Abstract:
A pipe cleaning device has a housing movable along a pipe to remove a coating. A stripper head, preferably water jets, are located in the housing to remove the coating from the pipe. The coating is removed from the housing by a vacuum hose and a comminuation device is located in the housing to reduce the size of the stripped coating and facilitates passage along the hose. The comminuation device includes a rotor driven by an external motor and aligned with the axis of the hose.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Application No. 61/231,841 filed on Aug. 6, 2009; the contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates, generally, to pipeline surface preparation systems. More particularly, it relates to machines that travel along the length of a pipeline and remove coating therefrom by the application of water jets at ultra high pressure. 
       DESCRIPTION OF THE PRIOR ART 
       [0003]    Pipelines used to carry materials such as oil, gas and water are usually coated on their exterior surface to inhibit corrosion of the pipe material. As part of the maintenance protocol, it is necessary periodically to remove the coating and prepare the surface for recoating. 
         [0004]    Pipelines are typically buried and removal of the coating requires the pipeline to be excavated and lifted to allow access to the pipe. Machines have been proposed that are intended to be supported on and move along the pipe to remove the coating. However, earlier devices are so heavy that a crane is needed to lower them into position atop a pipe. The weight of such devices causes the pipe to sag and thus limits the length of pipeline that can be excavated at any one time. When a crane drops a heavy pipeline surface preparation systems onto a pipeline, there is a risk of damage and ultimately catastrophic explosions may occur. 
         [0005]    U.S. Pat. No. 5,238,331 to Chapman describes a pipeline surface preparation system that is sufficiently light-in-weight to enable a team of two workers to place it into position around a pipeline in the absence of weight-lifting machinery. A frame surrounds the pipeline and supports wheels that engage the surface of the pipeline and enable the pipeline surface preparation system to travel along the extent thereof. The Chapman apparatus employs water jets to strip coating from a pipeline. Water nozzles are circumferentially spaced about the perimeter of the pipeline and limit switches are employed to cause the frame that carries the nozzles to reciprocate along a circumferential path of travel so that hoses connected to the apparatus are not wrapped around the pipeline as the apparatus advances along the length thereof. 
         [0006]    The debris generated by the pipe coating removal process requires careful handling. Old coating commonly includes asbestos and other materials that require special handling. However, the pipeline surface preparation system shown in Chapman does not adequately address the debris-handling problem. The conventional wisdom is that Visqueen® plastic or other suitable sheet material should be placed in overlying relation to the ground below the pipeline undergoing reconditioning. Asbestos and other debris is thus collected atop the plastic sheet material as the machine travels along the extent of the pipeline. Workers then carefully fold the plastic sheet material in an attempt to contain the hazardous materials deposited. The inadequacies of this well-known procedure are readily apparent. Asbestos in small pieces may easily float in the air beyond the reaches of the plastic sheet material and enter the lungs of workers in the vicinity. Asbestos may also enter the lungs of those who attempt to collect it by folding the plastic sheet material into a collection means. 
         [0007]    U.S. Pat. No. 6,832,406 to Boos describes a machine that addresses a number of these problems by enclosing the pipe within a shroud. Debris removed from the pipe surface is removed from the shroud by a vacuum line so it may be filtered and disposed of effectively. The machine shown in U.S. Pat. No. 6,832,406 has been used commercially with success. The arrangement of water nozzles and controls avoids the potential damage to the pipe surface if the machine encounters unforeseen obstacles and the overall design allows the machine to be positioned on the pipeline by workers and operate within the confines of the excavation. 
         [0008]    The water jet action used in the Boos machine is intended to produce relatively small particles so that the asbestos can be controlled. However, the nature of the coating is such that large pieces may be removed due to the lack of adhesion of the coating to the pipe. The presence of these pieces within the shroud inhibits the operation of the machine and requires human intervention to remove them once detected. 
         [0009]    It is known to provide an external shredding means to reduce the debris particles to a more manageable size. The price of an external shredder increases the cost of the system, the time required to operate the external shredder decreases productivity, and the operation of the shredder could potentially add to environmental concerns with hazardous wastes. Moreover, such a shredder is only effective after the particles have been removed from the shroud. 
