The built-in controller adjusts the oil skimmer’s operating and pause times, allowing the oil layer to be removed regularly while minimising the amount of wash water entering the waste-oil collection tank.
At a manufacturer of textile-machine components, many small parts must be hardened. After oil-bath hardening, the parts must be cleaned before further processing. Because the very small components are quenched in baskets in the oil bath and then washed, large quantities of oil are carried into the wash water.
During the night shift, a FRIESS Type 3H oil skimmer was used to remove the entrained oil. The skimmer had operated for more than 15 years without any problems. Continuous removal of the washed-off oil provided a satisfactory wash-water service life and consistently clean parts. After production changed to three-shift operation, however, there was no longer enough time for the entrained oil to settle. The wash water circulated continuously, so the tramp oil could not collect on the bath surface and could no longer be removed by the skimmer.
Following the recommendation of the FRIESS GmbH factory representative—and based on the plant’s positive experience with the Type 3H oil skimmer—the management selected a Skimmtelligent 20 oil separator. Contaminated wash water is continuously drawn from the degreasing bath through a floating suction device.
A compressed-air diaphragm pump is used as the feed pump. Its key advantage is that finely dispersed oil droplets in the water are not broken up further and reduced in size, making subsequent oil separation much easier. If the volume of an oil droplet is reduced by 50%, its buoyancy falls by 75%. In other words, the smaller the droplet, the slower it separates—and the larger the droplet, the more readily it separates. For this reason, every FRIESS oil separator uses a positive-displacement pump instead of a centrifugal pump.
Inside the Skimmtelligent oil separator, the wash water first flows into a settling chamber.
Coarse dirt particles with a specific gravity greater than 1 settle at the bottom of the chamber.
The collected sludge can be drained from the vessel through a ball valve as required.
The wash water then passes over a baffle into the main separation chamber containing a coalescing insert. As the wash water flows from top to bottom toward the outlet chamber, larger oil droplets remain directly on the surface. Small oil droplets dispersed throughout the wash water pass through the coalescing insert with the water. The droplets strike the coalescing media and adhere to it. As several small droplets combine into a larger droplet, buoyancy increases and the enlarged droplet rises to the surface.
To support separation in the coalescing chamber, exhaust air from the compressed-air diaphragm pump is introduced into the separator from below. A needle valve regulates the air volume, creating additional lift in the wash water so that individual droplets are carried upward by the air bubbles.
The de-oiled wash water flows beneath a baffle into the next chamber and then returns by gravity through a large drain hose to the degreasing system, free of oil.
Oil floating in the Skimmtelligent separator is removed automatically at intervals by a FRIESS Type 1U oil skimmer.
The built-in controller adjusts the oil skimmer’s operating and pause times, allowing the oil layer to be removed regularly while minimising the amount of wash water entering the waste-oil collection tank.
The pump’s operating and pause times can also be set independently. With oils of higher specific gravity in particular, allowing the wash water to rest can further improve separation performance.
The pump delivery rate is continuously adjustable. At higher flow rates, large quantities of oil can be removed quickly. At lower pump output, the longer residence time of the liquid inside the oil separator optimises separation performance.
