Abstract:
A Filter for the removal of water from oil, the filter includes a distillation element having an inlet pipe that in one end is to be fluidly connectable to a reservoir of oil to be filtered, and in the other end being fluidly connected to a distillation head, said distillation head including a plurality of compressing tubes for injecting under pressure said oil into an evaporation chamber, whereby eventual water within the oil droplet evaporates from said decompressed oil, the filter further including a tubular core with a plurality of apertures and a hollow interior, said core having an open end for fluid communication with the hollow interior, a length of yarn wound around an outer surface of the core, wherein the filter further includes a device for blowing air or an inert gas into the evaporation chamber for removal of the water vapor during use of the filter. A method of manufacturing such a filter, as well as a method of removing water of is also disclosed. The water removal unit is part of a modular system, which makes the whole filter unit scalable within fixed steps. When water removing block with attached start block and end block, are stacked upon each other, and connected to filter unit, it becomes scalable complete cleaning equipment. Pump and motor must be adapted to each configuration.

Description:
[0001]    The present invention pertains to a method and apparatus for removing water from oil. The present invention furthermore pertains to a method and apparatus for removing water from oil in combination with a tubular filter for filtering solid particles from said oil and a method of manufacturing said filter and a method of filtering oil. 
       INVENTION BACKGROUND 
       [0002]    The technical industries have problems with water contaminations in oils for lubrication, different power transmissions or transformers (hydraulics, gears, valves, etc.), wherein even small quantities of water severely impair the properties of said oils. Such contaminated lubricating oil used in internal combustion engines and other equipment is a principal cause of excessive wear and deterioration of engine parts and related equipment. At present, most internal combustion engines employ only a conventional mechanical filter for extracting materials such as dirt, carbon, soot, metal particles and other similar foreign material from lubricating oil. Liquid contaminants such as condensates, water and fuel, are often emulsified in the lubricating oil and cannot be separated by a conventional filter. It is therefore necessary for the lubricating oil of internal combustion engines using such mechanical filters to be changed at frequent intervals in order to minimize engine damage by contaminants entrained therein. 
         [0003]    In recent years, the increasing worldwide price of oil has made it imperative to develop ways of reconditioning oil, e.g. lubricating oil, so that it may be used and reused for a longer time than hitherto. In this way, only small amounts of additional lubricating oil are required by engine usage. 
         [0004]    The problem of liquid contaminants has been recognized, and some efforts have been made to develop devices, which use heat as a mechanism for separating oil and contaminants. Exemplary previous devices of this type are disclosed in U.S. Pat. No. 2,635,759, U.S. Pat. No. 2,785,109, U.S. Pat. No. 2,839,196, U.S. Pat. No. 3,550,871, U.S. Pat. No. 3,616,885, U.S. Pat. No. 3,915,860, U.S. Pat. No. 4,006,084, U.S. Pat. No. 4,146,475 U.S. Pat. No. 4,349,438. 
         [0005]    These filters are, however not very efficient in removing water from oil. Therefore, these conventional oil filters, largely, are only slightly superior to the prior disposable filters, which remove only solid contaminants. With this oil filtering devices the engine lubricating oil may only be used for a slightly longer time than with conventional solid contaminant removing filters. The marginal improvement in oil recycling life that results from removing a small amount of the liquid contaminants cannot justify the incremental cost required to achieve this improvement. 
         [0006]    In addition to the above-mentioned kind of filtering devices, it has for example been suggested in WO 86/04830 and WO 2007/015644 to use atomizing nozzles in order to enhance the separation of water from lubricating oil. However, there has been a need in the marked for more efficient filters for removal of water, from oil, and for efficient filters, which are able to effectively remove both water and solid particle contaminants in oil. 
         [0007]    Traditionally, existing fluid filters that are adapted for filtering particles from fluids, are surface filters in the sense that the filtering occurs at just the outer surface of the element where the fluid first enters the element. With very fine surface filter elements, particles tend to accumulate at the outer surface, thereby loading the filter element and cutting off the flow of fluid through it. As a result, filtering is degraded and the element must be changed more frequently than desired. This has been a particular problem with high viscosity fluids such as oil, engine oil in particular. In order to alleviate this surface build-up problem so called string/yarn wound filters wherein a yarn is wound on a tubular bobbin have been developed. These filters have the advantage, that the fluid is filtered all the way along the thickness of the wound yarn. Examples of such yarn wound filters are known from EP 0489157, U.S. Pat. No. 5,552,065, U.S. Pat. No. 4,761,231, U.S. Pat. No. 5,772,952, FR 2097502 and WO 2007/015643. 
         [0008]    This filter alleviates some of the problems associated with the other types of filters mentioned above and known in the art. However, it has been observed that some of the water that evaporates from the oil tend to condensate on the inner surface of the ventilation chamber, and thereby flow back together with the oil. Furthermore, it has proven to be technically complicated in praxis to provide adequate (i.e. enough, but not too much) heating of the distillation head, especially when the filter is used to filter water from a highly flammable type of oil, such as diesel. 
       SUMMARY OF THE INVENTION 
       [0009]    It is thus an object of the invention to provide an improved, and less complicated, method and apparatus for removing water from oil. 
         [0010]    It is a further object of the invention to provide an improved, and less complicated, method and apparatus for removing both water and solid particle contaminants in oil. 
         [0011]    According to the present invention, the above-mentioned and other objects are fulfilled by a first aspect of the invention pertaining to a filter for the removal of water from oil, the filter comprising a distillation element having an inlet pipe that in one end is to be fluidly connectable to a reservoir of oil to be filtered, and in the other end being fluidly connected to a distillation head, said distillation head comprising a plurality of compression tubes for compressing said oil into an evaporation chamber, whereby eventual water within the oil evaporates from the said oil, the filter further comprising a tubular core with a plurality of apertures and a hollow interior, said core having an open end for fluid communication with the hollow interior, a length of yarn wound around an outer surface of the core, wherein the filter further comprises means for blowing air or an inert gas into the evaporation chamber for removal of the water vapor during use of the filter. 
