GB1561811A

GB1561811A - Method and apparatus for ultrasonic inspection

Info

Publication number: GB1561811A
Application number: GB41822/76A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1975-10-08
Filing date: 1976-10-07
Publication date: 1980-03-05
Also published as: FR2327541B1; MX142895A; FR2327541A1; JPS6045370B2; AU506655B2; JPS5253490A; AU1845376A; NL183777B; DE2645274A1; DK452476A; NL7611197A; NO148123B; NL183777C; IT1074730B; DE2645274C2; NO148123C; NO763393L

Description

(54) METHOD AND APPARATUS FOR ULTRASONIC INSPECTION (71) I, WILLIAM CARROLL LAMB, a citizen of the United States of America, of 3103 Cameron, P.O. Box 53887 OCS, Lafayette, Louisiana 70501, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an apparatus and method for the nondestructive ultrasonic testing of tubular members for the detection of small internal cracks and other types of discontinuities or imperfections.

The use of ultrasonic testing techniques, and specifically of ultrasonic crystals, for detecting discontinuities or other defects in metal articles is a common mode of nondestructive testing. The crystals employed are typically piezoelectric crystals made of a material such as quartz. These crystals produce ultrasonic vibrations in response to a voltage of appropriate frequency impresse,d upon the crystal. When inspecting a tubular metal article for internal flaws using a reflection method, the crystal is maintained in a fixed position relative to the surface of the article and caused to transmit a short duration sonic wave pulse which passes into the article at such an angle that a defect or discontinuity in the article will cause the waves to be reflected to the crystal and produce a voltage response in the crystal.Since the crystal is in a de-energized state immediately following the pulsed emission of a wave, reflected waves are received during deqenergized periods and hence the reflected waves will produce a disconcernible signal which may be monitored, for example, on a cathode ray tube or a strip chart recorder. Pulse repetition rates of between 60 and 2000 pulses per second are employed for various types of inspections.

Typically, an ultrasonic inspection device will be calibrated using a standard identical to the articles to be inspected. The standard may have one or more discontinuities of known magnitude so that the response of the device to known imperfections may be ascertained, and standards for accepting or rejecting the inspected articles may be established.

Ultrasonic inspection techniques are typically employed at the site of manufacture of the articles being inspected. Thus, plate or tubular articles are typically inspected at the manufacturing plant using techniques which are well known in the art. However, tbe on-site inspection of tubular articles presents different and unique problems.

In well drilling operations, drill pipe failure can be a costly and time-consuming occurrence. Washouts or drill string breakage can occur frequently if drill pipe with sufficiently serious imperfections is employed. Most frequently such failures result from internal flaws in the tubular goods being used. Confronted with such a failure, it becomes necessary to trip the pipe out of the borehole to replace the failed joint. In the case of drill string breakage, it is necessary to fish the parted portion of the string from the borehole before drilling can be recommended. Hence, the value of an efficacious method of on-site inspection of drill pipe, particularly for internal flaws, is obvious.

During drilling operations, the drill string is frequently tripped into and out of the borehole to replace a worn drill bit, to set casing at various levels or conduct other operations. During these trips, it is preferred to stack the drill pipe vertically within the well derrick rather than transport it from the elevated rig floor to racks maintained at ground level. In offshore drilling operations, it is also common to stack drill pipes vertically. Inspection of a drilling string is desirably conducted periodically, e.g. every two or three months, to detect the existence of flaws in drill pipes which would render the pipe susceptible to failure in subsequent drilling operations. Hence, for most efficient inspection of tubular goods in well drilling operations, it is necessary to provide an inspection device which can inspect tubular goods in a vertical position in the well derrick.With such a device inspections could be conducted during a tripping operation made necessary by factors such as replacement of a worn drill bit.

Furthermore, since it is necessary to join individual stands of pipe (comprising typically two or three pipe joints or sections) at the rig floor level when assembling a drilling string, it is necessary that a useful inspection device be readily engaged and disengaged from about the pipe being inspected.

The sensitivity of ultrasonic inspections, however, can be adversely affected by the severe conditions prevalent on a drilling rig. A suspended pipe can move laterally or can be vibrating as a result of the insertion or withdrawal operation. Such conditions make it difficult to maintain adequate sonic coupling between the search unit and the pipe. Moreover, such movement can alter the angles at which the sonic emissions enter the wall of the member being inspected.

It is accordingly necessary to provide a rugged device to conduct such on-site inspection to obtain the most accurate and dependable readouts.

In accordance with one aspect of the present invention, there is provided apparatus suitable for use in ultrasonic inspection of a substantially vertically disposed tubular member, which apparatus comprises a frame defining a passage for receiving a tubular member for movement therethrough in a direction substantially aligned with the longitudinal axis of the member, the frame being such that the tubular member can be admitted to the passage and withdrawn therefrom in a direction transverse to the longitudinal axis of the member; and a plurality of ultrasonic search units mounted on said frame for engaging the outer surface of the member, each of said search units including an electro-acoustic transducer adapted to be sonically coupled with the member and for transmitting ultrasonic pulses into said member and receiving reflected pulses.

