Abstract:
An apparatus and method to analyze fluid degradation in a closed system is disclosed. The method includes collection of a sample fluid from the closed system. The sample fluid collected is maintained at a sample fluid pressure, which is substantially equivalent to a pressure of the closed system. Thereafter, a change of a volume of the sample fluid is caused, which generates a change in the sample fluid pressure. A series of sample fluid pressures and volumes of the sample fluid are taken. Next, a bulk modulus of the sample fluid is determined. The bulk modulus of the sample fluid is compared with a baseline bulk modulus. Lastly, the method involves generation of a communication when the bulk modulus of the sample fluid breaches a tolerance.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates generally to an apparatus and a method to analyze degradation of a fluid in a hydraulic circuit. More specifically, the present disclosure relates to measurement of a bulk modulus and a compressibility of the fluid that may be detrimental to effective operation of the hydraulic circuit. 
       BACKGROUND 
       [0002]    Many work machines, such as earthworking machines, or the like, include hydraulic circuits to run motors and cylinders, for example. These hydraulic circuits typically include components, such as pumps and actuators, which have moving parts and sealing systems that may wear out and eventually fail. One reason for such failures is that the hydraulic fluids within these hydraulic circuits may compress and decompress due to pressure changes. An abrupt pressure change, for example, may cause the formation and subsequent implosion of gaseous bubbles within the hydraulic fluid. As a result, pressure waves are created that may lead to an increased rate of wear and cyclic fatigue failure of the components. In addition, a pump or a hydraulic component may sustain conditions such as cavitation (or the formation of cavities), which may harm the hydraulic circuit&#39;s efficiency. 
         [0003]    It is well known in the art to initiate preventive maintenance strategies and a fluid change to prevent such failures. However, without accurate determination of the fluid&#39;s characteristics, a machine&#39;s downtime may be inappropriately notified. For example, such notification may be generated well before the occurrence of an actual downtime. As a result, a component of the hydraulic circuit may have to be unduly replaced or repaired well before its warranted operational life. Conversely, an inability to timely determine an initial stage failure of components may lead to uncertainty and an increased possibility of a future catastrophic failure. Therefore, it has remained a challenge to determine an opportune time to schedule preventive maintenance strategies, given the difficulty in assessing a component&#39;s failure. Consequentially, losses in productivity may occur due to ineffectively scheduled maintenance programs. 
         [0004]    U.S. Pat. No. 2,880,611 A relates to an apparatus for the measurement of bulk modulus in a hydraulic circuit. Although the &#39;611 reference discusses the computation of a compressibility curve, the associated apparatus is integrated into a conduit from where it remains difficult to utilize the apparatus in multiple hydraulic assemblies. Moreover, room remains to further simplify a power system that samples and generates variation of pressure versus volume of a hydraulic fluid. This is because the apparatus of the &#39;611 reference is dependent upon external power, such as hydraulic power, to induce an associated pressure. 
         [0005]    Accordingly, the system and method of the present disclosure solves one or more problems set forth above and other problems in the art. 
       SUMMARY OF THE INVENTION 
       [0006]    Various aspects of the present disclosure illustrate a method to analyze fluid degradation in a closed system. The method includes a collection of a sample fluid from the closed system. The sample fluid is maintained at a sample fluid pressure, which is substantially equivalent to a pressure of the closed system. Thereafter, a change of a volume of the sample fluid is effectuated to generate a change in the sample fluid pressure. Thereafter, a series of sample fluid pressure and volume of the sample fluid is taken. A bulk modulus of the sample fluid is established. Subsequently, a comparison between the bulk modulus of the sample fluid to a baseline bulk modulus is conducted. If the bulk modulus of the sample fluid breaches a tolerance, the method ends with the generation of a corresponding communication. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a partial view of a power system, illustrated with an exemplary bulk modulus apparatus in a potential assembly position relative to the power system, in accordance with the concepts of the present disclosure; 
           [0008]      FIG. 2  is an enlarged perspective view of the bulk modulus apparatus of  FIG. 1 ; 
           [0009]      FIG. 3  is an exploded view of the bulk modulus apparatus of  FIG. 1 ; 
           [0010]      FIG. 4  is a schematic view of the bulk modulus apparatus of  FIG. 1 , in accordance with the concepts of the present disclosure; and 
           [0011]      FIG. 5  is a flowchart of an exemplary method of operation of the bulk modulus apparatus, in accordance with the concepts of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIG. 1 , there is shown an exemplary power system  100 . The power system  100  is partially shown for clarity and ease in depicting the aspects of the present disclosure. Although not limited, the power system  100  may be an engine, such as a spark-ignition engine or a compression ignition engine, which may be applied in construction machines, such as track-type tractors, hydraulic excavators, wheel loaders, motor graders, and large mining trucks. However, it will be appreciated that aspects of the present disclosure are focused to a hydraulic circuit  102 , which is incorporated within the power system  100 . Therefore, it may be well suited for one to apply and extend an applicability of the present disclosure to hydraulic circuits that operate elsewhere. For example, hydraulic circuits in transmission units, work implements, fuel systems, drivetrains, and the like, may suitably benefit from one or more aspects disclosed herein. An extension of the application to domestic and commercial application may also be contemplated. 