         [0012]    By providing a plurality of compression tubes for injecting the oil into the evaporation chamber, the oil is compressed as a liquid into the evaporation chamber. Due to the different thermodynamic properties of the oil and the water, they react differently to changes in heat and pressure. These vaporized contaminants; (steam) is then blown out of the evaporation chamber by the air or inert gas, which is blown into the evaporation chamber, while the oil is drained out in liquid form. A plurality of compression tubes is used in order to ensure an adequate flow rate, and the actual number of compression tubes needed may be chosen in dependence of the particular application of the inventive filter and oil types. 
         [0013]    The technical industries have particular difficulties with water contaminants in oils used for lubrication and different transmissions or transformers (hydraulics, gears, valves etc.). These contaminants arise from condensation, leaks, frost, etc. Non combusted fuel remnants, acids and eventually other alien liquids can also be present. Acids and bacterial growth may be formed in the presence of water. Thus, by removing water, a lot of related problems are solved. Furthermore, since the filter additionally employs a length of yarn that is wound around a tubular core, effective removal of slid particles is achieved as well as removal of water in one single operation. An inert gas instead of air is preferably used in case the oil to be filtered is highly flammable type of oil, such as diesel. 
         [0014]    In a preferred embodiment of the filter according to the invention, said means for blowing air or an inert gas into the evaporation chamber is for example a fan that is in fluid communication with said evaporation chamber via a pipe. 
         [0015]    In a further preferred embodiment of the filter according to the invention, the evaporation chamber comprises an outlet for the air or inert gas, which during use is blown into the evaporation chamber. 
         [0016]    Preferably, the compression tubes are made from a metal or metal alloy comprising aluminum, which has good heat conductivity and low reactivity with oil. 
         [0017]    In an embodiment the compression tubes have barrel sizes that are smaller than 7 mm, preferably smaller than 3 mm or between 0.5 mm and 7 mm, preferably between 0.5 mm and 3 mm, more preferably between 0.7 and 1.2 mm. Separation is achieved by selecting a barrel size that creates a significant pressure differential across the opening. The viscosity of different oils is largely dependent of temperature, so the barrel sizes are preferably chosen in dependence of the temperature increase the oil undergoes during friction with the barrels, and the type of oil to be filtered. To this end the applicant estimates that by using barrel sizes as mentioned above it would be possible to separate water from most types of oils. 
         [0018]    However, there is a delicate balance in selecting proper barrel opening sizes, because the opening size controls both the extent of separation and the flow rate through the filter. Selection of the barrel opening also controls the pressure differential between the oil inlet and the evaporation chamber. 
         [0019]    The compression tube have preferably a barrel that is rifled in order to thereby impart a rotational motion to the compressed injected oil and thereby enhance the separation (evaporation) of contaminants from them. 
         [0020]    In a preferred embodiment the length of the barrel of each of the compression tubes is between 4 mm and 40 mm. 
         [0021]    In a preferred embodiment the evaporation chamber has a sloped floor with an oil drain that during use is configured to be situated at the lowest place of the floor. Hereby is achieved that the oil—relieved form most of the water contaminants—may be drained from the bottom of the evaporation chamber, while the gaseous phase, water steam, is removed from an upper part of the evaporation chamber by blowing in an inert gas or air. Here the terms “lower” and “upper” refers to the lower and upper parts of the ventilation chamber, when the filter is installed in its correct use position. 
         [0022]    Advantageously, the oil is pressurized, e.g. to a pressure of between 8 bars and 40 bars, before it injected through the compressing tubes. 
         [0023]    In a preferred embodiment, the evaporation chamber has a sloped floor with an oil drain that during use is configured to be situated at the lowest place of the floor. Hereby is achieved that the oil—relieved form most of the water contaminants—may be drained from the bottom of the evaporation chamber, while the gaseous phase, water steam, is removed from an upper part of the evaporation chamber by blowing in an inert gas or air. Here the terms “lower” and “upper” refers to the lower and upper parts of the ventilation chamber, when the filter is installed in its correct use position. 
         [0024]    Advantageously, the oil is pressurized, e.g. to a pressure of between 10 bar and 20 bar, before it atomized through the nozzles. 
         [0025]    In a preferred embodiment of the filter, the yarn is wound in a series of at least 4 layers around the outer surface of the core, wherein the first layer closest to the surface of the core comprises at least 15 windings of the yarn, the second layer comprises at least 15 windings of the yarn and the third layer comprises at least 10 windings of the yarn, and wherein at least two consecutive layers have been wound in accordance with different winding patterns. 
         [0026]    Investigations performed by the applicant has shown that this particular way of building up the filter in a layered structure of yarn that wound onto the tubular core in accordance with winding patterns that are different for three consecutive layers and wherein the layers are built up with the minimum number of windings in the first, second, and third layer as stated above, is particularly effective filtering oil, for particles having a diameter or average particle size in the range from 0.5 μm to 50 μm, without having using excessive pressure, but merely by letting the fluid flow freely through the filter at a pressure that is usually used in engines, power transmissions, such as hydraulics, gears, valves etc. 
         [0027]    In one embodiment according to the invention each of the three layers have been wound in accordance with a winding pattern that is different from the winding pattern of the other layers. Hereby is achieved a filter wherein each layer mainly filters particles from the fluid up to a certain size. Thus, allowing a more effective utilization of the total volume of the filter for the filtering purpose. 
         [0028]    In another embodiment, the first layer comprises preferably less than 20 windings of the yarn, the second layer comprises less than 20 windings of the yarn, and the third layer comprises less than 15 windings of the yarn. 
         [0029]    In a preferred embodiment, the first layer comprises between 15 and 17 windings of the yarn, the second aspect of the invention the second layer comprises between 15 and 20 windings of the yarn, and the third layer comprises between 10 and 15 windings of the yarn. 
         [0030]    In order to facilitate a good flow of the fluid through the filter without applying excessive pressure, each of the three layers of the filter comprises, preferably, less than 45-65 windings of yarn. 
