NO148123B - PROCEDURE FOR INSPECTING A PIPE FORM USED BY DRILL OPERATIONS FROM A PLATFORM AND APPARATUS FOR EXECUTING THE PROCEDURE - Google Patents

Description

The present invention relates to a method for inspecting a tubular part which is used in drilling operations from a drilling platform, where ultrasonic search units are used which sonically connect to the tubular part, while it is lowered into or taken up by a borehole and is thereby vertically suspended in the platform's tower. The invention further relates to an apparatus for performing ultrasonic inspection

tion according to the aforementioned procedure. Both the method and the device keep the ultrasonic search units in a fixed and constant position in relation to the pipe, and enable inspection of this, as it is introduced into the borehole, so that it becomes possible to easily detect any defects in the tubular material, where defects can lead to to failure of the drill string if the material is used for drilling.

Application of testing techniques with ultrasound and in particular

with ultra crystals for the detection of cracks, cracks and irregularities in metal products, it is common for non-destructive testing. The crystals used are piezoelectric crystals made of a suitable material, e.g. quartz. These crystals produce ultrasonic vibrations when a voltage with an appropriate frequency is applied to the crystal. When tubular material is examined for internal imperfections using a reflection method, the crystal is held in a position relative to the surface of the product and a brief pulse of sound waves is sent into the product at an angle such that a defect or imperfection will cause the waves to be reflected against the crystal and create a voltage change in it. As the crystal is de-energized immediately after sending the wave pulse, reflected waves are received during the de-energized periods and the reflected waves will produce a detectable

lig signal that can be displayed e.g. on a cathode ray tube or strip printer. Pulse repetition rates of between 60 and 2000 pulses/sec are used for different types of examinations.

It is common for an ultrasound examination device to be calibrated using a standard that is identical to the material to be examined. The standard may have one or more defects or irregularities of known magnitude so that the device's sensitivity to known imperfections can be determined, and standard values for approval or rejection of the examined material can be obtained.

Examination techniques with ultrasound are often used to examine the material at the place where it is produced. Plate-shaped material or tubular material is therefore usually examined at the place of manufacture using techniques that are well known in the area in question here. However, examination of tubular material at the point of manufacture creates different and unique problems.

When drilling boreholes, failure of the drill pipe can be short-lived and time-consuming. Washout or breaks in the drill string can often occur if drill pipe with sufficiently serious imperfections is used. Failures of this nature are most often due to internal imperfections in the tubular material used. If you are faced with such a failure, it will be necessary to pull the pipe out of the borehole to replace the joint that has failed. In the case of breaks in the drill string, it is necessary to fish up the separated parts of the string from the drill hole before drilling can continue. The importance of a safe inspection method, especially for internal imperfections in a drill pipe, is thus clear.

During drilling operations, the drill string is often taken in and out

of the borehole when replacing a worn drill bit or to place reinforcements at different heights or perform other operations. For this work, it is appropriate to set up the drill pipe vertically at the derrick instead of transporting the pipe from the higher drilling platform to racks, which are at the same level as the ground. Also in offshore drilling operations, it is common to set up the drill pipe vertically. It is desirable to carry out inspection of a drill string periodically, i.e. every two or three months in order to

show any imperfections in the drill pipe that would make the pipe susceptible to failure during later drilling operations. For the most efficient inspection of tubular material during drilling operations, it is therefore necessary to have a test device that can examine tubular material in a vertical position at the derrick. With such a device, examinations could be carried out when the tube is taken out or put in place, e.g. due to a worn drill bit having to be replaced. As it is necessary to join individual pipe strings (which may comprise two or three pipe joints or sections) at the drilling rig's working plane when a drill string is assembled, it is further necessary that the test or investigation device can be easily brought into place and removed from the pipe being examined.

In connection with drilling operations, reference must be made to

US patent no. 3,248,933 describes a vertically oriented frame with an opening forming a horizontal passage, which provides opportunities for introducing a tubular part across. However, here the frame is clamped to the tube so that these components are stationary in relation to each other, and the purpose of the invention is to come up with a method and an apparatus which makes it possible to carry out investigations by moving the tubular part in relation to the frame. Thus, the ultrasound examination can be carried out continuously and at the same time as other work operations take place.