         [0013]    The hydraulic circuit  102  may be a closed system, incorporated within the power system  100 . The hydraulic circuit  102  may be utilized for execution of one or more functions associated with the power system  100 . As an example, the hydraulic circuit  102  may be configured to actuate a gas exchange valve of the power system  100 . In another example, the hydraulic circuit  102  may be operably connected to the power system  100  and may be used to run an associated fan drive unit (not shown) of the power system  100 . In some embodiments, the hydraulic circuit  102  may use the same oil as the power system  100 &#39;s lubricating system, for the performance of one or more applications. 
         [0014]    The hydraulic circuit  102  is inclusive of a conduit  104 , which facilitates passage of a hydraulic fluid from one portion of the hydraulic circuit  102  to another. The conduit  104  is connected to a sample flow line  106 , which may be interchangeably referred to as a test line  106 . In an embodiment, the test line  106  may be a closed loop bypass connection within the hydraulic circuit  102  that facilitates passage of a portion of the hydraulic fluid, and returns that portion to the hydraulic circuit  102 . The test line  106  may be subject to a passage of an amount of hydraulic fluid during an operation of the hydraulic circuit  102 . The test line  106  may be conducted within an existing line of the hydraulic circuit  102 . However, it is envisioned that the test line  106  may differ from other passages, and is retrofitted to the hydraulic circuit  102 . 
         [0015]    The test line  106  includes a quick-disconnect coupler  108  that facilitates a temporary fluid connection between the hydraulic circuit  102  and a working hydraulic accessory, such as a bulk modulus measurement apparatus  110  (or simply, a bulk modulus apparatus  110 ). The quick-disconnect coupler  108  is of a type which prevents the hydraulic fluid from flowing out of the test line  106  when the quick-disconnect coupler  108  is uncoupled. The quick-disconnect coupler  108  may be a widely available standardized coupler unit adapted for relatively quick connections and disconnections with a counter-mating coupler, such as a counter-mating coupler  112  of the bulk modulus apparatus  110 . As an example, the quick-disconnect coupler  108  may be a female coupler unit, into which a male counter-mating coupler  112  is threadably fitted or press-fitted, for assembly. 
         [0016]    As illustrated in  FIG. 1 , the bulk modulus apparatus  110  is in an exemplary assembly position relative to the hydraulic circuit  102 . The bulk modulus apparatus  110  is generally portable and is configured to be manually held by an operator  114   114 , as shown. As the bulk modulus apparatus  110  is provided with a counter-mating coupler  112 , a connection between the test line  106  and the bulk modulus apparatus  110  is attainable, which, in turn, allows the bulk modulus apparatus  110  to retrieve a sample of the hydraulic fluid that passes through the test line  106 . 
         [0017]    Referring to  FIGS. 2 and 3 , the bulk modulus apparatus  110  is shown in greater detail. The bulk modulus apparatus  110  includes a primary cylinder  116 , a secondary cylinder  118 , a pressure gauge  120 , and an open/close ball valve  122 . 
         [0018]    The primary cylinder  116  and the secondary cylinder  118  (or simply cylinders  116  and  118 ) are generally longitudinal, hollow members capable of accommodating, at least temporarily, a fluid extracted from the test line  106  of a charged hydraulic circuit  102 . The cylinders  116  and  118  are generally positioned at right angles to each other, although this configuration is not limited and a plurality of angular placement between the primary cylinder  116  and the secondary cylinder  118  is envisioned. The primary cylinder  116  is larger in dimension in relation to the secondary cylinder  118 . Accordingly, the primary cylinder  116  is adapted to hold a higher quantity of the hydraulic fluid as compared to the secondary cylinder  118 . 