The provision of a frame adapted to admit and discharge the tubular member, for example a pipe, in a direction transverse to the longitudinal axis of the member enables the inspection to be conducted, for example, when tripping pipe in. and out of a borehole. If a serious discontinuity or imperfection in the pipe is detected, the tripping operation may be stopped, the ultrasonic inspection device withdrawn from the pipe and the joint of pipe containing the flaw may be removed from the drilling string. When the string is reassembled, the ultrasonic inspection device may be readily replaced in inspecting position around the pipe to continue monitoring of the pipe as it passes into the borehole.

When a pipe is being tripped out of a borehole, the surface of the pipe is typically covered with drilling mud and drilling debris. Also, there may exist liquid films flowing on the interior of the pipe as the pipe is withdrawn from a liquid-filled borehole.

The existence of drilling mud or debris on the exterior of the pipe can create coupling difficulties with an ultrasonic inspection device. Moreover, liquid films flowing down a pipe can create false "reflections" which would mask the existence of discontinuities or flaws which are sought to be detected.

Accordingly, unless a drill pipe can be substantially cleaned during its with drawal from the borehole, the device of the present invention is most suitably employed to conduct the ultrasonic inspection during a pipe tripping operation into the borehole.

The frame may, for example, be hinged to swing open for accepting the pipe transversely into the vertical passage through the frame. Alternatively, the frame may have an opening to provide access of the pipe transversely to the vertical passage.

The ultrasonic inspection apparatus may be employed to detect flaws which are transverse to the longitudinal axis of the tubular member. In such an arrangement, the search units emit a sonic wave which is sonically coupled to the tubular member at an acute angle to the longitudinal axis of the member. Sufficient ultrasonic devices are arranged about the pipe in order that the combined beam spread of the search units will survey the entire circumference of the tubular member.

A plurality of ultrasonic search units are mounted in the frame of the apparatus.

These search units advantageously comprise rolling wheels having a flexible surface, in the nature of an inflated tyre, adapted to conform to the shape of the tubular member. The surface material is generally transparent to the ultrasonic signal.

Each such search unit includes within the wheel a piezoelectric type crystal and a coupling agent to transmit the sonic signal from the crystal to the flexible material comprising the wheel surface. A further coupling agent, such as water may then be injected between the flexible surface of the rolling wheel and the tubular member in order to assure transmission of the sonic signal from the rolling wheel into the wall of the tubular member being inspected.

Conveniently the inspection apparatus may be positively stabilized with respect to the tubular member while permitting relative movement of the tubular member through the inspection device.\The tubular member may be so stabilized within the device by means of a plurality of guides or stabilizers mounted on the frame. Such stabilizers are advantageously independently mounted from the search units on the frame and are pressed against the tubular member with a force greater than any forces maintaining the search units in sonically coupled relation with the tubular member.

Hence any movement of the tubular member is absorbed by such stabilizers which then maintain the frame in position to preserve the sonic coupling of the search units through the movement.

The apparatus desirably further comprises means for yieldably urging the search units into contact with the member. Such urging means is preferably adapted to maintain constant the angular relation between the transducers and the tubular member, and hence provide accurate inspection information. Such urging means is preferably also adapted to permit radial movement of the search units with respect to the tubular member so that the search units are selfadjusting to accomodate variations in the external dimensions of the tubular member under inspection.

The frame of the inspection device advantageously also supports an ultrasonic inspection instrument comprising a pulseri receiver to energize the piezoelectric crystals within the ultrasonic search units and also to detect reflected waves. The inspection instrument may also include a display in the form of a cathode ray tube, a strip chart recorder of the like to produce a readable response to reflected waves indicating the presence of discontinuities. An audible indication of the existence of discontinuities might alternatively be provided.

The entire apparatus may be advantageously suspended from an overhead line in the well derrick from a point proximate the centre of gravity of the apparatus thus facilitating the manual manipulation of the device into and out of engagement with the tubular goods being inspected.

Desirably, a single pulser unit is used to pulse all the search units, and a single display or other indication is produced from the combined response of the search units to reflected waves indicative of discontinuities. Thus, a device operable by one man on the derrick floor may be provided.

A preferred embodiment of the present invention provides apparatus for simultaneously conducting a plurality of different inspections on a tubular member, such as those used during well operations. An inspection of primary interest involves ultrasonic monitoring of a tubular member for discontinuities transverse to the longitudinal axis of the member. Such an inspection is conducted by sonically coupling a plurality of ultrasonic search units around the member to be inspected to provide a combined beam spread which covers the entire circumference of the member. In such an operation, the search units are disposed to transmit ultrasonic pulses into the wall of the tubular member at an angle acute to the longitudinal axis of the member being inspected and in a direction coextending with the longitudinal axis, as generally desscribed above.

However, such an ultrasonic inspection generally is not indicative of the existence of discontinuities parallel to the longitudinal axis of the tubular member. In addition, wall thickness of a tubular member is another parameter which is of interest in determining the potential failure characteristics of tubular goods, such as those used in drilling operations.

