Patent Application
20060278584
The present invention relates generally to a fluid cleaning system and more particularly, to a system and method for cleaning oil flow. The system and method are particularly suited for removing contaminants from an industrial oil flow stream, and may employ one or more types of fluid cleaning devices and cleaning methods, including electrostatic fluid cleaning.
Industrial oils are commonly used in lubrication and hydraulic systems. Common industrial oils include hydraulic oils, turbine oils, compressor oils, gear oils, and circulating oils. It is generally known that a high percentage of failures experienced by machinery that incorporate one of these industrial oil systems is caused by a reduced performance or failure in the part of the industrial oil. In particular, the accelerated degradation of the oil and/or introduction of contaminants in the oil typically lead to such reduced performance and failures. Typical contaminants include water, metal wear particles, dust, fibers, and other debris. As the oil ages and oxidation occurs, oxidation byproducts provide another source of contamination. These byproducts include tars, varnishes, sludge and like materials.
Filtration systems are often incorporated with these industrial oil systems and employed to filter contaminants from the oil. Prior art filtration methods typically employ mechanical or barrier filters. Mechanical filtration may be employed to filter fine particles as low as one to three microns in size. For smaller, submicronic contaminants, mechanical filtration has proven to be significantly less effective in large commercial systems.
An alternative to mechanical filtration (i.e., the use of mechanical or barrier filters) is electrostatic oil cleaning (i.e., the use of electrostatic fluid filters). In an electrostatic oil cleaner, the oil is allowed to flow between electrodes with a high DC voltage across them. As the oil flows in between the charged electrodes, the submicronic particles are drawn towards the electrodes and, thereby, removed from the oil. A discussion of electrostatic fluid cleaners may be found in U.S. Pat. No. 6,129,829, which is hereby incorporated by reference for all purposes and made a part of the present disclosure.
In one aspect of the present invention, an oil cleaning system is provided. The system includes an oil source and an oil flow conduit that is in fluid communication with the oil source and operable to draw a flow stream therefrom. Preferably, this oil flow conduit is a re-circulating line that draws from the oil source and returns cleaned oil flow into the oil source. The inventive system also includes a barrier filter positioned in the oil flow conduit to filter contaminants from the flow stream. An electrostatic fluid cleaner is positioned in the oil flow conduit downstream of the barrier filter so as to remove contaminants from oil flow exiting the barrier filter. Furthermore, a selectively operable bypass conduit is provided and is fluidly connected to the oil flow conduit upstream of the electrostatic fluid cleaner. The oil cleaning system further includes a sensor that is operatively associated with the bypass conduit and is positioned to detect a predetermined aqueous content in the flow stream upstream of the electrostatic fluid cleaner and to divert the flow stream into the bypass conduit.
In another aspect of the present invention, a method is provided for removing contaminants from industrial oil. The method includes drawing an oil flow stream from a source of industrial oil (e.g., an oil reservoir) and passing the flow stream through an oil flow conduit. Further, the flow stream is passed through a barrier filter so as to filter contaminant particles therefrom. The filtered flow stream exiting the barrier filter is then passed through an electrostatic fluid cleaner to further remove contaminants from the flow stream. Moreover, the method provides for detection of an aqueous content in the flow stream upstream of the electrostatic fluid cleaner. Upon detection of a predetermined aqueous content in the flow stream, the flow stream is diverted upstream of the electrostatic fluid cleaner into a bypass conduit.
The present invention may be best understood by way of example and in conjunction with the accompanying drawings, in which:
The present invention relates generally to a fluid cleaning system, and more particularly, a system and method for cleaning oil flow. The inventive system and method may be incorporated with or adjacent to an industrial oil system (e.g., hydraulic oil, turbine oil, etc.) so as to pass oil through one or more fluid cleaning devices and to remove target contaminants from the oil flow.
The present invention takes advantage of the capability of electrostatic oil cleaners to remove insoluble submicronic contaminants from oil flow. In one aspect of the invention, the system effectively combines electrostatic oil cleaning with mechanical filtration (i.e., the use of mechanical or barrier filters). Among other things, the use of mechanical filters can generate a pressure differential that is undesirable in many applications. The oil flow through a barrier filter can also generate friction and thus, can generate static electricity in the oil flow. The accumulation of static electricity can cause a spark discharge at the outlet of the barrier filter or in the body of the fluid as the fluid finds an appropriate grounding location. Furthermore, at a temperature of several thousand degrees, the spark discharge quickly degrades the oil that it contacts. The present inventive system and method addresses these concerns, in one respect, by maintaining a relatively oil flow rate. The present inventive system and method also controls the aqueous content in the oil flow.
As used herein, the term “contaminants” shall refer to target particles, material, byproducts, and the like which are undesirable and thus removed from the industrial oil flow (according to the present method). Furthermore, the terms “removing contaminants” shall refer to a process of removing these “contaminants” from oil flow by way of filtering, electrostatic oil cleaning, or other processes.
