CA2208191C - Hydrocleaning of the exterior surface of a pipeline to remove coatings - Google Patents

Abstract

Hydrocleaning apparatus for pipelines and the like includes a frame capable of advancing lengthwise of the pipeline, such frame carrying a plurality of liquid jetting modules which, in use, are disposed in an array around the pipeline surface to enable cleaning of the entire surface to be effected. The frame can be opened up to allow the apparatus to be fitted to or removed from a continuous pipeline. The frame arrangement and module mounting system are designed to provide good cleaning efficiency and proper orientation of the various modules in spite of pipeline irregularities including out-of-round conditions, uneven coating thicknesses and wrinkles. A pivoting module mount helps to maintain cleaning efficiency in the case where thick coatings are being removed. The frame drive wheels are disposed forwardly of the modules to avoid contamination of the cleaned surfaces by deposits that may build up on the wheels. A shroud system connected to the modules prevents substantial escape of contaminating liquids and debris into the environment.

Description

HYDROCLEANING OF THE EXTERIOR SURFACE OF
A PIPELINE TO REMOVE COATINGS
This is a divisional of Canadian application Serial No. 2,011,196 filed February 28th, 1990.
CROSS RFFE F C TO FT ATFn APPT Tr'~a~rrn~.r Reference may be had to our European Patent Application No. 0343878 published November 29th, 1989 which describes an apparatus and method for to the hydrocleaning of the exterior surface of a pipeline to remove various types of coatings.

. CA 02208191 2000-02-09 BACKGROUND & SUMMARY OF THE INVENTION
The present invention relates generally to improvements in apparatus for effecting hydrocleaning of the exterior surfaces of pipelines and the like, including pipeline sections, so as to remove coatings and miscellaneous contaminants from the pipeline exterior surface.
As described in the above-noted published European patent application , oil and gas transmission pipelines of large diameter (e. g. 12 inches - 60 inches) are usually coated and then buried before being used for transportation of fluid. The coatings serve to reduce corrosion caused by the various soils and weathering conditions encountered. Various forms of coating materials have been used over the~years. Coal tar products were and are well known as coating materials and, more recently, polyethylene tape layered coatings have been used. However, over the years, these coatings have deteriorated in many instances and several pipeline operators have experienced failures in old coatings. These failures usually involve debonding between parts of the coating and the pipe. Despite the use of cathodic protection, the debonded areas are subject to pitting corrosion and to stress corrosion cracking and in very severe cases pipe failures have occurred under pressure. As a result, many operators have initiated coating rehabilitation projects.
The preferred form of apparatus described in the above-noted European patent application incorporated a main frame adapted to at least partially surround a portion of a pipeline and suitable means for advancing the frame relative to the pipeline in the lengthwise direction when in use. A multiplicity of liquid jetting modules were mounted to the frame in circumferentially spaced relation to each other so as to substantially surround the pipeline when in use.
Each such module included a rotary swing arm nozzle thereon having a rotation axis, in use, disposed substantially normal to the pipeline surface for directing liquid jets onto the pipeline surface in a series of closely spaced overlapping convolutions during movement of the frame .relative to and lengthwise of the pipeline. Suitable guides, e.g. guide wheels located on each module, made contact with the pipeline surface during movement relative thereto. Suitable suspension linkages connected each module to the frame and a biasing arrangement was provided for urging the respective modules toward the pipeline surface while permitting independent movement of the modules relative to the frame and to one another radially inwardly and outwardly relative to the pipeline as the respective guides contacted and followed the pipeline surface when in use.
The frame configuration for the above-noted hydrocleaner typically included an upper section shaped to surround an upper portion of the pipeline when in use and a pair of lower frame sections pivotally mounted to lower opposed extremities of the upper section for movement between open and closed positions.
When the lower sections were in the open position the frame could be lowered downwardly onto the pipeline and the lower sections thereafter closed around the lower portion of the pipeline so that. the frame at least partially surrounded the pipeline. Certain of the liquid jetting modules were mounted to the upper frame section while others were mounted to the respective pivotal frame sections. Drive wheels were mounted to the upper frame section for engaging the pipeline surface and advancing the frame relative to the pipeline while the lower frame sections were provided with idler wheels and/or further drive wheels which acted generally in opposition to the drive wheels on the upper frame section thereby to help provide the required tractive forces. An actuator system for pivoting the lower frame sections was provided with suitable biasing means thereby to ensure that the lower idler and/or drive wheels were kept in close pressurized engagement with the pipeline surface so as to provide the required tract~ve force.
The present divisional provides, in one aspect, apparatus for moving along an exterior surface of a pipe having a longitudinal axis, said apparatus ' comprising:
a frame having at least two pivotable frame sections which are pivotally mounted so as to be movable with respect to each other between an open position and a closed position, the pivotable frame sections in the open position allowing the frame to be lowered downwardly onto the pipe, and the pivotable frame sections in the closed position closing about the lower portion of the pipe such that the frame at least partially surrounds said pipe;
a drive assembly mounted to said frame and including at least one drive wheel for engaging the pipe and advancing the frame along the exterior surface of the pipe in the direction of the longitudinal axis of the pipe;
an adjustable hinge stop establishing a preset position for one of said at least two pivotable frame sections; and at least one actuator to move the at least two pivotable frame sections relative to each other from the open position to a closed position as determined by the adjustable hinge stop.

