All preservatives do not function equally well in a particular product. Sometimes a more expensive preservative is more economical than a cheaper one because the interval between treatments is greater and the amount of material required is less. Sometimes it is more economical to purchase a more expensive coolant and treat it with a cheaper preservative than buying an expensive preservative and using it in a cheap coolant. The purpose of microbiological control is to reduce costs, but companies have practiced coolant control without initiating studies to determine if costs are actually reduced. Once an individual has learned to determine the microbial load of a working system and has selected the proper preservative, there are a number of things which should be kept in mind. FACTORS THAT INFLUENCE DETERIORATION CONTROL It is impossible to entirely prevent the introduction of organisms into working fluids; 11 however, it is possible to minimize contamination of a system. Construction of a new plant offers an opportunity to take advantage of a number of factors which may influence coolant life. Plants should never be placed downwind of sewage treatment plants, flour mills, bakeries, feed mills, fertilizer plants or cooling towers which may produce either airborne nutrients or contaminants. The internal construction of the plant should be engineered so that it can be cleaned properly with a minimum of effort. Consideration should be given to the design of the circulation system, floor elevation, dragout recovery, coolant storage area, pipe work, pump rates, reclamation equipment and other factors, 37,38 Machines should be selected which minimize coolant contact with workers and the environment. Newly acquired reconditioned machines can be sources of major contamination problems and should be thoroughly steam cleaned before being put into operation. Many companies design their systems so that there is too much agitation of the coolant. This practice is usually done in order to move chips or to prevent or reduce coolant odors. Few individuals appear to recognize that the greater the agitation of a coolant, usually the greater the microbial attack. 39 Circulation should be adequate for desired performance but it should not be overdone. Petroleum-base fluids normally are subject to bacterial deterioration while synthetic and semisynthetic products are more likely to encounter mold (slime) problems. Formaldehyde- releasing preservatives are somewhat weaker against molds than against bacteria. 28,29,40 Extra care must be taken when using this type of preservative in synthetic and semisynthetic coolants because if the system is improperly treated, slime problems can occur. A circulation system should never be underdosed 41 with a preservative. Most antimicrobial agents will markedly stimulate growth when employed in low concentrations. 42 The use of a small amount of preservative in a system may produce more growth than if nothing is done. Preservatives should never be mixed indiscriminately. Practically all combinations of the readily available preservatives are incompatible with each other and mixing them can result in less control than using one product alone. Coolant control in one system cannot normally be applied to other systems. 41 Each system has characteristics which are unique for that system alone. The character of each system must be learned through tests and observations. Machines, floors, circulation systems, and parts should be kept as clean as is possible. Stock stored in outside yards may be dirty and serve as a source of contamination of the coolant. Tote baskets holding parts should be designed so that the stock can be subjected to high-pressure water jets prior to being moved to the machines. It is sometimes necessary to shut down machines or systems for extended periods of time. If the system is to be inactive for only a few days, it is best to treat with a biocide and Volume II 375 Copyright © 1983 CRC Press LLC continue to circulate the coolant. If the shutdown period is going to be prolonged, and if it is possible and practical, it is advisable to drain and clean the circulation system and leave it dry until it is operated again. If possible, the drained coolant may be used as makeup for working systems. There is a misconception that when a coolant develops odor or slime it has spoil and is beyond recovery. If other criteria are used, such as rust protection, tool life, emulsion