9.5 m of level variation.
Continuous floating oil removal.
Two 500 m³ buffer tanks operated with liquid-level fluctuations of up to 9.5 m. FRIESS fitted a housed S100 to each tank and designed a floating tube guide to maintain contact with the surface at high and low levels without knotting. Recovered oil was pumped to a storage tank 80 m away.
Case background and operating requirements
A rising oil load in the incoming waste coolant was leaving more residual oil in the treated water than expected.
The operating team evaluated a range of technologies to reduce the oil content in the clean water. It decided to install an oil skimmer in each buffer tank to remove floating free oil. The team expected that removing free oil would reduce the load on the coolant separation system, improve separation performance and lower residual oil in the treated water.
Each buffer tank was a cylindrical vessel with a capacity of 500 m³. During normal operation, the liquid level in both tanks could fluctuate by as much as 9.5 m. Oil therefore had to be removed reliably at every liquid level. The installation also required an extremely robust, fail-safe solution capable of fully automatic operation 24 hours a day, seven days a week.
The Solution: FRIESS S100 Oil Skimmer
Drawing on its experience with FRIESS oil skimmers in various water treatment systems, the operating team contacted FRIESS GmbH and other suppliers. The FRIESS engineering team proposed a special version of the S100 oil skimmer to meet the specification.
The key challenge was to remove oil at every liquid level. FRIESS developed a solution using one housed S100 oil skimmer on each tank. Both tanks had sheet-metal roofs. A rectangular opening was cut into each roof, and a matching flange was welded into place. The S100 oil skimmer and its housing were then mounted directly on the flange.
Installing the S100 Oil Skimmer with Housing
The oil-collecting tube passes through the roof opening to the liquid surface. At the maximum liquid level, up to 18 m of tube can float on the water. Under unfavorable conditions, such a long tube could form knots. To prevent this, FRIESS developed a floating guide: the tube is routed through a floating pontoon, which is itself guided along a stainless-steel cable.
At the highest liquid level, the oil-collecting tube extends as far away from the skimmer as possible. At lower levels, a small loop of tube floats on the liquid surface beneath the skimmer. Even at the minimum level, approximately 0.5 m of tube remains on the surface to collect floating oil. This arrangement allows the tube to follow the changing liquid level without forming knots.
Oil-Collecting Tube Routing at the Lowest Level
Oil recovered by the skimmer flows by gravity through a DN 100 pipeline into a small collection vessel. An eccentric screw pump then transfers the recovered oil to a waste-oil storage tank located 80 m away.
The FRIESS GmbH team coordinated the complete installation, including the piping, pump, control cabinet, electrical wiring and mounting components.
Control Cabinet for the Skimmer, Heater and Pump
Solution summary
- The oil-collecting tube reaches the liquid surface through the tank roof.
- The floating guide lets the tube follow changing levels without forming knots.
- The S100 removes floating oil reliably across the full 9.5 m level range.
Large level fluctuations in your coolant buffer tanks and high residual oil levels?
Please share the tank volume and height, liquid-level range, incoming oil concentration, circulation flow rate, target oil concentration in the treated water, tank-roof structure and continuous operation requirements. Our China engineering team can recommend the number of S100 oil skimmers, floating tube guides, pumping arrangement and control system for your operating conditions.