'1 In another aspect there is provided apparatus for moving along an exterior surface of a pipe having a longitudinal axis, said apparatus ,comprising:

5 a frame,~said frame including an upper frame section;
and a pair of lower frame sections, each of said lower frame sections being pivotally mounted to a respective one of opposite sides of the upper frame section for movement between.open and closed positions, the lower frame sections in the open position allowing the frame to be lowered downwardly onto the pipe, and the lower frame sections in the closed position closing about the lower portion of the pipe such that the frame at least partially surrounds said .Pipe:
a drive assembly mounted to said upper frame section and including at'least one drive wheel for engaging the pipe and advancing the frame along the exterior surface of the pipe in the direction of the longitudinal axis of the pipe;
and a pair of adjustable hinge stops,, each of said adjustable hinge stops establishing a preset position for a respective one of said lower frame sections; and at least one actuator to move each of the lower frame sections from its open position to its closed position as determined by the respective adjustable hinge stop.
Each of said lower frame sections preferably ha s a t lea st one idler wheel moun ted there on f or engag ing the p ipe in a manner to as si st the engagement with the pipe of at Least one of the at least one drive wheel, whereby each of said lower frame sections automatically adjusts its position as the at least one idler wheel mounted thereon follows irregularities of the pipe surface.

A plurality of nozzles are mounted to said frame, with at least one of said plurality of nozzles being mounted to said upper frame section, at least one of said plurality of nozzles being mounted to a first one of said lower frame sections, and at least one of said plurality of nozzles being mounted to a second one of said lower frame sections.
The drive assembly preferably comprises at least one front wheel mounted to said upper frame section at a first location and at least one rear wheel mounted to said upper frame section at a second location which is spaced along the length of said pipe from skid first location, at least one of said at least one front wheel and said at least one rear wheel being said at least one drive wheel, and wherein said plurality of nozzles are mounted to said frame at at least one location intermediate said first location and said second location to cause material from the plurality of nozzles to impinge an annular region of the exterior surface of said pipe as said apparatus moves longitudinally relative to said pipe.
In a preferred f orm o~ the invention each of said lower frame sections has at least one idler wheel mounted thereon for engaging the pipe in a manner to assist the engagement with the pipe of at least one of the at least one front wheel and the at least one rear wheel, whereby each of said lower frame sections automatically adjusts its position as the at least one idler wheel mounted thereon follows irregularities of the pipe surface during longitudinal movement of said apparatus along the exterior surface of said pipe.
A plurality of jet modules are provided each of said plurality of jet modules having at least one of said plurality of nozzles mounted thereon, wherein when said lower frame sections are in their closed position the jet modules are approximately evenly spaced about the circumference of said pipe.

Each of said plurality of jet modules may be mounted to the frame by a suspensi~ which maintains the re spec tive je t module a t a prede termined distance fr can the exterior surface of the pipe when said frame is in the closed position about the pipe.
Further features and advantages of the invention will become readily apparent from the following description of a preferred embodiment of same.

