STRAIGHT THROUGH AND BACKSCATTER RADIATION INSPECTION APPARATUS FOR TUBULAR MEMBERS AND METHOD

• US 3,569,708 A
• Filed: 07/26/1967
• Issued: 03/09/1971
• Est. Priority Date: 07/26/1967
• Status: Expired due to Term

• Current Assignee: Tuboscope Incorporated (National Oilwell Varco Incorporated)
• Original Assignee: Michael H. Badger
• Inventors: Badger, Michael H.
• Application Number:
  US04/656,088
• Time in Patent Office: 1,322 Days
• US Class Current: 378/90
• CPC Class Codes: G01B 15/045 by measuring absorption
• CPC Class Codes: G01N 23/203 Measuring back scattering

Abstract

This invention pertains to a combination straight through and backscatter inspection of pipe wall thickness in a rotating arrangement. The source is located outside the pipe, one detector is located thereopposite and the other detector is located to receive backscatter emissions. Each detector and related circuit comprises a scintillation crystal, a photomultiplier controlled by a DC-to-DC converter and adjustable low voltage source, an electrical speed compensation circuit, a cross section integrator and a curve fitting amplifier. The two detector circuit outputs are correlated to increase sensitivity. The speed determining and position sensing means may be a selsyn motor. The speed compensating circuit may be a field effect transistor having its drain-source resistance variable with the speed voltage and included in a time constant circuit, thereby making the output independent of the speed of rotation.

Claims

1. A device for determining the wall thickness of a tubular member, comprising:

a penetrating ray source located outside of the member for directing a penetrating ray diametrically through the tubular member;

a detector means disposed on the opposite side of the tubular member from said source in the path of said ray and operative to produce an electrical output that is a function of the energy of said ray, after having passed through said tubular member;

means for effecting relative rotation between the tubular member and both said source and detector means;

rotational position sensing means for producing an output upon completion of a predetermined relative rotational advancement between the tubular member and both said source and detector means; and

signal storage means connected to said detector means and to said rotational position sensing means for producing an output that is a measure of the average wall thickness of the member as measured during said predetermined relative rotational advancement.

2. A device in accordance with claim 1, wherein said rotational position sensing means produces an output upon completion of a rotational advancement of one-half of a revolution, and wherein said signal storage means produces an output that is a measure of the average wall thickness of the member around its entire periphery.

3. A device for determining the wall thickness of A tubular member, comprising:

a penetrating ray source located outside of the member for directing a penetrating ray at the wall of the tubular member;

a detector means disposed on the outside of the member to receive backscattered emissions from said wall to produce an electrical output that is a function of the energy of the backscatter emissions;

means for effecting relative rotation between the tubular member and both said source and detector means;

rotational position sensing means for producing an output upon completion of a predetermined relative rotational advancement between the tubular member and both said source and detector means; and

signal storage means connected to said detector means and said rotational position sensing means for producing an output that is a measure of the average wall thickness of the member as measured during said predetermined relative rotational advancement.

4. A device in accordance with claim 3, wherein said rotational position sensing means produces an output upon completion of a rotational advancement of one revolution, and wherein said signal storage means produces an output that is a measure of the average wall thickness of the member around its entire periphery.

5. A device for determining the wall thickness of a tubular member, comprising:

a penetrating ray source located outside of the member for directing a penetrating ray diametrically through the member;

a detector means disposed on the opposite side of the member from said source in the path of said ray and operative to produce an electrical output that is a function of the strength of said ray;

means for effective relative rotation between the tubular member and both of said source and detector means;

speed indicating means for producing an output voltage that is a function of the speed of said relative rotation; and

a field effect transistor coupled to the output of said detector means, the output voltage of said speed indicating means connected as a control voltage for said field effect transistor, causing the drain resistance thereof to be a function of said speed.

6. A device for determining the wall thickness of a tubular member, comprising:

a penetrating ray source located outside of the member for directing a penetrating ray at the wall of the tubular member;

a detector means disposed on the outside of the member to receive backscattered emissions from said wall to produce an electrical output that is a function of the energy of said backscatter emissions;

means for effecting relative rotation between the tubular member and both said source and detector means;

speed indicating means for producing an output voltage that is a function of the speed of said relative rotation; and

a field effect transistor coupled to the output of said detector means, said speed indicating means connected as a control voltage for said field effect transistor, causing the drain resistance thereof to be a function of said speed.

