Abstract:
A non-destructive examination pipe scanner that employs a main carriage on which a sensor is mounted, a tensioner carriage and an idler carriage. The main carriage and the tensioner carriage are positioned around the pipe at spaced locations and connected on either side by a spring band. The idler carriage is slidably supported by the spring band in between the main carriage and the tensioner carriage. The sensor on the main carriage collects data about a circumferential weld on the pipe as the main carriage drives the tensioner carriage and the idler carriage around the circumference. The tensioner carriage has a variable length connection that adjusts the tension on the spring band to urge the main carriage, idler carriage and tensioner carriage into contact with the surface of the pipe.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention pertains generally to non-destructive pipe scanners and, more particularly, to pipe scanners that are designed to operate in tight clearance areas. 
         [0003]    2. Description of the Related Art 
         [0004]    Non-destructive examination of pipes and, more particularly, pipe welds, has a number of applications, few more critical than the inspection of pipe welds in fossil fuel power generating facilities and nuclear power plants. In power plants, the pipes are often arranged close to each other and extend through concrete structures providing little room to maneuver and inspect the pipe seams over their 360° circumference to detect flaws in the welds. A number of the pipes can only be accessed from one axial end through a blind opening and have limited access circumferentially with clearances as little as 1.35 inch (3.4 cm). Furthermore, a number of the pipes vary in diameter from 6.63 inches (16.8 cm) to 24 inches (61 cm) or larger, which makes it difficult to find scanners that can effectively monitor the welds on such piping. Accordingly, there is an increasing demand for highly specialized scanners to deliver sensors such as phased array ultrasonic probes too difficult to access areas. 
         [0005]    Thus, it is an object of this invention to provide such a scanner that can inspect the circumferential welds on piping of various diameters that range from 6.63 inches (16.8 cm) to 24 inches (61 cm) or larger, in confines with as little as 1.35 inch (3.4 cm) clearance. 
         [0006]    Furthermore, it is an object of this invention to provide such a scanner system that can inspect the pipe welds over the entire 360° circumference of the pipe. 
         [0007]    Additionally, it is an object of this invention to provide such a scanner system that is relatively easy to set up and disassemble. 
       SUMMARY OF THE INVENTION 
       [0008]    This invention achieves the foregoing objectives by providing a scanner system for non-destructively scanning the outer circumference of a ferrous or nonferrous tubular object. The scanner system includes a main carriage with wheels at either end and a frame that extends therebetween that supports a non-destructive sensor. The system also includes a tensioner carriage with wheels at either end and a frame with a variable length connection therebetween. Additionally, the system includes one or more idler carriages having wheels at either end and a frame that extends therebetween. A spring band extends from one end of the main carriage around the tubular object and over the idler carriage to one end of the tensioner carriage which is preferably positioned approximately diametrically opposed to the main carriage. Similarly, a spring band extends around the other side of the circumference of the tubular object from the other end of the main carriage over an idler carriage to the other end of the tensioner carriage. The variable length connection on the tensioner carriage is adjusted to place the spring band under tension and urge the main carriage, the tensioner carriage and the idler carriages against the outer circumference of the tubular object. The main carriage can then be driven around the outer circumference of the tubular object so that the on-board non-destructive sensor can scan the weld over the 360° circumference. 
         [0009]    Desirably, the main carriage frame has an adjustable frame member that indexes the sensor in an axial direction along a longitudinal dimension of the tubular object. The adjustable frame member may be manually or motor driven and can have an encoder to index the sensor&#39;s position. Preferably, at least one wheel of the main carriage has an encoder attached thereto to index the data received from the sensor. 
         [0010]    In one embodiment, at least one of the wheels of the main carriage is a drive wheel that is magnetic to gain traction on the tubular object. The drive wheel may be motorized and remotely operated. 
         [0011]    In another embodiment, the variable length connection on the tensioner is a scissor mechanism that spans the frame between the forward and rear wheels. Desirably, the scissor mechanism is opened and closed by the rotation of a single screw that preferably cannot be back driven. 
