Filter system for removing and/or neutralizing undissolved oils, greases, and salts and/or metal abrasion debris on and in emulsions containing water

Abstract

A filter system for removing and/or neutralizing undissolved oils, greases, and salts on/in water-containing emulsions from, in particular, tanks and baths that are used to hold and store emulsions, which are used to cool and lubricate workpieces and tools during machining, comprising at least one emulsifier filter, a downstream suction/pressure pump, a unit for gas enrichment, an adhesion filter having an automatic deaerator, a downstream oil-collecting vessel, and a capillary filter, wherein these are combined as a unit, such that the oil/grease film and the emulsion can be mechanically, chemically, and biologically treated.

Claims

1. A filter system for removing and/or neutralizing undissolved oils, greases and salts in/on aqueous emulsions from tanks and baths, which are used for holding and storing emulsions, which are in turn used for cooling and lubricating workpieces and tools during machining, the filter system comprising: a tangential feed into an emulsifier filter; an injector for gas enrichment; an adhesion filter having an automatic ventilator; and an oil collecting vessel having a drain, wherein the filter system is configured to treat the emulsion containing insoluble oil/grease droplets mechanically, physically and biologically, such that an oil/grease layer is then discharged from the filter system.

2. The filter system according to claim 1, wherein the filter system has a skimmer for suction removal of the emulsion and the oil/grease layer from an emulsion bath/tank, wherein a skimmer suction connection is provided, optionally using an immersion pump.

3. The filter system according to claim 1, wherein the filter system has a capillary filter.

4. The filter system according to claim 2, wherein the skimmer is designed so that both the emulsion and the oil/grease layer enter the skimmer from an emulsion surface and can be sucked out of the emulsion bath/tank.

5. The filter system according to claim 1, wherein the emulsifier filter includes floating filter elements with a density of less than 1 kg/dm.sup.3.

6. The filter system according to claim 1, wherein at least one filter selected from a group consisting of the emulsifier filter, the adhesion filter and a capillary filter is formed from a plastic capable of diffusion.

7. The filter system according to claim 1, comprising filter elements made of polyamide or containing mainly polyamide.

8. The filter system according to claim 1, comprising spherical filter elements.

9. The filter system according to claim 1, comprising filter elements made of filter plates having a capillary action.

10. The filter system according to claim 1, further comprising filter elements including a plurality of plastic plates arranged side by side and combined to form a body, the plastic plates constructed of a plastic having a water uptake capacity of more than 1%.

11. The filter system according to claim 10, wherein the plastic plates are constructed of polyamide.

12. The filter system according to claim 10, wherein the body is spherical.

13. The filter system according to claim 12, wherein the filter element has a diameter of at least 25 mm.

14. The filter system according to claim 10, wherein the filter system is connected to the tank or the bath via an inlet and a drain.

15. The filter system according to claim 1, wherein the emulsifier filter includes floating filter elements comprising anaerobic bacteria settled on surfaces of the floating filter elements.

16. The filter system according to claim 15, further comprising a capillary filter and a bypass between an outlet of the capillary filter and an inlet of the emulsifier filter, wherein the bypass supplies gas/air to the anaerobic bacteria.

17. A method for removing and/or neutralizing undissolved oils, greases and salts in/on aqueous emulsions from tanks and baths in particular, which are used for holding and storing emulsions, which are in turn used for cooling and lubricating workpieces and tools during machining, the method comprising: removing an oil/grease film and parts of the emulsion from a tank or a bath using a skimmer; and filtering the oil/grease film and parts of the emulsion through at least one element including a plurality of plastic plates, the plurality of plastic plates arranged side by side and combined to form a body, the plastic plates constructed of a plastic having a water uptake capacity of more than 1%.

18. The method according to claim 17, wherein the method is carried out in a filter system comprising: a tangential feed into an emulsifier filter; an injector for gas enrichment; an adhesion filter having an automatic ventilator; and an oil collecting vessel having a drain, wherein the filter system is operative to treat the emulsion containing insoluble oil/grease droplets mechanically, physically and biologically, such that an oil/grease layer is then discharged from the filter system.

19. A method for removing metal abrasion debris from aqueous emulsions from tanks and baths, which are used for holding and storing emulsions, which are in turn used for cooling and lubricating workpieces and tools during machining, the method comprising: removing an oil/grease film and parts of the emulsion from a tank or a bath using a skimmer; and filtering the oil/grease film and parts of the emulsion through at least one element including a plurality of plastic plates, the plurality of plastic plates arranged side by side and combined to form a body, the plastic plates constructed of a plastic having a water uptake capacity of more than 1%.

Description

(1) The invention is explained in greater detail below and described on the basis of the exemplary embodiments depicted in the drawings and an exemplary application.