         [0031]    One way of providing a particular winding pattern is by using a particular winding angle, and the applicant has found it advantageous if the first layer of yarn has been wound around the outer surface of the core at an angle larger than 55 degrees with respect to an axis parallel to the tubular core, and the second layer of yarn has been wound around the outer surface of the core at an angle larger than 50 degrees with respect to an axis parallel to the tubular core, and the third layer of yarn has been wound around the outer surface of the core at an angle larger than 45 degrees with respect to an axis parallel to the tubular core. Preferably, the angle with which the yarn has been wound around the core is different for two consecutive layers, in order to facilitate winding patterns that are able to trap particles of different sizes. 
         [0032]    Preferably, the yarn comprises a mix of natural and synthetic fibers. Since natural fibers are hydrophilic, while synthetic fibers generally are hydrophobic, a filter wherein the yarn is made of a mix of both natural and synthetic fibers has the additional advantage that in addition to being able to filter particles from the fluid, also water may be absorbed by the yarn and thereby filtered from the fluid without having to heat the filter. 
         [0033]    In a preferred embodiment, the natural fibers are chosen from a list of fibers comprising cotton and/or wool and the synthetic fibers are chosen from a list of fibers comprising any of the following materials: acryl, polyester, flax, polyamide, acetate and/or viscose. Cotton and wool are cheap natural fibers that are easy to mix with any or a plurality of the synthetic fibers mentioned above. Thus facilitating an effective, yet cheap yarn that for the filter. 
         [0034]    In one embodiment according to the invention, the yarn comprises less than 15% natural fibers. In another embodiment, the yarn comprises more than 45% acryl. In yet another embodiment the yarn comprises more than 20% polyester, and in yet even another embodiment the yarn comprises more than 25% flax. 
         [0035]    Preferably, the yarn comprises between 4% and 5% polyamide or between 5% and 10% polyamide. 
         [0036]    In an alternative embodiment, the yarn comprises more than 2% viscose, or between 2% and 4% viscose. 
         [0037]    Another embodiment of the first aspect of the invention the length of yarn is wound in a series of at least four layers around an outer surface of the core, at least three of the at least four layers being wound in accordance with different winding patterns, the yarn comprising a mixture of natural and synthetic fibers, wherein the natural fibers constitutes less than 15% of the yarn, and the reminder constitutes fibers or a mix of fibers made from one or more of the following synthetic materials: acryl, polyester, flax, polyamide, acetate. 
         [0038]    By providing a layered filter with a yarn that is made from a mix of natural constituting less than 15% (of the yarn) and synthetic fibers made from any of the synthetic materials mentioned above, a filter is achieved that is particularly effective for filtering particles having a diameter or an average particle size between 0.5 μm and 50 μm from oil. 
         [0039]    In one embodiment according to the invention each of the three layers have been wound in accordance with a winding pattern that is different from the winding pattern of the other layers. Hereby is achieved a filter wherein each layer mainly filters particles from the fluid up to a certain size. Thus, allowing a more effective utilization of the total volume of the filter for the filtering purpose. 
         [0040]    According to a preferred embodiment of any of the aspects of the invention, the outer surface of the tubular core is covered with a fluid permeable sheet that covers the core at least one time, the sheet being placed between the outer surface of the core and the first layer of yarn. The sheet is preferably a piece of textile, preferably a tightly woven textile. 
         [0041]    According to an embodiment of the invention, the filter may further comprise a housing that completely encloses the tubular core and yarn. The housing further comprises a first opening that is fluidly connected to the hollow interior of the tubular core, and a second opening that is fluidly connected to the layers of yarn. Preferably, the second opening functions as a fluid inlet, and the first opening functions as a fluid outlet. Hereby is achieved a self-contained unit that that may be adapted to be mounted in connection with a power transmission system, such as an engine, hydraulics, gears, valves etc. Furthermore, this self-contained unit may be used as a bypass filter for providing additional filtering in already existing installations and power transmission systems. The housing is preferably made from metal. 
         [0042]    In order to facilitate easy exchange of the filter, e.g., when it is worn out, without having to change the whole housing as well, the housing may comprise a container and a cap that is releasable attached to the container. 
         [0043]    In one embodiment of any of the aspects of the invention, the first opening is placed in the cap and the second opening is placed in the container, and in another embodiment the second opening is placed in the cap and the first opening is placed in the container. 
         [0044]    However, in a preferred embodiment of any of the aspects of the invention both the first and the second openings are placed in the cap. Hereby is achieved an embodiment wherein the filter may be replaced in an easy manner without having to unplug one or both if the first and second openings of the housing. The container may for example just be screwed of the cap and the filter replaced. Alternatively, both the first and second opening is placed in the container. 
         [0045]    According to an embodiment of any aspects of the invention, the longitudinal extension of the yarn-covered core is between 4-8 times the total radial thicknesses of the layers as measured from the outer surface of the tubular core. The dimensions that are chosen in any particular case may be chosen in dependence of the capacity needed, i.e. how much fluid is needed to be filtered pr. hour. For example, a filter according to any aspects of the invention having a longitudinal extension between 24 cm and 70 cm will be suitable for filtering up to 300-2500 l/h (liters/hour). 
         [0046]    The above mentioned and further objects are achieved by a second aspect of the invention, pertaining to a method of manufacturing a filter as described above, the method comprising the steps of
       mounting a tubular core with a plurality of apertures and a hollow interior, said core having an open end for fluid communication with the hollow interior, in a winding machine,   rotating the core at a rate controlled by the winding,   feeding a yarn to the core through a head in such a way that it winds onto an outer surface of the core,   moving the head forward and backwards along the longitudinal axis of the core,   winding a first layer of yarn onto the core comprising at least 15 windings of yarn, a second layer comprising at least 15 windings of the yarn and a third layer comprising at least 10 windings of yarn, by varying the speed of rotation of the core and/or speed of movement of the head between each layer.       
 
         [0052]    In an embodiment, the method further comprises the step of winding each of the three layers in accordance with pre-programmed winding patterns different from the winding patterns of the other layers. 
         [0053]    In a further embodiment, the method further comprises the steps of
       winding less than 17 windings of the yarn in the first layer,   winding less than 20 windings of the yarn in the second layer, and   winding less than 10 windings of the yarn in the third layer.       
