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Exothermic Reactions in Parts Washers

How to Safely Add Soap to your Parts Washer

No one wants to hear about safety processes.  Many people believe they can ignore safety processes until they have been hurt. This article is about a danger that many people do not recognize while working with a Parts Washer.  It is a sudden explosive chemical reaction caused by adding detergent to the washer bath.  The reaction is called an exothermic explosion.

An exothermic process is a chemical reaction that gives off heat. This heat is transferred to the surroundings. Many common chemicals undergo exothermic reactions. For example, simply dissolving sodium hydroxide (NaOH, lye, caustic soda) in water produces enough heat that if this is not done carefully it could melt a plastic container!

The heat that a chemical reaction gives off can quickly heat the surrounding area (or rest of the chemicals in the container) to a very high temperature. As temperature increases, the rate of the chemical reactions increases as well. Once an exothermic reaction begins, it can quickly "run away" – feeding on itself and accelerating its rate because of the heat produced. Therefore, it is very important to take appropriate safety precautions when adding chemical to a washer bath to prevent a dangerous exothermic reaction.


Safety Equipment

The best method to add soap to a parts washer is as follows:  BE SAFE: Always wear the proper safety gear – goggles, face shield, full body apron and gauntlet style chemically resistant gloves.

Safety Guidelines

For Powder Chemicals

Open the washer door. Add chemicals onto the drip pan beneath the turntable or onto the reservoir cover inside of the cabinet then close the washer door and run a wash cycle to mix the powder with the water in the reservoir.  DO NOT pour the chemicals directly into the washer bath.

For Liquid Chemicals

Open the washer door. Slowly pour the chemical over the front door frame angle onto the internal reservoir cover and let the chemical run into the washer bath.  Pour a little at a time and be vigilant for any kind of exothermic reaction.   Stop after you have added about ½ of the chemical and run a short wash cycle to mix the chemicals into the bath.  Slowly open the door and add the remaining chemical.