| Water-dilutable
MRF: recovering
(or go to recycling)
go to
straight oils
click on the hyperlinks at right to learn about
testing MRF
recycling
water-dilutable
MRF
recycling
straight oils
settling
centrifuging
filtration
vacuum distilling
absorptive filtration
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| A recovery system applies to those operations that have
individual machine sumps instead of a central system. |
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The metal removal fluid is premixed with water by a proportioner and fed
into a dual-compartment recovery unit (one dirty and one clean tank) that transports the
fluid to the individual machines. After pumping the used fluid through a filter basket
into the used fluid compartment, the recovery unit then pumps fresh coolant into the sump.
The dirty fluid is then transported back to a centrally located holding tank. Here, a
settling tank is used in combination with a cyclone
filter or a pressure filter
to remove swarf and chips. The filtered fluid then has any remaining particles and tramp
oils removed.
Once the fluid is cleaned, it can be held in a clean fluid reservoir and
aerated to prevent stagnation. The metal removal fluid should also be tested to evaluate the pH, concentration, and microbial contamination levels. Should any of
these areas fall outside the manufacturer’s acceptable limits, the cleaned metal
removal fluid should be treated with additives before being sent out to the shop floor.
Once treated, the metal removal fluid can then be fed into the clean side of the recovery
unit and returned to the machines as makeup.
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For maximum life and performance, fresh metal removal fluid should be used
to charge the machine tool reservoirs; the cleaned fluid is then used for makeup only.
Also, should the metal removal fluid not fall within the recommended parameters (i.e. pH,
odor, bacteria, etc.), the fluid should be properly disposed of through the
facility’s waste treatment system.
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| In a central system, MRF is recycled.
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How is water-dilutable MRF recycled?
The metal removal fluid is transported to a holding tank for removal of
tramp and free oils. It is then piped to an emulsion-breaking tank where the coolant is
chemically or physically separated (oil, some fluid ingredients, and other contaminants
are removed from the water). Ultrafiltration is often used to further purify the water
stream for reuse in the plant. The water may then be suitable (without additional
treatment) for use as makeup water in the same metal removal fluid, but will probably need
further treatment first by a reverse osmosis unit attached to the ultrafiltration unit.
The ultrafiltration removes gross contamination and reverse osmosis further cleans the
water by removing salts and minerals.
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| Remember that the best way to maintain water-dilutable fluids is to treat
them before they go bad. Bad coolant before it is "recycled" is still bad
coolant after the process. Good coolant going in for "recycling and cleaning"
should yield good coolant. |
How is straight
oil MRF recycled?
| As with water-dilutable fluids, several things must be considered when
using a straight oil fluid for repeated use. These are as follows: |
 | Start with a high-quality product |
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| Frequently sample the oil in use, preferably from the bottom of the machine reservoir,
and test for water content |
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| Periodically sample the oils to verify that the additive package meets new oil
specifications. Make sure that nothing has caused the additive package to break down or
fall out |
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| Monitor viscosity, total acid number (TAN),
and total base number (TBN). |
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The processes by which the straight oil removal fluids can be recycled include
| Gross settling: The oil is placed in the settling tank to allow time
and gravity to take effect. This will remove 95% of the water and the bulk of the
particulate matter. Through the bottom drain, the water and particulate are extracted from
the tank and the remaining oil becomes a raw material for further processes or, in some
cases, reuse. |
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| Centrifuging: Usually performed at around 7200 G’s, this method
effectively removes particulate down to 5 micrometer and drops the water content to
approximately 100 PPM or less. |
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| Filtration: Regardless of previous processing, filtration should always
be done. The oil is pumped through a 1-3.5 mm filter system. The filter system will
protect the downstream equipment and insure a very clean, particulate-free finished
product. |
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| Vacuum distillation: This process is capable of removing practically
all volatile contaminants. The 3 mm filters are included as part of the system. |
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| Absorptive filtration process: This restores color, removes oxidation
products, reduces the neutralization number, and removes residual solvents. |
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All the above processes may be accomplished as a batch operation and may be processed
independent of each other.
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Contact Chris Roman, 