       SUMMARY OF THE INVENTION 
       [0010]    The novel structure includes a vacuum shroud having a main wall that surrounds a longitudinally-extending section of a pipeline. The vacuum shroud has end walls that are apertured to receive the pipeline. A plurality of equidistantly and circumferentially spaced apart nozzle openings are formed in the main wall and an ultra high pressure water nozzle is positioned within each of the nozzle openings. 
         [0011]    A carrier assembly causes the vacuum shroud to travel along the extent of the pipeline in a predetermined direction. An oscillating means oscillates the vacuum shroud in a first rotational direction and in a second rotational direction opposite to the first rotational direction as the vacuum shroud travels along the pipeline. 
         [0012]    A vacuum opening is formed in the vacuum shroud at a lowermost end thereof. A vacuum hose has a leading end connected to the vacuum opening and a trailing end adapted to be connected to a remote source of negative pressure. A filter trap disposed between the vacuum opening and the remote source of negative pressure collects debris stripped from the pipeline. Accordingly, debris collected within the filter trap is not discharged into the atmosphere. 
         [0013]    The main wall of the vacuum shroud has a cylindrical main body and a wedge-shaped lower body formed integrally therewith. The lower body has a lowermost point positioned coincident with a vertical plane that bisects the pipeline when the machine is in a position of equilibrium so that debris created when said coating is stripped from the pipeline falls under the influence of gravity into the wedge-shaped lower body. 
         [0014]    A comminuation device is incorporated within the wedge shaped lower body so that coating must pass through the device to the vacuum opening. 
         [0015]    Preferably the comminuation device extends parallel to the axis of the pipeline between the end walls of the shroud. As a further preference the device is driven by a motor external to the housing that is either pneumatically or hydraulically driven. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The features of the invention will become more apparent in the following detailed description in which reference is made to the appended drawings wherein: 
           [0017]      FIG. 1  is a side elevational view of a pipeline surface preparation system; 
           [0018]      FIG. 2  is a top plan view taken along line  2 - 2  in  FIG. 1 ; 
           [0019]      FIG. 3  is an end view taken along line  3 - 3  in  FIG. 1 ; 
           [0020]      FIG. 4  is a sectional view taken along line  4 - 4  in  FIG. 1 ; 
           [0021]      FIG. 5  is a sectional view taken along line  5 - 5  in  FIG. 1 ; 
           [0022]      FIG. 6  is a side elevational view of a vacuum shroud; 
           [0023]      FIG. 7  is an end view partly in section of the vacuum shroud; 
           [0024]      FIG. 8  is an enlarged perspective view of a portion of the shroud of  FIG. 6 ; 
           [0025]      FIG. 9  is a sectional view on the line IX-IX of  FIG. 5 ; 
           [0026]      FIG. 10  is an enlarged view of a seal system shown in  FIG. 9 ; and 
           [0027]      FIG. 11  is a view similar to  FIG. 8  of an alternative embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Referring now to  FIG. 1 , a pipeline surface preparation machine  10  has two primary parts, namely a carrier  12  and a stripping head  14 . The carrier  12  performs the function of advancing machine  10  along the extent of pipeline  11 . The stripping head  14  performs the function of removing coating from the pipeline  11 . 
         [0029]    In  FIG. 1 , the direction of travel of machine  10  is denoted by directional arrow  16 . Pipe coating to be removed is denoted  18  and surface of the pipe from which the coating has been removed is denoted  20 . 
         [0030]    Carrier  12  has an open frame construction as depicted so that it is light-in-weight. Carrier  12  contains all major mechanical, electrical, hydraulic, and pneumatic components and controllers. If any part of the assembly fails, the entire drive system can be quickly replaced and subsequently repaired off-line. It is standard to a number of pipe sizes so a spare may always be available. 
         [0031]    As best understood in connection with  FIG. 2 , leading drive wheel  22  and trailing drive wheel  24  are rotatably mounted on axles having their opposite ends supported by mounting plates  21 ,  23 , respectively, that form a part of the frame assembly. Drive wheels  22 ,  24  are in longitudinal alignment with one another and are typically of rubber construction. Each of said drive wheels is contoured as depicted in  FIGS. 2 and 8 . The concave curvature of each wheel matches the convex curvature of the pipeline to enhance the traction between the wheels and the pipeline. Moreover, the surface of each wheel has a saw tooth or gear tooth tread to further enhance the traction. Wheels  22 ,  24  drive the machine  10  at a controlled constant rate of forward speed along the pipeline. Machine  10  is driven by wheels  22 ,  24  up inclines as steep as fifty degrees or down declines of the same degree. Carrier  12  will also follow long radius pipeline curves. 