7. In a radiation inspection apparatus for determining the wall thickness of a tubular member including:

a substantially uniform penetrating ray source located outside of the member for directing a penetrating ray into the wall of the member;

detector means located to receive rays emanating from the tubular member after being affected by the wall thickness of the member;

rotating means for effecting relative rotation at a nominal speed between the member and both of said source and said detector means to move the wall of the member therepast;

said detector means producing a voltage that is a function of the strength of the received emanating rays for a unit of circumferential length of the pipe moving therepast;

the improvement comprising;

speed sensing means for producing a voltage that is a function of said relative rotation; and

speed compensating means including a voltage adjustable time constant network operatively connected to the dEtector means as an input and to said speed sensing means as an adjustable voltage for said time constant network to make the output substantially a function of the unit circumferential length of the pipe regardless of the relative rotational speed variance from the nominal speed.

8. In a radiation inspection apparatus as described in claim 7, the further improvement comprising:

revolution position sensing means for producing an output upon the completion of a predetermined relative rotational advancement; and

voltage storage means connected to said speed compensating means and to said revolution position sensing means for producing an output that is a measure of the average wall thickness of the member over the circumferential length of the member corresponding to said predetermined relative rotational advancement.

9. In a radiation inspection apparatus as described in claim 8, wherein the detector means is located on the opposite side of the member from the source in the path of said ray, the further improvement wherein said revolution position sensing means produces an output for an integral number of one-half revolutions of relative rotational advancements, the resulting output from said signal storage means thereby becoming a measure of the average wall thickness of the member around its entire periphery.

10. In a radiation inspection apparatus as described in claim 8, wherein the detector means is located on the outside of the member to receive backscattered emissions from the wall of the member, the further improvement wherein said revolution position sensing means produces an output for an integral number of complete revolutions of relative rotational advancements, the resulting output from said signal storage means thereby becoming a measure of the average wall thickness of the member around its entire periphery.

11. A radiation inspection apparatus for determining the wall thickness of a tubular member, comprising:

a substantially uniform penetrating ray source located outside of the member for directing a penetrating ray into the wall of the member;

straight through detector means located on the opposite side of the member from the source in the path of said ray;

backscatter detector means located on the outside of the member to receive backscattered reflections from the wall of the member;

rotating means for effecting relative rotation at a nominal speed between the member and each of said source, said straight through detector and said backscatter detector means;

said straight through detector means producing a voltage that is a function of the strength of the received emanating rays for a unit of circumferential length of the member moved with respect thereto at nominal speed;

said backscatter detector means producing a voltage that is a function of the strength of the received emanating rays for a unit of circumferential length of the member moved with respect thereto at nominal speed;

speed sensing means for producing a voltage that is a function of said relative rotation;

first speed compensating means including a voltage adjustable time constant network operatively connected to said straight through detector means as an input and to said speed sensing means as an adjustable voltage for said time constant network to make a straight through output that is substantially a function of the unit circumferential length of the member regardless of the relative rotational speed variance from the nominal speed;

second speed compensating means including a voltage adjustable time constant network operatively connected to said backscatter detector means as an input and to said speed sensing means as an adjustable voltage for said time constant network to make a backscatter output that is substantially a function of the unit circumferential length of the member regardless of the relative rotational speed variance from the nominal speed; and

correlation means for receiving said straight through output and said backscatter output to produce a composite output that is a function of the products of both.

12. A radiation inspection apparatus as described in claim 11, and including:

first revolution position sensing means for producing an output upon the completion of an integral number of one-half revolutions of relative rotational advancements of said member and said straight through detector means;

first voltage storage means connected to said first speed compensation means and to said first revolution position sensing means for producing a straight through output that is a measure of the average wall thickness of the member around its entire periphery;

second revolution position sensing means for producing an output upon the completion of an integral number of revolutions of relative rotation advancements of said member and said backscatter detector means; and

second voltage storage means connected to said second speed compensating means and to said second revolution position sensing means for producing a backscatter output that is a measure of the average wall thickness of the member around its entire periphery.