(2) FIG. 1 shows a schematic diagram of the filter system unit according to the invention, embodied as a flow chart.

(3) FIG. 2 shows a schematic diagram of the rotational circulation of the filter balls according to the invention in the emulsifier filter.

(4) FIG. 3 shows a schematic diagram of the collision of the filter balls according to the invention in the rotational circulation, which serves to create the oil/grease treatment in the emulsifier filter.

(5) FIG. 4 shows a cross-sectional diagram of the skimmer according to the invention with a connection from above.

(6) FIG. 5 shows a cross-sectional diagram of the skimmer according to the invention with a connection from beneath.

(7) FIG. 6 shows a three-dimensional diagram of the filter element according to the invention as filter balls.

(8) FIG. 7 shows a cross-sectional diagram of the skimmer according to the invention, having an integrated immersion pump, and

(9) FIG. 8 shows an automatic valve as a float valve.

(10) FIG. 9 shows a filter system for processing emulsions from several machining tools.

(11) FIGS. 10a-10e show the particle size distribution of the oil content in the emulsion during the use of a filter system according to the invention in a metal cutting and lathing machine.

(12) FIG. 11 shows a preferred embodiment of the adhesion filter or a filter system for removing metal abrasion debris.

(13) FIG. 12 shows a preferred embodiment of the ventilator and the oil collecting vessel.

(14) FIG. 1 shows schematically one embodiment of the filter system according to the invention as a whole.

(15) The system as a whole is preferably reserved as belonging to a metal cutting system and its supply bath or tanks in the emulsion. The inlet line and the drain line to and from the emulsion bath and/or tank belong to the emulsion to be cleaned.

(16) The main components of the filter system include, first, the suction removal of the emulsion 5 in conjunction with the proportional oil/grease film 6 by means of a skimmer 7 as a skimmer suction connection from above 7a or, in the case of multiple machines, with the support of an immersion pump in the skimmer and a downstream collecting line or as a skimmer suction connection from beneath 7b, depending on the type and embodiment of the emulsion bath/tank 4, the emulsifier filter 1, the adhesion filter 2 and the capillary filter 3. The functioning and design of the individual components will be described in succession.

(17) The emulsion 5 containing water to be cleaned, which is used for cooling and lubricating workpieces and tools during machining of workpieces, is cleaned by using a skimmer 7 and the skimmer drain 11, as described in the more detailed design on the basis of FIG. 4 and FIG. 5 and then initiated by means of a pipeline or a tube line and then fed as a tangential feed 12 into the emulsifier filter 1 for workup.

(18) At the same time, the skimmer 7 removes the emulsion 5 and the oil/grease film 6 from the emulsion surface in the emulsion bath/tank 4 by suction. The floating oil/grease film 6 is sucked over the edge of the float 10. The float 10 is carried by gases 30a as a gas cushion at the surface of the emulsion while it is held in position by a stationary cylinder protruding into the float 10. There is a gap between the cylinder and the float, to which suction is applied in its width for a suction power of 1-100%, preferably 90% of the emulsion feed from beneath the surface of the emulsion as a skimmer feed 9 at the bottom. This effect ensures that the emulsion oil/grease film component 6 is less than 1/1, preferably less than 1/20 of the quantity of liquid removed by suction.

(19) The effective skimmer suction height 7c depends on the delivery performance of the emulsion 5 and on the density of the oil/grease film 6 and the downward flow in the skimmer 7. At a downward flow of >0.1 cm/sec but <20 cm/sec, preferably 1 cm/sec, the effective skimmer suction height 7c is >1 cm and <100 cm, preferably 10 cm.

(20) The stationary cylinder of the skimmer 7 is provided with a closed bottom. In the embodiment in FIG. 4 with suction at the top, to prevent the development of an air plug, the skimmer drain 11 is positioned with a deflecting flange 11a, preferably at the center of the skimmer 7, and is fixedly secured in the tub by means of spacers. In the embodiment in FIG. 5 with downward suction, the skimmer drain 11 is preferably positioned at the center of the skimmer 7 with a deflecting cap 11b to prevent the development of air plugs and is fixedly secured in the tub by means of spacers.

(21) The emulsion 5 loaded with oil/grease film 6 is sucked out of the emulsion bath/tank 4 by means of the skimmer 7 and a pipeline-hose connection into the emulsifier filter 1. A vacuum develops in the emulsifier filter 1 and in the emulsion 5 when the solution is pumped out by means of a suction/pressure pump 27. This is also used at the same time for degassing the emulsion 5 to then remove the excess gas from the emulsifier filter 1 by means of automatic level control 17.

(22) The mechanical level control 15 is a tubular cylinder situated at the axial center, leading vertically downward into the emulsifier filter 1, starting beneath the container cover, so that the rotational flow 20 moves around the axial center, which does not result in any flow breakaway at the axial center and an oil/grease film 6 is built up there.