However, when there is movement between the frame and the tubular part, especially when the tubular part is a suspended pipe in a drilling rig, the sensitivity of the ultrasound examinations can be adversely affected. A suspended pipe can move in the transverse direction and can vibrate as a result of the movement into or out of the borehole. Such conditions make it difficult to maintain adequate audio coupling between the search unit and the pipeline. Furthermore, movement can change the angles of incidence of the sound radiation against the wall of the part being examined. For that reason, it is a further object of the invention to arrive at a robust device for carrying out on-site examination, so that the most accurate and reliable readings are obtained.

When a pipe is taken out of a borehole, the surfaces of the pipe will be covered with drilling mud and particles from the drilling, and it is also conceivable that there are liquid films on the inside of the pipe when the pipe is pulled out of a liquid-filled borehole. Drilling mud and drilling particles on the outside of the pipe can create difficulties when it comes to the connection to an ultrasonic test device. Furthermore, the liquid films that seep down a pipe can create false reflections that would cover up any cracks and scratches or imperfections that you want to detect. If a drill pipe cannot therefore be properly cleaned when it is pulled out of the drill hole, the device according to the invention must instead be used for ultrasound examination when the pipe is put back in the drill hole. According to the invention, a device has been arrived at for ultrasound examination of mostly vertically standing pipe parts, comprising a frame that can be placed around the pipe part while it stands vertically, and ultrasound transducers which are guided towards the tubular part when the frame is around the pipe . The use of a removable frame through which the pipe can be passed across the axis of the pipe makes it possible to carry out investigations, e.g. when the pipe is fed in and out of a borehole. If a weakness or imperfection is detected in the pipe, the assembly or disassembly is stopped and the ultrasonic testing device is withdrawn from the pipe,

and the pipe joint that has the proven weakness can be removed from the drill string. When the drill string has been reassembled, the ultra-sound examination device can easily be put in place in examination position around the pipe and continue to examine this as it is guided down the borehole.

The invention is characterized by the features reproduced in the claims and will be explained in more detail in the following with reference to the drawings where: Fig. 1, in perspective, shows an ultrasonic inspection device made according to the invention, in place around a drill pipe and placed above the rotary table on the drilling platform,

fig. IA shows, in perspective, the ultrasonic inspection device of fig..l, seen from above,

fig. 2 shows, in perspective, the ultrasonic search unit used in the inspection device in fig. 1, where you can particularly see the joint mechanism that holds a rolling wheel in contact with the pipe to be examined,

Fig. 3 shows, seen from the side, the ultrasound transducer and the joint mechanism of fig. 2,

fig. 4 shows a partial section through the ultrasound transducer in fig. 2 and 3,

fig. 5 shows, viewed from the side and greatly simplified,

a stabilizer used in the inspection device on

fig. 1,

fig. 6 schematically shows a multidisciplinary inspection device according to the present invention,

fig. 7 shows, seen from above, the upper layer of the multidisciplinary inspection device shown in fig. 6, seen along the line 7-7,

fig. 8 shows, seen from above, the middle group of search units used in the device of fig. 6, set after the line 8-8,

fig. 9 shows, seen from above, the lower section of search units used in the device of fig. 6, set after the line 9-9 and

fig. 10 schematically shows the ultrasound inspection device and associated equipment for reading and recording examinations.

In fig. 1 shows, in perspective, an ultrasonic inspection device 11 made according to the invention and placed around a pipe section 13, which protrudes through the opening in the rotating table in the platform 15 on a drilling rig. The pipe 13 is connected by the joint 12 to another section of the pipe and hangs in a tower, not shown, by means of an elevator or similar device, which is also not shown. The ultrasound device comprises a frame with two largely parallel, horizontally located parts 17 and 19 which are connected to each other with a connecting piece 21. Two base plates 23 and

2 5 is hinged for swing movement with the frame at points 24

and 26. A latch 71 at the opposite end of the plates 23 and 25 serves to keep the plates closed together around the tube 13. An opening in the base plates 23 and 25 in the middle of these forms a central vertical passage 30 in the device. A sheath 28 with a corresponding central passage and four separate compartments surrounds the central part of the ultrasound device 11.