13. A radiation inspection apparatus as described in claim 12, and including:

a first nonlinear compensating network for receiving the output voltage from said first voltage storage means and producing an output that is a linear measure of the average wall thickness of the member around its entire periphery; and

a second nonlinear compensating network for receiving the output voltage from said second voltage storage means and producing an output that is a linear measure of the average wall thickness of the member around its entire periphery.

14. The method of inspecting pipe for wall thickness determination, which comprises:

penetrating the two opposing walls of the pipe with a narrow beam penetrating ray;

straight through detecting the ray beam following the traversing of both walls as a measure of average wall thickness of said two walls;

developing an electrical signal that is a function of the received straight through ray;

detecting the reflected backscattered rays from the nearest one wall of the pipe as a measure of near wall thickness;

developing an electrical signal that is a function of the received reflected backscatter ray;

correlating said developed signals as a single output;

effecting rotation of the beam and of means for detecting the beam while penetrating and detecting; and

storing the developed electrical signals during a predetermined relative rotation so as to make the output a function of a known circumferential length of pipe.

15. The method as described in claim 14, further comprising correcting each developed electrical signal so that it is a linear function of pipe wall thickness prior to correlation.

16. A device for determining the wall thickness of a tubular member, comprising:

a penetrating ray source located outside of the member for directing a penetrating ray diametrically through the tubular member;

a detector means disposed on the opposite side of the member from said source in the path of said ray and operative to produce an electrical output that is a function of the strength of said ray, said detector means including a scintillation crystal and a photomultiplier connected thereto;

means for controlling the sensitivity of said detector means as determined by an applied adjustable voltage, said controlling means including a DC-to-DC converter, the output of which is applied to the dynodes of said photomultiplier, the input of which provides means to control the output from said converter and thereby the amplification of said photomultiplier; and

means for effecting relative rotation between the tubular member and all of said source, said detector means and the portion of said controlling means including said DC-to-DC converter, the applied adjustable voltage for said DC-to-DC converter being applied From a nonrotating source through slip rings.

17. A device as described in claim 16, and further including:

second detector means disposed on the outside of the member to receive backscatter emissions from said wall to produce an electrical output that is a function of the strength of said emission, said second detector means including a second scintillation crystal and a second photomultiplier connected thereto;

second means for controlling the sensitivity of said second detector means as determined by a second applied adjustable voltage, said second controlling means including a second DC-to-DC converter, the output of which is applied to the dynodes of said second photomultiplier, the input of which provides means to control the output from said second converter and thereby the amplification of said second photomultiplier; and

said second detector means and the portion of said second controlling means including said second DC-to-DC converter being connected for relative rotation with respect to the tubular member, the second applied adjustable voltage for said second DC-to-DC converter being applied from a second non rotating source through slip rings.

18. A device for determining the wall thickness of a tubular member comprising:

a penetrating ray source located outside of the member for directing a penetrating ray at the wall of the tubular member;

detector means disposed on the outside of the member to receive backscatter emissions from said wall to produce an electrical output that is a function of the strength of said emissions, said detector means including a scintillation crystal and a photomultiplier connected thereto;

means for controlling the sensitivity of said detector means as determined by an applied adjustable voltage, said controlling means including a DC-to-DC converter, the output of which is applied to the dynodes of said photomultiplier, the input of which provides means to control the output from said converter and thereby the amplification of said photomultiplier; and

means for effecting relative rotation between the tubular member and all of said source, said detector means and the portion of said controlling means including said DC-to-DC converter, the applied adjustment voltage for said DC-to-DC converter being applied from a nonrotating source through slip rings.

