Filter Ferrous Particles Down to 1 µm,
Keep Oil Flowing During Backwashing
A Japanese automotive manufacturer’s engine plant in China adopted ASMF 5 self-cleaning magnetic filtration to remove ferromagnetic particles down to 1 µm from honing oil at approximately 150 L/min. The existing magnetic drums provide backup filtration, keeping two honing machines supplied during backwashing. Since commissioning, the system has operated successfully and met the customer’s requirements.
Case Background
Two honing machines process engine blocks at the plant. Ferritic wear particles contaminate the circulating honing oil. The original two magnetic drums removed particles only down to approximately 70 µm. Contaminated oil flowed into tanks beneath the machines, passed through the drums into two clean-oil tanks, and returned to the honing machines.
Project Requirements
Rising quality requirements led the plant to seek a filtration system capable of removing particles down to 1 µm. Because the team wanted to avoid waste, the system also had to operate without consumable filter media. Based on its experience with magnetic drums, the plant specifically looked for a magnetic filtration system that would deliver substantially higher performance.
Operators were also dissatisfied with the handling and maintenance of the existing magnetic filtration station. The main shortcomings were:
- The control cabinet did not meet current automotive-industry standards, and the system had multiple leaks.
- The magnetic drum used to clean the backwash fluid did not operate reliably.
Solution: Automatic Self-Cleaning Magnetic Filtration
The operator requested concepts and quotations from several manufacturers in the United States and Europe. Together with its sales partner in China, FRIESS GmbH developed a concept integrating an ASMF 5 automatic self-cleaning magnetic filter.
FRIESS Modular Magnetic Filtration Station
The new magnetic filtration system was planned between the existing dirty-oil tank and the existing magnetic drums.
The proposed system layout offers the following advantages:
- The honing machines continue to receive honing oil even if the magnetic filtration system is offline.
- Honing oil remains available while the magnetic filtration system is backwashing.
- The existing magnetic drums serve as backup and guard filters if the ASMF 5 lifting cylinder fails.
After comparing the proposed solutions and prices, the customer selected the FRIESS GmbH concept. The decisive factors were:
- Compliance with all relevant specifications, including at least 9,000 gauss at the magnetic filter rods
- Compact design with a footprint of less than 1 m²
- Components from established manufacturers, including Siemens, Rittal, Festo and Brinkmann
- Reliable continuous operation
- Safe honing-machine operation even if the magnetic filtration system is offline
- No consumables
- Good value for money
- Flow rate of approximately 150 L/min
The modular magnetic filtration station supplied comprised:
- ASMF 5 automatic self-cleaning magnetic filter
- Splash-protected collection funnel for backwash fluid
- Magnetic drum for removing metal particles from the backwash fluid
- Submersible pump
- PLC control system with Siemens LOGO! and speed control for the feed pump
Design of the FRIESS ASMF 5 Magnetic Filter
The self-cleaning FRIESS ASMF 5 consists of a filter housing with five magnetic filter rods. Dirt particles entering with the process fluid are attracted by the high-strength magnets and adhere to the outside of the stainless-steel sheath tubes. The cleaned honing oil then flows through the existing magnetic drums into the clean-oil tanks. Special flow routing inside the filter slows the liquid as it passes through the magnetic field, enabling particles down to 1 µm to be removed. The special magnet arrangement also reliably prevents the filter from clogging.
The offset arrangement of the inlet and outlet ensures that the liquid flows along the full length of the magnetic filter rods.
Fully Automatic Magnetic Filter Cleaning
The magnetic filter is cleaned automatically under PLC control. The inlet and outlet valves close, the magnetic rods are withdrawn from the sheath tubes, and the sludge drain valve opens. The collected particles leave the filter housing with a small amount of liquid. The filter can also be flushed with a small volume of process fluid.
After backwashing, filtration resumes automatically. The filtration interval as well as the duration and number of flushing pulses can be adjusted to suit operating requirements.
Backwashing Process
Each backwash cycle produces approximately 20–40 litres of heavily contaminated backwash fluid. The fluid is first collected in a funnel beneath the magnetic filter and then flows very slowly across the magnetic drum.
Disposal of Grinding Sludge
Fine particles have already agglomerated into larger clusters in the magnetic field of the filter rods, so they can be separated even by the magnetic drum’s lower field strength of 2,700 gauss. The flow across the magnetic drum is only 10 L/min, giving the contaminated liquid a long residence time in the magnetic field and optimizing particle separation.
The sludge separated by the magnetic drum is collected in a separate container and disposed of as grinding sludge. The cleaned backwash fluid returns to the dirty-oil tank and remains in use.
Technical Data
- Maximum flow rate: 150 L/min (honing oil)
- Operating temperature: 5–40 °C
- Maximum operating pressure: 10 bar
- Inlet/outlet connection: 1½ in.
- Magnetic flux density at the stainless-steel sheath tube surface: 9,000 gauss
- Magnetic flux density at the magnetic drum surface: 2,700 gauss
Key Features of the Modular Filtration Station
- Easy to maintain and operate
- Direct valve control via PLC
- Freely adjustable filtration and flushing cycles
- Low flushing volume
- Cleaned backwash fluid returned to the process
- Fail-safe operation: the drain valve closes automatically if compressed air or power supply fails
Results
Following successful preliminary acceptance at the manufacturer’s plant, installation, commissioning and final acceptance were carried out by the FRIESS representative in China. The system has operated continuously and successfully since commissioning and has met all of the end customer’s expectations.
Fine ferromagnetic particles continuing to build up in your honing oil?
Please share your reservoir volume, circulation flow rate, oil viscosity, particle material and target particle size, existing filtration rating and continuous operation requirements. Our China engineering team can recommend ASMF self-cleaning magnetic filtration system specifications, the number of magnetic rods and a sludge discharge arrangement for your conditions.