Abstract:
A machine for surface preparation of a pipeline includes a vacuum shroud that encircles the pipeline. Three manifolds, each housing a plurality of ultra high pressure water nozzles, are mounted in the vacuum shroud at circumferentially spaced intervals. A carrier assembly advances the vacuum shroud along the pipeline at a rate that avoids contact between the water jets and uncoated pipe. The shroud also oscillates about a longitudinal axis of the pipeline so that a short extent of the pipeline is subjected to the force of the water for each oscillation. The vacuum in the shroud carries away all debris created by the coat-stripping process to a closed loop filtration and recycling system. The nozzles are mounted a constant stand-off distance from the pipeline to avoid creation of hot spots during the stripping process. All motions are electronically monitored and detection of any movement failure results in system shutdown.

Description:
BACKGROUND OF INVENTION 
     1. Field of the Invention 
     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. 
     2. Description of the Prior Art 
     The disclosure made in U.S. Pat. No. 5,238,331 to Chapman is believed to be relevant to the present invention because it 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 said frame supports wheels that engage the surface of the pipeline and enable the pipeline surface preparation system to travel along the extent thereof. Moreover, 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. 
     The invention disclosed in said patent therefore solves several problems left unsolved by earlier advances in the field. 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 one of the early heavy pipeline surface preparation systems onto a pipeline, catastrophic explosions may occur. 
     However, the art has not heretofore solved all of the outstanding problems associated with pipeline surface preparation systems. One of the outstanding, unsolved problems relates to handling of debris generated by the pipe coating removal process. Old coating commonly includes asbestos and other materials that require special handling. However, the pipeline surface preparation systems of the prior art do 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 thereatop. 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. 
     A pipeline surface preparation system that prevents asbestos and other hazardous debris from escaping into the atmosphere and that minimizes total contaminated waste is clearly needed. 
     The earlier pipeline surface preparation systems also slip from time to time as they travel along a pipe because insufficient engagement is provided between the pipe surface and the rollers or wheels that rotatably engage said surface to cause the pipeline surface preparation system to travel along the pipe. When a pipeline surface preparation system slips, the pipeline can be damaged because the water jets have extended dwell time on the surface. It is very important that the extremely high pressure water jets that are used to strip away pipe coating be applied to the surface with controlled speed and rotation. When a pipeline surface preparation system carrier means slips, exposed pipe is subjected to the full power of the high pressure water jets for an extended time and pipeline damage may occur. A pipeline surface preparation system having improved traction is therefore needed. 
     A closely related problem is known in the industry as the “hot spots” problem. A “hot spot” is a location on a pipe surface that is subjected to more water pressure than other sections. A hot spot is created whenever a nozzle passes closer to the surface of the pipe in one location than it does in another. Thus, a hot spot may be created by slippage of the transported means as just mentioned, or it may be created by the inherent structural features of the pipeline surface preparation system. The prior art includes a nozzle assembly where a pair of nozzles is mounted to opposite ends of a rotating conduit that is straight in configuration. As a result, the nozzles pass closer to the surface of the pipe in some locations than others, giving rise to the problem of hot spots. 
     A need therefore exists for a structural design that eliminates hot spots by ensuring that all nozzles are spaced equally from the pipe surface at all times. 
     It is also important to monitor the air supply and the operation of all water-emitting nozzles because any failed movement will direct a high pressure water stream to a single spot and thereby damage the pipe. Automatic monitoring means should therefore be connected to the air supply, each nozzle, and other movable parts. A means should be provided for sending a “shut-down” signal to the ultra high pressure system when any required motion fails. 
     Yet another outstanding problem relates to the debris created by the stripping action of the water jets. The known pipeline surface preparation systems produce debris in large particle size. The art has addressed this problem by providing 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. 
     However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the art how the known pipeline surface preparation systems could be improved. 
     SUMMARY OF INVENTION 
     The long-standing but heretofore unfulfilled need for a machine that performs surface preparation of pipelines by stripping coating therefrom is now met by a new, useful, and nonobvious invention. 
