Self-cleaning Magnetic Filter System Cleaning of Honing Oil
In the Chinese plant of a big Japanese car manufacturer two honing machines are used in order to machine engine housings. During the honing process the honing oil is contaminated with ferritic particles. In order to clean the honing oil the company uses two magnetic rolls. Because of the working principle of the magnetic rolls particles down to 70 µm are removed from the oil. Smaller particles remain in the oil. The honing oil flows over the work piece and the tools in order to cool the honing tools and in order to flush away the particles. The oil flows into a collecting tank under each machine. The contaminated honing oil is pumped from the tank to the magnetic roll and flows from the magnetic roll into two clean tanks. From the clean tanks the honing oil is pumped back to the honing machine.
In order to improve the surface of the engines the company was looking for a filter system, which is able to remove ferritic particles down to 1 µm. The car manufacturer is interested in reduction of waste. For this reason they were looking for a cleaning system, which is able to work without consumables. Because of the generally good experience with magnetic roll they decided to install a magnetic filter system. Of course they were looking for a magnetic filter system with much better performance than the existing magnetic rolls.
The maintenance managers were not satisfied with the performance and the necessary maintenance of existing magnetic filter systems for other production machines. For this reason they were looking for alternative solutions. The main problem with the existing magnetic filter systems were as follows.
- Switchbox is not built in accordance with the typical standards of automotive industry
- Leakage at different points
- The magnetic roll, which is necessary for the cleaning of the flushing fluid, does not work properly
The maintenance team asked for concept and price offer from different manufacturers from United States and Europe. The engineers of Friess GmbH designed together with the Chinese sales partner of Friess GmbH a filter system based on the automatic self-cleaning magnetic filter ASMF 5.
The idea was to install the new magnetic filter system between existing tank for dirty oil and the existing magnetic rolls. The suggested design of the magnetic filter systems offers advantages as follows.
- Even in case of failure of the new magnetic filter systems the supply of honing oil to the honing machine is guaranteed.
- During the time of flushing of the magnetic filter system the supply of honing oil to the honing machine is guaranteed.
- The existing magnetic rolls work as backup-filter. In case of failure of the pneumatic cylinder of the magnetic filter ASMF 5 the oil will be cleaned with the existing magnetic roll.
After a comparison of the different solutions and the different prices the management decided to install the Friess magnetic filter system ASMF 5. Main reasons for this decision are as follows.
- Compliance with all important standards, in example minimum field force of the magnetic field at the magnetic filter rod of 9000 Gauss
- Compact design with a footprint of less than 1 m²
- Installation of components of well reputed manufacturers like Siemens, Rittal, Festo, Brinckmann and so on
- Reliable continuous operation
- Safe operation of the honing machine even in case of failure
- No consumables required
- Very good price performance ratio
- Flow rate of around 150 l/min
The solution suggested by Friess GmbH included
- Automatic self-cleaning magnetic filter ASMF 5
- Funnel with protection against splash in order to collect the flushing fluid
- Magnetic roll in order to remove the filter particles from flushing fluid
- Submersible pump
- PLC control with Siemens Logo and frequency converter for pump
The self-cleaning Friess magnetic filter ASMF 5 is made of a filter housing with five build-in magnetic rods. The dirt particles, which are flushed with the process liquid into the filter housing, will be attracted by the extreme strong magnetic field force and will stick on the outside of the stainless steel pipes around the magnets. The cleaned honing oil flows from the magnetic filter over the existing magnetic rolls into the clean tank. The special designed flow in the Friess magnetic filter makes sure, that the liquid will flow very slowly through the magnetic field. The slow flow makes it possible, that ferritic particles down to 1 µm will be attracted by the magnetic field and will be removed from the honing oil. The special arrangement of the magnetic filter rods avoids blocking of the filter system.
The offset arrangement of inlet and outlet makes sure, that the oil will flow parallel along the whole length of the magnetic rods.
The cleaning of the magnetic filter is controlled by a PLC. The PLC automatically closes inlet and outlet. After that the magnetic rods will be pulled out of the stainless steel pipes. In a next step the sludge valve opens and the collected dirt particles flow with a small volume of liquid out of the filter housing. If necessary it is possible to flush the filter housing with additional fluid.
After flushing the filtration process starts again.
The time for filtration and the time for flushing pulse and the number of flushing pulse can be set according to customers need.
During flushing the filter the filter will produce around 20 l – 40 l extreme dirty flushing fluid. Flushing fluid is collected underneath the filter in a funnel. The dirty fluid flows from the funnel very slowly to a small magnetic roll. The fine ferritic particles are agglomerated in the magnetic field of the magnetic filter. These agglomerated particles are big enough, that they can be attracted by the weak magnetic field of the magnetic roll. The time the fluid rests in the magnetic field of the magnetic roll is very long, because the flow rate is approx. 10 l/min only. The long resting time of the dirty fluid helps to separate the ferritic particles from the liquid. The sludge collected by the magnetic roll is collected in a separate container and can be disposed as grinding sludge. The cleaned flushing fluid flows from the magnetic roll back into the dirty tank and can be used again.
- 150 l/min maximum flow (honing oil)
- Working temperature 5 °C – 40 °C
- Max. pressure 10 bar
- Connection inlet/outlet 1 ½“
- Magnetic field force at the surface of the stainless steel pipe around the magnetic rods inside the filter housing 9000 Gauss
- Magnetic field force at the surface of the magnetic roll 2700 Gauss
Main features of the modular self-cleaning Friess magnetic filter system:
- Simple maintenance and handling
- Direct control of the valves by PLC
- Flexible setting of filtration time and flushing times
- Low volume of flushing fluid
- Flushing fluid is re-used
- Safe operation in case of failure of air supply or electric supply. The sludge drain valve will close self-reliant.
After successful start-up in the workshop of Friess GmbH the unit was shipped to the customer in China. Installation, start-up and commissioning was made by the Chinese partner of Friess GmbH. Since start-up the system is continuously in operation and fulfills all expectation of the customer.
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