(23) To ensure the level surface of the filter elements 18 of <1 kg/dm.sup.3 floating in the rotational flow 20, the excess gases are removed from the gas space of the emulsifier filter 1 beneath the cover from the top into the centrally arranged tubular cylinder, which is held at a distance and is gas permeable. A second smaller tubular cylinder, which is fastened in the cover and sealed, protrudes to the surface of the level surface of the emulsion, so that the excess gases 30a flow from beneath into the smaller tubular cylinder with the expansion of the gas space 16 until the pipe is closed off by the emulsion 5 due to the rise in level.

(24) If the excess gases 30a are removed from the emulsifier filter 1 and from the gas space 20, then an emulsion 5, which is free of an oil/grease film 6, flows out of the filter elements 24 of >1 kg/dm.sup.3 from underneath and into the tubular cylinder, which is then detected in the automatic level control and used for switching.

(25) Filter elements 18 of <1 kg/dm.sup.3, preferably in a spherical shape 45, float on the surface of the emulsion space 19 in the emulsifier filter 1 and are then induced to rotational flow 20 around the mechanical level control 15 due to the tangential feed 12. In doing so, the filter elements 18 of <1 kg/dm.sup.3 move with the oil/grease film 6, which is forming as shown in FIG. 2. In rotational flow 20, this leads to a filter element collision 21, which results in the formation of small oil/grease droplets, as shown in FIG. 3, which are then entrained in the downward flow with the emulsion 5.

(26) The emulsion 5 then flows around the filter elements 24 of >1 kg/dm.sup.3 made of a preferred plastic (polyamide) that is capable of diffusion, wherein up to 10% liquids, salts and gases 30a diffuse into the filter element 38 and thus ensure a constant osmotic exchange between the emulsion and the filter element 38. Anaerobic bacteria settle preferentially on the surface of the filter element 38 and are constantly supplied with energy from the osmotic exchange and thereby degrade a portion of the excess salts.

(27) The filter element 38 is preferably embodied in spherical shape 45 because the flow around a bed of balls ensures an optimum distribution of resistance. The osmotic pressure, which occurs due to the preferred material (polyamide), can even flow through a bacterial colony because great pressure differences can occur. This ensures that the interspaces between the filter ball plates do not become clogged due to this constant osmotic pressure adjustment.

(28) The emulsion flows through the sieve plate 25 out of the emulsifier filter 1 and is pumped by the suction pressure pump 27 into the adhesion filter 2. The emulsion 5 is preferably supplied with the gas/air supply 30 in the injector 28. In doing so, a foamy emulsion 5 is formed in the gas emulsion distribution space 36. The foamy emulsion 5 is then distributed preferably in spherical form 45 on the underlying filter elements 38 by means of trickle elements 37 and thus the emulsion 5 becomes enriched with gases 30a and oxygen. The phases are separated here due to the difference in the adhesion effect 38a of the emulsion 5 and of the oils/greases so that the gas bubbles are formed from the oils/greases and then coalesce on the polyamide balls drop due to the force of gravity through the sieve plate 25 and then onto the level surface 41a. Due to the difference in density between the emulsion 5 (approximately 0.98 kg/dm.sup.3) and the oils/greases (approximately 0.85 kg/dm.sup.3), the lighter oil/grease gas bubbles float as an oil/grease form 41b beneath the sieve plate 25 on the level surface 41a of the emulsion 5.

(29) The excess gas 30a and the oil/grease foam 41b are separated from the emulsion 5 beneath the sieve plate 25, so that the enriched emulsion 5 leaves the container at the bottom of the adhesion filter 2. The excess spent gas 30a flows with the oil grease foam 41b into the automatic ventilator 39 by means of the oil/grease/exhaust air connection 40a. In overflow of the gases 30a out of the adhesion filter 2 into the automatic ventilator 39, the oil/grease foam 41b collecting on the level surface is separated due to the rupturing of the bubbles so that the excess gases 30a are removed from the automatic ventilator 39, while an oil/grease layer 6a is formed and then flows over the oil separation connecting line 39c into the oil collecting vessel 39d. Due to the difference in density between the emulsion 5 and the oil/grease, the result is an under-/overflow so that the heavier emulsion 5 flows back out of the oil collecting vessel 39d into the automatic ventilator 39 on influx of the light oils/greases and then they leave the system through the level adjusting device 41. The oil/grease enriched with gases 30a is separated in the head space of the oil collecting vessel 39d, so that the gas excess is removed through the ventilation 39e. The oil/grease layer 6a, which is dammed up at the bottom, is measured by means of a suitable measurement technique (e.g., detector 39a with an alternating electromagnetic field for differentiation of the dielectric properties). Thus the oils/greases can be differentiated from the emulsion 5, so that either manual or automatic discharge of the oils/greases is made possible.