It should first be noted, however, that the system and method illustrated in these Figures and the accompanying description are provided for exemplary purposes only. It will become apparent to one skilled in the mechanical, chemical, or other relevant art, upon a reading of the present description and/or viewing of the accompanying drawings, that variations and modifications to the system and a method associated therewith may be made, without departing from the scope and spirit of the invention. Thus, the description of exemplary applications as provided herein should not be construed to limit the invention to the specific methods and structures described.
In one aspect of the invention, the re-circulating conduit 110 is provided with a bypass conduit 130. The bypass conduit 130 is fluidly connected to the re-circulating conduit 110 at a tee or intersection intermediate the series of fluid flow cleaning devices 122, 124, 126 and the pump 116. Preferably, a pair of control valves 132, 134 are appropriately situated in the bypass conduit 130 and the re-circulating conduit 110, respectively, to direct the flow stream 120 in a predetermined manner. In further applications, a three-way valve may be employed in lieu of multiple valves. As will be further described below, in the normal operation, the oil flow 120 is directed through the open control valve 134 and through the fluid flow cleaning devices 122, 124, 126. In the normal operation, the control valve 132 upstream of the fluid flow cleaning devices 122, 124, 126 is set in the closed position.
In one aspect of the invention, one or more control mechanisms are provided on the re-circulating conduit 110 and in communication with the oil flow 120 discharged from the pump 116. For example, a temperature sensor 136 may be positioned between the reservoir 112 and the fluid flow cleaning devices 122, 124, 126 as shown in
In many applications, the temperature of the oil flow on the oil in the oil reservoir will gradually reduce and stabilize. For example, a temperature increase may have been caused by a spike or other irregularity in the relevant machinery or system (e.g., oil cooling system). In one embodiment, a preferred temperature sensor 136 is set at about 140° F. (60° C.). Such a setting is intended to protect elements of the electrostatic cleaner and the barrier and water filters from the effects of high temperature. Specifically, this temperature setting protects seals and other components found in the cleaning system. One suitable type of temperature is a thermocouple mounted on the oil flow conduit 110.
In another aspect of the invention, a water monitor or sensor 138 may be provided on the oil flow conduit 110 upstream of electrostatic fluid cleaner 126 and downstream of oil reservoir 112, and in fluid communication with the oil flow 120. Preferably, the water sensor 138 is provided at a location intermediate the pump 116 and the bypass conduit 130. The water sensor 138 may be set to sense or detect an aqueous content of the oil flow 120. Upon detection of this predetermined aqueous content, water sensor 138 actuates control valves 132, 134, in a manner similar to that described above in respect to temperature sensor 136. Specifically, control valve 134 is moved to the closed position while control valve 132 is moved into the open position. In this way, oil flow 120, which has been indicated to maintain an aqueous content above a predetermined level, is diverted into bypass conduit 130 and returned to oil reservoir 112.
Preferably, the barrier filter 122 is any one of various commercially available and suitable mechanical type filters. The barrier filter 122 includes a filter media selected to remove target contaminant particles in the oil flow and enhance the performance or longevity of the electrostatic fluid cleaner 126. Preferably, the filter media is selected to remove particulates as small as about 5 to 10 microns and, more preferably, as small as about 0.5 to 1.0 micron.
One suitable type of water filter is a water absorbent filter. When placed downstream of the barrier filter 122, as in the illustrated system, the filter rating of the water filter 124 can be higher (e.g., to reduce pressure drop in the system). In one embodiment, the water filter is configured to have the capacity to remove free and emulsified water to less than about 5 ppm. Such a water filter 124 may have a 3 to 5 micron rating for particle removal and a water holding capacity of 2 to 4 quarts.
As will become apparent to one skilled in the art, having the present disclosure, the water filter 124 becomes optional with inclusion of the bypass conduit 130 and water sensor 134. When employed in combination with the bypass conduit 130 and water sensor 134, the water filter 124 may function to remove aqueous content that is not quickly diverted from the electrostatic cleaner 126 by way of the bypass conduit 130. The water filter 124 may also function to filter intermittent aqueous content that may be below the limit set for the diversion of the oil flow via the bypass conduit 130 or that may pass by the water monitor 134 undetected, or pass during system irregularities. Inclusion of the water filter 124 does provide, however, additional protection and insurance that a high aqueous content oil flow does not reach the electrostatic cleaner 126. It should also be noted that the water filter 124 may be positioned intermediate the barrier filter 122 and electrostatic cleaner 126, as shown in
Referring to
Furthermore, the water filter 124 is advantageously positioned upstream of the electrostatic cleaner 126 so as to prevent the introduction of water into the electrostatic cleaner 126. The presence of water in the oil flow increases the conductivity of the oil. As the oil (which includes a high content of water) flows through the electrostatic cleaner, and more particularly, between the electrodes of the electrostatic cleaner, a higher current flow is established. The higher current flow presents a less than desirable situation, from a safety standpoint. Thus, the removal of aqueous content in accordance with the present invention is a preventative safety measure. Preferably, operation of the bypass conduit 130 will avoid such an introduction and reliance on the water filter 124 to fulfill this function. Moreover, the higher current flow would, otherwise, reduce the voltage in the electrostatic cleaner, thereby reducing the effectiveness of the electrostatic cleaner.
