Removing 2-Part Polyurethane from Paint Guns and Pressure Regulators

November 20th, 2015

A plastic spray painting operation at Blue Ridge Industries

A plastic spray painting operation at Blue Ridge Industries

An explosion-proof ultrasonic cleaner speeds removing hardened 2-part polyurethane from spray paint guns and pressure regulators used by Blue Ridge Industries’ plastic painting services.  According to BRI’s Steve Sierra, the automated paint line provides a high throughput but the paint can be very hard to remove from small holes in paint guns and pressure regulator configurations.

In the fall of 2014 Blue Ridge Industries ordered a 3.9 gallon Electrowave EW-12 EXP explosion-proof ultrasonic cleaner from Tovatech as an alternate to soaking paint guns and pressure regulators in MEK (Methyl Ethyl Ketone) solvent.  Due to the flammability of MEK (flash point -7⁰ C) soaking was done in a sealed container, followed by manually brushing paint from parts after soaking.

By switching to ultrasonic cleaning BRI was able to use less flammable MAK (Methyl n-Amyl Ketone, flash point flash point approx. 47⁰ C) for the solvent cleaning process and at the same time substantially improve throughput over soaking and brushing.  This is because ultrasonic cavitation created by the EW-12 EXP’s generator-powered transducers produces millions of minute bubbles that reach all immersed surfaces and implode on contact to quickly blast loose and carry away urethane residues.

Two Steps to Safe Cleaning with Flammable Solvents

Flammable solvents call for specialized ultrasonic cleaners that cannot ignite spilled solvent or vapors by sparks generated by the equipment’s internal electronics.

Electrowave EXP explosion-proof ultrasonic cleaners solve this because their internal electronics are completely sealed in high-density foam.  For this reason they conform to National Electrical Code and National Fire Protection Association guidelines and carry the “Explosion Proof Apparatus” label.  For more on this see our post on safety ratings.

But operating the equipment creates what is called a “hazardous area” because spilled solvent and fumes generated during the cleaning process can be ignited by other sources.  The equipment, therefore, must be properly located and vented to direct fumes outside, all electrical components in the area must be designated as explosion proof, and personnel working in the area must not use personal electronic devices.  See our post on safety guidelines for additional recommendations.

The Cleaning Cycle for Removing Dried Urethane Paint

Add solvent to the ultrasonic cleaner tank until it is at least half full but not overfilled.  Note that solvent level is critical because if the level drops below half full the unit may be damaged.  Operators should pay attention to solvent level loss due to evaporation.

Place the lid on the tank and operate the equipment for 10-15 minutes to drive off cavitation inhibiting trapped air.  This process, called degassing, should be undertaken every time solvent is replaced.  The tank lid reduces evaporation and also helps mute the sound.

Place parts to be cleaned in the unit’s stainless steel basket.  Lower the basket into the solvent, replace the lid and set the timer for 30 minutes.  Actual cleaning time depends on the condition of the parts.  At the end of the cycle inspect the parts.  Minor post-cleaning brushing may be required in some instances.

When the solvent loses its efficiency the tank is drained and cleaned. Dispose of paint residues and spent solvent following local regulations.

Contact our experts for information on Electrowave explosion-proof cleaners and for advice on cleaning solvents and procedures to increase the efficiency of your operations.