         [0032]    Wheels  22 ,  24  prevent rotational slippage of carrier assembly  12  relative to pipeline  11 . This ensures that pipe stripped of its coating will not be impinged by a stationary jet for extended periods. 
         [0033]    As perhaps best understood in connection with  FIG. 2 , wheels  22  and  24  are driven by hydraulic motor  26  although electrical or mechanical drives may be used if preferred. More particularly, output shaft  28  is connected in driving relation to gears  29 ,  31  that drive belts  30 ,  32 , respectively. Belts  30 ,  32  drive gears  33 ,  35  that are mounted on axles  34 ,  36  upon which drive wheels  22 ,  24  are mounted, respectively. 
         [0034]    Control lever  38  is connected as depicted to gearbox  39  and enables an operator to place motor  26  into forward, stop or reverse. 
         [0035]    As best understood in connection with  FIG. 3 , frame  40  includes a top part  40   a , first bottom part  40   b , and second bottom part  40   c . Each of said parts has a frame-like construction so that it is light-in-weight. Top part  40   a  is positioned above the pipe in spaced relation thereto. First side part  40   b  is releasably connected to a first end of top part  40   a  by quick-release coupling means  42  and second side part  40   c  is releasably connected to a second end of top part  40   a  by quick-release coupling means  44 . First and second side parts  40   b ,  40   c  are releasably connected to one another by quick-release coupling means  46 . Two workers lift top part  40   a  into position. Workers standing on opposite sides of the pipeline then engage first and second parts  40   b  and  40   c  thereto and to one another. 
         [0036]    Wheels  46   a  and  46   b  ( FIG. 1 ) are circumferentially spaced one hundred twenty degrees from drive wheels  22 ,  24  and are on opposite sides of carrier  12 . Wheels  48   a  and  48   b  of the same construction are also circumferentially spaced one hundred twenty degrees from drive wheels  22 ,  24  and the same number of degrees from wheel  46   a ,  46   b  and are also on opposite sides of carrier  12 . Wheels  46   a ,  46   b  and  48   a ,  48   b  are mechanically compressed against cleaned surface  20  and cooperate with drive wheels  22 ,  24  to maintain the frame of driving apparatus  12  in concentric alignment with the pipeline. Wheels  46   a ,  46   b ,  48   a , and  48   b  are passive, however, and do not provide any motive force to the travel of driving apparatus  12  along the extent of the pipeline. 
         [0037]    The stripping head  14  includes vacuum shroud  50  that circumscribes pipeline  11  in advance of the carrier  12 . Vacuum shroud  50  includes a first cylindrical wall  52  that circumscribes pipeline  11  and a pair of centrally apertured end walls. End wall  54  is depicted in  FIG. 5  and end wall  56  is depicted in  FIG. 4 . The shroud  50  is formed in two parts  50   a ,  50   b  that are hinged to one another by a hinge  50   c . The parts  50   a ,  50   b  are connected by a quick release fastener  50   d  with seals between the two parts to maintain the integrity of the shroud  50 . The shroud  50  may therefore be opened, placed on the pipeline  11  and secured to encompass the pipeline. 
         [0038]    As best understood in connection with  FIGS. 1 and 5 , a wedge-shaped debris collection chamber  51  is integrally formed with vacuum shroud  50  at its lowermost end. Vacuum hose  53  has a trailing end, not shown, in fluid communication with a remote source of negative pressure. The leading end of said vacuum hose  53  is in fluid communication with a cylindrical trough  51   a  located at the apex of the wedge-shaped debris collection chamber  51  as depicted to provide a material handling system to remove debris from the collection chamber  51 . It should be understood that the hollow interior of vacuum shroud  50  and the hollow interior of wedge-shaped debris collection chamber  51  are in open communication with one another. Debris created by removal of the pipe coating thus falls under the influence of gravity into debris collection chamber  51  and into trough  51   a.    
