METHOD AND APPARATUS EMPLOYING LASER RANGING FOR MEASURING THE LENGTH OF PIPE SECTIONS

Abstract: A laser ranging device (L) is used in association with a reflector (R) to measure the length of pipe sections (10). Access to ends of pipe sections recessed in a stack is obtained by an extender (25a, 25b) attached to the laser ranging device (L) and by an elongated handle (24) attached to the reflector (R).

Description: METHOD AND APPARATUS EMPLOYING LASER RANGING FOR MEASURING THE LENGTH OF PIPE SECTIONS SPECIFICATION This invention relates to the measurement of the length of pipe sections, more particularly well pipe sections of varying length stacked horizontally. , Background of the Invention Pipe or tubing, such as production tubing, hollow drill strings, and liners employed in the oil well industry, is provided in sections or units of varying length (hereinafter referred to simply as "pipe sections") that are joined end-to-end and extended into a well or bore hole. Industry accounting practices require that the length of each pipe section be measured several times in the interval between its manufacture and ultimate installation. Conventionally, the measurement of the length of pipe sections is performed by two workers using a tape measure or similar device. A third worker is usually, required to record the measurements as they are made. Pipe sections are usually stored horizontally in racks, and it is common practice to intermix pipe sections of different lengths, and even of different diameters and types. With the aforementioned conven- tional measurement techniques, the length of most of the pipe sections can only be measured as the pipe sections become accessible during stacking or unstacking. Moreover, the ends of the pipe sections are not flush at the ends of the stack, increasing the difficulty of making accurate length measurements by the aforementioned conventional techniques. When the lengths of the pipe sections are totalled and the monetary value of the pipe sections is computed, gross errors are very likely. Brief Description of the Invention The present invention solves the foregoing problems by a method and an apparatus using laser ranging in the measurement of the length of pipe sections. In one of its broader aspects the invention resides in a method of measuring the length of pipe sections, that comprises coupling a laser ranging device to one end of a pipe section with the laser beam axis approximately aligned with the axis of the pipe section, coupling a reflector to the opposite end of the pipe section with the reflector disposed to reflect a laser beam from the laser ranging device back to the laser ranging device, and operating the laser ranging device to transmit a beam of laser light from said one end to said reflector at said opposite end and to determine the length of the pipe section from the transmitted beam reflected by said reflector. In another of its broader aspects, the invention resides in an apparatus for measuring the length of pipe sections, comprising, in combination, a laser ranging device having means for coupling the same to one end of a pipe section with the device oriented to transmit a laser light beam along the axis of the pipe section to the opposite end of the pipe section, and a reflector having means for coupling the same to said opposite end with the reflector disposed to reflect the light beam back to the ranging device. The invention will be further described in conjunction with the accompanying drawings, which illustrate preferred (best mode) embodiments. Brief Description of the Drawings Fig. 1 is a perspective view illustrating the use of the invention in measuring the length of pipe sections stored horizontally in a stack; Fig. 2 is an elevation view illustrating in greater detail the apparatus of the invention; Fig. 3 is an exploded elevation view illustrating a laser ranging device having an extension tube in accordance with the invention; Fig. 4 is an end view of the laser ranging device of Fig. 3; Fig. 5 is an opposite end view of the laser ranging device; Fig. 6 is an elevation view of another extension ' tube that may be employed with the laser ranging device, particularly for pipe sections of large diameter; Figs. 7 and 8 are elevation views of reflector apparatus comprising reflectors and handles employed in the invention; Fig. 9 is an end view of a modification; Fig. 10 is an exploded longitudinal sectional view of the modification, and Fig. 11 is a block diagram of an electrical system that may be employed in the invention. Detailed Description of Preferred Embodiments As shown in Fig. 1, the invention may be employed in the measurement of the length of pipe sections 10 that may be stored horizontally in a stack. A suitable rack or frame normally employed to hold the stack has been omitted from Fig. 1 for simplicity of illustra¬ tion. It will be noted that the pipe sections in the stack are of varying length and that the ends of the pipe sections are not flush at the ends of the stack. Hence, certain pipe sections