Abstract:
A system and method are disclosed for protecting bearings operating in dirty environments. The system may include a reservoir of lubricant, a bearing, and a regulator. The bearing may border on both the dirty environment and the reservoir. Accordingly, the bearing may be exposed to the solid particles carried by the fluid within the environment, as well as the lubricant of the reservoir. The regulator may ensure that the pressure within the reservoir is greater than the pressure of the dirty environment. Due to the higher pressure within the reservoir, the bearing may be preferentially filled with lubricant rather than dirty fluid from the environment.

Description:
BACKGROUND 
     1. Field of the Invention 
     This invention relates to bearing systems for use in dirty environments and, more particularly, to apparatus and methods for bearing systems suitable for use on a pipeline inspection tool. 
     2. Background of the Invention 
     Oil, petroleum products, natural gas, hazardous liquids, water, and the like are often transported using pipelines. The majority of these pipelines are constructed from steel pipe. Once installed, a pipeline will inevitably corrode or otherwise degrade. Proper pipeline management requires identification, monitoring, and repair of defects and vulnerabilities of the pipeline. For example, information collected about the condition of a pipeline may be used to determine safe operating pressures, facilitate repair, schedule replacement, and the like. 
     Typical defects of a pipeline may include corrosion, gouges, dents, cracks, and the like. Corrosion may cause pitting, general wall loss, or cracking, thereby lowering the maximum operating pressure of the pipeline. Vulnerabilities may also include combined stress and chemical or biological action such as stress corrosion cracking. Without detection and preemptive action, all such defects and vulnerabilities may lead to pipeline failure. 
     Information on the condition of a pipeline is often collected using an in-line inspection (ILI) tool. While collecting such information, an in-line inspection tool is exposed to the adverse environment within a pipeline. That is, pipelines carrying material such as crude oil, natural gas, petroleum products, and raw water typically operate with both high pressure and suspended debris. This environment is often worsened by the presence on an in-line inspection tool, which tends to loosen and stir settled debris as it passes through the pipeline. 
     The adverse pipeline environment can damage an in-line inspection tool. For example, bearings used on an in-line inspection tool are susceptible to frequency failure. Attempts have been made to seal bearings for use in dirty environments. However, in a high pressure environment like a pipeline, seals tend to be limited in their effectiveness. 
     In view of the foregoing, what is needed is a debris resistant bearing suitable for use in dirty environments such as the environment within a pipeline. 
     SUMMARY 
     A bearing system in accordance with the present invention may prolong the life of one or more bearings operating in a dirty environment. For example, a bearing system may protect the bearings of an odometer operating in a pipeline environment. A bearing system may protect a bearing by imparting, to the bearing, lubricant at a greater pressure than the pressure of the surrounding environment. Accordingly, as a bearing rotates, the pressurized lubricant may preferentially work its way into and through the bearing, both blocking lower pressure, environmental contaminants from entering the bearing and flushing the bearing free of debris. 
     In selected embodiments, a bearing system may include a reservoir containing lubricant. Accordingly, a bearing may border on both a dirty environment and a reservoir. By created a higher pressure within the reservoir, the bearing may be preferentially filled with lubricant rather than unwanted material from the surrounding environment. Moreover, the reservoir may ensure that a flow of lubricant through a bearing continues for a period of time sufficient to accomplish the intended mission. 
     A bearing system may include a regulator ensuring that the pressure of the lubricant (e.g., the pressure within the reservoir) is greater than the pressure of the surrounding environment. In selected embodiment, an axle and a plunger translating in the axial direction within the axle may combine to form a regulator in accordance with the present invention. 
     For example, a plunger may have a first surface bounding the dirty environment and a second surface bounding the reservoir. These first and second surfaces may each define a footprint in the axial direction. The footprint of the first surface may be larger in area than the footprint of the second surface. This differential in area may be used to create a differential in pressure between the environment and the reservoir. 
     That is, a plunger may be free to translate within an axle. Accordingly, the plunger may move until it reaches an equilibrium position at which the axial force urging it in one direction is equal to the axial force urging it in an opposite direction. With pressure being equal to force divided by area, when the axial forces are equal, a larger area will result in a lower pressure. Accordingly, by making the footprint of the first surface larger in area than the footprint of the second surface, the bearing system may ensure that the pressure within the reservoir is always greater than the pressure of the surrounding environment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: 
         FIG. 1  is a side elevation view of one embodiment of an in-line inspection tool in accordance with the present invention; 
         FIG. 2  is a perspective view of one embodiment of an odometer for tracking the distance traveled and speed of an in-line inspection tool, the odometer having a bearing system in accordance with the present invention; 
         FIG. 3  is a perspective exploded view of the odometer of  FIG. 2 ; and 
         FIG. 4  is a cross-sectional view of the odometer of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     It will be readily understood that the components of the present invention, as generally described and illustrated in the drawings herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the system and method of the present invention, as represented in the drawings, is not intended to limit the scope of the invention as claimed, but is merely representative of various embodiments of the invention. The illustrated embodiments of the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. 
