Typically it uses petroleum, chlorine, dry ice or alcohol based solvents to dissolve the machining fluids and other contaminants that might be on the part.
[1] To begin with, a cleaning agent is applied directly to the surface by spraying, brushing, blasting or wiping.
This process removes oil, grease, dirt, loose particles, and any other contaminants that may exist on the surface of the material.
The part is immersed in a tank of solvent and usually agitated like a washing machine for clothes to get all of the contaminant off.
Solvent degreasing equipment is available in a wide variety of sizes and shapes and mainly consists of a submersion tank.