Each base plate carries two search units with transducers and two joint mechanisms for mounting the transducers. More specifically, the base plate 23 has joint mechanisms 29 and 31 (not visible in Fig. 1) for the transducers, while the base plate 25

has joint mechanisms 2 7 and 33 for transducers. Each of the transducer mechanisms is similar in construction and the following description therefore only applies to the joint mechanism 33 for mounting the transducers.

It should be emphasized here that within the scope of the invention, any desired number of ultrasonic search units can be used when examining the pipe. The embodiment shown has four search units placed around the pipe at distances of 90°. It may, however, be satisfactory, depending on the size of the pipe, for the examination to be carried out and the beam spread of the ultrasound transducers used, to have more or fewer ultrasound search units. When scanning the pipe to find imperfections or breaks across the pipe's axis, the number is sufficient when the beam spreading units enable examination of the entire circumference of the pipe as it passes through the device. Three or four units are often used to investigate transverse irregularities.

For examination of longitudinal irregularities, the electroacoustic transducers are placed in a plane parallel to the axis of the pipe to send a beam which propagates around the pipe in a section generally perpendicular to the longitudinal axis. A number as small as two and up to four coplanar search units are used for this examination, depending primarily on the diameter of the tubular part to be examined.

Thickness measurements are carried out with a sound beam that is sent perpendicular to the pipe's surface. This beam measures thickness only below the search units. For this reason, up to four and perhaps more units can be used depending on how well the thickness is to be measured. For large diameter pipes, a complete thickness survey may require more than four units. On the other hand, it will also be sufficient to use two search units for thickness measurement, where the prerequisite is that these units should only give a general indication of the pipe's condition and not necessarily detect all areas with wear or corrosion.

In fig. IA, the ultrasound device 11 is shown in top view

from with the cover 28 removed. The joint mechanisms 27, 29, 31 and 33 of the search units are equally distributed around the tube 13 during the examinations so that the perimeter is completely irradiated. Between the search units are stabilizers 82, 110 and 120 which exert an inward force on the pipe 13 to prevent the pipe 13 from swaying when it is placed in or removed from the borehole. The force exerted by the stabilizers is naturally much greater than the force exerted on the tube by the search unit.

The frame comprising parallel parts 17 and 19 and the connecting plate 21 is open at the end facing from the plate 21. The open end makes it possible to remove the examination device from the pipe 13 easily and quickly after the base plates 23 and 25 have been locked free and swung outwards . In order to be able to scan for imperfections across the longitudinal axis of the tubular part, each search unit preferably has its piezoelectric crystal placed at an angle of approximately 45° on the axis of the tubular part to be examined. This angle can vary according to the size and wall thickness of the pipe being examined. E.g. it has been found, for pipes with a diameter of between 9 and 11 cm, that an angle of attack for the sound beam from the piezoelectric crystal is optimal at an angle of 43^° in relation to the longitudinal axis of the pipe when the pipe is examined for transverse imperfections. In determining the optimal placement of the piezoelectric crystal, however, it is preferred to begin with a calibration of the device on a standard test tube section with an imperfection or fracture of known dimension. The unit is started up and the angle of attack of the piezoelectric crystal is adjusted until the known irregularity or break gives the maximum electrical reading. Available search units have options for adjustment in relation to the part to be examined, and the use of such search units with an adjustable beam angle is preferable.

It is desirable to be able to set up the examination equipment with the optimum beam angle and to utilize the device for examination of tubular parts with different diameters without making corrective adjustments for resetting the beam angle. The joint mechanism 33 provides this desirable feature.

In fig. 2 shows in perspective an embodiment where the joint mechanism 33 holds the search unit in position in relation to the tube 13. The joint mechanism 33 comprises a vertically standing part 39 with a rectangular opening 40 at the upper end and a slot 41 at the lower end. The vertical part 39 is attached to the base surface 25 so that the search unit is held firmly in position. An upper arm 42 protrudes through the opening 40 and is held in this by a bolt 43, so that the upper arm 42 can swing in the vertical plane. A shorter lower arm 44 stands in the slot 41 and can pivot in the vertical plane about a bolt 45. A rectangular adapter plate 46 is designed to hold the base plate 38 for the wheel search unit which is attached e.g. with countersunk screws 47, 48, 49 and 50. A claw 51 is arranged at the upper edge of the adaptation plate 46 and a similar claw 52 is found at the lower edge of the plate 46. The claw 51 and the claw 52 form pivotable attachments for the upper arm 42 and the lower arm 44, respectively, so that the adaptation plate 46 is movable. The rearward-directed part of the upper arm 42 has threads for a bolt 53. A spring 54 or other biasing device is attached to the lower end of the bolt 53 and also to the base plate 25. The bolt 53 enables regulation of the tension of the spring and subsequently also regulation of the force which acts on the arm 42, so that it gets the right size.