         [0012]    In still another embodiment, the frame on the main carriage is arched between the forward and rear wheels. Preferably, the frames on the tensioner carriage and the idler carriages are similarly arched. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    A further understanding of the invention can be gained from the following description of the preferred embodiment when read in conjunction with accompanying drawings in which: 
           [0014]      FIG. 1  is a front view of two concentric pipes with a small clearance therebetween in which the scanning system of this invention is mounted with a second system mounted on the outer circumference of the larger pipe; 
           [0015]      FIG. 2  is a plan view of the main carriage of this invention; 
           [0016]      FIG. 3  is a side view of the main carriage shown in  FIG. 2 ; 
           [0017]      FIG. 4  is a cross-sectional view taken through the lines  4 - 4  of  FIG. 3 ; 
           [0018]      FIG. 5  is a cross-sectional view taken along the lines  5 - 5  of  FIG. 2 ; 
           [0019]      FIG. 6  is perspective view of the tensioner carriage of this invention; 
           [0020]      FIG. 7  is a plan view of the tensioner carriage illustrated in  FIG. 6 ; 
           [0021]      FIG. 8  is a side view of the tensioner carriage illustrated in  FIG. 6 ; 
           [0022]      FIG. 9  is a plan view of the tensioner carriage shown in  FIG. 6  with the variable length connection substantially completely extended; 
           [0023]      FIG. 10  is a plan view of the tensioner carriage shown in  FIG. 6  with the variable length connection substantially retracted; 
           [0024]      FIG. 11  is a plan view of the idler carriage of this invention; and 
           [0025]      FIG. 12  is side view of the idler carriage illustrated in  FIG. 11 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]      FIG. 1  is a mock-up of a power plant piping system that shows two concentric pipes  12  and  14  with a narrow clearance  26  therebetween in which the carriages of this invention  16 ,  18  and  20  are mounted. The carriages  16 ,  18  and  20  are urged against the outer circumference of the inner pipe  14  by the spring bands  22  that are connected between the main carriage  16  and the tensioner carriage  20  and over the idler carriages  18 . The outer circumference of the outer pipe  12  has a similar scanner arrangement to illustrate that the scanner system of this invention can be used to inspect circumferential welds on almost any size pipe and more preferably those having outside diameters which range from 6.63 inches (16.8 cm) to 24 inches (61 cm) or larger. The main carriage  16  includes a flat bearing way  50  that supports the sensor  24 . In this embodiment, the sensor  24  extends from the side of the main carriage  16  and can focus a transducer such as an ultrasonic phased array on the weld as the main carriage  16  drives around the outer circumference and over the weld of the pipe or other tubular object. The main carriage  16  also drives the idler carriages  18  and the tensioner carriage  20  through the spring bands  22 . 
         [0027]    The main carriage  16  is shown in more detail in  FIGS. 2-5 .  FIG. 2  is a plan view of the main carriage  16  and  FIG. 3  is a side view of the main carriage shown in  FIG. 2 . As can best be seen from  FIG. 3 , the main carriage has an arched frame  26  that supports the axels  32  and  40  (shown in phantom) on which the laterally spaced wheels  28  and  30  and  36  and  38  rotate. The axels are captured and held in place by the axel nuts  34 . A front and rear frame extension  40  and  42  extend outwardly from the central frame between the wheels  36  and  38  and  28  and  30 . Each frame extension  40  and  42  include two screws  46  that are used to anchor the ends of the corresponding spring band. The front axel  40  has a motor/encoder for driving the wheels  36  and  38  and indexing the position which corresponds to the data received by the sensor  24  so that the location of defects can be identified. The sensor  24  can be an ultrasonic phased array, an eddy current probe, a video camera or any other non-destructive sensor that is capable of surveying the weld. Preferably, the wheels  36  and  38  are magnetized to increase their traction on the pipe surface. The sensor  24  is supported with a lead screw  52  and a flat bearing way  50 . The lead screw  52  is used to translate the sensor  24  axially along the pipe for fine tuning or indexing. The lead screw  52  may be operated manually or may be motorized and include an encoder for indexing the sensor&#39;s position. The motor/encoder is figuratively shown in  FIG. 2  as  102 . As can be seen from  FIG. 5 , which is a cross section taken along the lines  5 - 5  of  FIG. 2 , the sensor  24  is biased with the springs  54  against the surface of the pipe to accommodate anomalies in the pipe surface and assure good signal coupling. 