Accordingly, the above-mentioned preferred embodiment of the present invention provides apparatus capable of performing, during the same tripping operation, a plurality of inspection functions including searching for discontinuities transverse to and generally parallel to the longitudinal axis of a tubular member and monitoring the thickness of a single wall of the tubular member. This embodiment includes a multi-tiered inspection buggy having a generally vertical passage accessible by the tubular member from a direction transverse to its longitudinal axis. Each tier of the buggy includes search units sonically coupled to the tubular member and disposed to conduct one of the desired search operations, i.e., search for transverse discontinuities, parallel discontinuities and monitor wall thickness.A plurality of stabilizers sufficient to maintain the tubular member in stable position relative to the buggy are provided; however, it is not necessary that stabilizers be included on each inspection tier. Preferably, each of the search units on each tier is independently mounted to maintain a constant angle between the electro-acoustical transducers within the search unit and the tubular member being inspected.

In accordance with a further aspect of the present invention, there is provided a method of inspecting a tubular member used in well drilling operations on a drilling platform of a well derrick while said member is being inserted or retrieved from a well borehole, which method comprises vertically suspending said tubular member within the well derrick; sonically coupling around the periphery of the tubular member a plurality of ultrasonic search units each containing an electro-acoustical transducer disposed in a specific angular relation to the surface of the tubular member; moving said tubular member vertically relative to said borehole while maintaining the transducers within said search units in fixed angular position relative to the surface of the tubular member; simultaneously causing said transducers to transmit ultrasonic pulses into the wall of the tubular member; detecting ultrasonic pulses reflected from within said tubular member with said transducers and producing electrical signals functionally related to said reflected ultrasonic pulses; and producing a sensible indication responsive to said electrical signals.

Embodiments of the present invention are illustrated by way of example in the accompanying drawings, in which: FIGURE 1 is a perspective view of an ultrasonic inspection apparatus in accordance with the present invention, shown in place on a drill pipe and disposed over the rotary table on a drilling platform; FIGURE lA is a top plan view of the inspection apparatus of Figure 1; FIGURE 2 is a perspective view of an ultrasonic transducer search unit device employed in the inspection apparatus of Figure 1, specifically showing a mounting linkage urging a rolling wheel search unit into contact with a pipe under inspection; FIGURE 3 is a side schematic view of the ultrasonic transducer device and mounting linkage of Figure 2; FIGURE 4 is a part-sectional plan view of the ultrasonic transducer device of Figures 2 and 3;; FIGURE 5 is a schematic side view of a stabilizer employed in the inspection apparatus of Figure 1; FIGURE 6 is a schematic view of a multi-tiered inspection apparatus in accordance with the present invention; FIGURE 7 is a horizontal section on line 7-7 of Figure 6; FIGURE 8 is a horizontal section on line 8-8 of Figure 6; FIGURE 9 is a horizontal section on the line 9-9 of Figure 6, and FIGURE 10 is a schematic illustration of an ultrasonic inspection apparatus in accordance with the present invention and associated peripheral devices for displaying and recording inspection runs.

Figures 1 and 1A show an ultrasonic inspection apparatus 11 positioned around pipe section 13 vertically disposed through the rotary table opening on a drilling rig floor 15. Pipe 13 is joined at joint 12 to another section of pipe and is suspended in a well derrick (not shown) by means of an elevator or like device (not shown). The ultrasonic inspection apparatus comprises a frame having two generally parallel horizontally disposed members 17 and 19 spanned by brace 21. Two base plates, 23 and 25, are pinned at points 24 and 26, respectively, for pivotal movement parallel to the frame. Latch 71 at the opposite end of plates 23 and 25 serves to hold the plates in a closed position around the pipe 13.

A pair of registering recessed portions in base plates 23 and 25 defines a central vertical passage 30 in the apparatus. A shroud 28 (not shown in Figure 1A) having a corresponding central passage and four separate compartments encloses the ultrasonic inspection apparatus 11.

The frame comprising parallel members 17 and 19 and brace 21 is open at the end opposite the brace 21. The open end permits the inspection apparatus to be removed from pipe 13 quickly and easily after base plates 23 and 25 have been unlatched by means of latch 71 and pivoted outwardly from the closed position to an open position.

Each base plate 23 and 25 supports two electro-acoustic transducer wheel search units each containing a piezoelectric crystal, and also supports two transducer mounting linkages. Specifically, base plate 23 supports transducer mounting linkages 29 and 31, while base plate 25 supports transducer mounting linkages 27 and 33.

It will be understood that any desired number of ultrasonic search units may be used to effect the pipe inspection. The embodiment illustrated in Figures 1 and 1A has four such search units arranged symmetrically around the pipe section 13 at 90-degree intervals. However, it may be satisfactory, depending upon the size of the pipe to be inspected, the particular inspection operation, and the beam spread of the ultrasonic transducers employed, to utilize more or less ultrasonic search units.

When scanning the pipe for imperfections or discontinuities transverse to the axis of the pipe being inspected, sufficient search units should be provided to obtain a beamspread that will survey the entire circumference of the pipe as it passes through the apparatus. Generally, three or four search units are used for the detection of transverse discontinuities, although more may be required for large diameter pipes.

For longitudinal discontinuity inspection, the electro-acoustic transducer search units are arranged in a plane parallel to the axis of the pipe to transmit a beam which travels around the pipe in a section generally perpendicular to the longitudinal axis. As few as two and up to four coplanar search units are used for this operation depending primarily on the diameter of the member being inspected.