It is clear that the joint mechanism 33 enables an inward movement of the search unit towards the central passage 30', while the base plate 38 of the search unit is kept parallel to the tubular part 13. For this reason, the beam angle from the piezoelectric crystal will be able to be set to an optimal value and held in this position regardless of the size of the tubular part to be examined.

In fig. 3 shows schematically how the wheel search unit and the joint mechanism in fig. 2 works, and you can see the advantages of the joint mechanism.

When the pipe 13 has a small diameter, the joint mechanism will

33 have the upper arm 42 and the lower arm 44 largely horizontal. The transducer 130, which is carried inside the wheel 35, has its optimal angle in relation to the tube 13.

When a pipe with a larger diameter is to be examined

or when a joint 12 is encountered, the arms 42 and 44 move downward to an inclined position. In that the adaptation plate 46

is pivotally attached to the arm 42 and 44 and thus forms a parallelogram-like structure, the adaptation plate 46 is moved downwards, but remains in an upright position. Since the position of the adapter plate 46 remains unchanged, the transducer 130 also retains its previous orientation,

and as a result the beam angle will not change.

The search unit used by the device according to

to the invention is preferably a wheel search unit with an adjustable beam angle of the type that is well known in the area that applies here. Such wheel finder units are manufactured by Sperry Division of Automation Industries Incorporated. The wheel search unit generally comprises a flexible tire-like wheel 35 which is rotatably mounted on an axis carried by a bracket 37. The piezoelectric crystal is mounted on a non-rotating shaft inside the wheel. The flexible tire 35 is filled with a suitable coupling agent. The coupling agent which has been used in this connection includes glycols or glycol ethers, e.g. Cellusolv products sold by Union Carbide Corporation.

Search units with shoes that are pulled over the surface of the pipe and also other search units that do not have rotating wheels should be avoided under the difficult conditions found in drilling rigs, but they can be used.

The wheel 35 is shown partly in section in fig. 4 with the flexible outer coating 36 pressed firmly against the tube 13. The flexible outer coating 36 is attached to side parts 32 and 34 of the wheel 35, and when the wheel is pressed against the tube 13, the outer coating will shape itself according to the curvature of the tube exterior. The side parts 32 and 34 prevent the wheel tire 36 from being blown

out by limiting the possible deformation of the flexible tire 36. A search unit of this type is described in US patent no. 3,628,375.

The wheel 35 is pressed against the tube 13 with a suitable contact pressure by means of a force exerted by the spring 54 in the joint mechanism 33 and the force acts through the upper arm 42. The force exerted can, however, be regulated by adjusting the screw 53 in the upper arm 42.

In order to achieve coupling between the flexible tire 35 and the tubular part 13 to be examined, it is advantageous to apply a liquid coupling agent to the surface of the pipe. There are therefore water conduits, such as 49 (Fig. 1) which stand above each wheel search unit and are designed to direct a constant flow of water towards the pipe, so that a uniform film is formed between the flexible deck 35 and the pipe to be examined, and this film serves as a sound coupling medium. The pipe 49 is fed from a branch pipe 72 which receives water from a supply line 73. The supply line 73 is connected to a suitable source of water (not shown) through a valve 61. Water flowing under the influence of gravity is satisfactory in forming the coupling means. for the search units even if pumped water can also be used. It will be clear to professionals in the area that applies here that other coupling agents can be used instead of water when the device is in use. However, water works satisfactorily and is naturally the most readily available and cheapest coupling agent that can be used on the outside of the pipe being examined.

