A large manufacturer of transmission and engine components operates a central emulsion filtration system with a volume of approximately 30 m³. Because the emulsion is used as a quenching medium rather than only as a machining coolant, the tramp-oil content must be kept as low as possible.
Even 50 litres of tramp oil in the 30 m³ system was enough to impair quenching performance and create soft spots in the workpieces. Strong turbulence in the central filtration system kept the incoming oil dispersed instead of allowing it to rise. The operator therefore needed to reduce the tramp-oil content far enough to eliminate this quality risk.
Contaminated emulsion is continuously drawn in through a large suction float. An air-operated diaphragm pump transfers it to the oil separator.
Unlike a centrifugal pump, the diaphragm pump does not break existing oil droplets into smaller ones. The gentle transfer preserves the droplet size, making the oil easier to separate.
When the volume of an oil droplet is halved, its buoyancy falls by 75%, so very small droplets separate much more slowly. Inside the oil separator, the flow velocity is reduced to give them time to rise.
The coalescer accelerates separation even for the smallest oil droplets. As contaminated emulsion passes through it, fine droplets adhere to its surface. Their small size gives them too little buoyancy to overcome the flow resistance in the emulsion, but the higher viscosity of the oil helps them adhere more readily than the water-based fluid.
The Skimmtelligent separator therefore uses a FRIESS 1U oil skimmer instead of a fixed overflow edge. Floating oil adheres to the outside of the collection tube, is pulled into the skimmer and scraped off into a waste-oil tank.
The clean tube returns to the surface to collect more oil. Because the skimmer runtime can be matched to the actual oil volume, the separation between oil and emulsion can be controlled very precisely.
Conventional separators often remove the surface oil through an overflow edge. Its height must match the liquid level exactly. If set too low, large quantities of emulsion are lost with the oil, increasing fluid consumption and disposal costs. If set too high, a thick oil layer develops, blocks oxygen transfer and encourages anaerobic bacteria.
After the FRIESS Skimmtelligent oil separator was installed, tramp oil throughout the circuit remained well below 50 litres. Scrap caused by inadequate heat dissipation during quenching fell substantially. The system paid for itself in less than six months, while emulsion service life increased to as much as one year.