have ends that are recessed in the stack and that are difficult to reach. It is apparent that conventional techniques for measuring the length of pipe sections, employing tape measures, for example, are extremely difficult to implement with any degree of accuracy. As will be seen hereinafter, the present invention provides excep¬ tionally accurate length measurements. In accordance with the invention a first worker Wl couples a laser ranging device L to one end of a pipe section and a second worker W2 couples a reflector R to the opposite end of that pipe section. The coupling of laser ranging device and reflector with a pipe section is shown more clearly in Fig. 2. The laser ranging device L comprises a housing 12 having a handle 14 and having an output tube lβ provided with an apertured plate 18 adapted to abut an end of the pipe section. Plate 18 is perpendicular to the axis of tube 16. As shown in Fig. 5, plate 18 has a central aperture 20, the center of which is aligned with the beam of laser light produced by the laser ranging device. The reflector R may comprise a metal disc 22 supported on an end of an elongated handle 24 (perpendicular to the length thereof) and adapted to abut an associated end of a pipe section opposite to the end associated with the laser ranging device L. The reflective surface of the disc may be constituted by reflective tape with a large backscatter angle. Other types of reflectors, such as a corner reflector or corner reflecting prism, may also be used. When plate 18 and reflector disc 22 abut respective ends of a pipe section, approximately centered thereon, the transmitted and reflected laser beam will be approximately aligned with the axis of the pipe section. Since the ends of the pipe sections may be recessed in the stack by different amounts, it is preferred that the effective length of the output tube 16 of the laser ranging device be adjustable. This may be accomplished, for example, by providing a set of extension tubes 25a, 25b of different lengths, as illustrated in Figs. 3 and 6. In the form shown each tube has at one end an apertured plate 18' or 18" adapted to abut an end of a pipe section and has at the opposite end another apertured plate 18a or 18b that may be attached to plate 18, as by thumb screws 26 threaded into corresponding threaded openings in plate 18 through openings in plate 18a or 18b. The axis of the extension tube will then be aligned with the axis of output tube 16, and plate 18' or 18" will be parallel to plate 18. Plates 18' and 18" may have a diameter appropriate to the diameter of the pipe section to be measured. Similarly as shown in Figs. 7 and 8, additional reflectors 22' and 22" may be provided attached to handles 24' and 24" of different lengths to accommodate different amounts of recess of the associated pipe section ends. The reflectors may have diameters appropriate to the diameters of the pipe sections. Typically the laser ranging device L shown in Figs. 3-5 may be about 12 inches long and approximately 5 inches high and 5 inches wide. Tube 16 may have an inner diameter of 2 inches and plate 18 may have a diameter of 3.3 inches (the same as plate 18'). Plate 18" (appropriate for a 6-inch pipe) may have a diameter of about 6 inches. Reflectors 22' and 22" may have the same diameters as plates 18' and 18", respectively. Plates, such as 18", of different diameters may be attached interchangeably directly to plate 18 to accommodate corresponding pipe section diameters, and discs, such as 22", of different diameters may be attached interchangeably to the same handle to accommo¬ date corresponding pipe section diameters. Figs. 9 and 10 illustrate a modification of the invention. As shown in Fig. 9, a cruciform apertured plate 18A may be used, rather than an annular plate, to abut an end of a pipe section for coupling the laser ranging device thereto. Frequently the ends of pipe sections are covered by end protectors that become scuffed or gouged. By using a plate 18A having radial arms, the arms may be oriented about the axis of a pipe section to avoid contact with burrs or other protru¬ sions (or recesses) of the end protector that might misalign the laser beam with the axis of the pipe section. The elimination of some of the material of an annular plate also reduces the weight of the apparatus. A further advantage of multi-arm plates, such as 18A, is that the arms of the plate can be made some¬ what flexible, so that the alignment of the laser beam relative to the axis of a pipe section can be adjusted while the plate 18A remains fixed against an end of the pipe section. The laser ranging device may be provided with a signal strength meter and may be deflected in different lateral directions until the signal strength is maximized. At that time a measurement can be made with assurance that the laser beam is substantially aligned with the axis of the pipe section. To provide greater flexibility, a compressible gasket 27 may be interposed between plate 18A and flange 29 at the end of an extension tube 25a (or the