As shown in fig. 1 there are stabilizers on the base plates 23 and 25 which are normally surrounded by the cover or jacket 28. In the drawing, only one stabilizer 82 is visible. The stabilizers serve to exert a radially inward force at several points around the tubular member 13 to reduce swaying of the member as it is passed through the examination device to be examined.

The stabilizer 82 comprises a support 85 which protrudes above and below the base plate 25 parallel to the center line of the central passage 30. At each end of the support 85 is attached a swing arm 87, 89 with a fastening 91, 93 for the stabilizer's wheel 95 , 97. A spring 99 forms a connection between the attachment 91 and the support 85 so that the wheel 95 is driven towards the tubular part 13, and in the same way a spring 103 connects the attachment 93 and the support 85 so that the wheel 97 is kept in contact with the tubular part 13, and in this way a holding force is exerted on the tubular part 13.

Although three stabilizers are used in the preferred embodiment (see Fig. 1A), additional stabilizers may be used. The maximum number will naturally depend on the size of the pipe to be examined. It is further advantageous to have the upper and lower pipe contact parts of the stabilizers located at a good distance from the search units and in a plane that is different from the plane where these are located.

The upper part of the stabilizer 82 protrudes

the fixed base plate 25 as shown in fig. 5. Fig. 5 shows the operation of the stabilizer 82 and its ability to work with different pipe diameters and allow the passage of pipe joints. As shown, the structure formed by the pivoting arm 87 and bracket 91 is pivotally supported at the upper end of the vertical support 85. A bolt 98" extends from the lower portion of the bracket 91 and through the support 85, and is pre- seen with a spring 99 which is kept compressed.A stabilizer wheel 95 sits on the mount 91 by means of a bracket 100

and is held in contact with the pipe 13 by the spring 99.

When pipes with a large diameter are to be examined, the swing arm 87 and the wheel 95 swing around the upper end of the support 85, and the wheel thereby moves inwards and somewhat downwards. The spring 99 is further compressed and exerts a sufficiently large and radially inward force on the tube. As shown by dashed lines in fig. 5, the stabilizers also allow an easy passage of pipe joints, while the pipe 13 is stabilized.

Opposite the search units on the support frame it extends

a platform 6 3 of suitable size and dimensions to carry the ultrasound apparatus 59. The ultrasound apparatus 59 for the test includes a pulse generator and a receiver unit as well as an oscilloscope. Ultrasound devices of this type are well known, and e.g. Sperry Division of Automation Industries offers a 10M pulser/receiver unit fully assembled with oscilloscope type UM, design 50E533 which can be used together with the research device according to the invention. Small battery-powered search instruments are also available and these can also be used successfully.

The pulse generator in the device sends a series of pulses

which is simultaneously fed to the piezoelectric crystals in the wheel search units through a transmission line 57 connected to a connection block 60. It is common that the available search units only provide a simple pulse output. The switch block 60 simply divides the signal into the four transmission lines and thereby provides for feeding the signal transmission path to each wheel search unit. Techniques with impedance matching are well known in the area that applies here and will not be described in detail. During the periods when the piezoelectric crystals are not energized, signals reflected from imperfections in the tubular portion are sensed and the signals are sent through the transmission lines 57 to the junction block 60 which provides a single output signal at the input 6 2 of the pulse generator/receiver portion of the apparatus. The signal is amplified in the pulse generator/receiver part of the device 59 and displayed on an oscilloscope. As previously mentioned, however, a strip printer can be used instead of or alongside the reproduction on the oscilloscope.

The construction of the search units, the connection block, the pulse generator/receiver and the cathode ray tube or strip printer can best be seen from the schematic representation on

fig. 10. In fig. 10 produces the pulse generator/receiver 77

in the apparatus 59 a series of pulses which are simultaneously sent to piezoelectric crystals 79 in each of the wheel search units 35 through the transmission lines 57, via the connection block 60, with all switches 86 in the closed position. Commonly available search devices only provide a simple pulse output from the pulse generator/receiver. The switch block 60 only divides the signal into the four transmission lines and has means for impedance matching to the transmission lines and thus for optimal tuning of the signal sent to each wheel search unit. Such impedance matching techniques are well known and may include a suitable RC circuit or a resistance-inductance combination.

