Title:
CONTROL SYSTEM FOR WELDING INSPECTION MACHINE
United States Patent 3691385


Abstract:
This patent discloses a crawler for moving through a pipeline and emitting rays at the location of circumferential welds in the pipeline to expose film positioned about the exterior of the pipe to check the weld. Movement of the crawler and control of the emission of the rays is provided by control circuitry responsive to a signal received from exterior of the pipeline.



Inventors:
Ketchbaw, Thomas E. (Houston, TX)
Foster, Robert D. (Houston, TX)
Arvanetakis, Kiryako (Houston, TX)
Application Number:
04/735061
Publication Date:
09/12/1972
Filing Date:
06/06/1968
Assignee:
HOUSTON GAMMA RAY CO.
Primary Class:
Other Classes:
378/91
International Classes:
G03B37/00; (IPC1-7): G03B41/16; G01T1/16
Field of Search:
250/65F,93,43
View Patent Images:



Primary Examiner:
Lawrence, James W.
Assistant Examiner:
Willis, Davis L.
Claims:
What is claimed is

1. A crawler comprising,

2. A crawler comprising,

3. The crawler of claim 2 wherein safety means includes a time delay means which releases all restraints on movement of the source and resilient means moves the source into the camera shield.

4. A crawler comprising, a body,

5. The crawler of claim 4 wherein if the source is not in the shield a selected time after the stepping means moves to its fourth position a time delay means releases all restraints on movement of the source and resilient means moves the source into the shield.

6. The crawler of claim 4 wherein means are provided for moving said source into said shield in the absence of a retract signal from said signal generator a selected time after the source is moved out of the shield.

7. The crawler of claim 4 wherein means are provided responsive to the stepping means moving to its fifth position for reversing the motor and for stopping the motor responsive to the stepping means moving to its sixth position.

8. The crawler of claim 7 wherein a time delay is provided in the reversing means whereby the motor will not reverse if the stop signal is received within the time delay.

9. A crawler comprising,

10. The crawler of claim 9 wherein means are provided for moving the source into the shield in the absence of a signal from said signal generator a selected time after the source is moved out of the shield.

11. The crawler of claim 9 wherein means are provided responsive to the stepping means moving to its fifth position for reversing the crawler motor and for stopping the motor responsive to the stepping means moving to its sixth position.

12. The crawler of claim 11 wherein a time delay is provided in the reversing means whereby the motor will not reverse if the stop signal is received within the time delay.

13. The crawler of claim 9 wherein the clutch is electric and releases the source motor from the source in the absence of electric power.

Description:
This invention relates to checking of circumferential welds in a pipeline, and particularly relates to a crawler for moving through a pipeline and exposing film wrapped around the pipeline at selected circumferential welds.

In the past weld inspection machines utilizing X-ray tubes have been run inside of a pipeline. Movement of the machine, as well as operation of the X-ray device, was controlled by cables extending to the end of the pipeline. The length of pipeline which could be inspected was thus restricted. Also, great difficulty was experienced in locating the crawler in the pipeline opposite a weld.

In recent years, radio-active source material has been used to expose film, but there has been no known device for moving the radio-active source along the inside of the pipeline. The use of this type of source has been from the exterior of the pipeline in the same manner as X-ray machines have been positioned exteriorly of the pipeline in the past. This is disadvantageous, as with both the X-ray machine and the radio-active source a number of shots are taken to X-ray a complete circumferential weld. Thus, if a machine be available for moving either an X-ray tube or radio-active source through a pipeline and exactly positioning it at a weld without the need for elaborate cables extending through the pipeline to control the machine, then the speed with which circumferential welds could be inspected would obviously be greatly increased.

It is an object of this invention to provide a weld-inspection crawler which can be controlled from the exterior of a pipeline without direct connections.

Another object is to provide a weld-inspection crawler for moving a source of radio-active material through a pipeline to inspect the welds.

Another object is to provide a weld-inspection crawler which may be made to move forward or back or stop at selected locations without the use of cables or the like extending down the pipeline.

Another object is to provide a weld-inspection crawler which may be controlled in its movement in both directions and caused to stop at a particular location and generate rays for exposing film by remote control.

Another object is to provide a weld-inspection crawler as above with adequate safety features so that the emission of rays exteriorly of the pipe will be stopped after a selected time in the event of malfunction of the crawler.

Another object is to provide a simple inexpensive control system for a crawler which will remotely control the movement of the crawler in both directions in a pipeline and will control the emission of rays to the exterior of the crawler to inspect a weld utilizing successive signals to simplify controls.

Another object is to provide a simple inexpensive control system for a crawler which will, by remote control, determine movement of the crawler through the pipeline in either direction, stop the crawler at an exact location within the pipe, and control the movement of a radio-active source out of and return it into a shield to inspect a circumferential weld in a pipeline.

Other objects, features and advantages will be apparent from the drawings, the specification and the claims.