. _ BRIEF DESCRIPTION OF THE VIEWS OF DRAWINGS:
FIGURE 1 is a cross-section view of a hydrocleaning apparatus according to the invention; certain details, such as the drive assemblies, having been omitted;
FIGURE 2 is a front end elevation view of the frame assembly and drive, the liquid jetting modules and their suspension linkages having been omitted;
FIGURE 3 is a side elevation view of the hydrocleaning apparatus, several of the liquid jetting modules and their suspension linkages and shrouds having been omitted;
FIGURE 4 is a side elevation view of a liquid jetting module and its suspension linkage;
FIGURES 5, 6 and 7 are top, side and top views respectively of various components of the module suspension linkage;
FIGURES 8 and 9 are section and side elevation views respectively of the overall shroud assembly with shrouds in their overlapping relationship, the swing arms being shown in phantom and the rest of the machine having been omitted;
FIGURES 10, 11 and 12 are plan, end elevation and side elevation views of a shroud;
FIGURES 13A and 13B are side elevation views of a module and its suspension linkage showing the module at various pitch angles relative to the pipeline surface; and FIGURE 14 is a schematic of the hydraulic system .

DETAILED DESCRIPTION Or PREFERRED EMBODIMENT
The basic principles relating to hydrocleaning of a pipeline surface are set out in detail in our above-noted published European application and need not be repeated here.
The above published European application also describes all the various pieces of support equipment required including the side boom tractor, pipe cradle and bridle assembly, water and hydraulic pumps, prime mover and water supply tanks etc.
Referring now to the drawings, the hydrocleaning apparatus 10 includes a frame 12 adapted to at least partially surround a portion of a pipeline P when in use. The frame 12 is supported and driven along the pipeline P by way of spaced apart fore and aft drive assemblies 14, 16 (FIGURE 2 and 3) including pairs of drive wheels 18, 20 which engage the pipeline surface to propel the entire apparatus forwardly.
A plurality of liquid jetting modules 22 are mounted to the frame 12 in circumferentially spaced relation so as to substantially surround the pipeline when in use. Each module 22 has a rotary swing arm nozzle 24 thereon, each being rotated about an axis (which in use is substantially normal to the pipeline surface) for directing liquid jets on to the pipeline surface in a series of closely spaced overlapping convolutions during forward advance of the frame 12 along the pipeline P. The cleaning paths thus defined by the several swing arm nozzles 24 ideally overlap somewhat at their marginal edges, as indicated by the letters OL in FIGURE I, thus helping to ensure that no uncleaned longitudinal streaks are left on the pipeline. The jetting modules 22 are mounted to the frame 12 by respective suspension linkages 26 which - l~ -allow radial motion of the modules inwardly and outwardly relative to the pipeline axis.
Each of the modules is provided with a shroud 28 (shown in section in FIGURE 1 for purposes of clarity), these shrouds being disposed in an overlapping configu ration all around the pipeline and the swing arm nozzles 24 to reduce escape of contaminants into the environment and for safety reasons, all as will be described in further detail hereafter.
Returning now to the frame 12, it will be seen that it is made up from sturdy tubular members welded and connected together to provide the necessary strength and rigidity. Frame 12 includes an upper frame section 40 of a generally inverted U-shape, as seen end-on, so as to surround the upper portion of the pipeline P when in use, section 40 comprising three sub-sections 42 rigidly connected together by welds and including longitudinal frame elements 44 rigidly securing fore and aft frame portions together. Frame 12 also includes a pair of lower opposed frame sections 46 pivotally mounted via hinges 48 to lower opposed extremities of the upper section 40 for movement between open and closed positions. When these lower sections 46 are in the open position, the entire hydrocleaner can be lowered downwardly onto a pipeline (as described in the above-noted European application) and the lower frame section 46 then closed around a lower portion of the pipeline as shown in FIGURE I.