 
         [0057]    In a further embodiment, the method further comprises the steps of
       winding between 15 and 17 windings of the yarn in the first layer,   winding between 15 and 20 windings of the yarn in the second layer, and   winding between 10 and 15 windings of the yarn of the third layer.       
 
         [0061]    In a further embodiment, the method further comprises the steps of
       winding less than 30-48 windings of yarn in each of the three layers,   winding the first layer of yarn around the outer surface of the core at an angle larger than 55 degrees with respect to an axis parallel to the tubular core,   winding the second layer of yarn around the outer surface of the core at an angle larger than 45 degrees with respect to an axis parallel to the tubular core, and   winding the third layer of yarn around the outer surface of the core at an angle larger than 40 degrees with respect to an axis parallel to the tubular core.       
 
         [0066]    In a further embodiment of the method, the yarn comprises a mix of natural and synthetic fibers. 
         [0067]    In a further embodiment of the method, the natural fibers are chosen from a list of fibers comprising cotton and/or wool and wherein the synthetic fibers are chosen from a list of fibers comprising any of the following materials: acryl, polyester, flax, polyamide, acetate. 
         [0068]    In an embodiment of the method, the yarn comprises less than 15% natural fibers, and in a further embodiment of the method, the yarn comprises more than 45% acryl, in a yet further embodiment of the method, the yarn comprises more than 20% polyester, and in an yet even further embodiment of the method, the yarn comprises more than 25% flax. 
         [0069]    In a further embodiment of the method, the yarn comprises less than 10% polyamide or between 4% and 5% polyamide. 
         [0070]    In a further embodiment, the method further comprises the step of varying the winding resistance of the yarn by varying the speed at which the yarn is fed through the head relative to the speed of rotation of the tubular core. 
         [0071]    In a further embodiment, the method further comprises the step of winding the yarn around the outer surface of the core with different winding resistance in at least two of the three layers. 
         [0072]    In a further embodiment, the method further comprises the step of winding the yarn of the first and third layer around the outer surface of the core with a winding resistance that is larger than the winding resistance used for the second layer. 
         [0073]    In a further embodiment, the method further comprises the step of winding the yarn of the first layer around the outer surface of the core with a winding resistance that is larger than the winding resistance used for the second layer, and winding the yarn of the second layer around the outer surface of the core with a winding resistance that is larger than the winding resistance used for the third layer. 
         [0074]    In a further embodiment, the method further comprises the step of covering at least in part the outer surface of the tubular core with a fluid permeable sheet prior to the step of winding the yarn onto the core. 
         [0075]    The above mentioned and further objects are achieved by a method for removing water from oil, the method comprising the following steps:
       injecting the oil under pressure into the evaporation camber through a plurality of compression tubes, whereby the oil is decompressed when entering the evaporation chamber,   removing a part of a gaseous phase of the water from the evaporation chamber by blowing air or an inert gas into the evaporation chamber at a predetermined speed, and   draining a liquid phase of the oil from the evaporation chamber.       
 
         [0079]    According to an embodiment of the method of removing water from oil, the oil is pressurized to a pressure of between 8 bars to 40 bars before injecting it into the evaporation camber through the plurality of compression tubes. 
         [0080]    According to a further embodiment of the method of removing water from oil, the compression tubes have rifled barrels for imparting a rotational movement to the oil that is injected into the evaporation chamber through the compression tubes. 
         [0081]    The above mentioned and further objects are achieved by a method for removing water from oil, the method comprising the following steps:
       injecting the oil into the evaporation camber through a plurality of atomizing nozzles, whereby the oil is atomized when entering the evaporation chamber,   removing a part of a gaseous phase of the water from the evaporation chamber by blowing air or an inert gas into the evaporation chamber at a predetermined speed, and   draining a liquid phase of the oil from the evaporation chamber.       
 
         [0085]    According to an embodiment of the method of removing water from oil, the oil is pressurized to a pressure of between 10 bars to 20 bars before injecting it into the evaporation camber through the plurality of atomizing nozzles. 
         [0086]    According to a further embodiment of the method of removing water from oil, the nozzles have rifled barrels for imparting a rotational movement to the oil that is injected into the evaporation chamber through the nozzles. 
         [0087]    The method of removing water from oil, may further comprise the steps of,
       leading the oil through at least four layers of yarn that are wound around an outer surface of a tubular core into an hollow interior of the core, wherein the first layer closest to the surface of the core comprises at least 15 windings of the yarn, the second layer comprises at least 15 windings of the yarn, and the third layer comprises at least 10 windings of the yarn, and wherein at least two of the at least three layers have been wound in accordance with different winding patterns.       
 
         [0089]    In a preferred embodiment of the method of filtering oil, said method may utilize a filter manufactured according to any of the above-mentioned embodiments of manufacturing a filter according to the invention. 
         [0090]    The above mentioned and further objects are also fulfilled by a filter battery comprising a plurality of filters as described above, said filters being fluidly connected in series for consecutive filtering of oil, through said filters. The oil is first filtered through the first filter in the series, and then through the next, etc., until it reaches the last filter, from which it leaks back to the circuit from where it originated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0091]    A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings. In the following, preferred embodiments of the invention is explained in more detail with reference to the drawings, wherein 
           [0092]      FIG. 1  shows a tubular core with a plurality of apertures, 
           [0093]      FIG. 2  shows an embodiment of a filter element, 
           [0094]      FIG. 3  shows a cross section of an embodiment of a filter element, 
           [0095]      FIG. 4  shows a cross section of a filter comprising the synthetic filter and mounting. 
           [0096]      FIG. 5  shows an embodiment of a distillation element, 
           [0097]      FIG. 6  shows an embodiment of a compression tube, 
           [0098]      FIG. 7  shows an open evaporation chamber, wherein the compression tubes can be viewed 
           [0099]      FIG. 8  shows a partial longitudinal cross sectional view of an embodiment of a filter element, 
           [0100]      FIG. 9  shows another cross sectional view of an embodiment of a filter element, 
           [0101]      FIG. 10  shows a tubular core that has been placed in a winding machine, 
           [0102]      FIG. 11  shows an embodiment of a method of manufacturing a filter element, 
           [0103]      FIG. 12  shows a flow diagram of an embodiment of a method of removing water from oil, 
           [0104]      FIG. 13  shows a complete unit with water removal unit start and end block. 