         [0019]    The primary cylinder  116  is generally barrel shaped and has a substantially circular cross-sectional profile. The primary cylinder  116  includes a primary piston  126  ( FIG. 3 ), a piston plunger  128 , and a primary hex head  130 . The primary piston  126  is configured to move back and forth along an elongation, A, (or a longitudinal axis  150 ) of the primary cylinder  116 , during applications. The primary piston  126  ( FIG. 3 ) is generally positioned into a depth of the primary cylinder  116  so as to vary a holding volume of the primary cylinder  116 . This variation is possible by manipulating the primary hex head  130 , which is accessible to an operator  114  deployed outside of the primary cylinder  116 . Further, the piston plunger  128  is connected between the primary piston  126  ( FIG. 3 ) and the primary hex head  130 , and, in that way, the piston plunger  128  allows the primary piston  126  to be varied in depth upon a manipulation by the primary hex head  130 . 
         [0020]    The primary cylinder  116  is generally closed at its two ends  132  and  144 . The primary cylinder  116  includes a cylinder head  134  and an end cap  152  positioned at one end  132 , and a cylinder base  142  at the other end  144  ( FIG. 2 ). These facilitate sealing of the primary cylinder  116  at the ends  132  and  144  ( FIG. 2 ). Moreover, the primary cylinder  116  includes tie rods  140 , which are exemplified in the present disclosure as being four in number. The tie rods  140  are assembled along the primary cylinder  116 ′s outer structure to affirm a tightened connection between the cylinder head  134  and the end cap  152  at the one end  132  ( FIG. 2 ), and the cylinder base  142 , at the other end  144  ( FIG. 2 ). In this manner, the primary cylinder  116  is positively sealed at both ends  132  and  144  ( FIG. 2 ). As is customary, tie rods  140  may generally be ‘long bolts’ that have bolt heads  138  at one end  132  and threads  154  ( FIG. 3 ) at the other end  144 . The bolt heads  138  of the tie rods  140  engages the end cap  152 , while the threads engages the cylinder base  142  and are secured by hex nuts  156 , as is customary. Further, the end cap  152  includes a collar  136  positioned at an interface between the piston plunger  128  and the end cap  152 . The collar  136  provides the piston plunger  128  with guidance to effectively accomplish the motion associated with the back and forth movement of the primary piston  126 . 
         [0021]    The secondary cylinder  118  is positioned at substantial right angles relative to the primary cylinder  116 , as already noted. However, this configuration is purely exemplary in nature. Therefore, the secondary cylinder  118  may be positioned at an incline to the primary cylinder  116  so as to make the bulk modulus apparatus  110  more compact, for example. In structure, the secondary cylinder  118  may be similar in shape and function to the primary cylinder  116 . However, the secondary cylinder  118  is much smaller is size than the primary cylinder  116 , as noted above. At an outer end  160  ( FIG. 2 ) of the secondary cylinder  118 , there is included a secondary hex head  148 , which is adapted to linearly manipulate a secondary piston  146  ( FIG. 3 ) positioned generally within the confines of the secondary cylinder  118 . Therefore, as with the primary piston  126 , the secondary piston  146  may be moveable across an elongation, B, of the secondary cylinder  118 , as well. At the opposite end  162  of the secondary cylinder  118 , the secondary cylinder  118  merges with the primary cylinder  116  and is in fluid communication with the primary cylinder  116 . In an embodiment, it may be beneficial to have both the cylinders  116  and  118  formed as an integrated unit. 
         [0022]    Referring to FIGS,  2 ,  3 , and  4 , the cylinder base  142  ( FIGS. 2 and 3 ) is generally block-shaped, and forms a connection interface between the primary cylinder  116  and the secondary cylinder  118 . In the depicted embodiment, the secondary cylinder  118  is mounted to this block-shaped cylinder base  142  so as to be fluidly connected with the primary cylinder  116 . In this manner, both the cylinders  116  and  118  define a common volume or a chamber  164  ( FIG. 4 ). Further, by manipulation of the primary hex head  130  and the secondary hex head  148 , both cylinders  116  and  118  may receive a sample hydraulic fluid (or simply sample fluid) and affect a volume of the cylinders  116  and  118 . The primary cylinder  116  is configured to vary volume of a housed fluid in relatively larger degree, while the secondary cylinder  118  is configured to affect volume of the housed fluid in a relatively smaller or a finer degree. 