     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. 
     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. 
     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. 
     The carrier assembly includes a frame having a leading end that circumscribes the pipeline, a trailing end that circumscribes the pipeline, and interconnecting frame members that interconnect the leading end and the trailing end to one another. Stand-off means in the form of a plurality of wheel members that are rotatably mounted to the frame rollingly engage the pipeline and position the frame in concentric, encircling relation thereto. 
     The carrier assembly further includes a driving wheel assembly that includes a leading drive wheel and a trailing drive wheel that are in line with one another and which rollingly engage the pipeline at longitudinally spaced apart points. The driving wheel assembly surmounts the pipeline. 
     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. 
     Each of the nozzle openings is formed in the cylindrical main body so that each high pressure water nozzle is spaced a common distance from the pipeline so that hot spots are not created when the machine is in operation. 
     An automatic motion sensing system sends a signal to a shut-down control system to immediately deactivate the machine when a motion failure is electronically detected. 
     A closed loop filtration system filters and recycles liquid used in a cleaning process of the machine. 
     An important object of the invention is to provide a pipeline surface preparation system that substantially prevents hazardous materials from entering the atmosphere and minimizes waste to be disposed of during a pipe reconditioning process. 
     Another important object is to provide a carrier means that provides an increased amount of traction between the surface of the pipeline and the wheels or rollers that engage said surface. 
     Still another important object is to provide non-destructive cleaning of a pipeline that eliminates the “hot spot” problem that has troubled the industry for many years. 
     Another object is to provide a control means that automatically deactivates the system when any required motion fails so that damage caused by such motion failure may be prevented. 
     Yet another object is to provide a pipeline surface preparation system that shreds debris into very small particles so that no external shredder means is required. 
     The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a side elevational view of the novel pipeline surface preparation system; 
     FIG. 2 is a top plan view taken along line  2 — 2  in FIG. 1; 
     FIG. 3 is an end view taken along line  3 — 3  in FIG. 1; 
     FIG. 4 is a sectional view taken along line  4 — 4  in FIG. 1; 
     FIG. 5 is a sectional view taken along line  5 — 5  in FIG. 1; 
     FIG. 6 is a side elevational view of novel vacuum shroud means; 
     FIG. 7 is an interior view of the vacuum shroud means; and 
     FIG. 8 is a simplified end view depicting how the drive wheels are contoured to fit the contour of a pipeline undergoing surface preparation. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, it will there be seen that a preferred embodiment of the invention is denoted as a whole by the reference numeral  10 . 
     Pipeline surface preparation system  10  has two primary parts. The first part is denoted  12  as a whole and performs the function of advancing machine  10  along the extent of pipeline  11 . The second part is denoted  14  as a whole and performs the function of removing coating from said pipeline. 
     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 pipe from which the coating has been removed is denoted  20 . 
     First part  12 , hereinafter referred to as carrier assembly  12 , has an open frame construction as depicted so that it is light-in-weight. Carrier assembly  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 is always available. 
     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 sawtooth or geartooth tread to further enhance the traction. Wheels  22 ,  24  drive pipeline surface preparation system  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 assembly  12  will also follow long radius pipeline curves. 
     Wheels  22 ,  24  prevent slippage of carrier assembly  12  relative to pipeline  11 . This ensures that pipe stripped of its coating will not be subjected to extended dwell time. 
     As perhaps best understood in connection with FIG. 2, wheels  22  and  24  are driven by hydraulic motor  26 . 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. 
     Control lever  38  is connected as depicted to gearbox  39  and enables an operator to place motor  26  into forward, stop or reverse. 
     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. 
     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. 
     Second part  14  includes vacuum shroud  50  that circumscribes pipeline  11  in leading relation to driving apparatus  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 . 
     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 wedge-shaped debris collection chamber  51  as depicted. 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 . The rocking motion of vacuum shroud  50  further serves to facilitate collection of debris within said debris collection chamber. 