19. A device for determining the wall thickness of a tubular member, comprising:

a penetrating ray source located outside of the member for directing a penetrating ray through the tubular member;

detector means disposed on the opposite side of the member from said source in the path of said ray and operative to produce an electrical output signal that is a function of the energy of the detected ray after having passed through said tubular member;

said detector being controllable in sensitivity of detection by means of a controllable high voltage applied thereto;

converter means connected to said detector means and operable to receive a low DC voltage and produce an output high DC voltage whose magnitude is a function of said input low voltage;

rotary mounting means for mounting said ray source, said detector means, and said converter means for rotation coaxially about said tubular member;

rotary contact means for effecting electrical connection between said converter means and a nonrotating low DC voltage source separate from said rotary mounting means; and

voltage adjustment means located separate from said rotary mounting means and connected to said low voltage source for adjusting the magnitude of the low voltage coupled to said rotary contact means, whereby the adjustment of the magnitude of said low voltage by the voltage adjustment means results in the adjustment of the magnitude of the high voltage output from the converter means, thereby to adjust the sensitivity of the detector means.

20. A device as claimed in claim 19, wherein the detector means includeS:

a scintillation crystal and a photomultiplier connected thereto; and

wherein the output high DC voltage of the converter means is applied to dynodes of said photomultiplier.

21. A device for determining the wall thickness of a tubular member;

comprising a penetrating ray source located outside of the member for detecting a penetrating ray at the tubular member;

detector means disposed on the outside of the member to receive backscatter emissions from said wall to produce an electrical output signal that is a function of the energy of detected backscatter emissions from said wall;

said detector being controllable in sensitivity of detection by means of a controllable high voltage applied thereto;

converter means connected to said detector means and operable to receive a low DC voltage and produce an output high DC voltage whose magnitude is a function of said input low voltage;

rotary mounting means for mounting said ray source, said detector means, and said converter means for rotation coaxially about said tubular member;

rotary contact means for effecting electrical connection between said converter means and a nonrotating low DC voltage source separate from said rotary mounting means; and

voltage adjustment means located separate from said rotary mounting means and connected to said low voltage source for adjusting the magnitude of the low voltage coupled to said rotary contact means, whereby the adjustment of the magnitude of said low voltage from the voltage adjustment means results in the adjustment of the magnitude of the high voltage output from the converter means, thereby to adjust the sensitivity of the detector means.

22. The device claimed in claim 21, wherein the detector means includes:

a scintillation crystal and a photomultiplier connected thereto; and

wherein the output high DC voltage of the converter means is applied to dynodes of said photomultiplier.

23. The device claimed in claim 5, wherein said field effect transistor is included in a time constant network and the operation of said transistor causes the output of the time constant network to be a function of wall thickness and to be compensated for said speed of relative rotation.

24. The device claimed in claim 23, wherein the output of said time constant network is a nonlinear function of measured wall thickness, said device further including, a compensating network for receiving the output of the time constant network and producing a voltage that changes linearly with a linear change in measured wall thickness.

25. The combination claimed in claim 24 wherein said compensating network comprises:

an amplifier having an input and an output;

a first resistor operatively connected to said amplifier;

a plurality of parallel circuits for compensating for respective predetermined voltage ranges of an applied voltage;

each of said parallel circuits including a diode series connected to a resistor;

the first one of said plurality of parallel circuits being connected in parallel with said first resistor and each next successive one of the plurality of parallel circuits being connected in parallel with the next preceeding one of the plurality of parallel circuits; and

said plurality of parallel circuits being interconnected so that only said first one is connected directly between the input and output of the first resistor.

26. The combination claimed in claim 25, wherein said first resistor is connected as an input resistor to said amplifier.

27. The combination claimed in claim 25 wherein said first resistor is connected between the input and output of said amplifier.

28. The combination claimed in claim 24, wherein said compensating network comprises:

an amplifier having an input and an output;

a first resistor operatively connected to said amplifier;

a plurality of parallel circuits for compensating for respective predetermined voltage ranges of an applied voltage;

each of said parallel circuits including;

a pair of matched diodes connected anode-to-cathode to form a parallel combination;

a resistor connected to one end of the parallel connected diodes to form a series circuit therewith;

the first one of said plurality of parallel circuits being connected in parallel with said first resistor and each next successive one of the plurality of parallel circuits being connected in parallel with the next preceeding one of the plurality of parallel circuits; and

said plurality of parallel circuits being interconnected so that only said first one is connected directly between the input and output of the first resistor.