(30) The gas-enriched emulsion 5 leaves the container at the bottom of the adhesion filter 2 and then flows without gas bubbles from beneath into the capillary filter 3. The same filter elements 38 that are capable of diffusion, like those already described for the first two filters, are used in the container for the capillary filter 3. The enriched emulsion 5 here flows opposite the force of gravity over the filter elements 38, so that there can be capillary retention of the remaining oils/greases between the cavities in the filter plates. The cleaned emulsion 5 then flows in the head space of the capillary filter 3 out of that space as a return flow 44, so that it is retained in the emulsion bath/tank 4 by means of pipe or hose connections. Then a transverse flow develops in the emulsion bath/tank 4, so that the emulsion 5 is again used for cooling and lubricating the workpiece and the tool.

(31) In case of need, the cleaning of the emulsion 5 from the emulsion bath/tank 4 can be interrupted. Then the emulsion flow can be short-circuited between the outlet of the capillary filter 3 and the inlet of the emulsifier filter 1 in the bypass 46. Thus, an adjusted gas/air supply 30 can be ensured for the bacteria by means of the flow regulator 31.

(32) The emulsion 5 flows opposite the force of gravity from the container bottom upward in the head space of the capillary filter 3, while the buffer gases 30a from the emulsion 5 are depressurized because the pressure resistance in the capillary filter 3 is lower than that in the adhesion filter 2. This depressurization of the gas can be determined by means of an oxygen sensor SS because its position indicates the saturation limit of the liquid, i.e., of the emulsion 5. For example, fresh water can buffer approximately 9.1 mg/L of oxygen at 20 C. and a standard pressure of 1013 mbar, so this is 100% saturation. At an excess pressure of approximately 100 mbar (1113 mbar), this would then be approximately 10 mg/L, and consequently 110% saturation. This pressure is reduced during the upward flow in the capillary filter 3 because the static liquid column decreases toward the top in the capillary filter 5. Due to the pressure reduction, the buffered gases 30a are decompressed and thereby produce small gas bubbles at their surface when then pick up the residual oils and greases not retained in the adhesion filter 2 and then in the automatic ventilator 39 and in the oil collecting vessel 39d. A conductivity probe, which is also installed in the head space of the capillary filter, measures the salt content of the emulsion 5. This value is 0 S/cm in the case of distilled water, because, consequently, no salts are present. This value is approximately 400-700 S/cm in domestic tapwater. This value can also be much higher in an emulsion because it can also be far greater than 1000 S/cm due to the evaporation of water from the emulsion and due to the entrainment of dirt during machining. A conductivity probe functions according to the resistance principle, in which an electric voltage is applied between two stainless steel electrodes, for example, so that a few millivolts are measured on the positive electrode by means of liquid resistance of the emulsion as a function of the temperature on the second negative electrode. It has been found here that an almost stable value is displayed in liquids without an oil/grease film 6. If gas bubbles loaded with oil or grease flow over the electrodes, the contact between the liquid and the electrode is temporarily reduced and thus the measured and displayed conductivity value is also reduced due to the adhering oils and greases. This may result in fluctuations of several 100 S/cm or even several 1000 S/cm in the measured values. These fluctuations stabilize the lower the oil/grease foam in the emulsion 5. This state of affairs can therefore be used an indicator and as a manipulated variable and control variable for a cleaned emulsion 5 and can therefore be used for controlling the pressure resistance, the emulsion flow and gas enrichment.

(33) FIG. 7 shows an exemplary embodiment in which an immersion pump 47 is used in the skimmer 7 to pump out the oil/grease film. FIG. 8 shows a feed regulator in the form of an automatic float valve 48 in the emulsion for regulating the amount of cleaned recycled material, so that a certain filling level is maintained in the return flow of the filter system to the emulsion bath/tank 4.

(34) As shown in FIG. 9, the filter system may also be used for processing emulsions from a plurality of processing machines. The emulsions from the individual emulsion baths/tanks 4 are preferably supplied by means of immersion pumps 47 to a collecting forward line SV and from there to the emulsifier filter 1. The return flow passes through a collecting return line SR, from which individual lines LR lead via the float valves 48 into the individual emulsion baths/tanks 4 of the respective machine.