Measurement of the wall thickness of the pipe is effected by a sonic beam transmitted perpendicular to the surface of the pipe.

This beam measures thickness of the pipe only beneath the search units. Hence up to four or even more units may be employed depending upon how closely thickness is to be monitored. On a large diameter pipe, a complete thickness inspection could require more than four units. Often it may be suf ficient, on the other hand, to use two search units to monitor thickness, cognizant that these units will give only a general indication of pipe condition, and are not likely to pick up all areas of wear or corrosion.

In order to scan for discontinuities trans verse to the longitudinal axis of a tubular member, each search unit should preferably have its piezoelectric crystal disposed at an angle approximately 45 degrees to the axis of the tubular member being in spected. This angle may vary depending upon the size and wall thickness of the pipe being inspected. For example, on some pipe having a diameter between 3-1/2 and 4-1/2 inches, it has been found that an at tack angle of the sonic beam from the piezoelectric crystal is optimal at an angle 43-1/2 degrees to the longitudinal axis of the pipe when inspecting for transverse dis continuities. However, in determining the optimal disposition of the piezoelectric crystal, it is preferred to initially calibrate the unit with a standard test pipe section having a discontinuity of known dimen sion.The unit is activated and the angle of attack of the piezoelectric crystal is ad justed until the known discontinuity gives the maximum electrical response. Avail able search units have the capability of ad justing to the member being inspected and use of such variable angle beam search units is preferred.

It is thus desirable to be able to set up the inspection apparatus with the optimum beam angle and utilize the apparatus to in spect tubular members of various diameters without making correction adjustments to reset the beam angle. Mounting linkage 33 provides this desirable feature.

Figure 2 shows in perspective mounting linkage 33 positioning a search unit proxi mate pipe 13. Mounting linkage 33 comprises a vertically standing member 39 having a rectangular-shaped opening 40 formed at the upper end and a slot 41 at the lower end. Vertical member 39 is securely affixed to base plate 25 to hold the search unit rigidly in position. An upper arm 42 extends through the opening 40 and is pivotable in a vertical plane about pin 43. A shorter, lower arm 44 extends into into slot 41 and is similarly pivotable in the same vertical plane about a pin 45. A rectangular adapter plate 46 co-operates with base plate 38 of the wheel search unit and is mounted thereon, for example, with counter-sunk screws 47, 48, 49 and 50. A clevis 51 is formed on the top edge of the adapter plate 46, a similar clevis 52 being formed on the bottom edge of plate 46.

Clevis 51 and clevis 52 pivotally receive upper arm 42 and lower arm 44, respectively, thereby pivotally supporting adapter plate 46.

The rearwardly extending portion of upper arm 42 is threaded and receives a bolt 53. A spring 54 or other biasing means extends between the lower end of bolt 53 and the base plate 25. Bolt 53 permits the spring tension and consequently the force acting on arm 42 to be adjusted to a desired magnitude.

As can be seen from Figure 3, the construction of mounting linkage 33 permits downwards movement of the wheel search unit towards the central passage 30, and yet maintains the base plate 38 of the search unit parallel with the tubular member 13.

With a smaller diameter pipe 13, the mounting linkage 33 is so positioned that the upper arm 42 and the lower arm 44 are in a substantially horizontal position.

Transducer 130 carried within the wheel 35 is positioned for the optimum beam angle with respect to pipe 13.

When a larger diameter pipe is being inspected, or a joint 12 is encountered, arms 42 and 44 pivot to an inclined position. Because adapter plate 46 is pivoted to the ends of arms 42 and 44, thereby forming a parallelogram-like structure, adapter plate 46 moves downwardly and maintains its vertical disposition. With adapter plate 46 remaining unchanged in its attitude, the transducer 130 in wheel 35 also remains in its prior orientation and consequently the beam angle does not change.

The search unit employed in the device of this invention is preferably a variable angle beam wheel search unit of a type well known in the art. Such wheel search units are manufactured by Sperry Division of Automation Industries, Inc. The wheel search unit typically comprises a flexible tyre-like wheel 35 mounted for rotation about an axis supported by bracket 37. A piezoelectric crystal is mounted on a nonrotating axle within the wheel. Accordingly, the beam angle from the piezoelectric crystal in the wheel search unit can be set to the optimum value and so maintained regardless of the size of tubular member that is being inspected. The flexible wheel 35 is then filled with a suitable sonic coupling agent. Coupling agents which have been used in the art include glycols or glycol ethers, for example, the Cellusolve products sold by Union Carbide Corporation.

Wheel 35 is shown in partial section in Figure 4, with flexible outer covering 36 pressed firmly against pipe 13. Flexible outer covering 36 is securely attached to side supports 32 and 34 of wheel 35, and, when pressed against pipe 13, the outer covering conforms to the curvature of the outside pipe surface. Side supports 32 and 34 prevent wheel covering 36 from blowing out by limiting the extent to which the flexible covering 36 can be deformed. A search unit of this type is disclosed in U.S. Patent No. 3,628,375.