         [0023]    The chamber  164  ( FIG. 4 ) houses a volume of the sample fluid extracted from the charged hydraulic circuit  102 , during applications. The chamber  164  ( FIG. 4 ) is generally L-shaped. However, this shape may be dependent upon the angular configuration between the primary cylinder  116  and the secondary cylinder  118 . Moreover, the chamber  164  is adapted to receive pressure variations from either of the cylinders  116  and  118 . 
         [0024]    Both the primary piston  126  and the secondary piston  146  are threadably engaged respectively to the primary cylinder  116  and the secondary cylinder  118 . Threads associated with these arrangements are calibrated to affect a precise volume within the cylinders  116  and  118 , such that every unit change in volume is attributed to a rotation of the associated hex heads  130  and  148 . In effect, changes in rotary position of the primary hex head  130  and the secondary hex head  148  are directly proportional to changes in the internal volume of the chamber  164  ( FIG. 4 ). 
         [0025]    The pressure gauge  120  is affixed to the cylinder base  142 , as the cylinder base  142  offers communicability to the chamber  164  where the extracted sample fluid is housed. This arrangement facilitates calibration of the sample fluid&#39;s pressure variations relative to the changes made in the volume by the rotation of the hex heads  130  and  148 . Consequentially, a bulk modulus may be computed as a pressure variation is sustained corresponding every unit change in the volume of the chamber  164  ( FIG. 4 ). The pressure gauge  120  is generally an analog apparatus, used to read the fluid pressure within the chamber  164 . However, a digital pressure gauge may be applied. 
         [0026]    The open/close ball valve  122  is positioned at the cylinder base  142 , between the primary cylinder  116  and the quick-disconnect coupler  108 . The open/close ball valve  122  may be adapted to be manually operated and to isolate the sample fluid within the chamber  164  from ambient  166 . In an embodiment, the open/close ball valve  122  may be supplemented with a generally unidirectional valve  158  ( FIG. 4 ). The unidirectional valve  158  ( FIG. 4 ) may be positioned upstream to the open/close ball valve  122 . The unidirectional valve  158  is integrated with the quick-disconnect coupler  108  to prevent leakage once the quick-disconnect coupler  108  is removed from the counter-mating coupler  112  of the test line  106 . 
         [0027]    Referring to  FIG. 5 , an exemplary methodology of the bulk modulus apparatus  110  is explained by means of a flowchart  500 . The method begins at step  502 . 
         [0028]    At step  502 , an operator  114  collects a sample fluid from the hydraulic circuit  102  (closed system). To comply with the original pressure conditions of the hydraulic circuit  102 , the chamber  164  maintains the collected sample fluid at a pressure equivalent to the pressure of the hydraulic circuit  102 , after the sample fluid is isolated and the bulk modulus apparatus  110  is dislodged from the test line  106 . The method proceeds to step  504 . 
         [0029]    At step  504 , the operator  114  varies a volume of the sample fluid in the chamber  164  to generate a change in the sample fluid pressure. This change is attained by incrementally varying the volume of the primary cylinder  116 , and varying a volume of the chamber  164  in finer incremental steps by the secondary cylinder  118 . The incremental variation of the primary cylinder  116  is to attain larger degrees of volume variation in the chamber  164 , while incremental variation of the secondary cylinder  118  may be attuned for correction of the volume of the chamber  164 . Effectively, the finer incremental steps are generally minimalistic in nature so as to attain a closer to a precise volume of the chamber  164 . The method proceeds to step  506 . 
         [0030]    At step  506 , as each incremental variation of the volume of the cylinders  116  and  118  directly and proportionally affects a pressure of the housed sample fluid, multiple readings that pertains to change in pressure versus change in volume is noted. To this end, the operator  114  takes and records data that corresponds to a series of sample fluid pressure and sample fluid volume of the sample fluid. The method proceeds to step  508 . 
         [0031]    At step  508 , since a change in pressure is obtained corresponding to the variation of volume of the sample fluid, the operator  114  determines a bulk modulus of the sample fluid. Moreover, the operator  114  at this stage is able to generate a compressibility curve for the sample fluid. The method proceeds to step  510 . 
         [0032]    At step  510 , the operator  114  compares the bulk modulus of the sample fluid with a baseline bulk modulus. This stage also allows the operator  114  to ascertain an actual bulk modulus of the sample fluid. This assists in a determination of a health of the sample fluid and a level of degradation sustained by the sample fluid. A compressibility of the sample fluid is determined. As the sample fluid mimics a condition of the hydraulic fluid that runs within the hydraulic circuit  102 , a state of the hydraulic fluid is determined. The method proceeds to end step  512 . 