stability or finish, they may indicate that the coolant is beyond salvage. On the other hand, even though slime or odor has developed, if the engineering qualities are still satisfisfactory it may be possible to save the system via effective preservative treatment. When a system which contains a great deal of slime or odor is under treatment, precautions should be taken. The breakdown of millions of microbes killed by the preservative can produce considerable amounts of organic matter which produces frothing. When this occurs foaming will start 24 to 48 hr after the addition of the preservative. This is a temporary phenomenon which will last only a few hours. Unfortunately the coolant is often discarded after the foam appears when the addition of a small amount of antifoam agent would have eliminated the problem. Pumps and filtration equipment should be watched when biocide treatment is underway. A system that has accumulated large amounts of slime can give trouble when this material is dislodged in large masses. This release can temporarily increase the viscosity of the coolant, placing an increased load upon the pump motors and it may plug lines and pumps These obstructing masses should be removed as soon as they are detected. Additional factors can influence rancidity control. As confidence is gained in protecting working coolants, the engineer may wish to achieve even better coolant life by understanding these factors. General discussions of these factors have been published; 2,17,38,43 however, those interested in more detained treatments can study reports which deal with the effects of coolant tem- perature, 11,44 water hardness, 45,46 water quality. 17,47,48 urine, 17 metals, 38 dragout, 36 hydraulic fluids, 36,38 oil-water ratios, 49 differences in the sensitivities of different systems to preserv- atives, 50 and chelating agents. 30 Those interested in medical problems 51–53 or disposal problems 54,55 may wish to read these communications. Coolant control is not difficult to accomplish. Doing nothing more than determining the microbial content of a working coolant at periodic intervals and adding a preservative when the count reaches a certain level can produce a significant increase in coolant life. Where coolants have lasted a few weeks, it is possible to experience a doubling of coolant life. Where coolants have functioned properly for several months, a 60% improvement in coolant life is not unusual. Some users have already undertaken quality control of their fluids and two publications have appeared concerning their success in this area. 10,56 REFERENCES 1. Kane, E. L., A Chart for Recording and Analyzing Factors Influencing Coolant Life, ASLE Preprint No. 73AM-4C-2, American Society of Lubrication Engineers, Park Ridge, III., 1973. 2. Bennett, E. O., The biological testing of cutting fluids, Lubr. Eng., 30, 128, 1974. 3. Hill, E. C., Gibbon, O., and Davies, P., Biocides for use in oil emulsions, Tribology, 121, June 1976. 4. Hill, E. C., Some aspects of microbial degradation of aluminium rolling coolants, Proc. 3rd Int. Biodegrad. Symp., 3, 243, 1976. 5. Holdon, R. S., Microbial spoilage of engineering materials. VI. Improving monitoring and control, Tri- bology. 10, 273, 1977. 376 CRC Handbook of Lubrication Copyright © 1983 CRC Press LLC 6. Yanis, R. J. and Wolfe, G. F., Test procedures for the evaluation of culling fluids, Lubr. Eng., 164, April I960. 7. Hill, E. C., Microbiological examination of petroleum products, Tribology, 5, February 1969. 8. Rossmoore, H. W., Methylene blue reduction for rapid inplant detection of coolant breakdown, Int. Biodetn. Bull., 7, 147, 1971. 9. Rossmoore, H. W., Holtzman, G. H., and Kondek, L., Microbial ecology with a cutting edge, Proc. 3rd Int. Biodegrad. Symp., 3, 221, 1976. 10. McCoy, J. S., A practical approach to central system control, Lubr. Eng., 34, 180, 1978. 11. Kane, E. L. and Pfuhl, W., Preservation and preservatives in the aluminum hotrolling and beverage can processing industry, Lubr. Eng., 32, 249, 1976. 12. Bennett, E. O., The deterioration of metal cutting fluids, Prog. Ind. Microbiol., 13, 121, 1974. 13. Tant, C. O. and Bennett, E. O., The isolation of pathogenic bacteria from used emulsion oils, Appl. Microbiol., 4, 332, 1956. 14. Tant, C. O. and Bennett, E. O., The growth of aerobic bacteria in metal-cutting fluids, Appl. Microbiol., 6, 388, 1958. 15. Bennett. E. O., The role of sulfate-reducing bacteria in the deterioration of cutting emulsions, Lubr. Eng., 13, 215, 1957. 