Cleaning of process liquids with centrifugal force technology

Efficient separation of liquids and solids

A wide spectrum of industrial liquids, like the process water, coolants from machining and saw cutting operations, paint sludge and other contaminated process liquids, require treatment, i.e. must be cleaned. The effectiveness and cost efficiency of this cleaning process depends to a large extent on the utilized cleaning technologies.

The cleaning and recycling of process liquids poses not only an ecological challenge, but also requires careful consideration of treatment costs. The robust, high performance Rösler centrifugal force systems (available as 2- and 3-phase units) can be used for a wide range of applications and can be easily tailored to the specific customer requirements. In the semi-automatic systems (Z 800) the removal of the sludge with a PU basket is done manually, whereas the Z 1000 series is equipped with a fully automatic sludge discharge system.

Designed for heavy duty operation and easy to maintain

The Rösler centrifuges and their key components, like drive motor, pumps, valves, rotary drum and peeling knife, are characterized by their extremely sturdy design. This ensures a high separation performance, reliability and equipment availability under the most severe operating conditions. For easier maintenance, the Rösler systems are equipped with indirect drive, i.e., the drive motor is linked to the rotating drum with a drive belt. This concept not only allows the optimum sizing of the motor and drum bearings, but it also ensures the lowest possible bearing loads. The rotary drums, with a sludge capacity of up to 66 lbs (30 kg), are available in aluminum and stainless steel. To prevent corrosion in the rotary drum, stainless steel is generally used for process liquids that are acidic, contain salts, SiC or glass particles.

High performance in round-the-clock operation

Depending on the specified cleanliness requirements and the physical limits regarding particle size and weight, the Rösler centrifugal systems offer a capacity of up to 1500 gallons/h (6000 l/h). The extremely high acceleration in the rotary drum of up to 2000 g separates solid particles larger than 2.0 µ from the liquid phase and deposits them on the inside wall of the rotating drum as stable sludge. The utilization of environmentally friendly process water cleaning compounds even permits the separation of much smaller solid particles. For example, the use of such cleaning compounds in coolant cleaning applications results in a significantly longer life of this particular process liquid. The removal of the tiny particles greatly reduces the risk of contamination with bacteria. Depending on the application, the cleaned process liquid is picked up by a collecting tube in the rotating drum and is then either discharged or re-circulated back into the system.

For the automatic discharge of the sludge deposited on the inner drum wall Rösler offers a technical solution: while conventional peeling centrifuges have a peeling knife that is driven by a gear motor, which is constantly rotating, the peeling knife in the Z 1000 series centrifuges is stationary. Once the system signals that the sludge must be discharged from the drum the peeling knife, driven by a pneumatic cylinder, moves to the drum wall and peels out the sludge. Upon completion of the peeling process the inside of the rotary drum is completely rinsed to remove any residual sludge. This is very important as such sludge residuals could cause an imbalance in the drum, which poses the risk of bearing failure during the subsequent peeling processes. For this reason, all Rösler centrifuges are equipped with an imbalance monitoring system.

Proven performance – also for the treatment of coolants

Besides being used for the cleaning and recycling of mass finishing process liquids Rösler centrifuges are also utilized for the de-watering of paint sludge, in the wood processing and glass industry, in the wafer production, for ECM (electro chemical machining) applications as well as for the cleaning of coolants used in CNC machining centers and saws. For example, the machine tool manufacturer Waldrich Coburg GmbH has over 20 Rösler systems in operation for the treatment/cleaning of coolants. All these units are designed as 3-phase systems. This allows not only the separation and removal of solids from the liquid phase but also the removal of cutting oil used for tapping (thread cutting) operations. The separated oil is removed from the rotary drum with a second collecting tube. Contrary to the traditional cleaning of coolants with paper belt filter systems, the Rösler centrifuges do not require the use and discharge of any expensive consumable materials like filter paper.
In order to prove the performance and reliability of its centrifugal systems Rösler makes semi-automatic test units available for separation trials at the customer location.