(35) FIG. 11 shows a preferred embodiment of the adhesion filter 2 or a filter system for removing metal abrasion debris. The emulsion 5 loaded with bedways oil is enriched with air/gas 30a and then flows in the feed into the head space of the adhesion filter 2. By means of a trickle element 37, the mixture is then distributed to the filter elements 38, so that there is friction on the filter elements 38, which thereby develop a positive charge. The negatively charged debris (e.g., metal abrasion debris) in the emulsion 5 adheres to the surface of the polyamide filter balls 38. At the same time, a wedge liquid 49 is formed preferably from the insoluble bedways oils, which then flow downward with the force of gravity as a flowing adhesive liquid. With an increase in the oil/grease layer on the filter elements 38, oil droplets 51 are then formed on the underside of the sieve plate 50 and then drop onto the level surface 41a where they form the oil/grease layer. This oil/grease layer floating on the emulsion surface is then driven out of the adhesion filter 2 by means of a gas excess through a nozzle 53, for example, a borehole of approximately 7 mm. The oil/grease foam 41a is thereby removed in the oil/grease foam/exhaust air connection 40a. The level surface moves up and down in the level of the nozzle 53, for example, by approximately 7-8 mm, because the air excess displaces the emulsion 5 downward, so that the gases can flow out in displacement of the nozzle cross-sectional area and thereby also remove the carpet of oil. Downstream from the nozzle 5, the nozzle jet is depressurized to a larger diameter than the nozzle, so that the gases can then be separated from the insoluble oils.

(36) It has surprisingly been found that metal abrasion debris is deposited as adhering particles 52 on the filter element 38 due to frictional charging. Therefore, such an adhesion filter 2 can also be used for removing metal abrasion debris without necessarily having to perform a separation, in particular a thorough separation of the oil/grease from the emulsion and without any additional filters, for example, an emulsifier filter and/or a capillary filter being connected upstream or downstream. The adhesion filter 2 by itself is instead suitable as a filter system for removing metal abrasion.

(37) FIG. 12 shows a preferred embodiment of the ventilator and of the oil collecting vessel. By means of mechanical float valves (which are also possible, however, with electronic level detection and automatic valves), the gas is separated via the head space of the ventilator 39 when there is a gas excess. The float, which opens and closes the outlet valve, operates here through the buoyancy force, which it maintains due to the rise or fall of the level. The level moves up and down by only a few mm to cm. an oil/grease layer develops at the surface of the level due to the lighter insoluble bedways oil and spreads downward with an increase in the amount of bedways oil and thereby displaces the emulsion. Beneath the level surface of the float, the oil/grease layer, becoming thicker and thicker, flows over the oil drain connecting line and into the oil collecting vessel 39d. Since the oil collecting vessel 39d releases the gas excess in the head space by means of automatic mechanical ventilation, the oil collecting vessel is filled with emulsion at the start of operation. The emulsion is then displaced due to the influx of the lighter bedways oil downward into the double jacket 55 of the automatic ventilator 39 and then flows out of the level adjusting device 41 into the capillary filter 3. Since the gas-oil discharge from the adhesion filter 2 through the nozzle 53 into the exhaust air connection 40a to the automatic ventilator 39 is pulsating, so that the flow to the float 57 is prevented by means of the double jacket 55, so that the excess gases in the double jacket 55 are separated from the bedways oil and then flow through adjusting boreholes 56 into the float head space. This prevents any problematical up-and-down movement of the float 57, so that the level adjustment for the float 57 is completed from beneath by means of a clean emulsion.

(38) The oil collecting vessel 39d with the ventilation 39e has a float ball 54, which prevents a return flow of the oil/grease film 6, at a low level of the emulsion 5 in the oil collecting vessel 39d because it then sinks to the bottom and closes the inlet (broken-line ball in FIG. 12).

EXAMPLE: USE OF A FILTER SYSTEM ACCORDING TO THE INVENTION IN A METAL CUTTING AND LATHING MACHINE

(39) A filter system according to the invention was connected to a metal cutting and lathing machine of the Tatung-Okuma ES-L8 II-M model (made in Taiwan, serial no. ME063). This machine has a high consumption of bed track lubricating oil (bedways oil) of up to approximately 4 L per week. The filter system was designed as shown in the figures.

(40) Design of the Skimmer:

(41) The low filling level (approximately 70-120 mm) of emulsion in the baths beneath the metal cutting machines made it difficult to suck the emulsion out without air by means of the skimmer because the skimmer design consists of a stationary lower inside cylinder and an outside cylinder inverted over the former and floating there. The inside cylinder has an outside diameter of 100 mm, for example, and the floating outside cylinder has an inside diameter that is approximately 1-3 mm larger, so that the floating outside cylinder is guided and positioned on the stationary inside cylinder. The buoyancy of the outside cylinder is then ensured by means of air/gas chambers in the head region. This air buoyancy chamber is converted into the interior of the cylinder by a type of double folding (290). Since this air chamber at the same time provides internal flow deflection, the internal deflecting cylinder is longer than required for buoyancy by the air chamber because of the flow pattern, which is directed downward. In order to obtain only as much buoyancy as needed to keep the float at the surface of the emulsion, the excess air gases are diverted by way of level adjusting boreholes that are somewhat larger than those for pure water because they more easily become clogged due to the adhering deposits of the bedways oils and therefore they retain more gas, which then results in greater buoyancy and an inferior surface suction (water approximately 3-5 mm DN, now 7-8 mm DN). A sufficient amount of emulsion should always be resupplied to adjust a change in the height level of approximately 20-40 mm in the emulsion, which occurs due to evaporation and losses during machining. This can easily result in the filling level moving above the guided upper limit of the outer float cylinder, when topping off the emulsion, and moving out of the guided zone of the internal fixed cylinder. In order for the float not to then drift out of position, preferably four round vertical rods, for example, from the internal radius of 1-2 mm distance from the floating cylinder, prevent it from losing its position.