The lower frame sections 46 each comprise a pair of independently pivotable frame portions 50, 52 (FIGURES) each of rigid triangular outline configuration. The first frame portions 50 are pivotable from the open position into a predetermined or fixed closed position relative to the upper frame section 40 about their hinges 48. The predetermined closed position is shown in FIGURE 1, such closed position being provided by adjustable hinge stops 54 co-acting between a rigid extension arm 56 fixed to each frame portion 50 and a bracket 58 fixed to the lower portions of the upper frame section 40. The adjustable stop 54 may comprise a threaded stud and lock nut configuration well known as such.
The first frame portions 50 serve to each mount a respective water jetting module 22 via a respective parallel arm suspension linkage 26 to be described in detail later on. When frame portions 50 are in the predetermined closed positions against stops 54, the rotation axes of the respective swing arm nozzles 24 (including those mounted to the upper frame section) all pass substantially through the axis of the pipeline and this condition is maintained regardless of out of round pipeline and other irregularities as noted previously. Hence, a shorter swing arm length can be used while still providing the desired amount of overlap OL of the cleaning paths provided. For example it was found that five swing arms could be used around pipe as small as 16 inches OD without the risk of the swing arms touching each other when set at normal stand-off distances. Streaking problems and side stand-off distance variations were greatly reduced.
The second frame portions 52 serve to mount respective idler wheels 58 (FIGURE2) which engage the pipeline surface at locations generally opposed to the locations where the drive wheels 18, 20 (which are mounted to the upper frame section) engage the pipeline. The idler wheels may, if desired, be replaced with further sets of drive wheels and associated drive assemblies to provide extra tractive force. Multi-hole mounting plates 60 provide the ' -12-necessary radial adjustability to accommodate a wide variety of pipeline diameters.
The frame portions 50, 52 are each provided with their own hydraulic actuators 60, 62 respectively, each of which acts between a respective lug fixed to the upper frame section 40 and an associated extension arm fixed to the frame portion 50, 52. Actuators 60 for the first frame portions 50 (to which the lower modules 22 are mounted) are secured to the above-noted extension arms 56 while actuators 62 for the second frame portions 52 (to which the idler wheels 58 are mounted) are secured to similar extension arms 66 (FIGURE 2).
All of the actuators are supplied via a common hydraulic supply and control circuit 68 (FIGURE 14) of a conventional nature having a pre-charged pressure accumulator 70 therein. Hence, when the lower frame sections are closed, the first frame portions 50 are brought into the pre-set positions against the stops 54 while the second frame portions 52 are resiliently biased inwardly as a result of the action of the accumulator to bring the idler wheels into tight engagement with the pipeline surface thereby to enhance the tractive force the drive wheels 18, 20 are capable' of supplying. As the idler wheels 58 encounter pipeline irregularities of the type noted previously, the second frame portions 52 are free to pivot inwardly or outwardly. However, since the first frame portions 50 remain in their fixed positions against the steps 54, the relative orientations of the suspension linkages 26 for the water jetting modules are in no way affected by these motions of the frame portions 52 as the idler wheels follow irregularities in the pipeline surface.