         [0039]    As will be better understood as this description proceeds, the ultra high pressure and unique nozzle movement of the machine shreds the debris created by removal of the pipe coating into particles that are typically no larger than a quarter inch in diameter. 
         [0040]    A comminuation device  100  is located within the trough  51   a  of the housing  50  to ensure that coating  18  is below a particular size so it may be handled by the material handling system. As can be seen in  FIGS. 6 to 8 , the comminutating device  100  includes a shaft  102  that is rotably mounted in the housing  50  on bearings  104 ,  106  for rotation about a axis parallel to the pipeline  11 . The bearing  106  adjacent outlet  53  is supported on a spider  108  to provide clearance for material to flow to the outlet  53 . 
         [0041]    A plurality of fingers  110  extend radially from the shaft  102  and into close proximity to the wall of a cylindrical trough  51   a  of the wedge shaped portion  51 . The fingers  110  pass between stationary fingers  112  mounted on the housing  51  and extending toward the shaft  102 . 
         [0042]    The interdigitated fingers  110 ,  112  are axially spaced approximately the maximum size of particle that can be accommodated in the outlet  53 . 
         [0043]    A motor  114  is mounted on the exterior of the end wall  55  and drives the shaft  102 , either directly or through a gear train or chain drive. The motor  114  may be electrical, pneumatic or hydraulic, depending on the services available. 
         [0044]      FIGS. 9 and 10  provide an interior view of vacuum shroud  50 . The shroud  50  is sealed against the pipeline  11  by seal assemblies  55 ,  57  and is secured to an interior surface of leading shroud end wall  54  and trailing shroud end wall  56  respectively. 
         [0045]    Each of the seal assemblies  55 ,  57  is similar and therefore only one will be described in detail. 
         [0046]    A radial wall  58  extends toward the pipeline  11  and carries on inflatable seal  59  at its radially inner end. Each of the seals  59  is semi circular so as to extend around the radially inner edges of each half of the shroud  50   a ,  50   b . The seal  59  bears against the pipeline  11  and is inflated to provide a positive contact for the seal against the pipeline  11 . 
         [0047]    A pair of brushes,  61 , are mounted on opposite sides of the seal  59  to further inhibit egress of material from the shroud. 
         [0048]    The inflatable seals  59  deform to accommodate irregularities on the surface of the pipeline  11  as the shroud rotates and advances alone the pipeline  11 . 
         [0049]    The seal assemblies  55 ,  57  maintain water vapor and debris emissions such as asbestos, lead, and other hazardous materials, at levels well below exposure limits established by the Occupational Safety and Health Administration while maintaining the vacuum within shroud  50  as already mentioned. The waste generated by the cleaning process is then recycled through a closed loop filtration system that separates solids from reusable liquid, thereby substantially reducing the quantity of disposable waste. 
         [0050]    The oscillation of vacuum shroud  50 , relative to the longitudinal axis of pipeline  11 , as it advances along the length of pipeline  11  is best understood in connection with  FIG. 5 . The position of repose or top center of vacuum shroud  50  is indicated in solid lines and dotted lines indicate its respective positions when at the limits of its oscillation. When in its position of repose, a vertical plane passes through first limit switch actuator  50   a  and through the lowermost point of debris collection chamber  51 . Carrier assembly  12  does not oscillate. 
         [0051]    As best understood in connection with  FIGS. 2-4 , gear  70  and  72  are connected to the respective outputs shafts of motors  74 ,  76 , respectively secured to the carrier  12 . Gear assemblies  70 ,  72  include a plurality of circumferentially spur gears  73 ,  75  ( FIG. 3 ) respectively, that are connected to the output shafts  74   a  and  76   a  of motors  74 ,  76  and mesh with sprocket teeth formed on sprocket gears  78 ,  80 . 