When the piezoelectric crystals are energized, they send out a beam of sound at an acute angle into the tubular part to be examined. The wave is reflected between the opposite walls of the tubular part and propagates in the longitudinal direction. If the beam hits an irregularity, e.g. a break, a reflected signal will return and be sensed by the piezoelectric crystal. As explained earlier, the angle is usually around 45°, although this can be varied depending on the material being examined and the type of imperfection being searched for. The switches 86 (located inside the apparatus 59) enable the operator of the apparatus to start up and control each search unit individually or in any combination. During the periods when the piezoelectric crystals are not energized, reflected signals from imperfections present in the tube are sent back through the transmission lines 57 and through the junction block 60 to form a single output signal at the input 62 of the pulse generator/receiver section 77 of the apparatus 59. For best possible transmission is adapted to the length of the lines 57 so that they correspond to multiples of quarter wavelengths of the signal. The signal is amplified in the amplifier 89 in the pulse generator/receiver part 77 in the device 59 and displayed on the oscilloscope 64 and/or recorded on a strip recorder 83.

The frequency of the signal which gives energy to the crystals and which is used in examinations with the apparatus according to the invention can vary, which is known to those skilled in the art. Typical investigations can be carried out using signals with frequencies of 1 megahertz to 5 megahertz. Very good tests have been carried out on drill pipe using a frequency of 2.25 megahertz. The pulse repetition rate can vary between 60 and 2000 pulses/sec. The pulse duration is in the microsecond range, e.g. between 1 and 5 microsec. The instrument 59 is placed on the platform 63 by means of a strap 65 which is hooked at the upper end to a hook which projects from a carrier 75. The carrier 75 ends in an eye 67 or another connection which can be connected to a line or wire in the derrick. The eye 67 is preferably located above the center of gravity of the entire device so that only small transverse forces will act on the search units during operation when these are in contact with the tubular part to be examined.

When the device according to the invention is to be used, the lock 71 (fig. 1) is opened and the plates 23 and 25 are swung outwards so that the pipe 13 can be inserted between the carriers 17 and 19. The device is handled manually until the pipe 13 stands centrally between the carriers and the plates 23 and 25 are swung back to their original position, and locked in place with the lock 71. The springs 81, 54 and .. will then bring each wheel search unit into contact with the tubular part and the tube's passage down the borehole can begin. When the tubular parts have a joint 12, the bias springs will yield so that the search units can pass over the pipe joint.

It is then opened for the water flow from the pipes 49 to

connect the wheel finder units to the tube sonically. The pulse part of the device is started and the four wheel search units simultaneously send a pulse into the tubular part. The pulse is preferably directed upwards away from the rotating table at an acute angle to the longitudinal axis of the tubular part. The receiver part of the device measures reflected signals and displays the result on the oscilloscope 64.

When the inspection device 11 encounters a pipe joint 12,

the bias springs will yield allowing the search unit to pass over the thickened pipe joint. When a severe crack is detected by the oscilloscope 64, the latch 71 is opened and the apparatus is brought away from the tubular part. The defective section is then removed and the drill string spliced again, after which the inspection device is put in place for further investigations.

In fig. 6 shows, in the form of a simple schematic drawing, an ultrasonic device for examining pipes and with three compartments for measurements for cracks, cracks, breaks and the like across the longitudinal axis of the pipe and corresponding defects that run largely along the length of the pipe, and also the wall thickness can be measured. The wheel search units in a multi-disciplinary inspection apparatus are mounted in exactly the same way as the wheel search units in the embodiment of fig. 1. Here, a parallelogram-like joint mechanism (corresponding to the joint mechanism 33 in Fig. 3) will be used for each wheel search unit. Each group of search units 140, 150, 160 is mounted on a pair of base plates (corresponding to base plates 23, 25 in Fig. 1), with the three pairs of base plates connected to each other by means of vertical struts. When it becomes necessary to detach the three-phase apparatus from the pipe string, a retaining lock is opened so that the three-phase base plates with equipment can be separated from each other as two hinged halves.

