and equipment must be listed by a nationally recognized testing lab such as Underwriters Laboratories or Factory Mutual.
- Wiring components and equipment must be maintained as explosion proof. Loose or missing screws, gaskets, connections, seals or other tightness impairments must be corrected.
- An explosion proof exhaust system should be positioned over the ultrasonic cleaner to draw off fumes and protect personnel from inhaling them.
- No personal electronics should be used in proximity to the cleaners.
Flammable/volatile solvents are often required to meet strict cleaning specifications across a broad range of applications. Except in cases where beakers can be used for very small parts, explosion-proof ultrasonic cleaners with remote generators, exemplified by the SOL XP units, are critical when it comes to meeting strict national and local safety regulations.
If you are looking to purchase a code-compliant ultrasonic cleaner for flammable solvents, or replace equipment such as Electrowave units with internally mounted generators, contact the scientists at Tovatech. They will provide unbiased recommendations for ultrasonic cleaners with a remote generators that meet your needs.
* A flash point is the minimum temperature at which a liquid gives off vapor in sufficient concentration to form an ignitable mixture with the air near the surface of the liquid.