           [0105]      FIG. 14  shows a cross section through the water removal unit illustrated in  FIG. 13 . 
           [0106]      FIG. 15  shows an example of a complete assembly of an oil cleaning unit, 
       
    
    
     DETAILED DESCRIPTION 
       [0107]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. Like elements will, thus, not be described in detail with respect to the description of each figure. 
         [0108]      FIG. 1  shows a tubular core  2  with a plurality of apertures  4 , a hollow interior  8  and a longitudinal extension indicated by the double arrow  6 . The tubular core  2  has an outer surface  16  onto which a yarn may be wound. The illustrated core  2  has a generally cylindrical shape. However, other shapes could also be envisioned. 
         [0109]      FIG. 2  shows a filter element  10 . The illustrated filter element  10  comprises a tubular core  2  (not visible) as illustrated in  FIG. 1  onto which a yarn  12  has been wound. The outermost layer of yarn  12  has been wound onto the tubular core  2  at an angle λ with respect to an axis  14  that is parallel with the longitudinal extension of the tubular core  2 . In the illustrated case, the axis  14  is the symmetry axis of the tubular core  2 . 
         [0110]      FIG. 3  shows a cross section of a filter element  10 . The illustrated filter element  10  comprises a tubular core  2  with a plurality of apertures  4  and a hollow interior  8 . The tubular core  2  has an open end  18  for fluid communication with the hollow interior  8 . A length of yarn  12  has been wound around the outer surface  16  of the tubular core  2  in a series of 3 layers,  11 ,  13 , and  15 , wherein the first layer  15  closest to the outer surface  16  of the tubular core  2  comprises at least 15 windings of the yarn  12 . The second layer  17  comprises at least 15 windings of the yarn  12  and the third layer  10  comprises at least 10 windings of the yarn  12 . At least two consecutive layers of the three layers  11 ,  13  and  15  have been wound in accordance with different winding patterns. 
         [0111]    Preferably, the first layer  15  comprises between 15 and 17 windings of the yarn  12 , the second layer  17  comprises between 15 and 20 windings of the yarn  12 , and the third layer  10  comprises between 10 and 15 windings of the yarn  12 . 
         [0112]    One way of providing a particular winding pattern in the illustrated filter element  10  is by using a particular winding angle λ. The applicant has found it advantageous if the first layer  11  of yarn  12  has been wound around the outer surface  16  of the tubular core  2  at an angle λ larger than 55 degrees with respect to an axis  12  parallel to the longitudinal extension of the tubular core  2 , and the second layer  17  of yarn  12  has been wound around the outer surface  10  of the tubular core  2  at an angle λ larger than 45 degrees with respect to an axis  14  parallel to the longitudinal extension of the tubular core  2 , and the third layer  10  of yarn  12  has been wound around the outer surface  16  of the tubular core  2  at an angle λ larger than 40 degrees with respect to an axis  14  parallel to the longitudinal extension of the tubular core  2 . Preferably, the angle λ with which the yarn  12  has been wound around the tubular core  2  is different for two consecutive layers  10  and  12 , in order to facilitate winding patterns that are able to trap particles of different sizes. 
         [0113]    In another (not illustrated) embodiment, the filter element  10  may comprise additional layers, for example, the illustrated layer structure of 3 layers  11 ,  13  and  15  could be repeated for a suitable number of times. 
         [0114]      FIG. 4  shows a cross section of a filter comprising the synthetic filter and mounting. The housing further comprises an inlet opening  24  that are fluidly connected to the layers (not explicitly shown) of yarn  12 . 
         [0115]    Hereby is achieved a self-contained filter  27  that that may be adapted to be mounted in connection with a power transmission system, such as an engine, hydraulics, gears, valves etc., which is able to remove both solid particle contaminants as well as water from the oils. Furthermore, this self-contained filter  27  may be used as a bypass filter for providing additional filtering in already existing installations and power transmission systems. The housing  17  is preferably made from metal, such as Aluminum. 
         [0116]    In order to facilitate easy exchange of the filter element  10 , e.g. when it is worn out, without having to change the whole housing  17  as well, the housing  17  may comprise a container  23  that is releasable attached to the housing  17 . This releasable attachment could for example be provided by the illustrated threading  19 . 
         [0117]    In the illustrated embodiment both the drainage pipe  22  and the inlet opening  24  are placed in the cap  20 . Hereby is achieved an embodiment wherein the filter element  10  may be replaced in an easy manner without having to unplug one or both if the drainage pipe  22  and inlet opening  24  of the housing  17 . The container  23  may for example just be screwed of the cap  20  and the filter element  10  replaced. 
         [0118]    According to an embodiment the longitudinal extension  6  of the yarn  12  covered tubular cores  2  is between 5-10 times the total radial thicknesses  21  of the layers as measured from the outer surface  16  of the tubular core  2 . The dimensions that are chosen in any particular case may be chosen in dependence of the capacity needed, i.e. how much oil is needed to be filtered pr. hour. For example a filter  10  having a longitudinal extension  6  between 24 cm and 30 cm will be suitable for filtering up to 250-500 l/h (liters/hour) of oil, while a filter  10  that has a longitudinal extension  6  between 45 cm and 60 cm will be suitable for filtering up to 1000-1500 l/h. 
         [0119]      FIG. 5  shows a perspective view of a distillation element, comprising a number of bores  90  for the compressing tubes  78 . The bores  90  are situated in the distillation head  76 . The oil may undergo heating up to 70 degrees Celsius due to friction and pressure in the compressing tubes  78 , whereby separate heating of the distillation head  76  or oil is not needed. Hereby is achieved that the eventual water within the oil is close to or at its boiling temperature, which implies that it easier evaporates from the pressurized oil when injected into the evaporation chamber  80 . Moreover a larger quantity of water will evaporate from the droplets. The distillation head  76  are made from a metal or metal alloy comprising aluminum, which has good heat conductivity and low reactivity with oil. 