output tube 16) . Screws or bolts 26 (Fig. 3) may be employed to attach plate 18A to flange 29 and set the desired amount of compression in gasket 27, thereby permitting the end plate 18A to be abutted with an end of a pipe section while permitting adjustment of the axis of tube 25a for alignment of the laser beam with the axis of the pipe section. For very small pipe diameters, where precise alignment of the laser beam with the axis of a pipe section may be required, the laser ranging device may be bench tested to determine the accuracy of alignment of the laser beam with the output tube 16, and any misalignment corrected before the apparatus is used in the field. Fig. 11 illustrates an electrical system that may be employed in the invention. The laser ranging device L may comprise a Red-Mini Laser Ranger (infrared pulse) , a Z8 control computer, MC7806 voltage regula¬ tor, MC7805 voltage regulator, and RS232C power supply (all so-designated) all of which may be contained in the housing 12 and associated electronics box 12 ' illustrated in Figs. 2-5. The apparatus is energized by the closing of a power switch S^ and a length measurement is performed by depressing a pushbutton 8 switch S 2 . Completion of a measurement may be indi- . cated by the sounding of a miniature horn H. A signal strength monitoring circuit "SIG. STR." (includ¬ ing rectifier, filter, and meter) may be connected to the Red-Mini Laser Ranger as shown. As shown, the apparatus in housing 12 may be coup¬ led to one end of a 4-conductor cable (so-designated) by a connector pair Jl, J3. At the opposite end of the cable a further connector pair J4, J5 has conductors appropriately connected to a car battery, a DC/AC inverter, and a micro-computer (all so-designated) , the computer being connected to J5 by a further connector J6. The computer may receive its AC power from the inverter as shown. The apparatus enclosed in dash-line rectangle A may be situated remotely from the laser ranging device per se, in a van, for example. In the operation of the invention, the Z8 control computer may- initiate the laser distance measurement sequence, convert a parallel BCD output of the laser ranger to ASCII serial output, and actuate an audio tone end-of- sequence signal (via horn H) to notify the operator that the measurement is good. The HP-85 micro-computer may read the serial ASCII output of the Z8 control computer, test the distance data for logical limits, log the test data point on cassette tape for later processing and report formulation (by means of a more sophisticated computer and a printer) , log the cumula¬ tive measurement total, transmit the end-of-sequence control data to notify the operator of measurement completion, and transmit an end-of-sequence tape message and other housekeeping data. ' Referring again to Fig. 1, in the use of the invention, when worker Wl has coupled the laser ranging device L to one end of a pipe section and worker W2 has coupled the reflector R to the opposite end of that pipe section, worker Wl closes the power switch S ] _ and depresses the measurement switch S 2 to perform a measurement of the length of the pipe section. A beam of laser light from the laser ranging device L is transmitted from the laser ranging device along the axis of the pipe section and is returned to the laser ranging device after reflection from the reflector R. A length (distance) computation is then performed.by the laser ranging device in a conventional manner. A compensation factor may be entered into the computer employed in the laser ranging device so as to compen¬ sate ' automatically for the length of any extension sleeve (e.g., 25a or 25b) attached to the laser ranging device. Successive pipe section length measurements may be transmitted to the micro-computer and may be summed to provide a readout of the total length of pipe comprising all the pipe sections in the stack. Different types of pipe sections may be segregated in the micro-computer by well known programming tech¬ niques. By virtue of the invention, rapid, accurate measurements of the length of pipe sections can be made very efficiently, providing a vast improvement over conventional techniques. While preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes can be made without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims. For example, other types of apparatus may be employed for aligning the laser beam with the axis of a pipe section. Such apparatus may include movable jaws that remain parallel with the laser axis and that are forced against the inner surface of a pipe section by spring tension or applied mechanical, pneumatic, or hydraulic pressure. A precisely machined cylinder which fits into the end of a pipe section or a collar that fits over the end of a pipe section may also be used. If desired, the extension tubes may be provided with diverging lenses to spread the beam slightly. In practice, however, it has been found that the preferred alignment apparatus described earlier is simpler and performs entirely satisfactorily.