     As will be better understood as this description proceeds, the ultra high pressure and unique nozzle movement of the novel machine shreds the debris created by removal of the pipe coating into particles that are typically no larger than a quarter inch in diameter. No external shredder is therefore required. 
     FIG. 7 provides an interior view of vacuum shroud  50 . A first annular wiper ring  55  is secured to an interior surface of leading shroud end wall  54  and a second annular wiper ring  57  is secured to an interior surface of trailing shroud end wall  56 . The respective radially innermost ends of said wiper rings  55  and  57  bear against pipeline  11  in sealing relation thereto to maintain the vacuum within vacuum shroud  50 . 
     Annular brush  55   a  is secured to an interior surface of wiper ring  55  and another annular brush  55   b  is secured to said wiper ring in leading relation thereto. In a similar fashion, brushes  57   a  and  57   b  are secured to an interior side of trailing annular wiper ring  57  and brush  57   c  is secured to an exterior side thereof. The respective radially innermost ends of brushes  55   a ,  55   b  and  57   a ,  57   b , and  57   c  bear against pipeline  11  in sealing relation thereto. The wiper rings and brushes 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. 
     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. 
     As best understood in connection with FIGS. 2-4, gears  70  and  72  are mounted on the respective outputs shafts of motors  74 ,  76 , respectively. Gears  70 ,  72  include a plurality of circumferentially spaced apart truncate rods  73 ,  75  (FIG. 3) respectively, that are longitudinally aligned with a longitudinal axis of pipeline  11  and which are sandwiched between a pair of circular flat plates  74   a ,  74   b  (FIG. 2) and  76   a ,  76   b , respectively. Rods  73 ,  75  are respectively engaged by sprocket teeth formed on sprocket gears  78 ,  80 . 
     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  meshingly engage circumferentially spaced apart, longitudinally aligned truncate rods  86 ,  88  (FIG. 4) that form a part of gears  78 ,  80  (FIG.  3 ). Motors  74 ,  76  effect rotation of gears  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, said large ring gear rotates until limit switch actuator  50   a  (FIG. 5) contacts first limit switch  50   b  which is mounted on non-rotatable carrier assembly  12  as mentioned earlier. 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. Said gear  82  then rotates in said 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°) 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 combination of linear travel and oscillatory motion of vacuum shroud  50  further ensures against the creation of hot spots. 
     In a preferred embodiment, 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°) 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 said motions stop. This fail-safe control eliminates potential pipeline or surface damage caused by extended nozzle dwell time. 
     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 unique manifold of spinning nozzles provides a uniformly cleaned surface that is free of hot spots and surface damage. 
     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. This eliminates the hot spots created by earlier machines that mount nozzles on opposite ends of rotating conduits. 
     The novel machine, to be known commercially as the Pipe Viper™ pipeline surface preparation system, is constructed of modular components. The components are easily pinned, bolted, clamped or otherwise easily affixed into place. The apparatus may be disassembled and reassembled on a pipeline in less than one hour. Its low weight and small size makes it easy to handle and to maintain. 
     The components of the modular assembly are of manageable weight for two people. Two people can disassemble or reassemble the unit without employing cranes, hoists, or other lifting mechanisms. Thus, no large weights are suspended over the pipeline which could fall and damage it. This further eliminates the need to excavate the site to accommodate a crane or lifting hoist. Moreover, the light weight of apparatus  10  does not stress the pipeline. 
     The industry standard for clearance around a pipeline undergoing reconditioning is eighteen inches. The novel apparatus fits easily within said clearance area. 
     The modular design also increases productivity. A defective module can be quickly replaced in the field, thereby reducing downtime and increasing productive time. For example, the water jets are a wear item that require replacing from time to time. The modular design of the novel apparatus enables the entire nozzle assembly to be removed and replaced in the trench in less than five minutes. Exchanging nozzles in the nozzle holder can then be accomplished in a bench repair environment. The repair is accomplished in the absence of any need to disassemble the vacuum shroud or the carrier assembly. 
     It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained. Since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween. 
     Now that the invention has been described,