TECHNOLOGY FOCUS

SMALL SHOP MAINTENANCE OF METALWORKING FLUIDS
PART III - THE WATER

by Dom Ruggeri

September 2000:

Not too long ago I was working for a small formulating house servicing a very specialized niche of the metalworking industry.  This company had a soluble oil formulation that they considered workhorse.  Their claim; the formulation would work well in hard city water.  But what about hard well water or reprocessed water, or industrial water?

As their business grew they began selling tote-bins of this soluble oil overseas.  As with any new product, customer problems eventually developed, and the product was modified to resolve these problems.  However, in one area of the world this workhorse soluble oil refused to emulsify.  Since this was an account overseas and as such hours become days, and days become weeks I requested that our customer send samples of their water, and the particular batch of material causing the problem.  Further, I requested the lot number of that material.

I have been in the metalworking business long enough to always check the batch retains of my product first before the customer's lot sample arrives.  Should I find something amiss I know what path to take when the customer's sample arrives.  I was working with a consultant who was also my predecessor.  After we verified the quality control specifications; his recommendation was to check emulsion in distilled water, tap water, and synthetic hard water.  The emulsion was fine; when the customer samples arrived we ran the same tests, the soluble oil emulsion was fine in distilled water, tap water, and synthetic hard water.  However, in the customer's water the product would not emulsify.  We found the hardness of the customer's water to be 750ppm as Calcium Carbonate while our synthetic hard water was only 100ppm as Calcium Carbonate.  I mean, heck, my tap water at home is 260ppm.

 Without a doubt, water is the largest commodity used in the metalworking industry.  The large machining center will know all there is to know about the water coming into their shop.  However, in the small shop this knowledge may be a mystery, but it does not have to be an unsolvable mystery.

 1. City Water:

City water will be the most consistent water supply you can have.  The reason, the city is processing and controlling the water anything you need to know about your water quality is a telephone call away, of course you will have to wade through the levels of answering services to get the information you need.

 2. Natural Water (Wells, Rivers etc.):

These sources will vary with the season and other factors, such as rainfall and soil contamination.  The machine shop must keep a tight control on this type of water to avoid coolant-related problems.  However, by the time the problem is detected it could be too late and the dump and recharge may be the only solution.

 A. Hardness:

Water has a certain amount of dissolved Calcium and Magnesium carbonates; these compounds are measured and reported in parts per million (ppm) as calcium cabonate.  The higher the ppm the harder the water, hence, the more calcium and magnesium carbonate contained in the water.  The next question is what is considered soft water and what is considered hard water? I have been using the following scale for some 20 years and I offer it here as a suggestion:

1. 0 to 10ppm  as CaCO3 Soft Water

2. 11 to 200ppm as CaCO3 Normal City Water

3. 201 to 300ppm as CaCO3 High Normal City Water

4. >300ppm as CaCO3  Hard Water

There is a hardness titration kit available from Fisher Scientific for about $60.00.  Should you have a water consistency problem this kit is money well spent.

Suppose your water hardness is 130ppm and your metalworking fluid will not emulsify, yet it gives you a perfect emulsion in distilled water.  Contact your metalworking fluid supplier and have the Calcium to Magnesium ratio checked.  This ratio is normally 2 parts Calcium to 1 part Magnesium.  If this ratio is off, emulsion difficulties could occur.  Your metalworking fluid supplier will know how to handle this phenomenon.

How do we spot a potential water related problem? I know of only 2 ways; if the metalworking fluid does not emulsify in the shop water, or if you see a cottage cheese like substance float on the surface of your tank.  Either of these conditions could be the first signs of a water problem.  Contact your metalworking fluid supplier, since they are the experts and they can handle this problem.

How can you insure the quality of your incoming water?

1. Deionized Water (DI Water):

DI Water is city water passed through a series of filters to remove the Calcium and Magnesium from the water giving you water as close to ion free as distilled water.  However, there are drawbacks of which foam is one; softer water promotes foam generation.  One would need to add antifoam to the system at an added expense.  DI units are expensive to purchase and maintain.  Although this is another expense, the return may make these expenses cost effective.

2. Reverse Osmosis Water (RO Water):

Reverse osmosis water is city water passed through a membrane.  The membrane filters pull out all the hardness and just about everything else yielding the purest water available.  However, these membranes do clog and block and at that time they need to be replaced and that is expensive.  Further, the same problems associated with DI water, foam etc. will occur with ferocity.

In conclusion water is the largest single commodity used in the machine shop.  Maintain your fluids, and know the danger signals of water related problems and you will increase the usable life of your fluid. 

Good luck and if I can be of any help feel free to e-mail me through the magazine.

Dom