         [0120]    The illustrated main block  81  further having an inlet pipe  24  that in one end  79  is fluidly connected to a container, i.e. the housing  17 , adapted to temporarily store the oil to be filtered, and in the other end being fluidly connected to a distillation unit  81 , said distillation head comprising a plurality (only three visible) of compressing tubes  78  for injecting the oil into a evaporation chamber  80 . In the wall of the evaporation chamber  80 , there is provided an inlet  82  for blowing air or an inert gas into said evaporation chamber  80 . 
         [0121]    By providing a plurality of compression tubes  78  for injecting the oil into the evaporation chamber  80 , the oil is compressed as a liquid into the evaporation chamber  80 . Due to the different thermodynamic properties of the oil and the water, they react differently to changes in heat and pressure. These vaporized contaminants; (steam) is then blown out of the evaporation chamber  80  through an opening in the cap  91 , while the oil is drained out in liquid form through a drainage pipe  22 . A plurality of compressing tubes  78  is used in order to ensure an adequate flow rate, and the actual number of compressing tubes  78  needed may be chosen in dependence of the particular application of the inventive filter  27 . 
         [0122]    When oil enters the housing  17  through the inlet opening  24  in the cap  20  of the housing  17  it will flow into the hollow interior  25  of the container  23 . The oil will then flow through the layers (not illustrated explicitly) of yarn  12  along the total radial thickness  21  of the yarn  12  and into the hollow interior  8  of the tubular core  2  via the apertures  4 . During its flow through the layers (not explicitly illustrated in this figure, but see for example  FIGS. 3 and 6 ) of yarn  12 , particles present in the oil are deposited in the layers of yarn  12 . From the hollow interior  8  of the tubular core  2  the oil will flow through a hose  108 , into the inlet connector  79  to the main block  81  and injected through the compressing tubes  78  into the evaporation chamber  80  and eventually be drained out into the main block  81  through the drainage pipe  106 . 
         [0123]      FIG. 6  illustrates a cross section of an embodiment of a compression tube  78 . The compression tubes  78  have barrel openings  88  that are smaller than 7 mm, preferably smaller than 3 mm or between 0.5 mm and 7 mm, preferably between 0.5 mm and 3 mm, more preferably between 0.7 and 1.2 mm. Separation is achieved by selecting a barrel size that creates a significant pressure differential across the opening  88 . The viscosity of different oils is largely dependent of temperature, so the barrel sizes are preferably chosen in dependence of the temperature increase the oil undergoes during friction with the barrels, and the type of oil to be filtered. To this end the applicant estimates that by using barrel sizes as mentioned above it would be possible to separate water from most types of oils. 
         [0124]    However, there is a delicate balance in selecting proper barrel opening sizes, because the opening size controls both the extent of separation and the flow rate through the filter  27 . Selection of the barrel opening  88  also controls the pressure differential between the oil inlet  24  and the evaporation chamber  80 . 
         [0125]    The compression tube  78  have preferably a barrel  90  that is rifled in order to thereby impart a rotational motion to the compressed injected oil and thereby enhance the separation (evaporation) of contaminants from them. 
         [0126]    In a preferred embodiment the length of the barrel  90  of each of the compression tubes  78  is between 4 mm and 40 mm. 
         [0127]    The technical industries have particular difficulties with water contaminants in oils for lubrication and different transmissions or transformers (hydraulics, gears, valves etc.). These water contaminants mainly arise from condensation, leaks, frost, etc. Non combusted fuel remnants, acids and eventually other alien liquids can also be present, where especially acids may be formed in the presence of water. 
         [0128]      FIG. 7  shows a perspective view of an “open” evaporation chamber  80 , wherein the distillation head  76  with a number of compressing tubes  78  can be seen. The ventilation chamber  80  has a floor with drain  94  for leading the oil to the drainage pipe  22 / 106 . During proper use of the filter  27 , the drain  94  is configured to be situated at the lowest place of the floor. Hereby is achieved that the oil—relieved form most of the water contaminants—may be drained from the bottom of the evaporation chamber  80 , while the gaseous phase, i.e. steam, blown out from an upper part of the evaporation chamber  80  by blowing air or an inert gas into said evaporation chamber  80 . Here the terms “lower” and “upper” refers to the lower and upper parts of the evaporation chamber  80 , when the filter  27  is installed in its correct use position. 
         [0129]    Advantageously, the oil is pressurized, e.g. to a pressure of between 8 bars and 40 bars, before it is injected through the compressing tubes  78 . 
         [0130]    Also shown is the start block  89  and end block  72 . 
         [0131]      FIG. 8  shows a partial longitudinal cross sectional view of an embodiment of a filter element  10  according to the invention. Illustrated is a part of the tubular core  2  having a number of apertures  4 . Around the outer surface  16  of the tubular core  2  is wound a yarn  12  in a number of layers (not illustrated), wherein only the first two windings of the first layer is illustrated. 
         [0132]    The yarn  12  comprises a number of fibers  26 ,  28  and  30  (of which only three have been given designation numbers in order to increase the intelligibility of the figure). 
         [0133]    Preferably, the yarn  12  comprises a mix of natural and synthetic fibers. For example in the illustrated embodiment, the fibers  26  and  30  may be natural, while the fiber  28  may be synthetic. Since natural fibers  26  and  30  are hydrophilic, while synthetic fibers  28  generally are hydrophobic, a filter element  10  wherein the yarn  12  is made of a mix of both natural ( 26  and  30 ) and synthetic ( 28 ) fibers has the additional advantage that in addition to being able to filter particles from the oil, also water may be absorbed by the yarn  12  and thereby filtered from the oil. 