Claims: Claims; 1. A method of measuring the length of pipe sections, that comprises coupling a laser ranging device to one end of a pipe section with the laser beam axis approximately aligned with the axis of the pipe section, coupling a reflector to the opposite end of the pipe section with the reflector disposed to reflect a laser beam from the laser ranging device back to the laser ranging device, and operating the laser ranging device to transmit a beam of laser light from said one end to said reflector at said opposite end and to determine the length of the pipe section from the transmitted beam reflected by said reflector. 2. A method in accordance with Claim 1, wherein said coupling of the laser ranging device to the pipe section comprises connecting an extension tube to the laser ranging device through which the beam is trans- mitted and positioning an end of the tube remote from the laser ranging device at said one end of the pipe section. 3. A method in accordance with Claim 2, wherein said coupling of the reflector to the opposite end of the pipe section comprises positioning at said opposite end of the pipe section a reflector mounted on an elongated handle. 4. A method in accordance with Claim 1, wherein the first-mentioned coupling comprises adjusting the alignment of the beam of laser light with the axis of the pipe section to ensure that the intensity of the reflected light is substantially maximized. 5. A method in accordance with Claim 1, further comprising repeating the recited steps for different pipe sections and computing from such measurements the sum of the lengths of the pipe sections. 6. Apparatus for measuring the length of pipe sections, comprising, in combination, a laser ranging device having means for coupling the same to one end of a pipe section with the device oriented to transmit a laser light beam along the axis of the pipe section to the opposite end of the pipe section, and a reflector having means for coupling the same to said opposite end with the reflector disposed to reflect said light beam back to said ranging device. 7. Apparatus in accordance with Claim 6, wherein said means for coupling said laser ranging device to said one end of the pipe section comprises an extension tube having means for connecting the same to the laser ranging device in alignment with the laser beam transmitted by the device. 8. Apparatus in accordance with Claim 7, wherein the last-mentioned coupling means comprises a plurality of said tubes having different lengths whereby the distance between the laser ranging device and said one end of a pipe section can be adjusted. 9. Apparatus in accordance with Claim 6, wherein said means for coupling said reflector to said opposite end of the pipe section comprises an elongated handle having the reflector mounted on one end thereof. 10. Apparatus in accordance with Claim 9, wherein the last-mentioned coupling means comprises a plurality of said handles of different lengths. 11. Apparatus in accordance with Claim 6, wherein said means for coupling said laser ranging device to said one end of the pipe section comprises a plate attached to the laser ranging device in a plane perpendicular to the laser light beam, said plate being adapted to abut said one end of said pipe section. 12. Apparatus in accordance with Claim 11, wherein said plate has a plurality of radial arms adapted to engage said one end of said pipe section. 13. Apparatus in accordance with Claim 12, wherein said arms have sufficient flexibility to permit the alignment of the laser beam to be adjusted relative to the axis of said pipe section while said arms remain in contact with said one end of said pipe section. 14. Apparatus in accordance with Claim 11, wherein said plate is attached to said laser ranging device with a compressible gasket interposed there- between and with the gasket compressed to provide sufficient flexibility to permit the alignment of the laser beam to be adjusted relative to the axis of said pipe section while the plate abuts said one end of said pipe section. 15. Apparatus in accordance with Claim 6, wherein said apparatus includes means for computing the sum of successive pipe section length measurements.

Inventors: BENSON JOHN L, CLOUTIER PAUL A, OEHME DELBERT R, BENSON, JOHN, L., CLOUTIER, PAUL, A., OEHME, DELBERT, R.
Applicants: INNOVATUM INC, INNOVATUM, INC.
Application year: 1985
Main classification: G01B11
IPC codes: G01B11, G01S17