Patent Publication Number: US-9903364-B2

Title: Backup lubricant supply system

Description:
BACKGROUND 
     A centrifugal compressor includes one or more impellers that compress a fluid. The impellers are mounted on a rotating shaft which is supported by a plurality of bearings. The bearings require a steady supply of lubricant, which is oftentimes oil. However, in some recent applications, refrigerant has been used to lubricate the bearings rather than oil. Refrigerant lubrication can be used when, for example, the compressor is part of a refrigeration chiller. A refrigeration chiller removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. The cooled liquid may then be used to cool air (e.g., air conditioning) or in an industrial process. 
     A pump can be used to make the refrigerant to flow to the bearings. The pump may cavitate making it more difficult to supply the refrigerant to the bearings. There can also be operating conditions under which the supply of refrigerant is in inadequate supply or the state of the refrigerant is a mix of liquid and vapor such that it is unable to properly lubricate the bearings. Therefore, what is needed is a backup lubricant supply system that is capable of providing lubricant (e.g., refrigerant) to the bearings when the primary lubricant supply system is unable to lubricate the bearings. 
     SUMMARY 
     A lubricant supply system includes a tank defining an internal volume. A divider is positioned within the tank that separates the internal volume into a first portion and a second portion. A first pump is in fluid communication with the first portion of the internal volume and configured to introduce a liquid refrigerant into the first portion of the internal volume. 
     In another embodiment, the lubricant supply system includes a divider positioned within the tank that separates the internal volume into a first portion and a second portion. A liquid refrigerant is stored in the first portion of the internal volume, and a gas is stored in the second portion of the internal volume. A gas pump is in fluid communication with the second portion of the internal volume and configured to vary a pressure of the gas. A pressure of the refrigerant increases when the gas pump causes the pressure of the gas to increase. 
     A method for supplying a lubricant to a refrigeration chiller is also disclosed. The method may include introducing a liquid refrigerant into a first portion of an internal volume of a tank. A pressure of a gas in a second portion of the internal volume of the tank is increased. The refrigerant is supplied from the first portion of the internal volume of the tank to a bearing in a compressor. The compressor is positioned in the refrigeration chiller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitutes a part of this specification, illustrates an embodiment of the present teachings and together with the description, serves to explain the principles of the present teachings. In the figures: 
         FIG. 1  illustrates a schematic view of a system for supplying a lubricant to a machine, according to an embodiment. 
         FIG. 2  illustrates a schematic view of the system showing the divider as a piston, according to an embodiment. 
         FIG. 3  illustrates a schematic view of the system showing the divider as a bladder, according to an embodiment. 
         FIG. 4  illustrates a flowchart of a method for providing lubrication to a machine, according to an embodiment. 
       It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding of the embodiments rather than to maintain strict structural accuracy, detail, and scale. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawing. In the drawings, like reference numerals have been used throughout to designate identical elements, where convenient. In the following description, reference is made to the accompanying drawings that form a part of the description, and in which is shown by way of illustration one or more specific example embodiments in which the present teachings may be practiced. 
     Further, notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. 
     Additionally, when referring to a position or direction in a well, the terms “above,” “up,” “upward,” “ascend,” and various grammatical equivalents thereof may be used to refer to a position in a well that is closer to the surface than another position, or a movement or direction proceeding toward the surface (topside), without regard as to whether the well is vertical, deviated, or horizontal. Similarly, when referring to a position in a well, the terms “below,” “down,” “downward,” and “descend” and various grammatical equivalents thereof may be used to refer to a position in a well that is farther from the surface than another position, or a direction or movement proceeding away from the surface, regardless of whether the well is vertical, deviated, or horizontal. Moreover, the terms “upper,” “lower,” “above,” and “below,” when referring to components of an apparatus, are used to conveniently refer to the relative positioning of components or elements, e.g., as illustrated in the drawings, and may not refer to any particular frame of reference. Thus, a component may be flipped or viewed in any direction, while parts thereof may remain unchanged in terms of being “upper” or “lower” etc. 