Wheel 35 is pressed against pipe 13 to maintain adequate pressure contact therewith by the force applied to it from spring 54 of linkage 33, as it acts through upper arm 42. The force so applied can be changed by adjusting the length of bolt 53 extending through, upper arm 42.

In order to accomplish sonic coupling between the flexible wheel 35 and the pipe 13 being inspected, it is preferred to provide a liquid sonic coupling agent on the surface of the pipe. Accordingly, a water line 49 (Figure 1) is provided above each wheel search unit to inject a constant stream of water to create a uniform film between each flexible wheel 35 and the pipe being inspected to serve as a sonic coupling agent. The lines 49 are fed through manifold (not shown) which receives water through a water transport line (not shown) that is connected to a suitable water supply (not shown) through valve 61. A gravity flow of water is satisfactory to provide suitable coupling between the wheels 35 and the pipe 13, although a pumped source may also be employed.It will be understood by those skilled in the art that coupling agents other than water may be used during operation of the apparatus. However, water operates satisfactorily and is clearly the most available and least expensive coupling agent suitable for use on the exterior of the pipe being inspected.

Shoe type search units which are dragged over the pipe surface or other search units not using a rotating wheel may also be used, but are less suitable under the rugged conditions of a drill rig.

Referring again to Figure 1, also mounted on base plates 23 and 25 and normally enclosed by shroud 28 are three stabilizers of which only stabilizer 82 is in view. The stabilizers serve to apply a radially, inwardly directed force at several locations around tubular member 13 to minimize swaying motion of tubular member 13 as it is being moved through the inspection device for inspection.

Stabilizer 82 comprises a support 85 extending above and below base plate 25 parallel to the centreline of the central passage 30. At each end of support 85, there is attached a pivot arm 87, 89 which carries a mount 91, 93 to which stabilizer wheels 95, 97 are affixed. A spring 99 connects between mount 91 and support 85 to urge wheel 95 against tubular member 13, and similarly, a spring 103 connects between mount 93 and support 85 to urge wheel 97 against tubular member 13, thereby applying a restraining force to the tubular member 13.

Although three stabilizers are employed in the preferred embodiment (see Figure 1A), additional stabilizers could be utilized.

The maximum number will, of course, be dependent upon the size of pipe being inspected. Also, it is preferable to have the upper and lower pipe-contacting portions of the stabilizers vertically spaced from the search units.

The upper portion of stabilizer 82 extending through the base plate 25 is schematically illustrated in Figure 5. Specifically, Figure 5 illustrates the operation of stabilizer 82 and its ability to function with various pipe diameters and permit passage of pipe joints. As shown, the structure formed of pivot arm 87 and mount 91 is pivoted about the upper end of vertical support 85.

A bolt 98 extends from the lower portion of mount 91 and through support 85, the spring 99 being carried on bolt 98 and held in compression. Stabilizer wheel 95 is attached to mount 91 through a bracket 100 and is urged into contact with pipe 13 by spring 99.

When a larger diameter pipe is to be inspected, pivot arm 87 and wheel 95 pivot about the upper end of support 85, moving slightly downwardly and outwardly with respect to the pipe 13. Spring 99 compresses further, maintaining an adequate inwardly directed radial force on the pipe 13. Also, as indicated in dotted outline in Figure 5, the stabilizers easily permit passage of pipe joints while maintaining stabilization of the pipe 13.

As shown in Figure 1, the support frame is provided with a platform 63 that supports an ultrasonic inspection instrument 59.

Instrument 59 is retained on platform 63 by means of a strap 65 which is engaged at its upper end by a hook extending from support 75. Support 75 terminates in an eye 67 or other connecting device, which may be engaged to an overload line on the well derrick. Eye 67 is desirably provided over the centre of gravity of the entire apparatus so that during use, minimal lateral forces are imposed upon the search units engaging the tubular member being inspected.

Ultrasonic inspection instrument 59 includes a pulse generator and receiver unit as well as an oscilloscope. Such ultrasonic search instruments are well known in the art. For example, Sperry Division of Auto- mation Industries offers 10M pulse receiver unit packaged with a type UM, style 50E533 oscilloscope which may be used with the inspection device in accordance with the invention. Also, smaller battery operated search instruments are available and can be used satisfactorily.

Referring to Figure 10, a pulser/receiver 77 within the inspection instrument 59 generates a series of pulses which are simul taneously transmitted to piezoelectric crys tals 79 in each of the wheel search units 35 through transmission lines 57 exiting junc tion block 60, switches 86 being closed.

Typically available search instruments pro vide only a single pulse output on foe pul ser/receiver 77. Junction block 60 merely divides the signal to the four transmission lines ~ and contains means for impedance matching the transmission lines and hence optimally tuning the signal transmitted to each wheel search unit. Such impedance matching techniques are well known in the art and may include a suitable RC circuit or a resistor-inductor combination.