16. Kitzke, E. D. and McGray, R. G., The occurrence of moulds in modern industrial cutting fluids, paper presented at the I7th ASLE Meet., St. Louis. Preprint No. 62 AM 4B-3, 1962. 17. Bennett, E. O., The biology of metalworking fluids, Lubr. Eng., 28, 237, 1972. 18. Rossmoore, H. W. and Holtzman, G. H., Growth of fungi in cutting fluids, Dev. Ind. Microbiol., 15, 273, 1974. 19. Wort, M, D., Lloyd, G. I., and Schofield, J., Microbiological examination of six industrial soluble oil emulsion samples, Tribology, 35, 1976. 20. Guynes, G. J. and Bennett, E. O., Bacterial deterioration of emulsion oils. I. Relationship between aerohes and sulfate-reducing bacteria in deterioration, Appl. Microbiol., 7, 117, 1959. 21. Isenberg, D. L. and Bennett, E. O., Bacterial deterioration of emulsion oils. II. Nature of the relationship between aerobes and sulfale-reducing bacteria, Appl. Microbiol., 7, 121, 1959. 22. Vamos, E. and Csop, A., The microbiological corrosive action of metal machining oils, Corros. Week, 41, 1029, 1970. 23. Smith, T. F. H., Toxicological and microbiological aspects of cutting fluid preservatives, Lubr. Eng., 25, 313, 1969. 24. Paulus, W., Problems encountered with formaldehyde-releasing compounds used as preservatives in aqueous systems, especially lubricoolants — possible solutions to the problems, Proc. 3rd Int. Biodegrad. Symp., 3, 1075, 1976. 25. Pauli, O. and Franke, G., Behavior and degradation of technical preservatives in the biological purification of sewage, Biodeterioration of Materials, Vol. 2, Haisted Press, New York, 1972, 52. 26. Voets, J. P., Pipyn, P., Van Lancker, P., and Verstraete, W., Degradation of microbiocides under different environmental conditions, J. Appl. Bacteriol., 40, 67, 1976. 27. Rossmoore, H. W. and Williams, B. W., An evaluation of a laboratory and plant procedure for preservation of cutting fluids, Biodetn. Bull., 7, 55, 1971. 28. DeMare, J., Rossmoore, H. W., and Smith, T. H., Comparative study of triazine biocides, Dev. Ind. Microbiol., 13, 341, 1972. 29. Bennett, E. O., Formaldehyde preservatives for cutting fluids, Int. Biodetn. Bull., 9, 95, 1973. 30. Izzat, I. N. and Bennett, E. O., The Potentiation of the Antimicrobial Activities of Cutting Fluid Preserv- atives by EDTA, Preprint No. 78-AM-5C-1, American Society of Lubrication Engineers, Park Ridge, III., 1978, 1. 31. Pivnick, H. and Fabian, F. W., Methods for testing the germicidal value of chemical compounds for disinfecting soluble oil emulsions, Appl. Microbiol., 1, 204, 1953. 32. Kitzke, E. D. and McGray, R. J., Coolant microbiology: the role of industrial research, paper No. 59AM 3A-3, 14th ASLE Natl. Meet., Buffalo, 1959. 33. Brandeberry, L. J. and Myers, H. V., Test procedures for compounds used as preservatives in industrial coolants, Lubr. Eng., 16, 161, 1960. 34. Himmelfarb, P. and Scott, A., Simple circulating tank test for evaluation of germicides in cutting fluid emulsions, Appl. Microbiol., 16, 1437, 1968. 35. Rogers, M. R., Kaplan, A. M., and Baumont, E., A laboratory inplant analysis of a test procedure for biocides in metalworking fluids, Lubr. Eng., 31, 301, 1975. 36. Bennett, E. O., Effect of Dragout and Hydraulic Fluid Contamination on Rancidity Control in Cutting Fluids. Preprint No. 76-AM-18-1, American Society of Lubrication Engineers, Park Ridge, III., 1976, 1. 37. Smith, M. D. and West, C. H., How Plant Practices Affect Employee Health in the Presence of Metal- working Fluids. American Society of Lubrication Engineers, Park Ridge, III., August 1969, 321. Volume II 377 Copyright © 1983 CRC Press LLC 38. Bennett, E. O., Microbiological Aspects of Metalworking Fluids, Tech. Pap. No. MR73-826, American Society of Mechanical Engineers, New York, 1973, 1. 39. Rossmooore, H. W., Sceszny, P., and Rossmoore, L. A., Evaluation of Source of Bacterial Inoculum in Development of a Cutting Fluid Test Procedure, No. 76-AM-1B-2, American Society of Lubrication Engineers, Park Ridge, III., 1976, 1. 40. Rossmoore, H. W., De Mare, J., and Smith, T. H. F., Anti- and pro-microbial activity of hexahydro- 1,3,5-tris-2-hydroxyethyl-s-triazine in cutting fluid emulsions, in Biodeterioration of Materials, Vol. 2, Halsted Press, New York, 1972, 286. 41. Bennett, E. O., Factors involved in the preservation of metal cutting fluids, Dev. Ind. Microbiol., 3, 273, 1961. 