(42) Metal Shavings:

(43) Floating metal shavings are also pulled in by suction removal from the emulsion surface in the bath by means of a skimmer. Some of these shavings were several centimeters long and were often rolled up into a ring shape, which is associated with machining of the workpiece. Floating of the much larger mass of the shavings by a factor of 1 to 8 in the case of steel, for example, is promoted by the surface adhesion of the lighter bedways oils on the shavings, by the oil film on the emulsion surface, which at the same time results in a higher surface tension of the emulsion surface. These shavings can lead to blockage of the skimmer and the filter system. To prevent blockage of the filter system, a preferred prefilter was connected downstream from the skimmer. During the course of operation of the filter, the surface was freed of the floating bedways oils by filtering out the bedways oils by means of the emulsion filter system. There was thus a great reduction in surface tension and therefore, to a lesser extent, also a reduction in the floating of shavings and suction into the skimmer.

(44) Consumption of Emulsion:

(45) After only a few days of operation with the filter system according to the invention, a reduction in emulsion consumption due to adhesion losses on the shavings was detected. This is probably associated with saturation of the air gases in the emulsion, which occurs due to the treatment in the emulsion filter system, which then leads to a better drip behavior. Due to the additional removal of unemulsifiable bedways oils, the emulsion consumption is reduced by approximately 60% within a few weeks. The oil adhesions in the interior of the machine have then been reduced to such a great extent that the inspection window for the machine operator is free of oil haze.

(46) Flow Pattern in the Filter System:

(47) The velocity of flow in the filter stages depends on the burden due to the insoluble bedways oils, which are lighter in density (890 g/cm.sup.3) than the emulsion (<1 approximately 970 g/cm.sup.3). If the runoff rate in the emulsifier filter is too low, the oils will float and form a carpet of oil in the rotating inlet flow, becoming thicker and thicker over time and spreading upward and downward. Since the carpet of oil floats on the surface of the emulsion, it protrudes out of the rotating surface and binds the lighter filter balls floating in the emulsion, so that they no longer rotate about their central axis. Due to the vacuum in the filter, small gas bubbles may form in degassing the emulsion and then accumulate in the carpet of oil and are forced as an oil foam into the float switch and therefore into the degassing space. This may result in entrainment of foam into the exhaust air pump, which can lead to problems and damage the pump. An oil foam may be formed in a downward flow of 18 mm/sec. An optimum without formation of an oil foam occurred with a downward flow of 22 mm/sec. Those skilled in the art can readily select a suitable downward flow and adjust it.

(48) Filter Elements:

(49) Filter balls with a diameter of 12 mm were used in the emulsifier filter. This results in an occasionally turbulent mixing of the emulsion in the downward flow, so that the soluble oils in combination with the emulsifiers are re-emulsified, so that the droplet sizes of the dissolved oils are reduced in size and then result in an improved binding of water, which then leads to a greater cooling power. To some extent, the entrained superfine abrasion debris, in particular metal particles, are separated from the bedways oils in this turbulence.

(50) In the bottom drain downstream from the emulsifier filter, the circulating pump conveys the emulsion through the injector, so that atmospheric gas is mixed with the emulsion, which then flows as a gas-saturated emulsion into the head space of the adhesion filter. The emulsion stream was then distributed uniformly among the filter balls having a diameter of 33 mm by means of a nozzle plate with 24 holes. With this size, the balls had a greater air space in their packing density, so that turbulent mixing did not occur. The bedways oil adhered to and between the balls and then formed droplets in a slow gravitational downward flow, and these droplets then fell beneath the sieve plate onto the emulsion surface and were discharged from the adhesion filter via a discharge nozzle bore. The functioning of the separation of the insoluble bedways oils operates in this way, without being bound to the theory, according to the principle of mass concentration between the contact points of the balls. The filter balls are made of polyamide and are capable of diffusion and can absorb approximately 2.5-3.5% moisture. The bedways oils have a higher adhesion force than the emulsion and therefore wet the surface of the filter balls. The wedge of liquid, which is formed symmetrically in the space that is free of force fields, is deformed due to the downward separating force and is thereby forced downward. Finally, a droplet is formed from the wedge liquid and the adhesive liquid flowing after it, then the droplet separates and leaves behind a residual wedge of a smaller size.