Although the arrangement of the wheel search units in groups 140, 150, 160 can be varied, here is shown a group 140 which is intended for the detection of transverse imperfections, mounted as the upper section with transducers which direct sound waves upwards in the pipe 13 as shown by the arrows . The middle group 150 of wheel search units measures wall thickness and, as indicated by the arrows, the transducers direct sound waves radially inward. The lower group of search units 160 detects longitudinal imperfections in the pipe 13. The transducers in this group direct sound waves transversely into the pipe 13. It should be pointed out, however, that the upper group 140 and the lower group 160 can change places as the only requirement that is that the sound waves from the different groups must not interfere with each other.

Claims (20)

In fig. 7, 8 and 9, each subject's search units are shown separately. Fig. 7 shows the search units 142, 144, 146, 148 which are equally distributed around the circumference of the pipe 13. In fig. 7, the transducer in the search unit 148 is also shown placed at an angle with the transducer directed somewhat upwards. Fig. 8 shows in the same way, the search units 152, 154, 156 and 158 equally distributed around the pipe 13. The transducer in the search unit 152 is positioned so that it directs the sound waves directly into the pipe 13 without displacement in the transverse direction. Fig. 9 shows the three search units 162, 164 and 166 in the group 160 with the transducer for the search unit 164 set so that the sound waves are directed transversely into the pipe 13. From fig. 7-9 you will see that each of the search units in the three groups will roll along a separate and specific path. However, an equally effective inspection apparatus would be obtained if the search units in the groups were aligned to roll along common paths. Each group of search units can be associated with a separate reading, e.g. an ultrasonic search apparatus comprising a pulse generator/receiver and an oscilloscope with a cathode ray tube. The frame, which hangs from a hook and line, can instead be carried by a carriage that can move on the oil rig's platform or floor and be brought into position near the rotary table. With suitable modifications to the extension platform attached to the frame and by modification of the coupling block, a separate reading can be obtained for each wheel tracking unit. Patent claims. 1. Procedure for inspecting a tubular part (13) used in drilling operations from a drilling platform, where ultrasonic search units (27, 29, 31, 32) are used which are sonically connected to the tubular part (13) while it is being lowered into or is taken up by a borehole and is thereby vertically suspended in the platform's tower, characterized by the fact that a frame (17, 19, 21, 23, 25) with attached ultra sound search units (27, 29, 31, 32) is placed around the pipe shaped part (13), that the ultrasonic search units (27, 29, 31, 32) are connected sonically around the circumference of the tubular part (13), each search unit containing an electroacoustic transducer (130) which stands in a certain angular relationship to the surface of the hanging tubular part (13), that the transducers (130) in the search units are held in a fixed angular position in relation to the surface of the tubular part (13), while this is moved vertically in relation to the borehole, at the same time that the sonic coupling between the search units (27, 29 , 31, 32) and the tubular part (13) is also maintained by horizontal movement of the tubular part (13), and that the ultrasonic search units (27, 29, 31, 33) are simultaneously pulsed to transmit ultrasound signals to the wall of the tubular part (13) at an acute angle to the longitudinal axis of the part, whereby the combined ultrasound signals produce a beam spread that covers the entire circumference of the tubular part (13). 2. Method as stated in claim 1, characterized in that reflected ultrasound signals from irregularities in the tubular part (13) are captured in each of the detector units (27, 29, 31, 33) and produce electrical signals which are functionally linked to the reflected ultrasound signals, and that a measurable indication is produced as a result of the electrical signals to indicate the presence of an irregularity in the tubular part (13). 3. Method as stated in claim 2, characterized in that a pulse signal from a signal pulse source (59) is split to the various search units (27, 29, 31, 33) in order to transmit the ultrasound signals to the wall of the tubular part (13), and that the electrical signals are combined with the reflected ultrasound signals to produce a simple visual indication of the presence of an irregularity on a cathode ray tube (64) or a strip printer. 