Total Lubricants USA Technical Training Series: Metalworking Coolants

1. Total Lubricants USATechnical Training Series:Metalworking Coolants

2. Coolants • Water-containing fluids designed to: • provide lubrication between tool and workpiece • remove heat from surfaces • flush away debris created during machining • Coolants are used in place of cutting oils because: • heat removal is about 2-3 times faster than oil • much thinner in composition which allows faster machining with closertolerances • produce less misting than similar viscosity oils • typically are easier to dispose of

3. Coolant Use • Coolants are used to perform many different metalworking tasks including: • turning • boring • drilling • sawing • honing • milling • grinding • broaching • gear hobbing, etc.

4. Metalworking Fluid Selection • Selection of a particular MWF depends on the: • type of machine and operation • type of metal and speed of cut • machine lubrication requirements • MWF’s must provide effective rust & corrosion protection for the tool, workpiece, and machine • MWF’s consist of 4 basic types: • straight oils • emulsifiable (“soluble”) oils • synthetic fluids • semi-synthetic fluids

5. Types of Metalworking Fluids

6. Emulsifiable Oils • Known in the industry as “Soluble Oils” • Consist of about 75 - 90% oil • Usually formulated with naphthenic oils • Common additives include sulfur, chlorine, & fats • Form oil-in-water emulsions • Provide good tool life, anti-weld properties, and rust & corrosion properties • Typically provide the best lubricating properties

7. Synthetic Coolants • Contain large quantities of water but no oil • Form a clear or translucent solution when mixed with water • Have a higher pH than emulsifiable type oils • Provide benefits such as increased workpiece visibility, good wetting properties, stability, tramp oil rejection, and little rancidity • Formulated with rust & corrosioninhibitors, extreme pressure enhancers, biocides, surfactants, anti-foam agents, & more

8. Semi-Synthetic Coolants • Formulated much like a synthetic fluid but contain from 5 to 25% oil • Designed to combine the best features of both emulsifiable oils and synthetic fluids • Offer better lubricity than synthetic fluids and better visibility & tramp oil rejection than emulsifiable oils • Provide a good finish on most non-ferrous metals and recommended where other fluids are not practical

9. Coolant Performance • Successful performance of any coolant depends primarily on proper: • storage of the concentrate (neat coolant); • preparation of coolant dilutions for the initial charge and for daily makeup; • maintenance of coolant dilutions including the use of good housekeeping techniques; and • routine condition monitoring by a laboratory to detect and correct discrepancies before problems arise

10. Proper Storage • Storage methods are important to the success of the finished product • Improper handling can render a coolant useless or may lead to premature solution failure • Coolant concentrate should be stored inside between 50o and 100oF; outside storage should be avoided • Concentrate must be protected from moisture

11. Coolant Make-Up Water • Make-up water must be of suitable quality • The pH & water hardness along with chlorides, sulfate, and iron content must be considered • Hard water can split emulsions and form scum • Chlorides can split emulsions and create rust • Sulfates may promote microorganism growth • Hard water discourages foam; soft water provides the best emulsion stability

12. Coolant Dilutions • Coolant should be added at the point of maximum agitation • Coolant mixtures should be prepared using dedicated mixing equipment and containers • To initially charge a system, it is necessary to know the sump capacity of a machine or system

13. Maintenance of Coolant • Coolant maintenance is absolutely essential to ensure consistent quality of manufactured parts • Daily checks are needed since coolant dilutions are constantly changing through carry-off on parts, water evaporation, oil leaks, etc. • Individual operators have the best ability to detect potential problems and maintain coolant solutions by performing simple daily checks

14. Maintenance of Coolant • Daily checks by operators should include: • verifying coolant concentration • noting abnormal conditions such as excess tramp oil, solids, and/or foam, abnormal appearance or odor, etc. • Routine lab testing is performed by Total Lubricants to ensure satisfactory fluid performance • If a problem is detected from lab testing, corrective actions are implemented to ensure uninterrupted service from the coolant • Water vaporization from machine sumps usually makes it necessary to add makeup coolant at a reduced concentration level