       FIG. 1  illustrates a schematic view of a system  100  for supplying a lubricant to a machine  160 , according to an embodiment. The system  100  may include a tank  110  that defines an internal volume. A divider  112  may be positioned in the internal volume of the tank  110  that divides or separates the internal volume into two or more portions (two are shown:  114 ,  116 ). As shown, the divider  112  may be a diaphragm that is coupled to the inner surface of the tank  110 . The diaphragm  112  may be made of a material that is configured to bend or flex as the first portion of the internal volume  114  increases and decreases in response to a pressure differential between the first and second portions of the internal volume  114 ,  116 . 
     The tank  110  may have one or more openings (four are shown:  122 ,  132 ,  142 ,  152 ) that provide a path of fluid communication between the internal volume and the exterior of the tank  110 . A first pump  120  (referred to hereafter as a liquid pump) may be in fluid communication with the first portion of the internal volume  114  of the tank  110  through a first one of the openings  122 . As used herein, the term “pump” refers to all machines operable to increase and/or decrease a pressure in any type of fluid, whether gas, liquid, or a combination thereof. The liquid pump  120  may be used to introduce a liquid lubricant into the first portion of the internal volume  114  of the tank  110 . The lubricant may be an oil or a refrigerant. Illustrative refrigerants may include R-134a, R-123, R-1233zd, R-1234ze, and the like. 
     A valve  130  may be in fluid communication with the second portion of the internal volume  116  of the tank  110  through a second one of the openings  132 . The valve  130  may be used to allow gas to discharge (i.e. “bleed off”) from the second portion of the internal volume  116  of the tank  110  when the lubricant is being introduced into the first portion of the internal volume  114 . 
     A second pump  140  (referred to hereafter as a vacuum pump) may be in fluid communication with the second portion of the internal volume  116  of the tank  110  through a third one of the openings  142 . The vacuum pump  140  may be used to withdraw the gas from the second portion of the internal volume  116  to reduce the pressure of the gas and leave behind a partial vacuum. 
     A third pump  150  (referred to hereafter as a gas pump) may be in fluid communication with the second portion of the internal volume  116  of the tank  110  through a fourth one of the openings  152 . The gas pump  150  may be used to introduce a gas into the second portion of the internal volume  116  of the tank  110 . As such, the gas pump  150  may be or include a compressor. The gas may be air. 
     Referring again to the first opening  122  in the tank  110 , the first opening  122  may also be in fluid communication with a machine  160  via a conduit  162 . In at least one embodiment, a valve  124  may be positioned in the conduit  162  between the tank  110  and the machine  160 . A sensor (not shown) may be configured to sense when the lubricant supply to the machine  160  (e.g., from a primary lubricant supply system) is insufficient. When this occurs, the valve  124  may be switched from a closed position to an open position (e.g., manually or automatically) to supply the lubricant from the tank  110  to the machine  160 . 
     The machine  160  may be any machine having relative movement between two or more components. As shown, the machine  160  is a chiller (e.g., a refrigeration chiller). The chiller  160  may include at least one compressor  170 . In at least one embodiment, the lubricant may be the same fluid that the compressor  170  is compressing. The lubricant may be taken from either the evaporator or the condenser, depending on the operating conditions of the machine  160  and the state of the refrigerant. The compressor  170  may include a shaft  172  that is configured to rotate about a central longitudinal axis  174 . The shaft  172  may be supported by one or more bearings (four are shown:  176 ). The bearings  176  may each include an inner ring or “race”  178 , an outer ring or race  180 , and one or more rolling elements (e.g., balls)  182  positioned therebetween. As described in greater detail below, the lubricant may flow from the first portion of the internal volume  114  of the tank  110  and be introduced to the bearings  176  (e.g., between the inner and outer rings  178 ,  180 ). In some embodiments, the bearings  176  may have steel or ceramic rolling elements. 
       FIG. 2  illustrates a schematic view of the system  100  showing the divider  112  as a piston, according to an embodiment. In at least one embodiment, rather than the divider  112  being a diaphragm (as shown in  FIG. 1 ), the divider  112  may be a piston (as shown in  FIG. 2 ). The piston  212  may be positioned within the tank  110  and divide or separate the internal volume into the two portions  114 ,  116 . The piston  212  may be configured to move within the tank  110  as the first portion of the internal volume  114  increases and decreases in response to a pressure differential between the first and second portions of the internal volume  114 ,  116 . For example, the piston  212  may move in a first axial direction  214  (e.g., down as shown in  FIG. 2 ) when the pressure of the gas in the second portion of the internal volume  116  is greater than the pressure of the lubricant in the first portion of the internal volume  114 . Similarly, the piston  212  may move in a second axial direction  216  (e.g., up as shown in  FIG. 2 ) when the pressure of the lubricant in the first portion of the internal volume  114  is greater than the pressure of the gas in the second portion of the internal volume  116 . 