When the piezoelectric crystals are ener gized, they transmit a sonic beam at an acute angle into the tubular member being inspected. The wave is reflected between the opposing walls of the tubular member and progressing longitudinally. If the beam encounters a discontinuity, a reflected sig nal will return and be picked up by the piezoelectric crystal. As set forth above, the optimal angle is usually about 45 degrees though this may be varied depending up on the material being inspected and the type of discontinuity that is sought to be detected. Switches 86 (which would be in corporated within instrument 59) enable the operator to activate and monitor each search unit individually or in any combina tion.During periods when the piezoelectric crystals are de-energized, reflected signals from discontinuities sensed within the pipe are transmitted through transmission lines 57 and through junction block 60 to pro vide a single output signal 'at jack 62 of the pulser/receiver portion 77 of instrument 59.

For optimal transmission, lines 57 are cut to lengths which correspond to multiples of the quarter wavelength of the signal.

The signal is amplified in the amplifier 89 within pulser/receiver portion 77 of instru ment 59 and displayed on oscilloscope 64 and/or recorded on a strip chart recorder 83.

The frequency of the signal for energiz ing the crystals 79 employed in connection with inspection operations using the ap paratus of this invention may vary, as will be understood by those skilled in the art.

Typical inspection operations may be conducted using signals having frequencies of from 1 megacycle to 5 megacycles. Eminently successful inspections have been conducted on drill pipe utilizing a frequency of 2.25 megacycles. The pulse repetition rate may vary between 60 and 2000 pulses per second as is known in the art. Pulse duration is in the microsecond range, for example, between 1 and 5 microseconds.

Accordingly, when the apparatus is to be used, latch 71 (Figure 1) is released and plates 23 and 25 are pivoted outwardly to enable the pipe 13 to be received between members 17 and 19. The apparatus is manually manipulated until pipe 13 is disposed centrally between the members 17 and 19, and plates 23 and 25 are swung back to their closed position and latched in place with latch 71. Biasing springs 54 will then urge each wheel search unit into engagement with the pipe and the passage of the pipe into the borehole commences.

Water flow is then commenced from tubes 49 to couple the wheel search units sonically to the pipe. The pulser portion of instrument 59 is activated and the four wheel search units simultaneously transmit a pulse into the pipe 13. The pulse is preferably directed upwardly away from the rotary table and at an acute angle to the longitudinal axis of the pipe. The receiver portion of the instrument detects reflected signals and displays the result on the oscilloscope 64.

When the inspection apparatus 11 encounters tool joint 12, the biasing springs will yield permitting the search units to ride over the raised tool joint.

When a serious discontinuity in the pipe is detected by oscilloscope 64, last 71 is loosed and the apparatus is manually removed from the pipe. The faulty pipe section is then removed, the string reconnected and the inspection device is repositioned to resume the inspection operation.

With reference now to Figure 6, there is illustrated in a simple schematic drawing, a three tier ultrasonic pipe inspection apparatus for inspecting to detect the presence of discontinuities transverse to the longitudinal axis of the pipe and discontinuities running substantially longitudinally through the pipe, and also to monitor wall thickness of the pipe. The wheel search units in a multi-tier inspection apparatus are mounted in exactly the same manner as the wheel search units of the embodiment of Figure 1. Specifically, a parallelogram-like linkage (similar to linkage 33 of Figure 3) is utilized for each wheel search unit. Each group of search units 140, 150 and 160 is mounted on a pair of base plates (similar to base plates 23 and 25 of Figure 1) with the three pairs of base plates being con nected together by vertical stanchions.

Therefore, when necessary to remove the three tier apparatus from around a pipe string, a holding latch is released permitting the three tier base plate structure to separate into two pivoted halves.

Although the specific arrangement of the wheel search unit groups 140, 150 and 160 could be varied, the transverse discontinuity detecting group 140 is shown mounted as the top tier with the transducer directing sonic waves upwardly into the pipe 13 as shown by the arrows. The central group 150 of wheel search units monitors wall thickness: and, as indicated by the arrows, the transducers direct sonic waves radially inward. The lower group of search units 160 detects longitudinal discontinuities in pipe 13. The transducers in that group direct sonic waves laterally into the pipe 13. It is pointed out, however, that the upper group 140 and the lower group 160 can be reversed, as the only requirement is that sonic waves from the various groups must not create interference.

Referring now to Figures 7, 8 and 9, there are illustrated separate plan views of each tier of search units. Figure 7 shows the search units 142, 144, 146 and 148 which are symmetrically disposed about the circumference of the pipe 13. The transducer of search unit 148 is shown disposed at a slightly upwardly inclined angle. Figure 8 similarly shows the search units 152, 154, 156 and 158 which are symmetrically disposed about the pipe 13. The transducer of search unit 152 is shown directing sonic waves directly into pipe 13 without lateral offset. Figure 9 shows the three search units 162, 164 and 166 of group 160 with the transducer of search unit 164 directing sonic waves laterally into pipe 13.

From the plan views of Figures 7-9, it is observable that the search units in the three groups will each roll along a separate and distinct path. However, an equally effective inspection apparatus could have the search units of the groups aligned to roll along a common path.

Each group of search units can be provided with a separate visual display device such as, for example, an ultrasonic search instrument comprising a pulser/receiver and CRT oscilloscope.