15. Coolant Concentration • Concentration is the single most important factor to coolant success: • concentration must be maintained as consistently as possible within an established range • rich concentrations may cause an increase in skin irritation, produce excessive foaming, reduce the coolant’s ability to remove heat, & increase costs • lean concentrations can destroy tool life, create rust and corrosion problems, promote growth of microorganisms, and lead to rapid fluid failure

16. Concentration by Refractometer • A fast and easy method for checking coolant concentration is with a handheld refractometer. • A refractometer is an optical instrument that reads the amount of total solids by passing light through a sample of coolant. • Synthetic coolants produce the sharpest line on a refractometer; soluble oils are often difficult to read accurately • Tramp oil or chemical contaminantsmay cause inaccurate readings

17. Routine Lab Testing • Coolant condition monitoring tests include: • concentration • total alkalinity • total oil content (“soluble”/semi-synthetic) • pH • microbe activity (aerobic/anaerobic bacteria & fungi) • solids • tramp oil • cation levels (Ca, Mg, Na, Fe, Al) • conductivity • rust prevention properties

18. pH • pH expresses the hydrogen ion concentration in a solution • pH scale ranges from 0-14; 0-6.9 is acid; 7.0 is neutral; and, 7.1-14 is alkaline • pH is measured with pH paper or electronic meter • A high pH (8.5+) promotes good protection from corrosion and microorganisms • A low pH is best for non-ferrousmetals and is kinder to an operator’s skin.

19. Control of Microorganisms • Coolants provide an excellent environment for the growth and reproduction of microorganisms • Common microorganisms consist of bacteria and fungi (yeast and molds) • Microorganisms digest helpful ingredients and produce foul odors • Microorganism content is determined by growing cultures from coolant samples • Biocides may be added to fluid tocombat growth

20. Foam • Some foam is good since it cleans machine surfaces and promotes good wetting properties • Excessive foam, however, is a safety hazard and may cause pump cavitation • Foaming is dependent on coolant concentration, water hardness, type of coolant, agitation, and severity of the operation • Foam may be effectively controlledwith anti-foam agents

21. Tramp Oil • A layer which floats on the surface & consists of split-out oil, carry-over oil, and/or process oils • Tramp oil causes incorrect refractometer readings, severe loading of grinding wheels, and a reduction in heat removal capacity and wetting ability • Failure to control tramp oil often leads to an increase in the growth of microorganisms • Effective control can usually be obtained by using oil skimmers and felt-covered wipers

22. Solid Contaminants • Solids are formed during the machining process and consist of fines, shavings, and dirt • Solids which are not effectively removed can scratch surfaces and interfere with close tolerances • Solids provide additional breeding ground for microorganisms and promote operator dermatitis • Most solid contaminants can be reduced or eliminated through theuse of magnetic skimmers, filters, and chip separator devices

23. OperatorProcedures • Prior to the beginning of the shift & throughout the work day: • observe the holding tank to detect any significant changes in tramp oil levels, dirt, or fungal growth (slime) • slime-type growth on walls should be reported as soon as observed so that an anti-fungal treatment can be added (line clogging can quickly become a problem) • “dirty” sumps should be changed out as soon as production & maintenance schedules permit • operators will obtain a “feel” for the general operating condition of theirmachine through daily inspections

24. Dermatitis • Dermatitis is an irritation or inflammation to the skin • Coolants contain surfactants and wetting agents (soaps) which tend to dry skin • Alkaline cleaners, degreasers, solvents, and abrasive cleaners further irritate the skin • Common industrial irritants include kerosene, chlorinated solvents, acidic solutions, and metals includingchromates, zinc, cadmium, & mercury

25. Dermatitis • Factors external to the work environment which may cause dermatitis include: • poison ivy, poison oak, ragweed, and sumac • white pine, Frazier fir, & teak trees • lemons, oranges, & onions • penicillin, sulfa-drugs, & anti-histamines • dyes, bleaches, deodorants, & nail polishes • wool, silk, nylon, leather, & fur • detergents, polishes, & waxes

26. Dermatitis • Synthetic coolants tend to dry out skin the most • Dermatitis, by definition, is not caused by bacteria although bacteria may aggravate an existing case of dermatitis • Factors such as age, type of skin, previous exposure, & duration of contact determine an individuals’ susceptibility level to dermatitis • Proper fluid maintenance andoperator hygiene are key factors in preventing or reducing dermatitis