29. The device claimed in claim 6 wherein said field effect transistor is included in a time constant network and the operation of said transistor causes the output of the time constant network to be a function of wall thickness and to be compensated for said speed of relative rotation.

30. The device claimed in claim 29 wherein the output of said time constant network is a nonlinear function of measured wall thickness, said device further including, a compensating network for receiving the output of the time constant network and producing a voltage that changes linearly with a linear change in measured wall thickness.

31. A device for determining the wall thickness of a tubular member, comprising:

a penetrating ray source located outside of the member for detecting a penetrating ray toward the tubular member;

first and second detector means disposed, respectively, on the adjacent and opposite sides of the member from said source, each of said detector means being operative to produce a respective electrical output signal that is a function of the energy of the detected backscatter and direct rays emanating from said tubular member;

each of said detector means being controllable in sensitivity of detection by means of a respective high DC voltage applied thereto;

first and second converter means respectively connected to said first and second detector means and each operable to receive a respective low DC voltage and produce a respective output high DC voltage whose magnitude is a function of the respective input low DC voltage;

rotary mounting means for mounting said ray source, said two detector means, and said two converter means for rotation coaxially about said tubular member;

rotary contact means for effecting electrical connection between said two converter means and a nonrotating low DC voltage source that is located separate from said rotary mounting means;

first and second voltage adjustment means located separate from said rotary mounting means and each connected to said low voltage source and each connected through said rotary contact means to a respective one of said converter means; and

said two voltage adjustment means each being operable to adjust the magnitude of a low DC voltage coupled to its respective converter means on said rotary mounting means, whereby the high DC voltages applied to the two detector means may be independently adjusted external to said rotary mounting means thereby to adjust the sensitivities of the respective detector means.

32. The device claimed in claim 31, and further including:

first and second speed compensating means respectively connected to receive the outputs of said first and second detector means;

means respective to the speed of relative rotation of said rotary mounting means about said tubular member for producing a speed-dependent voltage whose magnitude is a function of said relative speed of rotation;

said speed compensating means being responsive to said speed-dependent voltage to produce a output voltage substantially independent of effects caused by a change in relative speed of rotation of the rotary mounting means about said tubular member; and

correlating means coupled to receive the outputs of said first and second speed compensating mEans and responsive thereto to produce a wall thickness signal which is a function of the produce of the outputs of said two speed compensating means.

33. the combination claimed in claim 32, and further including:

first and second cross section integrating means respectively coupled to the outputs of said first and second speed compensating means;

said first cross section integrating means integrating the input signal coupled thereto and producing an output signal that is a measure of the average wall thickness of the tubular member around its periphery;

said second cross section integrating means integrating the signal applied thereto and producing an output signal that is a measure of the average wall thickness of the tubular member around its entire periphery; and

correlating means respective to the outputs of said first and second cross section integrating means for producing an average wall thickness signal that is a function of the produce of the outputs of said two cross section integrating means.

34. A compensating network that produces an output which changes in magnitude according to a desired characteristic when responding to an input voltage whose magnitude changes in the same direction but not according to said desired characteristic, said network comprising:

an amplifier having an input and an output;

a first resistor operatively connected to said amplifier;

a plurality of parallel circuits for compensating for respective predetermined voltage ranges of an applied voltage;

each of said parallel circuits including;

a plurality of parallel circuits for compensating for respective predetermined voltage ranges of an applied voltage;

each of said parallel circuits including a diode series connected to a resistor;

the first one of said plurality of parallel circuits being connected in parallel with said first resistor and each next successive one of the plurality of parallel circuits being connected in parallel with the next preceeding one of the plurality of parallel circuits; and

said plurality of parallel circuits being interconnected so that only said first one is connected directly between the input and output of the first resistor.

35. The network claimed in claim 34, wherein said first resistor is connected as an input resistor to said amplifier and said applied voltage is connected to the input of said first resistor.

36. The combination claimed in claim 34, wherein said first resistor is connected between the input and output of said amplifier and said applied voltage is connected to the input of said amplifier.

37. The combination claimed in claim 34, and further including, another diode in each of said parallel circuits, the other diode in each of said circuits being parallel connected only with the first named diode in said circuit but oppositely poled with respect thereto.