FRIESS S100 Oil Skimmers for Cooling Water Oil Removal
A metalworking plant operated two parallel longitudinal settling basins separated by a common wall. Production introduced approximately 10–20 litres of oil per hour into the recirculating cooling water. Because of its lower density, the oil accumulated at the surface.
Since the oil had previously been removed only at irregular intervals, the circulation pumps repeatedly drew oil–water mixtures back into the cooling circuit. Even with the pump inlet about 2.0 m below the surface, the suction was strong enough to pull floating oil into the intake line.
The Problem
Oil circulating through the cooling-water system caused frequent failures and contamination of critical components:
- Oil-contaminated cooling water caused filter failures and high maintenance costs.
- Oil mixed with grease and dirt coated the inside of pipes, reducing cooling-water flow. Small nozzles in particular clogged frequently and had to be cleaned or replaced.
- Heavy oil contamination impaired system performance and contaminated product surfaces.
To optimize the cooling-water system and avoid costly cleaning, the maintenance team looked for a system that would continuously remove oil from the surface of the settling tanks. The requirements were:
- No interruption to production
- Rapid removal of oil from the cooling water
- Low investment and operating costs
The Solution: FRIESS S100 Oil Skimmers
After evaluating several options, the maintenance team selected two FRIESS S100 oil skimmers for the following reasons:
- The floating oil film is removed across the entire tank surface.
- The FRIESS oil skimmers operate continuously.
- Robust stainless-steel construction and ceramic scrapers provide long service life with minimal maintenance.
- Positive feedback from other users of FRIESS oil-skimmer systems
- FRIESS could meet the plant’s additional requirements: a tank with pump and a customized installation design.
Space around the basins was extremely limited: there was neither room to install the skimmers beside the basins nor space for a separate waste-oil container. FRIESS therefore designed a pump receiver tank mounted on the partition wall between the two basins. One S100 oil skimmer for each basin was installed directly above this tank.
Results
The S100 collection tubes run across the full width of the settling basins, perpendicular to the water flow. Their movement drives floating oil toward the skimmers; ceramic scrapers then remove the oil from the tubes, allowing it to flow vertically into the separation chamber of the pump receiver tank.
To keep the cooling water as clean as possible, the operator runs both skimmers continuously, 24/7. When the oil film becomes very thin, a small amount of water may therefore be collected together with the oil.
To minimize the water content of the waste oil and reduce disposal costs, the first chamber of the pump receiver tank serves as an oil–water separator. The collected mixture settles there: water sinks to the bottom while oil rises to the surface.
When the separation chamber reaches its maximum level, the floating oil passes over a partition into the storage chamber. At the same time, the settled water returns to the cooling-water basin through a dip pipe.
- The oil level in the main collection tank is monitored. At the maximum level, the recovered oil is pumped into a large disposal container.
- Using FRIESS S100 oil skimmers reduced the oil content in the cooling water by more than 90%.
- After an initial cleaning, the cooling-water filtration system operated without faults.
- Production stoppages caused by blocked nozzles were eliminated.