(51) Emulsion Buildup in Consideration of the Oil Droplet Size:

(52) Cooling lubricants are used during machining workpieces for cooling (water), lubricating (oil) and for removal of metal abrasion debris. The wear on machines and tools should be reduced and the heat (up to 1000 C.) should also be reduced. Machining at high cutting speeds and with a high heat production requires primarily a cooling effect. The best results can be achieved here by aqueous cooling lubricant emulsions or solutions. Additives are added to cooling lubricant concentrates to form a stable emulsion with surface-active substances (emulsifiers), which permit a distribution of the oil droplets by lowering the interfacial tension between the oil phase and the aqueous phase.

(53) The droplet size depends on the shearing and on the purity of the emulsion. Measurements have shown that when larger droplets of bedways oil are separated, the fineness of the emulsion to be emulsified is improved. This takes place without a reduction in the emulsion concentration. It has been found instead that the concentration to be measured increases because more droplets and finer droplets cause the emulsion to increase. Smaller droplets mean less oil is used for the same surface wetting and thus higher binding of water, which then also results in a better cooling performance.

(54) The emulsions were analyzed to determine their particle size and distribution by using a QUIXEL device for particle size analysis from Sympatec [System-Partikel-Technik], D-38678 Clausthal-Zellerfeld. This device is a wet dispersion system, which is suitable for particle size analysis in all types of suspensions and emulsions in the size range from 0.1 m to 3.5 mm. The droplet size distribution can be determined by means of laser diffraction. FIGS. 10a-10e show the results.

(55) When starting operation of the filter system, the droplets, i.e., particles, are determined and reported in three different sizes and in the percentage ratio. As shown in FIG. 10a, Q1=19.55% of the droplets (particles)<0.76 m, Q2=59.60%<1.71 m and Q3=79.05%<4.70 m. The average particle size VMD was 2.49 m. The surface wetting was 4.43 m.sup.2/cm.sup.3.

(56) Using an electron microscope, the size and distribution of the droplets were investigated. This revealed that some larger droplets had inclusions consisting of very small metallic abrasion debris enclosed in insoluble bedways oils. The fact that no larger agglomerates of metal abrasion debris particles were formed can be explained by the charge carried by these particles, making van der Waals forces ineffective.

(57) After one week of filter operation, the droplets had become smaller with regard to particle size and the surface coverage had increased by 9.5%, as shown in FIG. 10b.

(58) After three weeks of filter operation, the droplets had become even smaller with regard to particle size, and the surface coverage had increased again by 6.4%, as shown in FIG. 10c.

(59) After a total of six weeks of filter operation, as shown in FIG. 10d, the droplets had become even smaller with regard to particle size and the surface coverage had risen to 5.92 m.sup.2/cm.sup.3, which means a further increase by 14.7%.

(60) After several months of operation of the emulsion filter system, approximately 50% to 60% of the bedways oils added had been removed by the filter system. The purity and the droplet size, measured as particle size, were again improved, as shown by FIG. 10e. Due to the removal of the large droplets, the quantity of metal abrasion debris had decreased, on the one hand, while the emulsion fineness had increased, on the other hand. The oil content measured by means of refractometry did not show a negative influence. A further increase to 7.38 m.sup.2/cm.sup.3 has shown that the quality of the emulsion had increased and its cooling property was greatly improved. By comparing the quality at the start of filter operation with that at the last measurement, it is found that the surface coverage has increased by 67%.

(61) Metal Abrasion Debris:

(62) Electron micrographs showed metal abrasion debris, enclosed in bedways oil. The metal abrasion debris has therefore undergone a density adjustment, so that the combination with the bedways oil has a density similar to that of the dissolved oil emulsion and therefore the metal abrasion debris particles remain in suspension. This can lead to problems because the cooling water pump sucks in the metal abrasion debris along with the emulsion and then sprays it onto the workpiece and the tool, so that some of the abrasion particles become trapped in the blade clearance and therefore can result in a shortened lifetime of the tool blade.

(63) In investigating the polyamide filter balls, deposits of metal abrasion debris were found in the course of filtration in particular in the adhesion filter, increasing progressively with longer operating times. Without being restricted by a theory, these deposits are probably caused by electrostatic forces, since the polyamide balls become charged by the flow due to frictional forces, so that all the negatively charged abrasion debris will adhere to the balls like metal bonding.

(64) Due to the use of the filter system according to the invention, the proportion of metal abrasion debris has decreased in particular also due to deposition on the filter elements and removal of the large droplets, so that the problems associated with metal abrasion debris are definitely minimized. Eliminating the metal abrasion debris increases in particular the cutting capability and thus also results in a longer cutting capability. In the present experiment, the machine operator found an improvement by approximately 20-30%.