. CA 02208191 2000-02-09 The above-noted front and rear drive assemblies 14, 16 need not be described in detail. They are mounted to the upper frame section 40 by way of mufti-hole brackets 74 permitting substantial radial adjustment to accommodate a wide variety of pipe sizes as noted in our published European patent application. Each drive assembly includes a hydraulic motor 76 which is connected to a reduction gear box 78, the output of the latter being conveyed to the associated drive wheel 18, 20 via a chain and sprocket drive 80. The hydraulic supply and control system for the wheel drive motors 76 is shown in FIGURE I4 and includes main control valve 82 with on-off, reverse and forward functions and the usual over-pressure relief and safety valves, none of which need be described in detail.
Referring to FIGURES 4-7 one of the modules 22 is shown, partly in cross-section. Reference may be had to our published European patent application for details of the structure. The rotary swing arm assembly 24 is mounted to the output shaft 84 of a commercially available rotary swivel assembly 90 which is mounted to the module frame 91 and connected to the high pressure source (e. g. 20,000 to 35,000 psi) by supply lines (not shown). The swivel is driven in rotation at a suitable-speed (e.g. 1000 RPM depending on rate of advance and other factors as outlined in our prior patent applications) by way of hydraulic motor 92 and intermediate gear drive box 94. The high pressure water passes axially through the shaft 84 and thence along the swing arms 96 and through the jet nozzles 98 at the tips of the arms, all as described in our earlier published European patent application.
The previously noted suspension linkage 26 for mounting each module 22 to the frame 12 of the machine will be described in further detail. Essentially, the linkage ensures that the module can move in and out in a radial direction while the swing arm axis is maintained in substantial alignment with the pipeline axis. Thus each linkage 26 comprises a parallel arm linkage including upper and lower rigid control arms 100, 102. The forward ends of arms 100, 102 are pivotally mounted at spaced pivot points 104, 106 to a multi-hole adjustment bracket 108 which in turn is secured to the machine frame (the multiple holes accommodate adjustments in respect of a wide variety of pipe sizes). The trailing ends of arms 100, 102 are pivotally attached at spaced pivot points 108, 110 to an end link 112, the latter having a somewhat triangular configuration as seen side-on. A hydraulic cylinder 114 extends from a lug on adjustment bracket 108 to a lug 116 near the trailing end of the lower control arm 102. As cylinder 114 is advanced and retracted the parallel arm linkage is moved radially inwardly and outwardly relative to the pipeline surface along with the module 22 fixed thereto.
The control valves and hydraulic circuit for all the hydraulic cylinders 114 are shown in FIGURE 14.
The hydraulic circuit includes a pressurized accumulator 116 which acts to cause each cylinder to bias its associated linkage and attached module toward the pipeline surface when the equipment is in use.
The above-noted end link 112 of the suspension linkage 26 is connected to the module 22 by a pivot assembly 120 defining a transverse pivot axis passing through the rotation axis of the swing arm assembly 24.
Pivot assembly 120 includes a laterally spaced pair of eye bolts 122, each mounted in a respective flange 124 fixed to the end link 112. Transverse studs 126 pass through the "eyes" of these eye bolts 122 and into the frame 91 of the module 22. By adjusting the adjustment - IS -nuts 128 on the eye bolts, the swing arm rotation axis orientation can be adjusted in a plane transverse to the pipeline axis and passing through the pivot axis defined by the eye bolts. This enables the nozzle sid a stand-off distances ( see our published European application for details) to be adjusted and equalized.
With the pivot arrangement just described, the module 22 is free to pitch about the above-noted pivot axis during operation. It will of course be noted that each module includes fore and aft guide and support wheels 130, 132 for supporting the module on the pipeline surface. When the module 22 is entirely free to pitch about the above-described pivot axis, both of these guide wheels 130, 132 will be in contact with the pipeline surface at all times. In cases where thick coatings are being removed, the forward guide wheel 130 can ride up on the coating while the other guide wheel 132 rides on the cleaned pipeline surface. The whole module pitches to and fro to the extent needed to accommodate the changes in coating thickness encountered as well as any other surface irregularities. This helps to ensure that the minimum standoff distances (e. g. about 1/2 inch) at the fore and aft nozzle passes remain substantially equal -regardless of coating thickness. However, there are other situations, as where one is dealing with fairly thin coatings, where one wishes to keep the module parallel to the pipeline axis at all times and the rear guide wheel 132 clear of the pipeline surface as to prevent "tabbing" down of removed coating materials onto the pipeline surface by the action of this guide wheel. Therefore, in order to enable the module 22 to be effectively locked to prevent the pitching motion referred to, the end link 112 is provided with adjustable stops 134 in the form of studs which are rotated outwardly until they touch the top of the module frame as best seen in FIGURE 4. When this has been done, only the forward guide wheel 130 contacts the pipeline surface.
Another advantage associated with the module pivot axis arrangement noted is that any module 22 can be tilted forwardly or rearwardly (see FIGUREs 13A and 13B
for example) thereby to permit the swing arm nozzles to be inspected and repaired fairly readily.
It will be noted that the modules 22 are allocated rearwardly of the frame 12 of the machine in what might be termed a cantilever fashion and rearwardly of the fore and aft sets of drive wheels 18, 20. As noted previously, this is advantageous since the drive wheels cannot contact the cleaned pipeline surface and act to tamp down pieces of removed tape, adhesive and other debris onto the cleaned surface, reference being had to the earlier discussion regarding "tabbing" of the pipeline surface. When the rear module guide wheel 132 is held clear of the pipe surface by the adjustable stops 134 described previously, the tabbing problem should be substantially overcome.
The need for protective shrouding was discussed previously and the shrouds 28 were noted briefly in connection with FIGURE 1. With reference now to FIGURE