         [0134]    In a preferred embodiment, the natural fibers  26  and  30  are chosen from a list of fibers comprising cotton and/or wool and the synthetic fibers ( 28 ) are chosen from a list of fibers comprising any of the following materials: acryl, polyester, flax, polyamide, acetate and/or viscose. Cotton and wool are cheap natural fibers that are easy to mix with any or a plurality of the synthetic fibers mentioned above. Thus facilitating an effective, yet cheap yarn  12  for the filter element  10 . 
         [0135]    In one embodiment according to the invention, the yarn  12  comprises less than 15% natural fibers. In another embodiment, the yarn  12  comprises more than 45% acryl. In yet another embodiment the yarn  12  comprises more than 20% polyester, and in yet even another embodiment the yarn  12  comprises more than 25% flax. 
         [0136]    Preferably, the yarn  12  comprises less than 10% polyamide or between 4% and 5% polyamide. 
         [0137]    In an alternative embodiment, the yarn  12  comprises more than 2% viscose, or between 2% and 4% viscose. 
         [0138]      FIG. 9  shows the embodiment of a filter element  10  as illustrated in  FIG. 3  cut along the dashed line A in order to illustrate the layered structure of yarn  12  more clearly. Illustrated is the tubular core  2  with a number of apertures  4  and a hollow interior  8 . Around the outer surface  16  of the tubular core two is illustrated the first layer  11  of yarn that has been wound around the tubular core  2  in accordance with a particular winding pattern. Also illustrated is the second  13  and third  15  layer of yarn  12 . In addition to these layers  11 ,  13  and  15  additional layers may be provided in alternative embodiments as is illustrated by the layers  38  and  40 . 
         [0139]      FIG. 10  shows a tubular core  2  that has been placed in a winding machine  42 . The tubular core  2  is rotated with respect to the axis  15 , while the yarn  12  is fed through a head  44  to the tubular core  2 . The rotation of the tubular core  2  may be manually controlled, but is preferably automatically controlled by the winding machine  42  or a computer (not illustrated) controlling the winding machine  42 . Meanwhile the head  44  is moved back and forth (as illustrated by the double arrow  48 ) on the rail  46  parallel to the axis  14  at a controlled rate. By varying the speed of the head  44  along the rail  48  and/or rotation of the tubular core  2  with respect to the axis  14  varying winding patterns may be produced. In particular, a layered structure of yarn  12  with a certain number of windings of the yarn  12  and a certain winding pattern for each or some of the layers may be provided for. In the illustrated embodiment, the yarn  12  is provided from a yarn supply  50  holding a larger quantity of yarn  12 . 
         [0140]    In a preferred embodiment of any of the filter elements  10  illustrated in any of the  FIGS. 2-4, 8 and 9  the yarn  12  has been wound around the outer surface  16  of the core  2  with different winding resistance in at least two of the three layers ( 11 ,  13 , and  15 ). Hereby is provided a simple way to vary the density of the yarn  12  in the different layers  11 ,  13  and  15 . This influences the flow of the oil through the layers and therefore the way the particles are deposited in the different layers. In a particularly preferred embodiment, the yarn  12  of the first  15  and third  15  layer has been wound around the outer surface  16  of the core  2  with a winding resistance that is larger than the winding resistance used for the second layer  13 . Hereby the oil under a certain pressure will meet first a harder resistance then a lesser resistance and then again a harder resistance when passing through the filter media (the layers of yarn  12 ). This also has the effect of first slowing down, then accelerating and then slowing down again of the oil when passing through the filtration media (layers of yarn  12 ). By a suitable adjustment of the winding resistance, the filter  10  may be designed to be particularly effective in filtering particles of a particular size from the oil, which means that it can be optimized for a particular use, wherein particles of a certain size are a problem. 
         [0141]    The winding resistance may be adjusted by varying the speed at which the yarn  12  is fed through the head  44  relative to the speed of rotation of the tubular core with respect to the axis  14 . The winding machine  42  preferably automatically controls this adjustment of the winding resistance. 
         [0142]    In another embodiment of any of the filter elements  10  illustrated in any of the  FIGS. 2-4, 8 and 9 , the yarn  12  of the first layer  15  (closest to the core  2 ) has been wound around the outer surface  16  of the core  2  with a winding resistance that is larger than the winding resistance used for the second layer  17 , and wherein the yarn  12  of the third layer  15  has been wound around the outer surface  15  of the core  2  with a winding resistance that is larger than the winding resistance used for the second layer  13 . Hereby is achieved an embodiment wherein the fluid is slowed down more and more for each layer it passes through during its flow through the filtering media (the layers of yarn  12 ). 
         [0143]    While it has not been illustrated in any of the figures, the outer surface  16  of the tubular core  12  illustrated in any of the figures may also be covered with a fluid permeable sheet that covers the outer surface  16  of the tubular core  2  at least one time. The sheet, thus being placed between the outer surface  16  of the core  2  and the first layer  11  of yarn  12 . The sheet is preferably a piece of textile, preferably a tightly woven textile. 
         [0144]    In the following more specific examples of filter elements  10  are given, wherein 
       Example 1 
       [0145]    In a preferred embodiment of a filter element  10  as illustrated in any of the  FIGS. 2-4 and 8 , the first layer  15  comprises 15-17 windings of the yarn  12  that has been wound onto the tubular core  2  at an angle λ of 55 degrees (both ways), the second layer  17  comprises 15-20 windings of the yarn  12  that has been wound onto the tubular core  2  at an angle λ of 55 degrees (both ways) and wherein the third layer  15  comprises 15-17 windings of the yarn  12  that has been wound onto the tubular core  2  at the angle λ of 65 degrees. Specifically in the above-mentioned preferred embodiment of the filter element  10 , the first layer  15  may comprise 17 windings of the yarn  12 , the second layer  15  may comprise 15 windings of the yarn  12  and the third layer  15  may comprise 17 windings of the yarn  12 . Investigations have shown that a filter element  10  according to this specific example 1 is particularly well suited for filtering particles having a diameter or average particle size of 0.5 μm-50 μm from an oil, e.g. engine oil or hydraulic oil. A filter  10  according to this example 1 with a longitudinal length of 45-70 cm has the capacity of filtering up to 1000 L/h-2500 L/h of oil. 