42. Bauerle, R. H. and Bennett, E. O., The effects of 2,4-dinitrophenol an the oxidation of fatty acids by Pseudomonus aeruginsa, Ant. van Leeuwenhoek J., 26, 225, I960. 43. Hill, E. C., Biodeterioration of Metal Working Fluids and Its Significance, Publ. No. MR72-214, American Society of Mechanical Engineers, New York, 1972. 1. 44. Hill, E. C., The significance and control of microorganisms in rolling mill oils and emulsions, Met. Mater., 294, September 1967. 45. Feisal, E. V. and Bennett, E. O., The effect of water hardness on the growth of Pseudomonas aeruginosa in metal culling fluids, J. Appl. Bacterial., 24, 125, 1961. 46. Bennett, E. O., The Effect of Water Hardness on the Deterioration of Cutting Fluids, Tech. Pap. No. MR72-226, Society of Mechanical Engineers, New York, 1972, 1. 47. Humnicky, S., Pure water improves coolant mix, Tooling Prod., 48, February 1971. 48. Bennett, E. O., Water quality and coolant life, Lubr. Eng., 30, 549, 1974. 49. Carlson, V. and Bennett, E. O., The relationship between the oil-water ratio and the effectiveness of inhibitors in oil soluble emulsions, Lubr. Eng., 16, 572, I960. 50. Bennett, E. O., Adamson, C. E., and Feisal, V. E., Factors involved in the control of microbial deterioration. I. Variation in sensitivity of different strains of the same species, Appl. Microbiol., 7, 368, 1959. 51. Bennett, E. O. and Wheeler, H. O., Survival of bacteria in cutting oil, Appl. Microbiol., 2, 368, 1954. 52. Rossmoore, H. W. and Williams, B. W., Survival of coagulase-positive staphylococci in soluble cutting oils, Health Lab. Sci., 4, 160, 1967. 53. Holdom, R. S., Microbial spoilage of engineering materials. Are infected oil emulsions a health hazard to workers and to the public? Tribology, 9, 271, 1976. 54. Bennett, E. O., The disposal of metal cutting fluids, Lubr. Eng., 29, 300, 1973. 55. Bennett, E. O., The Disposal of Metal Cutting Fluids, Publ. No. 73AM-4C-EB, American Society of Lubrication Engineers, Park Ridge, III., 1973, 1 . 56. Vermooten, C. A. L., Microbiological destruction of soluble oil emulsion in steel plant hydraulic systems, paper read at South African Soc. Plant Pathol. Microbiol. Meet., 1975. 378 CRC Handbook of Lubrication Copyright © 1983 CRC Press LLC LUBRICANTAPPLICATION METHODS Edward J. Gesdorf INTRODUCTION Modern lubrication standards for industrial equipment in mass production industries such as automotive, steel, mining, rubber, etc. usually start with the following goals: safety of personnel, uninterrupted production, extended machinery life, and good housekeeping. A fifth item could easily be added — a reduction in operating costs. Since the days of low- cost labor and lubricants are gone, it now becomes extremely important to select the most efficient method of applying lubricants. TRADITIONALLUBRICANTAPPLICATION DEVICES Some of the older, simple lubricant application devices include: 1. Oil squirt can 2. Screw-type grease gun 3. Grease gun 4. Drop oiler 5. Vibrating pin bottle oiler 6. Thermal oiler 7. Wick-pad and waste-feed oilers 8. Splash-lubrication system 9. Ring, chain, and collar oilers 10. Mechanical positive-feed Design, selection, and maintenance of this equipment is covered in reference material. 1,2 During the early days of the industrial revolution the only devices available for applying oil or grease to a bearing were oil and grease cups as shown in Figure 1. To eliminate their feast or famine nature, automatic pressure feeding grease cups were introduced, as illustrated in Figure 2. In this device, the spring on top of the large piston exerts a constant pressure on the lubricant in the cup. This pressure forces the lubricant around the screw thread on the reservoir pin, which is closely fitted to the outlet bore. As grease is discharged to the bearing, the lowering compression of the spring is compensated by the screw thread of the resistance pin passing out of the discharge bore, lowering the resistance to flow. By this method a constant feed of grease is provided to the bearing. The constant pressure supplied by the spring, combined with a restricted orifice at the outlet, caused many greases to bleed or separate oil from the soap. The cup would then load up with a cake of hard soap preventing further delivery of lubricant. Special grease was therefore required to ensure proper operation of the device, whether the grease was suitable for the bearing or not. While many of these grease cups performed an outstanding job, they suffered limitations for universal application. During this period, mechanical