8-12, the shroud assembly is shown in further detail.
Each module 22 includes its own shroud rigidly fixed thereto and the shrouds of the adjacent modules are shown in FIGURES 1, 8 and 9 as defining an overlapping annular array fully enclosing the swing arm nozzle assemblies 24 all around the outside of the pipeline.
A substantial degree of overlap between adjacent shrouds is provided by the angled shroud overlap wings 140. The overlapping relationship between adjacent shrouds allows for substantial radial motions of the modules and their shrouds relative to one another while at the same time the formation of substantial gaps between the shrouds is substantially avoided. Also, resilient sealing flaps 142 extend between the overlap portions of adjacent shrouds to further inhibit the escape of liquid and debris.
One shroud is shown in detail in FIGURE 10-12. The shroud includes a flat top wall 143 which is bolted on to the frame 91 of the module (FIGURE 4). The fore and aft end walls 144, 146 extend normal to top wall 143 and in use project inwardly into close proximity to the pipeline surface, the free edges of these walls being curved to match the pipeline surface contour. These end walls also include mounting brackets 148 for mounting the above-noted fore and aft module guide wheels 130, 132. The overlap wing 140 is angled relative to the intermediate section of the shroud and is of somewhat greater dimension in the lengthwise (travel) direction than the intermediate shroud section thereby to accommodate the next adjacent shroud without interference. The opposing side of the shroud is also angled inwardly and provided with a flared marginal portion to which is connected a resilient flap 142, the flap extending.all along the free edge of that side of the shroud. When the shrouds are in their overlapping configuration, the flap 142 contacts the interior of the overlap wing 140 of the next adjacent shroud.
As will be seen from FIGURE 8, the shrouds are somewhat different from one another depending on their locations. The uppermost~shroud 28A, being overlapped on both sides by the overlap wings of shrouds 28B and 28C, does not have an overlap wing at all but is provided with a sealing flap 142 on both of its sides to effect sealing engagement with shrouds 28B and 28C.
The lowermost shrouds 28D and 28E differ from shrouds - Ig -28B and C by the inclusion, at their lower ends, of an enlarged collector portion 150, 152 shaped to form a recess or sump when the shrouds are fitted together which receives the downwardly draining liquids and debris. A suitable opening 154 allows this material to escape into a suitable collector.
As noted previously, the several modules 22 and their suspension linkages 26 are each provided with a hydraulic actuator 114 to move the modules 22 including their shrouds 28 toward and away from the pipeline surface as when moving over certain obstacles that might be encountered on the pipeline surface. In order to prevent interference between adjacent shrouds 28 during such radial movement, time delays are incorporated into certain of the hydraulic lines to the actuators 114 to achieve the desired result. The preferred way of avoiding interference is to move the modules and attached shrouds inwardly in the time sequence in which they naturally move under gravity.
For example, starting with all modules "out", the top (12 o'clock) module 28A will fall first, then the 10 and 2 o'clock modules 28B and C will fall simultaneously and finally the modules 28D and E at the 8 and 4 o'clock positions will rise simultaneously. An-orifice is fitted into the flow circuit of the actuator for the 4 o'clock position, module 28E, so that it rises into position after the 8 o'clock module 28D is in place thereby avoiding interference. When "opening"
up the modules, the above sequence is reversed.
As noted previously, many of the coatings that are to be removed from pipe contain hazardous materials, such as asbestos. Because of the degradation of the coating on the pipe being repaired, the asbestos is frequently in a friable condition, prone to ready disbursal of small fibers into the surrounding air space. Clearly, such contamination must be kept to a minimum.
During tests of the efficacy of an apparatus designed in accordance with teachings of the present invention on certain pipe coatings, specifically polyethylene tape, it was found that the particular cleaning action of the rotating swing arm nozzles 24 would tend to shred the tape and force the tape into the inner bend of the nozzles where it turns again along the axis of rotation of the nozzles to end in the nozzles themselves. The tape debris could be caught and wrapped about the arm in this inner bend to the point where it would affect the efficiency of the nozzles, and possibly even prevent them from rotating as designed. A solution to this problem was found by installing paddles 220 across the inner bend on the nozzles 22 as seen in FIGURE 4. The paddles shown cut across the inner bend at an angle of 45°, although it is clear that other angles may be utilized. Further, the inner edge of the paddle may be curved, rather than straight as shown, which would be expected to have even a more enhanced ability to deflect debris off the nozzle.
The manner of operation of the hydrocleaner described above will be readily apparent to those skilled in this art on review of this disclosure and the disclosures contained in our published European patent application.
Numerous variations and modifications will readily occur to those skilled in this-art upon reading the above description, and without departing from the spirit or scope of the invention. For definitions of the invention reference is to be had to the appended claims.