     Referring to  FIG. 1 , an in-line inspection tool  10  or vehicle  10  in accordance with the present invention may comprise various components including one or more inspection assemblies  12 , canisters  14 , driving cups  16 , couplers  18 , position sensors  20 , and the like. Depending on the configuration of the in-line inspection tool  10  and the size of the pipeline to be inspected, the arrangement and number of components (e.g., the number of canisters  14 ) may vary. 
     Canisters  14  may house equipment such as one or more processors, memory devices, and batteries. The driving cups  16  may center the tool  10  within the pipeline and enable fluid traveling within a pipeline to engage the tool  10 , thereby pushing the tool  10  through the pipeline. In selected embodiments, driving cups  16  may be formed of a somewhat flexible polyurethane or similar material. Couplers  18  may support bending of the tool  10 , enabling the tool  10  to accommodate bends in the pipeline. Like the driving cups  16 , in selected embodiments the couplers  18  may be formed of somewhat flexible polyurethane or similar material. Alternatively, couplers  18  may comprise a mechanical pivoting device. 
     An in-line inspection tool  10  may extend in a longitudinal direction  22  from a head end  24  to a tail end  26 . The various components  12 ,  14 ,  16 ,  18 ,  20  of an in-line inspection tool  10  may be arranged in series. For example, in the illustrated embodiment, the head end  24  of a tool  10  may comprise a head section  28  comprising one or more driving cups  16 . Following the head section  28  may be a primary sensor suite  30 . A coupler  18   a  may extend to connect the head section  28  to the primary sensor suite  30 . 
     In selected embodiments, an in-line inspection tool  10  in accordance with the present invention may include one or more inspection assemblies  12  connected to an interior structure  38  (e.g., interior cylinder  38 ). Each inspection assembly  12  may include one or more magnets  32 , signal sources, sensors, or combinations thereof positioned so as to travel along the interior of a pipe wall being inspected. Such signal sources and sensors may generate and receive a wide variety of signals oriented in any of many directions based on characteristics of the inspection technology or technologies being employed. Suitable inspection technologies may include magnetic flux leakage inspection, ultrasonic inspection, inspection using an electromagnetic acoustic transducer (EMAT), and eddy current inspection. 
     Following the primary sensor suite  30  may be a first canister  14   a . In one embodiment, the first canister  14   a  may house the hardware providing the processing and memory devices for the in-line inspection tool  10 . A coupler  18   b  may extend to connect the primary sensor suite  30  to the first canister  14   a.    
     The first canister  14   a  may be followed by another driving cup  16 . A coupler  18   c  may engage a first canister  14   a  and extend rearward to engage a second canister  14   b . In one embodiment, the second canister  14   b  may house batteries providing the power for the in-line inspection tool  10 . In selected embodiments, a driving cup  16  may connect to the second canister  14   b . One or more position sensors  20  may then engage the second canister  14   b , driving cup  16 , or some combination thereof to form the tail end  26  of the in-line inspection tool  10 . 
     Referring to  FIGS. 2 and 3 , in selected embodiments, a position sensor  20  in accordance with the present invention may comprise an odometer  20  positioned to roll along the interior surface of a pipeline, measuring the distance traveled by an in-line inspection tool  10 . In certain embodiments, an odometer  20  may include a wheel  40  for rolling along a pipeline, a mount  42  for connecting the wheel  40  to the rest of the in-line inspection tool  10 , and a bearing system  44  forming the interface between a mount  42  and a wheel  40 . 
     A mount  42  may provide a suspension system enabling a wheel  40  to roll along the interior of a pipeline despite irregularities therein or thereon. In selected embodiments, a mount  42  may include a base  46  bolted or otherwise fastened to the rest of an in-line inspection tool  10 . One or more swing arms  48  may extend from the base  46  to engage the bearing system  44 . A pin  50  may pivotably connected one or more swing arms  48  to the base  46 . 
     To bias a wheel  40  toward contact with the interior surface of a pipeline, a mount  42  may include one or more biasing members  52  (e.g., coil springs  52 ). A biasing member  52  may extend to connect a swing arm  48  to the base  46 . In certain embodiments, a mount  42  may include two swing arms  48 . In such embodiments, the mount  42  may include two biasing members  52 . One biasing member  52  may extend between a first swing arm  48  and the base  46 . The other biasing member  52  may extend between a second swing arm  48  and the base  46 . 