         [0028]    The tensioner carriage is more fully illustrated in  FIGS. 6-10 .  FIG. 6  shows a perspective view of the tensioner carriage  20 . As can be seen from  FIGS. 6-10 , the tensioner carriage  20  has a forward frame portion  56  and a rear frame portion  58  that is connected together with a variable length connection  60 . Though a scissor coupling arrangement is shown in  FIG. 6  for the variable length connection, it should be appreciated that other mechanical couplings that are adjustable to change the spacing between the front frame section  56  and the rear frame section  58  can be employed. The distance between the front frame portion  56  and the rear frame portion  58  is adjusted with a single screw  62  that is not back drivable, which means that the screw, once adjusted, retains its position during operation. The front frame section  56  is supported laterally with respect to the rear frame section  58  by a frame tie plate  64  that is connected via standoffs  68  to the frame sections  56  and  58  with bolts  70 . The spring bands are connected to the front of the tensioner carriage at the attachment plate  86  and to the rear of the carriage at the attachment plate  84  with the screws  80 . Alternately, a quick latching operation of the spring band to the rear attachment plate  84  can be achieved by inserting a clevis pin through the spring band and into the clevis slot  82 . The adjustment screw  62  allows for infinite adjustment within the operating range of diameters addressed rather than in finite increments. 
         [0029]      FIG. 7  is a plan view of the tensioner carriage illustrated in  FIG. 6  and  FIG. 8  is a side view of the tensioner carriage  20  illustrated in  FIG. 7 .  FIG. 9  is a plan view showing the scissor connection  60  between the front frame section  56  and the rear frame section  58  in the fully extended position.  FIG. 10  is a plan view of the tensioner carriage  20  with the variable length connection, e.g., the scissor connection illustrated in  FIG. 10 , in the fully retracted position. Turning the adjustment screw  62  in a direction that draws the rear frame portion  58  towards the front frame portion  56  adds tension to the spring band and urges the main carriage  16 , the idler carriages  18  and the tensioner carriage  20  against the outer surface of the pipe on which the scanning system of this invention is mounted. The arched curvature of the front frame portion  56  and the rear frame portion  58  permits the tensioner carriage  20  to accommodate the curvature of the pipe surface. 
         [0030]    A plan view of the idler carriage  18  is shown in  FIG. 11  and a side view of the idler carriage  18  is shown in  FIG. 12 . The idler carriage  18  has an arched frame  88  similar to that described for the main carriage. The frame  88  supports two laterally spaced wheel pairs  90  and  92  at one end and  94  and  96  at the other end. Two lines of screws  98  and  100  form a guide that slidably receives the spring band under the screw heads between the spring band bearing plates  102  and  104 . Thus, while the spring bands are connected to the main carriage  16  and the tensioner carriage  20 , the idler carriage  18  is free to slide along the spring band for ease of setup and can be locked in place with, for example, a screw  80  prior to scanning. The idler carriage&#39;s function is to raise the spring band above the surface of the pipe to minimize friction that might impede movement of the main carriage  16 . One or more idler carriages  18  may be employed depending upon the diameter of the pipe that is being surveyed. The spring bands that hold the carriages together may be constructed out of steel or other suitable material. In the event the drive wheels are magnetized it may be desirable to use a nonmagnetic material for the spring bands. The length of the spring bands are determined by the diameter of the pipe undergoing inspection. 
         [0031]    Thus, the invention provides a convenient relatively light weight inspection scanner tool that can fit in spaces having clearances of as little as 1.35 inch (3.4 cm) and can be used on various diameter piping by merely changing the length of the spring bands. The scanner of this invention can be used in blind passages by insertion through the open end and all of the necessary adjustments can be made from that one end. The scanner of this invention is designed to do a full 360° scan with the capacity to index the probe along the axis of the pipe to focus the probe if necessary. The indexing of the probe may be accomplished manually or through the use of a motorized drive. 
         [0032]    While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the breath of the appended claims and any and all equivalents thereof.