         [0052]    A large ring  82  ( FIG. 4 ) is fixedly secured to the trailing end of vacuum shroud  50  as depicted in  FIGS. 1 and 2  and has teeth  83  formed therein along about two hundred forty degrees) (240°) of its circumferential extent. Teeth 83 mesh with sprockets  86 ,  88  ( FIG. 4 ) that form a part of gears  78 ,  80  ( FIG. 3 ). Motors  74 ,  76  effect rotation of gear assemblies  70  and  72  which drive gears  78  and  80  and thus effect rotation of large ring  82 . A pair of limit switches are mounted on non-oscillating carrier assembly  12  in positions of sixty five degrees (65°) from either side of top center. Accordingly, as large ring gear  82  is rotated by motors  74 ,  76  in the manner described above, the large ring gear rotates until limit switch actuator  50   a  ( FIG. 5 ) contacts first limit switch  50   b . Limit switch  50   b , upon being thrown by said contact, sends a signal that reverses the direction of operation of motors  74 ,  76  so that large ring gear  82  begins rotating in an opposite direction. The gear  82  then rotates in the opposite direction until limit switch actuator  50   a  contacts second limit switch  50   c  and said second limit switch sends a signal that reverses said motors  74 ,  76 . An oscillation cycle of one hundred thirty degrees (130 .degree.) is thereby attained. Such oscillation of large ring gear  82  and hence of vacuum shroud  50  to which said ring gear is secured continues for as long as machine  10  is in operation. The rocking motion of vacuum shroud  50  further serves to facilitate collection of debris within said debris collection chamber. 
         [0053]    The combination of linear travel and oscillatory motion of vacuum shroud  50  further ensures against the creation of hot spots, resulting from stationary positioning of the shroud. 
         [0054]    In a preferred embodiment a stipping head to remove water from the pipe comprises, three ultra high pressure water manifolds are mounted on vacuum shroud  50  in circumferentially and equidistantly spaced relation to one another. Thus, the manifolds are spaced about one hundred twenty degrees (120 degree.) apart from one another. Two of the manifolds are visible in the side view of  FIG. 1  and said manifolds are collectively denoted  84 . Hose  84   a  delivers ultra high pressure (40,000 lbs/in 2 ) water or other suitable liquid fluid and hose  84   b  delivers air at a suitable pressure to drive air motors which in turn rotate the nozzles. Element  84   c  is an electrical sensor in electrical communication with a programmable logic controller that shuts down the ultra high pressure nozzle flow if nozzle movement stops or the system air pressure drops. Similar sensors monitor the forward advance of carrier assembly  12  and the oscillation of vacuum shroud  50  and shut down the system if either of the motions stop. This fail-safe control eliminates potential pipeline or surface damage caused by extended nozzle dwell time. 
         [0055]    Each manifold  84  includes four or five individual sapphire nozzles, each of which spins at three thousand revolutions per minute (3,000 rpm). This provides a uniform spray pattern over a two inch (2″) or so diameter area. This manifold of spinning nozzles provides a uniformly cleaned surface that is free of hot spots and surface damage. 
         [0056]    Mounting manifolds  84  in vacuum shroud  50  also ensures that the distance between each nozzle and the surface of the pipeline will always be a uniform distance and thereby produce a uniform effect on the surface of pipe  11 . 
         [0057]    The effect of the nozzles  84  is to remove the coating in relatively small pieces with the fibrous materials contained within a slurry. However, there is a tendency for some of the coating  18  to flake off as larger pieces that become lodged in the lower portion of the housing  50 . 
         [0058]    Relatively small pieces of coating will fall between the fingers  110 ,  112  as the housing  50  oscillates and pass freely to the outlet  53 . Larger pieces that may flake off do not pass between the fingers  110  and are carried by the fingers  110  into contact with the fingers  112 . The flakes are broken into smaller pieces through the interaction of the fingers  110 ,  112 , allowing them to pass through the outlet  53 . 
         [0059]    An alternative embodiment is shown in  FIG. 11  where like components will be identified by like reference numerals with a suffix ‘a’ added for clarity. In the embodiment of  FIG. 11 , a pair of shafts  102   a  are mounted between the end walls  55   a ,  57   a  adjacent to but spaced from the outlet  53   a . Each of the shafts  102   a  carries radially extending fingers  110   a  that interdigitate. 
         [0060]    The shafts  102   a  are connected by spur gears  120  and a motor  114  drives one of the shafts  102   a . Rotation of one of the shafts is transmitted to the other shaft through the gears  120  so that the shafts  102   a  counter rotate. 
         [0061]    In operation, as larger pieces fall toward the outlet  53   a , the fingers  102   a  interact to break them into smaller pieces that can be handled by the outlet  53   a.    
         [0062]    In either embodiment, the comminuation device  100  reduces the size of the removed coating to avoid blockage.