       FIG. 3  illustrates a schematic view of the system  100  showing the divider  112  as a bladder, according to an embodiment. In at least one embodiment, rather than the divider  112  being a diaphragm (as shown in  FIG. 1 ) or a piston (as shown in  FIG. 2 ), the divider  112  may be a bladder (as shown in  FIG. 3 ). The bladder  312  may be positioned within the tank  110  and divide or separate the internal volume into the two portions  114 ,  116 . More particularly, the bladder  312  may include a flexible “bag” that defines an internal volume that is configured to receive the lubricant. In at least one embodiment, the bladder  312  may be made from a polymer or elastomer (e.g., rubber). The bladder  312  may include an opening that is in fluid communication with the first opening  122  in the tank  110 . 
     With continuing reference to  FIGS. 1-3 ,  FIG. 4  illustrates a flowchart of a method  400  for providing lubrication to a machine, according to an embodiment. The method  400  may proceed by operation of an embodiment of the system  100 , for example, and may thus be best understood with reference thereto. However, it will be appreciated that the method  400  is not limited to any particular structure unless otherwise stated herein. In addition, the steps below may be conducted in any order, and the order described below is for illustrative purposes only. 
     The method  400  may include introducing a lubricant (e.g., a refrigerant) into a first portion of an internal volume of a tank, as at  402 . In one embodiment, the lubricant may be pumped into the first portion of the internal volume with a first or “liquid” pump. A valve that is in fluid communication with a second portion of the internal volume of the tank may be open as the lubricant is pumped into the first portion of the internal volume of the tank. This may allow a gas within the second portion of the internal volume to discharge from the second portion of the internal volume to make room for the lubricant in the first portion of the internal volume. The valve may be closed once the lubricant is stored in the first portion of the internal volume. 
     In another embodiment, instead of, or in addition to, using the liquid pump to introduce the lubricant into the first portion of the internal volume, a second or “vacuum” pump may withdraw at least a portion of the gas from the second portion of the internal volume, leaving behind a partial vacuum in the second portion of the internal volume. This partial vacuum may draw the lubricant into the first portion of the internal volume. 
     The method  400  may also include increasing a pressure of the gas in the second portion of the internal volume of the tank, as at  404 . In one embodiment, additional gas (e.g., air) may be pumped into the second portion of the internal volume with a third or “gas” pump to increase the pressure in the second portion of the internal volume. The gas pump may be controlled to maintain a predetermined pressure in the first portion of the internal volume and/or the second portion of the internal volume. For example, the pressurized gas in the second portion of the internal volume may exert a force on the lubricant in the first portion of the internal volume via a diaphragm, a piston, a bladder, or the like positioned between the first and second portions. This may cause the pressure of the lubricant in the first portion of the internal volume to increase, and the pressure may be maintained at this level until the lubricant is released to a machine, as discussed below. In one embodiment, the vacuum and gas pumps may be a single pump that includes a switch at the inlet and outlet sides so that it may serve to increase and decrease the pressure of the gas based on the position of the switch. 
     The method  400  may also include supplying the lubricant from the tank to a machine, as at  406 . More particularly, a sensor may sense when the lubricant supplied to the machine (e.g., from a primary lubrication system) is insufficient. When this occurs, a valve positioned between the tank and the machine may be switched to an open position, and the (now pressurized) lubricant may flow through the valve and to the machine. The lubricant may be supplied to one or more bearings in the machine. By using back pressure to facilitate the flow of the lubricant, the lubricant may flow easier than when compared to a conventional gravity-fed system. In addition, by using back pressure, the lubricant may be supplied in a sub-cooled liquid state. 
     While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the present teachings may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Further, in the discussion and claims herein, the term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal. 
     Other embodiments of the present teachings will be apparent to those skilled in the art from consideration of the specification and practice of the present teachings disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present teachings being indicated by the following claims.