     In selected embodiments, a mount  42  may include a cross bar  54  extending to connect two or more swing arms  48  together. A cross bar  54  may ensure that the swing arms  48  of a mount  42  pivot together. Additionally, in certain embodiments, a cross bar  54  may provide a location  56  for securing a sensor for monitoring the motion of a wheel  40 . 
     A wheel  40  in accordance with the present invention may include multiple radial slots  58  distributed evenly about the circumference thereof. Such slots  58  may enable a sensor (e.g., a sensor mounted to a cross bar  54 ) to detect incremental movement of the wheel as it rolls along the interior surface of a pipeline. For example, a wheel  40  may be formed of a ferrous material. A sensor positioned in a cross bar  54  may comprise one or more magnets producing a magnetic field. Disruptions in the magnetic field caused by the passage of a slot  58  thereby or therethrough may be detected. Thus, the speed, distance traveled, etc. of an in-line inspection tool  10  may be determined by monitoring the passage of slots  58 . 
     A bearing system  44  in accordance with the present invention may take many forms, depending on the nature of the larger system to which it is applied. While a bearing system  44  suitable for use on an odometer  20  will be described herein, the concepts disclosed may be applied to other systems. Thus, bearing systems  44  in accordance with the present invention are not limited to odometer applications. 
     In selected embodiments, a bearing system  44  may include an axle  60 , one or more bearing housings  62 , and one or more bearings  64 . In the illustrated embodiment, the bearing system  44  includes two bearing housings  62  and two bearings  64 . Each bearing  64  may include an inner race  66  and an outer race  68 . Each bearing  64  may be pressed into a corresponding housing  62  such that the outer race  68  statically engages (e.g., frictionally binds with) the bearing housing  62 . The bearings  64  and bearing housing  62  may then be pressed onto the axle  60 . Each bearing  64  may be pressed onto the axle  60  such that the inner race  66  statically engages (e.g., frictionally binds with) the axle  60 . 
     In certain embodiments, the bearings  64  and bearing housings  62  may be pressed along the axle  60  such that one set  62 ,  64  is one side of the wheel  40  and the other set  62 ,  64  is on the other side of the wheel  40 . The two sets of bearings  64  and bearing housings  62  may be pressed toward one another until the wheel  40  is properly positioned and sealed tightly between the two opposing bearing housings  62 . 
     A bearing housing  62  in accordance with the present invention may include various features facilitating engagement with a wheel  40 . For example, a central aperture extending through a wheel  40  may form a keyway  70 . Accordingly, one or both of the bearing housings  64  abutting a wheel  40  may have a key  72  matching or fitting the keyway  70 . Such an interface between a bearing housing  64  and a wheel  40  may tend to center a wheel  40  on the axle  60  (particularly in embodiments where a wheel  40  does not directly touch an axle  60 ) and ensure a rotationally static (e.g., non-slip) engagement therebetween. 
     In selected embodiments, the surface of a bearing housing  62  abutting a wheel  40  may have a groove  74  formed therein. When a bearing system  44  is assembled, the groove  74  may house a seal (e.g., an elastomeric O-ring). Accordingly, a bearing system  44  may be sealed against incursion of fluid and debris from a surrounding environment. 
     In certain embodiments, an axle  60  in accordance with the present invention may be formed as a hollow cylinder. On or more plungers  76  may be positioned to translate axially within the interior of the axle  60 . In selected embodiments, one plunger  76  may be positioned within a axle  60  proximate a first end of the axle  60 , while another plunger  76  is positioned within the axle  60  proximate a second end, opposite the first end. 
     The surface of a plunger  76  adjacent the interior surface of an axle  60  may have one or more grooves  78  formed therein. When a bearing system  44  is assembled, each groove  78  may house a seal (e.g., an elastomeric O-ring). Accordingly, a plunger  76  may seal the interior of an axle  60  against incursion of fluid and debris from a surrounding environment. 
     Referring to  FIGS. 3 and 4 , in selected embodiments, an axle volume  80  contained within an axle  60  and between opposing plungers  76  may be connected to a bearing volume  82  located exterior to the axle  60  and between opposing bearings  64 . The connection may be made by one or more apertures  84  extending radially through the cylinder wall of an axle  60 . Accordingly, the axle volume  80  and bearing volume  82  may be in fluid communication with one another. 
     Referring to  FIG. 4 , in certain embodiments, a bearing system  44  may protect one or more bearings  64  operating in a dirty environment  86 . For example, in the illustrated embodiment, a bearing system  44  may protect the bearings  64  of an odometer  20  operating in a pipeline environment  86 . Pipelines carrying crude oil, natural gas, petroleum products, or raw water typically operate with both high pressure and suspended debris. This environment  86  is often worsened by the presence on the in-line inspection tool  10  itself, which tends to loosen and stir settled debris as it passed through the pipeline. 