force-feed lubricators (Figure 3) came into use. These devices were originally designed for engine room lubrication where they still serve better than any other type of lubricator. Today many forced-feed lubricator applications have been incorporated in centralized systems. This enables up to several hundred bearings to be served without the necessity of running a bundle of pipes or tubing from one central box. Volume II 379 379-393 4/10/06 4:51 PM Page 379 Copyright © 1983 CRC Press LLC in moving from right to left, changes the porting at its center section to permit a flow of pressure to the left end of the lower piston to move to the right, displacing the lubricant in the right end of the bore to a bearing. In following the foregoing sequence, a continuous cycling mechanism operates as long as there is flow from the pump. Progressive Reversing System Figure 7 illustrates a loop system which operates on the principle of reversible flow in Volume II383 FIGURE 4.Multiple tube system. 379-393 4/10/06 4:51 PM Page 383 Copyright © 1983 CRC Press LLC 384 CRC Handbook of Lubrication TABLE 1 COMPARISON OF SIX SYSTEM PRINCIPLES Features Adjustable measuring valves Measuring valves operate Measuring valve actuation Metering principle Measuring valve indicators Measuring valve piston sealing System will handle grease System will handle oil Can add or subtract lube points economically Economical monitoring — main supply lines Measuring valve monitoring Currently popular 379-393 4/10/06 4:51 PM Page 384 Copyright © 1983 CRC Press LLC the main supply line. The measuring valves are progressive and nonadjustable, with indication at the end of the loop. The main system elements consist of a reservoir, pump, four-way valve, main supply Volume II 385 FIGURE 6. Progressive system — nonreversing. FIGURE 5. Single-line system, spring-actuated valve. 379-393 4/10/06 4:51 PM Page 385 Copyright © 1983 CRC Press LLC effective on the top side of the pilot piston in the measuring valve, causing it to move downward. After a certain amount of travel, an angle port is opened permitting lubricant to flow into the main measuring cylinder, forcing the main piston downward. As the main piston moves downward, lubricant in the lower portion of the cylinder is forced through a second angle port and out the discharge port to a bearing. Pumping is continued until all measuring valves have operated. To recycle the system, the hand lever of the four-way valve is shifted 90° which relieves the pressure in line 1 back to the reservoir and ports the pump to line 2. As pressure is developed in line 2, the measuring valve operation sequence described in the foregoing is repeated but with the valve pistons moving in the opposite direction. Indicator stems attached to the main pistons of the measuring valves provide a means for periodic inspection of valve operation. Valve discharge adjustment is accomplished with two flat adjusting screws in the packing gland which control main piston travel. Orifice Oil System Figure 9 illustrates an orifice metering system for oil which operates on the principle of pressurizing a common main supply line rapidly and bleeding the pressure off through various-sized orifices. The metering orifices operate independently of each other and are nonadjustable. The main system elements consist of a reservoir, pump, main supply line, and orifice meter assemblies. The lubricator is of the spring discharge type and is operated by pushing the lever down which raises the piston and compresses a spring. By releasing the lever a fixed volume of oil is discharged into the supply line which is then dissipated through the orifice meters at the bearings. Orifice Oil Mist System Figure 10 illustrates an orifice metering system for oil mist. Oil is broken up into fine particles and dispersed in air for conveying through pipeline to the point of application. The main system elements are a filter and water separator, solenoid-operated air valve, air pressure regulator, misting head, oil reservoir, mist distribution manifold, and reclassifying fittings at the bearings. Volume II387 FIGURE 8.Dual line system. 379-393 4/10/06 4:51 PM Page 387 Copyright © 1983 CRC Press LLC [...]... 