       Example 2 
       [0146]    In another preferred embodiment of a filter element  10  as illustrated in any of the  FIGS. 2-4, 8 and 9 , the yarn  12  comprises a mixture of fibers made from: 5%-15% cotton, 45%-48% acryl, 25%-27% flax, 20%-22% polyester, and 4%-5% polyamide. 
       Example 3 
       [0147]    In yet another preferred embodiment of a filter element  10  as illustrated in any of the  FIGS. 2-4, 8 and 9 , the layered structure of example 1 is used in combination with the composition of the yarn  12  used in example 2. Investigations have shown that a filter  10  according to this specific example 3 is even better suited for filtering particles having a diameter or average particle size of 0.5 μm-50 μm from an oil, e.g. engine oil or hydraulic oil. A filter element  10  according to this example 3 with a longitudinal length of 45-70 cm has the capacity of filtering up to 1000 L/h-2500 L/h of oil. 
         [0148]      FIG. 11  shows a flow diagram of a method of manufacturing a filter element  10  illustrated in any of the  FIGS. 2-4, 8 and 9 , where the method comprises the steps
       mounting the tubular core  2  with a plurality of apertures  4  and a hollow interior  8  in a winding machine  42 , as indicated by the block  54 .   rotating the core  2  at a rate controlled by the winding machine  42 , as indicated by the block  56 . This step  56  could for example be done manually or at a pre-programmed rate,   feeding a yarn  12  to the core  2  through a head  44  in such a way that it winds onto an outer surface  16  of the core  2 , as indicated by the block  58 .   moving the head  44  forward and backwards along the longitudinal axis  14  of the core  2 , as indicated by the block  60 .   winding a first layer  15  of yarn  12  onto the core  2  comprising at least 5 windings of yarn  12 , as indicated by the block  62 ,   winding a second layer  17  of yarn  12  onto the core  2  comprising at least 6 windings of the yarn  12 , as indicated by the block  64 , and   winding a third layer  15  of yarn onto the core  2  comprising at least 10 windings of yarn  12 , as indicated by the block  68 . The speed of rotation of the core  2  and/or speed of movement of the head  44  is varied between each layer  11 ,  13  and  15 , i.e. between each of the steps  62 ,  64  and  68 .       
 
         [0156]    The method illustrated by the flow diagram in  FIG. 11  may further comprise the step of varying the winding resistance of the yarn  12  by varying the speed at which the yarn  12  is feed through the head  44  relative to the speed of rotation of the tubular core  2  with respect to the axis  14 . 
         [0157]      FIG. 12  shows a flow diagram of a method for removing water from oil, the method comprising the following steps:
       pressurizing the oil to a pressure of between 10 bar to 20, as indicated by the block  96 ,   leading the oil through at least four layers of yarn  12  that are wound around an outer surface of a tubular core  2  into an hollow interior  8  of the core  2 , wherein the first layer  11  closest to the surface of the core  2  comprises at least 5 windings of the yarn, the second layer  13  comprises at least 6 windings of the yarn, and the third layer  15  comprises at least 10 windings of the yarn, and wherein at least two of the at least three layers have been wound in accordance with different winding patterns, as indicated by the block  98 ,   injecting the oil into the evaporation camber  80  through a plurality of atomizing nozzles  78 , whereby the oil is atomized when entering the evaporation chamber  80 , as indicated by the block  100 ,   removing a part of a gaseous phase of the water from the evaporation chamber  80  by blowing air or an inert gas into the evaporation chamber at a predetermined speed, as indicated by the block  102 , and   draining a liquid phase of the oil from the evaporation chamber  80 , as indicated by the block  104 .       
 
         [0163]      FIG. 13  shows a complete unit with water removal unit start and end block. The oil is first led to the first filter  27  via the inlet hose  110 , where it is filtered, and then through a hose to the start block  89 , inlet  79 , where the water is removed, and from which it leaks back to the circuit from where it originated via the outlet pipe  85 . The filters  27  are via air/gas pipes  82  fluidly connected to a blower  92  for blowing air or an inert gas into the evaporation chamber  80  during use in order to remove the water vapor within the evaporation chamber  80 . In those cases, wherein an inert gas is to be blown into the evaporation chamber  80 , instead of air, the blower  81  is connected to a source of inert gas (not shown). 
         [0164]      FIG. 14  is showing a partial cross section of the complete water removing unit illustrated in  FIG. 13 . 
         [0165]      FIG. 15  shows an example of a complete assembly of an oil cleaning unit. 
       LIST OF REFERENCES 
       [0166]    In the following is given a list of reference numbers used in the detailed description of the invention.
     2  tubular cores,     4  apertures in the tubular core,     6  longitudinal extension of the tubular core,     8  hollow interior of the tubular core,     10  filter element,     11  first layer of yarn,     12  yarn,     13  second layer of the yarn,     14  longitudinal axis of the tubular core,     15  third layer of the yarn,     16  outer surface of the tubular core,     17  housing,     18  open end of tubular core,     19  threading,     20  chamber component,     21  total radial thickness of the yarn,     22  drainage pipe,     23  containers,     24  inlet opening,     25  hollow interior of the container,     26  natural fibers,     27  filter unit,     28  synthetic fibers,     30  natural fibers,     38  additional optional layer of yarn,     40  additional optional layer of yarn,     42  winding machine,     44  head,     46  rails,     50  yarn supply,     54 - 68  method steps,     70  seals     72  end block     74  open end of pipe of the distillation element,     76  distillation head,     78  compression tube,     79  inlet connector,     80  evaporation chamber,     81  main blocks     82  inlet opening for blowing air or inert gas into the evaporation chamber,     83  filter battery,     84  drain plug     85  outlet pipe,     86  oil pipe connecting two filters,     87  oil outlet     88  compression tube opening,     89  start block     90  barrel of compression tube,     91  air/gas venting filter     92  air pump/gas generator     94  drain in the floor of the distillation chamber     96 - 104  method steps.     105  assembled water removing block     106  outlet pipe for oil to tank     107  oil inlet     108  oil hose(s) between  27  and  105       109  cover     110  oil hose from pump to  27