         [0033]    At end step  512 , the operator  114  generates a communication in response to the difference determined between the baseline bulk modulus and the bulk modulus of the sample fluid. More particularly, the communication is generated if the bulk modulus of the sample fluid is outside a tolerance. Thereafter, preventive maintenance strategies are initiated and a predictive strategy to prevent downtime of the power system  100  is effectively calibrated. The method ends at end step  512 . 
       INDUSTRIAL APPLICABILITY 
       [0034]    In operation, an operator  114  connects the bulk modulus apparatus  110  to the test line  106 . This connection is facilitated through a connection between the quick-disconnect coupler  108  and the counter-mating coupler  112 . Since the quick-disconnect coupler  108  is a female coupler, the counter-mating coupler  112  (which may be a male coupler) is inserted and press fitted or threadably fitted into the quick-disconnect coupler  108 . At this stage, the chamber  164  will have a minimal volume. Once the bulk modulus apparatus  110  is positively connected to the test line  106 , an operator  114  opens the open/close ball valve  122  and rotates the primary hex head  130  until a certain volume of sample fluid is obtained by suction into the chamber  164 . If the requirement is to have a precise volume of sample fluid, the operator  114  may operate the secondary hex head  148  to extract the finer volume of the sample fluid. At this stage, the hydraulic fluid (or the collected sample fluid) may be cycled in and out of the bulk modulus apparatus  110  to eliminate any trapped air before taking a sample fluid. Once a sample fluid is collected in the bulk modulus apparatus  110 , an operator closes the open/close ball valve  122  to facilitate isolation of the sample fluid. In that manner, the bulk modulus apparatus  110  is able to maintain the sample fluid at a pressure equivalent to the original hydraulic circuit pressure. As a result, the test line connection facilitates the acquisition of a sample fluid into the bulk modulus apparatus  110 . After a sufficient quantity of sample fluid is acquired into the chamber  164 , the operator  114  closes the open/close ball valve  122  and disconnects the bulk modulus apparatus  110  from the test line  106 . 
         [0035]    Thereafter, the operator  114  may incrementally vary a volume of the primary cylinder  116  by manipulating the primary hex head  130  of the primary cylinder  116 . This causes the primary piston  126  to move along the longitudinal axis  150  of the primary cylinder  116  and compresses the sample fluid acquired within the chamber  164 . Similarly, the operator  114  may adjust the secondary hex head  148  to vary and correct finer volumes of the sample fluid. Since change in volume leads to a change in pressure of the sample fluid, pressure readings are recorded for several different instances of volumes. As a result, the operator  114  calculates a bulk modulus of the sample fluid. As multiple readings are recorded for different volumes, multiple values of bulk modules are obtained. An operator  114  plots these values graphically and computes a compressibility curve of the sample fluid. The operator  114  then compares this compressibility curve, also referred to as an actual bulk modulus, to a baseline bulk modulus. Subsequently, the operator  114  generates a communication if the bulk modulus of the sample fluid breaches a tolerance. Additionally, by usage of the compressibility curves, the gaseous content in the sample fluid that may factor in the reproduction of the characteristic compressibility curve, are also determined. 
         [0036]    If such a communication is generated, it may be imperative for authorized personnel to initiate precautionary measures and preventive actions. As an example, precautionary measures may include change of the components and a change in the hydraulic fluid as one analyzes the degradation that the fluid has sustained along a prolonged operational period. 
         [0037]    If an initial stage failure is predicted or sensed prior to an imminent catastrophic failure, a deteriorated component may be replaced or repaired before damage to other components occurs. Additionally, it may also signal a change of fluid well before downtime affects a machine. Moreover, if imminent failure of a component is detected, preventive maintenance strategies on the component could be scheduled at the most opportune time to reduce productivity losses typically caused by such a maintenance operations. 
         [0038]    Advantageously, the portability of the bulk modulus apparatus  110  and provision of a standardized counter-mating coupler  112  on the bulk modulus apparatus  110  allows the bulk modulus apparatus  110  to be applicable on various other ports of the power system  100  that apply hydraulic power. Moreover, the counter-mating coupler  112  allows for relatively easy installation and removal of the bulk modulus apparatus  110  from the test line  106  of the hydraulic circuit  102 . Therefore, the bulk modulus apparatus  110  may be applied to machines and systems even outside the power system  100 . 
         [0039]    It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure may be obtained from a study of the drawings, the disclosure, and the appended claim.