     A bearing system  44  may protect a bearing  64  by imparting thereto lubricant (e.g., a high viscosity lubricant, oil, grease, etc.) at a greater pressure than the pressure of the surrounding environment  86 . Accordingly, as a bearing  64  rotates, the pressurized lubricant may preferentially work its way into and through the bearing  64 , both blocking lower pressure, environmental contaminants from entering the bearing  64  and flushing the bearing  64  free of debris. 
     In selected embodiments, a bearing system  44  may include a reservoir containing lubricant. Accordingly, a bearing  64  may border on both a dirty environment  86  and a reservoir. By created a higher pressure within the reservoir, the bearing  64  may be preferentially filled with lubricant rather than unwanted material from the surrounding environment  86 . Moreover, the reservoir may ensure that a flow of lubricant through a bearing  64  continues for a period of time sufficient to accomplish the mission at hand (e.g., one pipeline run). In the illustrated embodiment, the axle volume  80 , bearing volume  82 , and apertures  84  in the axle  60  may combine to form a reservoir in accordance with the present invention. 
     In certain embodiments, a bearing system  44  may include a regulator ensuring that the pressure of the lubricant (e.g., the pressure within the reservoir) is greater than the pressure of the surrounding environment  86 . In the illustrated embodiment, an axle  60  and a plunger  76  translating in the axial direction  88  therewithin may combine to form a regulator in accordance with the present invention. 
     For example, a plunger  76  may have a first surface  90  bounding the environment  86  and a second surface  92  bounding the reservoir (e.g., the axle volume  80 , which may form part of the reservoir). These first and second surfaces  90 ,  92  may each define a footprint in the axial direction  88 . However, the footprint of the first surface  90  may be larger in area than the footprint of the second surface  92 . This differential in area may be used to create a differential in pressure between the environment  86  and the reservoir. 
     That is, a plunger  76  may be free to translate within an axle  60  through a range of motion in the axial direction  88 . Accordingly, the plunger  76  may move within that range of motion until it reaches an equilibrium position, where the axial force urging it in one direction is equal to the axial force urging it in an opposite direction. While the axial forces may be equal to one another, the differential in area between the first and second surfaces  90 ,  92  may ensure that the pressure acting thereon will not be equal. With pressure being equal to force divided by area, when the axial forces are equal, a larger area will result in a lower pressure. Accordingly, by making the footprint of the first surface  90  larger in area than the footprint of the second surface  92 , the bearing system  44  may ensure that the pressure within the reservoir is always greater than the pressure of the surrounding environment  86 . 
     In selected embodiments, to accommodate a differential in area between the footprint of the first surface  90  and the footprint of the second surface  92 , an axle  60  may include a transition  94 . At a transition  94 , the interior surface of the axle  60  may transition from one inner diameter to another, smaller, inner diameter. 
     A plunger  76  may overlay a transition  94  of an axle  60 . Moreover, a plunger  76  may include a transition  96  of its own. At the transition  96  of a plunger  76 , the exterior surface thereof may transition from one outer diameter to another, smaller, outer diameter. The portion of a plunger  97  having the larger outer diameter may correspond to, and translate within, the portion of the axle  60  having the larger inner diameter. Additionally, the portion of a plunger  97  having the larger outer diameter may produce the end  90  having the larger footprint, when viewed in the axial direction  88 . 
     The range of motion of a plunger  76  within an axle  60  may have limits. In selected embodiments, one limit may correspond to the transitions  94 ,  96  formed in the axle  60  and plunger  76 . For example, once the transition of a plunger  76  contacts the transition  84  of an axle  60 , further motion in that direction may be precluded. The other or opposite limit to the range of motion may be imposed by a mechanical stop. In certain embodiments, the mechanical stop may be selectively removable, facilitating assembly and disassembly of the bearing system  44 . In one embodiment, a mechanical stop may comprise a locking ring position within a channel  98  formed in the axle  60 . 
     A plunger  76  may have an aperture  100  or channel  100  extending therethrough (e.g., axially therethrough). In certain embodiments, an aperture  100  may provide a conduit for charging or refilling a reservoir with lubricant. A check valve may be positioned to regulate the passage of material through the aperture  100 . For example, a check valve may be positioned to admit lubricant into the reservoir and resist release of lubricant from the reservoir. Alternatively, an aperture  100  may be fitted with a cap or seal. Accordingly, lubricant may be pumped through a plunger  76  and into a reservoir on the opposite side thereof, permitting a reservoir to be quickly and easily refilled without significant disassembly. 
     In selected embodiments, a bearing assembly  44  in accordance with the present invention may include only one plunger  76 . In such embodiments, the end of an axle  60  opposite the plunger  76  may be capped or sealed to form a static boundary to the axle volume  80  (e.g., reservoir). 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.