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Controlling Exposure By Filtering Coolant

Grinding Coolant Analysis (particles per cubic centimeter)

When and Why to Filter

In grinding operations you want to filter out all the particles that are larger than 10% of the grit size of the wheel, or 10% of the tightest dimension specified.  A way to explain this is the tire and 2x4 analogy.  An automotive tire is about twenty inches in diameter.  If you run over the two-inch dimension (10%) of a 2x4 you will feel a bump. The little divider bumps (wake-up bumps, turtles) in roads are generally much less than an inch and you sure feel those.   If particles of any size come between the tool and the work it will tend to damage both the tool and the surface of the work.  The same way that a rock in your shoe will try to make a hole in both your foot and the shoe.  

Machine damage is much harder to quantify.  One way of determining acceptable particle size is to ask; what grit sandpaper you would allow to be used on the hydraulic cylinders of the machine?  As the coolant gets sprayed it gets on extended hydraulic cylinders, and is then abraded as the cylinder moves in and out.

Filtering in Carbide Tool Grinding Operations

If you use wheel grit      Wheel   grit size             Filter to this level

(Sieve) Size                         in microns                    in microns

100                                        150                              15

200                                          75                                7

400                                          38                                4

635                                          20                                2 

Benefits of managing coolants

 1.  Chunks of diamond and carbide - The CP 2020 removes the chunks of diamond and carbide as well as oils and grease.  If you leave the carbide and diamond in the coolant then they get between the wheel and the Carbide.  This breaks down the diamonds and the carbide. With dirty coolant there is more dressing, the grinds are worse and wheel life is shorter.

2.  Oil, grease and used coolant – New coolant is made to form very small droplets.  As the coolant gets used the droplets get bigger.  There can also be hydraulic fluid, oil off saw bodies and similar products.  These clog the diamond wheel.  They also feed bacteria which further helps to break down coolant.  The blobs of dirty coolant, oil, etc. are large enough and sticky enough to get trapped in the filters.  

The savings in proper cleanliness, general maintenance as well coolant management and filtering can be as high as 20% of the annual expenses in the following areas. 

Make more money 

1.         Longer Machine Life

2.         Longer time between rebuilds

3.         Less downtime

4.         Less equipment replacement

5.         Faster operation 

6.         Faster cycle times

7.         Fewer tool replacements

Better quality 

9.         Measured as the smoothness of the worked surface

9.         Measured in SPC consistency 

10.        Produce better overall quality work

11.        Reduced rework

12.        Reduced scrap

13.        Tighter tolerances

Greater Lubricity with clean coolant

14.        No burning

15.        Clean coolant will also help prevent problems with heating of the tools.

16.        Less heat during machining therefore less change in surface condition 

17.        Smoother cuts and grinds

Reduced consumable costs 

18.        Longer tool run life per sharpening

19.        Longer tool life

20.        Longer coolant life

21.        Longer grinding wheel life

22.        Less dressing required

23.        More parts per dollar of raw material

Reduced Labor 

24.        Less machine maintenance

25.        Less tool maintenance

26.        Less finishing required

Cleaner workplace

27.        Perhaps increased operator safety  

28.        Retards bacteria growth

29.        Eliminate smells

30.        Help eliminate noise

Fewer problems than shops that use dirty coolants.   

31.        Less OSHA exposure

32.        Less EPA exposure

33.        Less waste

34.        Cleaner waste

35.        Lower coolant disposal or recycling costs

36.        Reduces non-coolant waste and waste disposal costs

Reduce Diamond Wheel Costs  save $3,000 to $10,000 per year

A good grinding operation will still dump huge amounts of oil and grease into the sump. We ran a test on a high production machine. In twenty-two days of double shift we pulled out about ten pounds of oil and grease.  This oil and grease clogs the wheel. Clogged wheels mean slower grinds, worse quality, and shorter wheel life. Clean coolant increases diamond wheel life by at least 30% overall, and as much as 50% depending on the wheel and the application. This is a saving of 25% to 35% in annual diamond wheel cost. Removes oils and greases. 

Longer Coolant Life - Save $1,000 a year per machine + the saving in labor.

If you filter your coolant, you will get much longer life. In actual tests we see coolant last six months and it is still doing an excellent job. This saves you on coolant costs, and the maintenance of sump cleaning and coolant changing.  

West Coast Saws in Tacoma, WA has been running our filter units for three years on five machines with a unit full time on each machine. They estimate that they save $5,500 a year in coolant costs not counting the tremendous saving in labor from fewer cleanings and coolant changes. 

Increase Machine Life - Save $2,000 to $8,000 per year

The big advantage in clean coolant is that it protects the machine. Dirty coolant can shorten machine life by 5% to 7% a year. Saw and tool grinding generates a huge amount of very small, very abrasive particles. These particles get into the coolant and then are sprayed all over. 

These particles get into controls, cylinders, rods and bearings where they increase wear and reduce quality. The CP 2002 removes particle down to one micron, and removes them with incredible efficiency. 

Removing Cobalt (free & chelated) From Saw Grinding Coolant 

Test of Cobalt remover

The cobalt remover looks and flows about like honey.  It removes metals chemically as well as physically binding very fine particles into a larger, filterable mass.  You will want to use it before a filter change as it plugs up filters.   However it I easily removed and will not cause problems with the new filters.   

Background: Coolants typically dissolve the cobalt matrix out of tungsten carbide during saw sharpening.    This situation can be greatly improved by coolant filtering.  However coolant filtering also means that coolants will only be changed once or twice a year.  

Laboratory tests show that there can be considerable coolant chelated (dissolved) in coolant after six months.  This is also visible with clear coolants as the cobalt typically imparts a reddish tinge.  

Test Procedure:  We took 1 liter of coolant that had been filtered constantly at the grinder using a 25-micron bag followed by a ten-micron cartridge filter.  We filtered this with a vacuum filtration setup using a filter paper in the 1 - 2 micron range and got a good coating of grit on the filter paper.  We then added the cobalt inhibitor and filtered using a 30-micron filter.  We got a huge amount of material out.  The filter cake was about as thick as a penny.  Finally we filtered the coolant with a filter in the 1 - 2 micron range and got a nice covering on the filter paper.  

We received one liter of coolant that the saw mill said was “used but clean”.  First, we filtered it and got 2.4 grams of sludge.  Then we added cobalt remover and filtered again.  We got another 6.8 grams.  Finally we used a fine filter (equivalent to our CP 2002 series filter units and got another 2.3 grams. 

The saw mill said the coolant was “Used but clean.”   We filtered out 11.5 grams from 1 liter.   9.1 grams of that came from the use of cobalt remover. 

Test Results: The first filtering got out all the very fine grit.  The cobalt inhibitor extracted the cobalt from the coolant and formed it into large, sticky clumps that could be readily filtered out.  The results are very visible.