The foregoing description of the invention has been directed to a particular preferred embodiment for purposes of explanation and illustration. It will be apparent, however, to those skilled in this art that many modiflcations and changes in both apparatus and method may be made without departing from the scope and spirit of the invention. For example, the frame which is supported from overhead by a hook and cable could instead be supported by a carriage adapted to move on the rig floor into position approximate the drilling table.

Also, with appropriate modifications to the extension platform attached to the frame and modification to the junction block, separate visual display of each wheel search unit could be provided.

WHAT I CLAIM IS: - 1. Apparatus suitable for use in ultrasonic inspection of a substantially vertically disposed tubular member, which apparatus comprises a frame defining a passage for receiving a tubular member for movement therethrough in a direction substantially aligned with the longitudinal axis of the member, the frame being such that the tubular member can be admitted to the passage and withdrawn therefrom in a direction transverse to the longitudinal axis of the member; and a plurality of ultrasonic search units mounted on said frame for engaging the outer surface of the member, each of said search units including an electro-acoustic transducer adapted to be sonic ally coupled with the member and for transmitting ultrasonic pulses into said member and receiving reflected pulses.

2. Apparatus according to claim 1, wherein each of said search units comprises a wheel adapted to be disposed in rolling contact with the outer surface of said member.

3. Apparatus according to claim 1 or 2, further comprising means for yieldably urging said search units into contact with said member.

4. Apparatus according to claim 3, wherein said urging means is adapted to maintain the transducers in fixed orientation with respect to the longitudinal axis of the member.

5. Apparatus according to claim 3 or 4, wherein said urging means is adapted to permit radial movement of the search units with respect of the tubular member so that the search units are self-adjusting to accomodate variations in the external dimensions of the tubular member under inspection.

6. Apparatus according to claim 4 or 5, wherein said urging means comprises a hinged parallelogram linkage on each search unit having one side fixed with respect to said frame and the opposing side fixed to said search unit.

7. Apparatus according to any one of the preceding claims, further comprising stabilizer means adapted to engage the outer surface of the member and maintain said frame in stable relation relative to said member upon relative horizontal movement between said frame and said member.

8. Apparatus according to claim 7, wherein said stabilizer means engages the tubular member in at least two positions

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. nected together by vertical stanchions. Therefore, when necessary to remove the three tier apparatus from around a pipe string, a holding latch is released permitting the three tier base plate structure to separate into two pivoted halves. Although the specific arrangement of the wheel search unit groups 140, 150 and 160 could be varied, the transverse discontinuity detecting group 140 is shown mounted as the top tier with the transducer directing sonic waves upwardly into the pipe 13 as shown by the arrows. The central group 150 of wheel search units monitors wall thickness: and, as indicated by the arrows, the transducers direct sonic waves radially inward. The lower group of search units 160 detects longitudinal discontinuities in pipe 13. The transducers in that group direct sonic waves laterally into the pipe 13. It is pointed out, however, that the upper group 140 and the lower group 160 can be reversed, as the only requirement is that sonic waves from the various groups must not create interference. Referring now to Figures 7, 8 and 9, there are illustrated separate plan views of each tier of search units. Figure 7 shows the search units 142, 144, 146 and 148 which are symmetrically disposed about the circumference of the pipe 13. The transducer of search unit 148 is shown disposed at a slightly upwardly inclined angle. Figure 8 similarly shows the search units 152, 154, 156 and 158 which are symmetrically disposed about the pipe 13. The transducer of search unit 152 is shown directing sonic waves directly into pipe 13 without lateral offset. Figure 9 shows the three search units 162, 164 and 166 of group 160 with the transducer of search unit 164 directing sonic waves laterally into pipe 13. From the plan views of Figures 7-9, it is observable that the search units in the three groups will each roll along a separate and distinct path. However, an equally effective inspection apparatus could have the search units of the groups aligned to roll along a common path. Each group of search units can be provided with a separate visual display device such as, for example, an ultrasonic search instrument comprising a pulser/receiver and CRT oscilloscope. The foregoing description of the invention has been directed to a particular preferred embodiment for purposes of explanation and illustration. It will be apparent, however, to those skilled in this art that many modiflcations and changes in both apparatus and method may be made without departing from the scope and spirit of the invention. For example, the frame which is supported from overhead by a hook and cable could instead be supported by a carriage adapted to move on the rig floor into position approximate the drilling table. Also, with appropriate modifications to the extension platform attached to the frame and modification to the junction block, separate visual display of each wheel search unit could be provided. WHAT I CLAIM IS: -

1. Apparatus suitable for use in ultrasonic inspection of a substantially vertically disposed tubular member, which apparatus comprises a frame defining a passage for receiving a tubular member for movement therethrough in a direction substantially aligned with the longitudinal axis of the member, the frame being such that the tubular member can be admitted to the passage and withdrawn therefrom in a direction transverse to the longitudinal axis of the member; and a plurality of ultrasonic search units mounted on said frame for engaging the outer surface of the member, each of said search units including an electro-acoustic transducer adapted to be sonic ally coupled with the member and for transmitting ultrasonic pulses into said member and receiving reflected pulses.

longitudinally spaced along the axis of the tubular member.

9. Apparatus according to claim 8, wherein said stabilizer means comprises at least two sets of coplanarly arranged wheels adapted to engage the surface of said tubular member.