4. Apparatus for performing ultrasonic inspection according to the method specified in claim 1, characterized in that it comprises a frame (17, 19, 21, 23, 25) with a vertical passage (30) for a tubular part (13), which frame gives access for the tubular part (13) to the passage (30) from a direction transverse to the longitudinal axis of the tubular part (13), that a series of ultrasonic search units (27, 29, 31, 32) are mounted on the frame (17, 19, 21, 23, 25) at a distance from the circumference of the part (13), while each of the ultrasonic search units (27, 29, 31, 32) comprises a wheel (35) which is placed in rolling contact with the tubular part (13), where each of the wheels (35) has an electroacoustic transducer (130) sonically coupled to the tubular part and placed in a fixed angular position in relation to the surface of the tubular part (13) in such a way that the ultrasound signals are sent in at an acute angle to the longitudinal axis of the tubular part (13), and that the by simultaneously sending out ultrasound signals from all ultrasound search units (27, 29, 31, 32), a beam spread is achieved that covers the entire circumference of the tubular part (13), and by the presence of devices (37, 39, 42, 44, 46 , 53, 54) which seek to hold the wheels (35) against the tubular part (13) when this is in the passage (30), as well as a source (59) for dig pulsing of the ultrasound search units. 5. Apparatus as specified in claim 4, characterized in that the ultrasonic search units (27, 29, 31, 32) are in the same plane. 6. Apparatus as stated in claim 4, characterized in that the wheels (35) are arranged to roll along a path which is parallel to the longitudinal axis of the tubular part (13). 7. Apparatus as set forth in claim 4, characterized in that the devices (37, 39, 42, 44, 46, 53, 54) which are to keep the wheels (35) in contact with the tubular part (13) are compliant to set the wheels (35) able to roll over external irregularities on the tubular part (13). 8. Apparatus as stated in claim 4, characterized in that the ultra-light zoom wheels (35) are sonically coupled by means of a liquid film between the wheels (35) and the tubular part (13) during liquid introduction. 9. Apparatus as stated in claim 4, characterized in that the electroacoustic transducers (130) are piezoelectric crystals. 10. Apparatus as stated in claim 4, characterized in that the electroacoustic transducers (130) stand in each of their associated wheels (35) at an angle of 43%° to the longitudinal axis of the tubular part (13). 11. Apparatus as stated in claim 4, characterized in that the electroacoustic transducers (130) are arranged to produce electrical signals as a result of sound waves reflected from irregularities in the tubular part (13), and by a device (59) for composition of the electrical signals to form a single signal indicating the presence of irregularities or breaks in the tubular part (13). 12. Apparatus as stated in claim 11, characterized in that the device (59) for composing the signals has a visual rendering device (64). 13. Apparatus as stated in claim 12, characterized in that the device (64) for visual rendering is an instrument with a cathode ray tube. 14. Apparatus as stated in claim 12, characterized in that the device (64) for visual rendering is a strip printer. 15. Apparatus as stated in claim 4, characterized in that it comprises a support (75) attached to the frame (17, 19, 21, 23, 25) and directed upwards to end in a connecting device (67) which stands directly above the center of gravity of the frame with all attached accessories. 16. Apparatus as stated in claim 4, characterized in that the devices which are to hold the wheels (35) in contact with the tubular part (13) comprise a joint mechanism (37, 39, 42, 44, 46, 53, 54) which holds each search unit (27, 29, 31, 33) on the frame to be compliantly brought into contact with the surface of the tubular part (13), for sonic coupling thereto, which joint mechanism also maintains a constant angle between the transducer (130) and the surface of the tubular part (13). 17. Apparatus as stated in claim 4, characterized in that it includes stabilization devices (82, 110, 120) which must hold the tubular part (13) firmly with a force greater than that prevailing between the tubular part (13) and the search unit (27, 29, 31) so that the frame (17, 19, 21, 23, 25) is held in a stable position in relation to the tubular part (13) when mutual horizontal movement occurs between the frame and the tubular share. 18. Apparatus as stated in claim 17, characterized in that the stabilization devices (82, 110, 120) rest against the tubular part (13) in at least two areas that are spaced apart in the longitudinal direction along the axis of the tubular part (13) . 19. Apparatus as stated in claim 18, characterized in that the stabilization devices (82, 110, 120) comprise at least two sets of wheels (95) which stand in the same plane and are arranged to rest against the surface of the tubular part (13). 20. Apparatus as stated in claim 16, characterized in that the joint mechanism '(37, 39, 42, 44, 46, 53, 54) comprises a hinged parallelogram mechanism for each search unit, with one side (39) fixed in relation to the frame and the opposite side (37, 38, 46) attached to the seeker unit.