The tramp oil is one of the most common contaminants in metalworking fluid, many manufacturers believe that its source is foreign pollutants such as: hydraulic fluid, way lubricant, gear lubricant, spindle lubricant , etc.
But for the hot-rolling aluminum industry, The result of our research is that the tramp oil is mainly produced by the emulsion itself:
1,Metal soap produced by chemical reaction between emulsion and aluminum powder.
2,Aluminum powder adheres to the big oil drops produced by the instability of the emulsion.
3, Carbonized lubricant produced during hot rolling
4, Bubbles are generated by the emulsion's own reaction and lubrication process as well as the transport process.
5,The well-maintained hot-rolling aluminum production line rarely produces lubricant leakage and produces tramp oil.
Although the current science has made lubricating oil particles into micron-sized, it cannot eliminate the instability of the emulsified mixture.The instability of the emulsion contains the following process :
1 – phase separation(creaming,Sedimentation)
2 – Ostwald ripening,3 – aggregation processes(flocculation,Coagulation,Coalescence)
4 – Phase inversion
Due to the instability of the emulsion, if the emulsion tank is still for more than 30 minutes, the emulsion concentration will have a gradient effect. The surface layer has a high emulsion concentration and a low concentration of the bottom layer.
If the static is more than 4 hours, the surface emulsion concentration is more than 3 times higher than the concentration of the bottom emulsion.
The traditional method of dumping after a period of static time undoubtedly dumps a lot of lubricating oil. This mode of operation is the source of waste of emulsified oil.
The traditional way of stopping the tank and then discharging it to remove the scum is undoubtedly to discharge the oil on the upper surface, causing huge waste.
Bubbles, aluminum soap, rolling oil, aluminum powder and other impurities flocculate into tramp oil.
The tramp oil are thickened to a water content of less than 10% (we call it concentrated tramp oil) and tested for ash values above 10,000 mg / l.
It's obvious that tramp oil is floc of emulsion contaminants, the function of coalescence together emulsion contaminants by tramp oil can be called emulsion self-purification.
Even in the filtered clean emulsion tank, it can be seen that the foam and tramp oil, which is the proof that the tramp oil cannot be filtered.
The main source of tramp oil is from the reaction of the emulsion itself. This finding can explain the contradiction between the equipment maintenance personnel and the production process personnel. Taking full advantage of the reaction can extend the emulsion life and purify the emulsion.
There are two different types of tramp oils in the emulsion, one is the tramp oils floating on the surface, we call it the surface tramp oils, and the other is suspended in the emulsion, which we call the suspended tramp oils.
The suspended tramp oil is mixed with the emulsion; it is the most harmful pollutant for the emulsion. It can form viscous substance to clog lines and sprays. When suspended tramp oil immerse in the product, the cooling effect of the emulsion is reduced, resulting in a shortened mechanical life, discoloration of the product, and a smoke atmosphere in the factory.