4/10/06 3 92 4:51 PM Page 3 92 CRC Handbook of Lubrication FIGURE 13 Typical gear spray system BULK GREASE HANDLING SYSTEMS Following broad acceptance of centralized systems, three important developments occurred in the lubrication field One was the introduction of multipurpose grease; the second was the acceptance of the standardized 181.436-kg (400-lb) container as a replacement for a variety of drum... 300—1160 1160 and above 65 65 25 0 25 0 and above in .2 cm2 8 6 4 1 .25 1.0 0.75 PUMPS The following system requirements governing pump size may also influence the choice of pump type Rate of flow — Some excess capacity must be provided as a safety margin to offset changes in system demand, a worn pump, wear in bearings, seals, etc Basic pump sizing is between 110 and 125 % of the equipment requirement for... Developments, Institute of Mechanical Engineers, London, 1980 43 4 Bloch, H.P., Application of pure oil mist lubrication Mech Eng., 103(5), 30, 1981 5 Faust, D.G., Standard Handbook of Lubrication Engineering, McGraw-Hill, New York, 1968, 25 Copyright © 1983 CRC Press LLC 395-411 4/10/06 4:54 PM Page 395 Volume II 395 CIRCULATING OIL SYSTEMS A J Twidale and D C J Williams INTRODUCTION Use of a circulating... height = length /2 Connections A sloping bottom of 1 in 30 with the pump suction at the high end and drain connections at the lowest point allows water and other impurities to be drained off A floating suction Copyright © 1983 CRC Press LLC 395-411 4/10/06 398 4:54 PM Page 398 CRC Handbook of Lubrication FIGURE 2 Typical reservoir layout between inlet and outlet, baffles enable the best use of the reservoir... plant safety and housekeeping, and most important — elimination of grease contamination REFERENCES 1 Clower, J I., Lubricants and Lubrication, 1st ed., McGraw-Hill, New York, 1939, chap 9 2 O’Connor, J J and Boyd, J., Standard Handbook of Lubrication Engineering, McGraw-Hill, New York, 1968, chap 25 3 Gulker, E and Huttenwerke, H., New oil mist lubrication concepts for higher efficiency and better environment,... foregoing section, only a comparison of the two is required (see Table 2) Air line lubricators as shown in Figure 11 provide a mixture of oil and air The mixture is usually generated by the Venturi principle and since the oil particles in the mixture are of a large size they can be conveyed only a short distance SYSTEM ACCESSORIES FOR CENTRALIZED SYSTEMS Accessories of one type of another — alarms, lights,... use of low-level alarms on lubricant reservoirs Lubricating systems then require only periodic inspection and reservoir filling SYSTEM PLANNING AND INSTALLATION Planning of a centralized lubrication system revolves around the question “How much lubricant does a bearing require per unit of time”? The basic premise for sleeve bearing lubrication by a centralized system is the need for replacing 1/3 of. .. pressure of 175,767 to 21 1,110 g/km2 (25 00 to 3000 psi) Grease under pressure is therefore instantly available to operate tote hoses, hose reels, fill centralized system reservoirs, operate area control panels, etc Several tangible and intangible benefits brought about by bulk grease handling systems including elimination of residual grease waste, drum cost and drum handling, improvement of plant safety... with reclassifier or condensing fittings at the lubrication points The reclassifier orifices cause the small oil particles in the dry mist to join and become heavier and wet, allowing the reclassifiers to discharge a wet spray, a wet mist, or oil droplets, all of which depends on the design or the reclassifier fittings While early applications of oil mist lubrication were limited to oils with viscosities... After a 24 -hr hydrostatic test, the painting should be completed Reservoir Heating Heaters should raise the oil from ambient to the specified operating temperature, normally 40°C, within 4 hr A further controlled increase in temperature will aid release of contaminants Permanent heating arrangements are usually electric or steam Steam heaters are normally in the form of a continuous coil of 3/4 in (20 mm) . Bacterial., 24 , 125 , 1961. 46. Bennett, E. O., The Effect of Water Hardness on the Deterioration of Cutting Fluids, Tech. Pap. No. MR 72- 226 , Society of Mechanical Engineers, New York, 19 72, 1. 47 Leeuwenhoek J., 26 , 22 5, I960. 43. Hill, E. C., Biodeterioration of Metal Working Fluids and Its Significance, Publ. No. MR 72- 214, American Society of Mechanical Engineers, New York, 19 72. 1. 44. Hill,. Louis. Preprint No. 62 AM 4B-3, 19 62. 17. Bennett, E. O., The biology of metalworking fluids, Lubr. Eng., 28 , 23 7, 19 72. 18. Rossmoore, H. W. and Holtzman, G. H., Growth of fungi in cutting fluids,