Claims (9)

CLAIMS:

1. Apparatus for moving along an exterior surface of a pipe having a longitudinal axis, said apparatus comprising:
a frame having at least two pivotable frame sections which are pivotally mounted so as to be movable with respect to each other between an open position and a closed position, the pivotable frame sections in the open position allowing the frame to be lowered downwardly onto the pipe, and the pivotable frame sections in the closed position closing about the lower portion of the pipe such that the frame at least partially surrounds said pipe;
a drive assembly mounted to said frame and including at least one drive wheel for engaging the pipe and advancing the frame along the exterior surface of the pipe in the direction of the longitudinal axis of the pipe;
an adjustable hinge stop establishing a preset position for one of said at least two pivotable frame sections; and at least one actuator to move the at least two pivotable frame sections relative to each other from the open position to a closed position as determined by the adjustable hinge stop.

2. Apparatus in accordance with claim 1, further comprising a plurality of nozzles mounted to said frame, with at least one of said plurality of nozzles being mounted to a first one of said at least two pivotable frame sections, and at least one of said plurality of nozzles being mounted to a second one of said at least two pivotable frame sections.

3. Apparatus for moving along an exterior surface of a pipe having a longitudinal axis, said apparatus comprising:
a frame, said frame including an upper frame section, and a pair of lower frame sections, each of said lower frame sections being pivotally mounted to a respective one of opposite sides of the upper frame section for movement between open and closed positions, the lower frame sections in the open position allowing the frame to be lowered downwardly onto the pipe, and the lower frame sections in the closed position closing about the lower portion of the pipe such that the frame at least partially surrounds said pipe;
a drive assembly mounted to said upper frame section and including at least one drive wheel for engaging the pipe and advancing the frame along the exterior surface of the pipe in the direction of the longitudinal axis of the pipe;
and a pair of adjustable hinge stops, each of said adjustable hinge stops establishing a preset position for a respective one of said lower frame sections; and at least one actuator to move each of the lower frame sections from its open position to its closed position as determined by the respective adjustable hinge stop.

4. Apparatus in accordance with 3, wherein each of said lower frame sections has at least one idler wheel mounted thereon for engaging the pipe in a manner to assist the engagement with the pipe of at least one of the at least one drive wheel, whereby each of said lower frame sections automatically adjusts its position as the at least one idler wheel mounted thereon follows irregularities of the pipe surface.

5. Apparatus in accordance with claim 3, further comprising a plurality of nozzles mounted to said frame, with at least one of said plurality of nozzles being mounted to said upper frame section, at least one of said plurality of nozzles being mounted to a first one of said lower frame sections, and at least one of said plurality of nozzles being mounted to a second one of said lower frame sections.

6. Apparatus in accordance with claim 5, wherein said drive assembly comprises at least one front wheel mounted to said upper frame section at a first location and at least one rear wheel mounted to said upper frame section at a second location which is spaced along the length of said pipe from said first location, at least one of said at least one front wheel and said at least one rear wheel being said at least one drive wheel, and wherein said plurality of nozzles are mounted to said frame at at least one location intermediate said first location and said second location to cause material from the plurality of nozzles to impinge an annular region of the exterior surface of said pipe as said apparatus moves longitudinally relative to said pipe.

7. Apparatus in accordance with claim 6, wherein each of said lower frame sections has at least one idler wheel mounted thereon for engaging the pipe in a manner to assist the engagement with the pipe of at least one of the at least one front wheel and the at least one rear wheel, whereby each of said lower frame sections automatically adjusts its position as the at least one idler wheel mounted thereon follows irregularities of the pipe surface during longitudinal movement of said apparatus along the exterior surface of said pipe.

8. Apparatus in accordance with claim 7, further comprising a plurality of jet modules, each of said plurality of jet modules having at least one of said plurality of nozzles mounted thereon, wherein when said lower frame sections are in their closed position the jet modules are approximately evenly spaced about the circumference of said pipe.

9. Apparatus in accordance with claim 8, wherein each of said plurality of jet modules is mounted to the frame by a suspension which maintains the respective jet module at a predetermined distance from the exterior surface of the pipe when said frame is in the closed position about the pipe.