10. Apparatus according to- any one of the preceding claims, wherein said ultrasonic search units are disposed in substantially the same plane.

11. Apparatus according to any one of the preceding claims, wherein said search units are arranged to move along a path parallel to the longitudinal axis of said tubular member.

12. Apparatus according to any one of the preceding claims, wherein said ultrasonic search units are sonically coupled with a liquid film formed between said units and said tubular member by liquid injection.

13. Apparatus according to any one of the preceding claims, wherein said electroacoustic transducers are simultaneously energized from a common source.

14. Apparatus according to any one of the preceding claims, wherein said electroacoustic transducers are piezoelectric crystals.

15. Apparatus according to any one of the preceding claims, wherein said electroacoustic transducers are adapted to produce electrical signals in response to pulses reflected from discontinuities within said tubular member, said electrical signals being combined to form a single signal.

16. Apparatus according to claim 15, further comprising a display device for visu ally displaying said single signal.

17. Apparatus according to claim 16, wherein said display device is a cathode ray tube instrument.

18. Apparatus according to claim 16, wherein said display device is a strip chart recorder.

19. Apparatus according to any one of the preceding claims, wherein said search units are arranged to detect discontinuities transverse to the longitudinal axis of the member.

20. Apparatus according to claim 19, wherein said electro-acoustic transducers are adapted to transmit ultrasonic pulses upwardly and into said tubular member.

21. Apparaus according to claim 19 or 20, wherein said electro-acoustic transducers are adapted to transmit ultrasonic pulses at an angle of 43+ with respect to the longi tudiDal axis of the tubular member.

22. Apparatus according to claim 20 or 21, wherein said electro-acoustic transducers are so arranged as to produce jointly a beam spread of pulses which covers the entire circumference of said tubular member.

23. Apparatus according to any one of claims 1 to 18, wherein said search units are arranged to detect discontinuities parallel to the longitudinal axis of the tubular member.

24. Apparatus according to claim 23, wherein said electro-acoustic transducers are adapted to transmit ultrasonic pulses perpendicular to the longitudinal axis of the tubular member, and laterally offset with respect to said axis.

25. Apparatus according to any one of claims 1 to 18, wherein said search units are arranged to monitor the wall thickness of the tubular member.

26. Apparatus according to claim 25, wherein said electro-acoustic transducers are adapted to transmit ultrasonic pulses radially with respect to the longitudinal axis of the tubular member.

27. Apparatus according to any one of the preceding claims, wherein said frame includes a laterally extending platform for accommodating an ultrasonic inspection instrument.

28. Apparatus according to claim 27, further comprising a support attached to said frame and extending upwardly to a connecting device disposed directly above the centre of gravity of the ultrasonic inspection apparatus.

29. Apparatus according to any one of the preceding claims wherein said frame comprises two or more longitudinally spaced apart horizontal mounting planes each having a plurality of search units disposed thereon, the search units on each mounting plane being arranged to perform different inspection operations.

30. Apparatus according to claim 29, wherein the search units on one of said planes are arranged to transmit ultrasonic pulses longitudinally within the wall of said tubular member in a direction away from the remainder of said planes to inspect for discontinuities transverse to the longitudinal axis of the member.

31. Apparatus according to claim 29 or 30, wherein said frame defines three mounting planes and the search units on the uppermost frame are arranged to inspect for discontinuities transverse to the longitudinal axis of the tubular member.

32. Apparatus according to any one of the preceding claims, wherein the frame comprises a horizontal base plate with an opening therein defining said passage.

33. Ultrasonic inspection apparatus substantially as described with reference to and as shown in Figures 6, 7, 8 and 9 of the accompanying drawings.

34. Ultrasonic inspection apparatus substantially as described with reference to and as shown in Figures 1, 1A, 2, 3, 4, 5 and 10 of the accompanying drawings.

35. A method of inspecting a tubular member used in well drilling operations on a drilling platform of a well derrick while said member is being inserted or retrieved from a well borehole, which method comprises vertically suspending said tubular member within the well derrick; sonically coupling around the periphery of the tubular member a plurality of ultrasonic search units each containing an electro-acoustical transducer disposed in a specific angular relation to the surface of the tubular member; moving said tubular member vertically relative to said borehole while maintaining the transducers within said search units in fixed angular position relative to the surface of the tubular member; simultaneously causing said transducers to transmit ultrasonic pulses into the wall of the tubular member; detecting ultrasonic pulses reflected from within said tubular member with said transducers and producing electrical signals functionally related to said reflected ultrasonic pulses; and producing a sensible indication responsive to said electrical signals.

36. A method according to claim 35, wherein said ultrasonic pulses transmitted into the wall of the tubular member are inclined to the longitudinal axis of the tubular member, the combined ultrasonic pulses producing a beam spread which covers the full circumference of the tubular member.

37. A method according to claim 35 or 36, further comprising dividing a pulse signal from a single pulse source to said plurality of search units to transmit the ultrasonic pulses into the wall of the member, and combining the electrical signals related to said reflected ultrasonic pulses to produce a single visible indication on a cathode ray tube or a strip chart recorder.

38. An inspection method substantially as described with reference to the accompanying drawings.