The present inventive system and method is particularly suited in applications wherein the industrial oil is used in conjunction with a plurality of servo valves and directional valves (e.g., hydraulic control systems). In these applications, degradation products in the submicron range (e.g., less than one micron) have the ability to escape the traditional or conventional filtering processes. These degradation products can collect on the surfaces of the servo valves and directional valves, thereby generating a tar or varnish on the surfaces. This varnish as well as additional particles that may stick to it is a primary cause for servo valves to malfunction or, more particularly, to “stick”. As a result, the hydraulic control system fails to operate in the expected or normal manner.
As a formulated oil (e.g., engine oils and most industrial oils) is used, it ages and oxidizes to form degradation products. Typically, the base oil is a mineral oil that is derived from refining of crude oil and generates oxidation products which are insoluble in the oil. The additives are also consumed and form their own degradation products. These oil degradation products are insoluble in the oil and contribute to the varnish and sludge that is generated by the aged oil. In one aspect of the present invention, the system and method are particularly suited for removing these oil degradation products from the oil. By employing the inventive method, the cleaned oil is free or is nearly free of oil degradation products. Accordingly, the potential for the generation of varnish and other material on the servo valves and directional valves of the hydraulic control system or other parts of the operating system is reduced, thereby enhancing the life and the performance of the system.
It should be noted that the above-described system and method is applicable to a number of industrial oil applications. In addition to turbine oil and hydraulic oil applications, the inventive system and method are applicable to use with compressor oils, gear oils, transformer oils and the like. Moreover, the system is not limited to implementation of a re-circulating conduit about a static reservoir. As will become apparent to one skilled in the art, having the present disclosure, the system may be modified for adaptation as an in-line system. Such in-line systems may be incorporated into portions of typical oil systems, i.e., systems which do not see regular flow from a main reservoir
The inventive method provides an advantageous method of removing target contaminants from an oil flow. First, the oil flow is drawn (step 210) from an oil source such as an oil reservoir. In further applications, the oil source may be a main fluid system, as opposed to a static reservoir. In yet further applications, the oil cleaning system according to the invention may be incorporated “in-line” with the main fluid system. In this latter embodiment, the oil source is the main fluid system itself.
In the embodiment discussed previously and in respect to
If the aqueous content is below the predetermined level, the oil flow is passed through a barrier filter (step 218). The barrier filter removes certain particles from the oil flow (generally, the relatively larger particles which are larger than the submicron-sized particles). Preferably, the flow stream is maintained below between about 3.785 to 45.42 liters/min (1.0 to 12.0 gpm), and more preferably less than about 22.71 liters/min (6.0 gpm) (and more preferably, between about 5.68 to 20.82 liters/min (1.5 to 5.5 gpm)). At this relatively low rate and reduced fluid velocities, the potential for static electricity generation is minimized. Furthermore, the potential for a build-up of charge in the barrier filter is minimized. By specifying an appropriate flow rate(s) at which the oil flow may be pumped through the barrier filter, the inventive method provides one of the conditions for practical and effective use of the combination of barrier filter and electrostatic fluid filter.
Thereafter, the filtered oil flow exiting the barrier filter is passed through an electrostatic fluid cleaner. It is noted that the oil flow, at this point, is substantially free of larger contaminant particles. As a result, the cleaning process effected by the electrostatic cleaner is generally enhanced. More specifically, the electrostatic cleaner is more effective in removing insoluble, submicron material from the oil flow. The resultant cleaner oil flow may be passed through a particle monitor or equivalent, to check the effectiveness and efficiency of the cleaning process. After the filtered particle monitor, the oil flow, which is substantially free of insoluble submicron particles and water contaminants, is returned to the oil reservoir (step 226).
The many features and advantages of the present invention are apparent from the Detailed Description, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the relevant mechanical, chemical and other relevant art, it is not desired to limit the invention to the exact structures and operations illustrated and described herein. For example, various arrangements of the components of the oil filtering system described above, and/or the inclusion or absence of one or more of the described components may be employed and will readily be apparent to one skilled in the art (upon a reading and/or viewing of the present disclosure). Thus, the invention encompasses all different versions that fall literally or equivalently within the scope of the appended claims.
The present application claims the benefit of pending U.S. Provisional Patent Application Ser. No. 60/684,006 filed May 23, 2005, the entire disclosure of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60684006 | May 2005 | US |