(65) Nitrite Burden in the Emulsion:

(66) The emulsion is loaded with the resulting nitrite due to the thermal stress on the bedways oils on the surface of the metal shavings at temperatures up to 1000 C. The usual weekly increase in the nitrite content of approximately 0.5 mg/liter was reduced by removing the bedways oils. This is associated with the elimination of the bedways oils, which then no longer burn up on the hot shavings.

(67) Bacterial Influence as a Function of pH:

(68) Studies have shown that there were no negative effects on the biological bacterial culture due to the filter system in the investigation phase. It was found that the stable pH was between 9 and 10 and the high conductivity value of >5000 S/cm has a limiting effect on a bacterial population. The concentration of bacteria in the cooling lubricant emulsion was approximately 2300 CFU/mL on the average over the sampling time, with fluctuations between 576 and 4933 CFU/mL. These concentrations can basically be assessed as low. The differences in concentrations are within the normal range of fluctuation.

(69) Since the removal of bedways oil was accomplished by means of intake air in the filter system, a preferred sterile air filter was additionally installed upstream from the air compressor. Since most bacteria in the ambient air are in the size range of >0.3 m, a sterile air filter with a pore size of <0.2 m ensures that the microorganisms are retained from the air. However, such a filter is not absolutely necessary due to the reduction in the quantity of bacteria.

(70) After starting operation of the filter system, an unpleasant odor could no longer be perceived after two days, which can be attributed in part to the degassing in the first filter and also to the oxygen saturation in the adhesion filter.

(71) In summary, the following advantages can be achieved by using the filter system according to the invention: The cooling lubricant (KSS) has a lighter color and a better purity accordingly. There are no foul odors. The cooling lubricant has a more fluid consistency. The amount of metal abrasion debris is greatly reduced. The adhering oil-metal abrasion deposits are greatly reduced. Less oil must be added to the cooling lubricant due to the smaller oil droplets. A definite decline in the amount of insoluble oils can be achieved. The salt content can be greatly reduced, which in turn leads to a reduction in foaming and in the abrasive particles that are precipitated. Foaming is reduced or even prevented. Only minor residues of cooling lubricant are deposited on the workpiece. The emulsion runs off the workpiece better in blow down. The pH remains stable or even increases slightly, so that bacterial growth is minimized. The cooling lubricant has a higher oxygen content, so that the cooling performance is improved. The formation of nitrite is reduced or prevented. There is little or no negative effect on the quality of the cooling lubricant at the lifetime of the machine. On the whole, the health burden due to operation of the machine is reduced in particular due to a lower burden of bacteria, fungi and nitrite.

LIST OF REFERENCE NUMERALS

(72) 1 emulsifier filter 2 adhesion filter 3 capillary filter 4 emulsion bath/tank 5 emulsion 6 oil/grease film 6a oil/grease layer 7 skimmer 7a skimmer suction connection from above 7b skimmer suction connection from beneath 7c effective skimmer suction height 8 skimmer inlet above 9 skimmer inlet beneath 10 float 11 skimmer drain 11a deflecting flange 11b deflecting cap 11c intake 12 tangential feed 13 rinse valve 14 rinsing liquid inlet 15 mechanical level control 16 gas space 17 automatic level control 18 filter elements <1 kg/dm.sup.3 19 emulsion space 20 rotational flow 21 filter element collision 22 oil/grease droplets 23 emulsion formation 24 filter elements >1 kg/dm.sup.3 25 sieve plate 26 drain emulsifier filter 27 suction pressure pump 28 injector 29 inspection window 30 gas/air supply 30a gases 31 flow regulator 32 return flow preventer 33 inlet adhesion filter 34 pressure monitoring 35 ventilation 36 gas emulsion distributor space 37 trickle element 38 filter elements 38a adhesion effect 38b capillary effect 39 automatic ventilator 39a detector (oil/water/emulsion) 39b drain (oil water/emulsion) 39c oil separation connecting line 39d oil collecting vessel 39e ventilation 40 exhaust air 40a oil/grease foam/exhaust air connection 41 level adjustment 41a level surface (oil/water/emulsion) 41b oil/grease foam 42 inlet capillary filter 43 temperature monitoring 44 return flow 45 spherical shape 46 bypass 47 immersion pump 48 automatic float valve 49 wedge liquid 50 sieve plate 51 oil droplets 52 particle adhesion 53 nozzle 54 floating ball 55 double jacket 56 adjusting borehole 57 float LS conductivity probe (measured value in pS/cm) SS oxygen probe (measured value in % saturation of the emulsion as a function of temperature) SV collecting forward line SR collecting return line