In the drawings, wherein an illustrative embodiment of this invention is shown, and wherein like numerals indicate like parts:

FIG. 1 is a bird' s-eye view of a crawler constructed in accordance with this invention;

FIG. 2 is a side view in elevation of the crawler shown in FIG. 1;

FIG. 3 is a front view in elevation of the crawler of FIG. 1;

FIG. 4 is a fragmentary view taken along line 4--4 of FIG. 3, partially in section, partially in elevation and partially in phantom, showing a pipe weld being inspected by a source of radio-active material carried by the crawler of FIG. 1;

FIG. 5 is a fragmentary view along the lines 5-- 5 of FIG. 1, illustrating the power means for extending and retracting the radio-active source from the camera;

FIG. 6 is a view partially in cross-section and partially in elevation, illustrating the source control motor, its self-locking gear drive, and the clutch utilized for safety purposes to provide for retraction of the source in the event of a power loss of malfunction of the system;

FIGS. 7, 8 and 9 are schematic diagrams showing the control system for the crawler; and

FIG. 10 shows an optional safety circuit which may be employed.

Reference is first made to FIGS. 1 through 6 which illustrate the mechanical details of the crawler.

The crawler body 10 is supported on the front by a pair of wheels 11 and 12 which will be seen in FIG. 3 to be spaced arcuately approximately 90°apart. In the rear the crawler is supported by the wheel 13 which arcuately bisects the two front wheels 11 and 12. It will be noted particularly from FIG. 3 that the center of gravity of the machine is very low and that the machine will be supported on the three wheels 11, 12 and 13 in the bottom of the pipe.

Means are provided on the body for moving the crawler through a pipe. Preferable this means includes a pair of drive wheels which are driven by motor 16 through gears not shown in the gear box 17 and through the chains 18 and 19. The drive wheel 15 is mounted on an arm 21 pivoted about the rotational axis of sprocket 22 (FIG. 3). In like manner, the drive wheel 14 is supported on an arm 23 which is pivoted about the center of rotation of the sprocket 24. A piston cylinder arrangement indicated generally at 25 extends between the shafts on which the two drive wheels 14 and 15 are mounted. Compressed air from container 26 exerts a force within the cylinder-piston assembly to urge the wheels 14 and 15 apart, and thus into firm engagement with the wall of the pipe. As the compressed gas is resilient in nature, the drive wheels will stay firmly in engagement with the pipe even though the pipe will change in its configuration along its length.

The motor 16 is of the reversing type and may be made to run in either direction to drive the crawler in either direction through a pipe.

Power for the motor 16 is provided by heavy duty 12-volt batteries in the battery box indicated generally at 27.

A source of rays for exposing film is carried by the body and in the preferred embodiment a source of radio-active material 28 (FIG. 4) is carried in the shield indicated generally at 29 when the source is not in use. Connected to the shield 29 is a spool-like shield 31 into which the source is projected when film is being exposed.

The shield 29 is conventional in construction and, as shown in the cut-away view, when the source 28 is retracted, the lead shielding prevents any rays from escaping as the passageway through the shield has two 90° bends with the source 28 between the bends when in retracted position. When the source is extended, it passes through the coupling indicated generally at 32, and the tube 33 which extends from the coupling into the center of the spool 31.

The spool 31 includes two spaced shield sections 34 and 35. These have confronting frusto-conical faces and are made of lead. The center section 36 is a short tubular piece of aluminum. A plurality of rods 37 are positioned circumferentially about the thick aluminum tubing 35 and the lead shield portion 36 is poured about these rods 37 to attach the shield 35 to the center section 36. A plurality of Allen-head screws 38 are spaced circumferentially about and attach the lead shield 34 to the central aluminum section 36.

In the use of the crawler, a film in a suitable plastic container indicated generally at 39 is wrapped about a weld 41. Through a suitable control system to be explained hereinbelow, a signal sent from the signal generator 42 is received by the signal receiver 43 and stops the crawler in the position shown in FIG. 4. Subsequent signals extend the source 28 to the position shown in FIG. 4 to expose the film in the carrier 39. Subsequent signal received by the receiver 43 retracts the source 28 to its position shown in the camera 29.

As shown in FIGS. 1 and 4, the source is extended and retracted by a cable 20 to which the source is attached. The cable 20 reciprocates within the flexible tube 30. Means are provided to reciprocate the cable 20 to move the source between a position within and a position without camera 29.

Referring to FIGS. 5 and 6, it will be seen that the tube 20 at its end remote from the shield is attached to a support 44 and the cable 20 is attached to a rack 45. The means for moving the source into and out of the shield 29 includes a reversing motor indicated generally at 46 connected through a gear train including the worm 47 and worm gear 48 (FIG. 6) and the clutch indicated generally at 49 to the rack 45. The worm 47 and worm gear 48 provide a self-locking gear train and the clutch 49 provides a means for releasing the rack 45 from the self-locking gear train. When released the source is returned to the camera by the resilient means provided by spring 51 exerting a force on the rack through cable 52 which is trained about pulley 53.

Referring to the clutch (FIG. 6) the output from the worm gear 48 is transmitted through gear 54 to the shaft 55. Shaft 55 has a bushing 56 thereon and the rack pinion 57 is rotatably mounted on the bushing 56. A friction clutch member 58 is non-rotatably mounted on the shaft 55 and cooperates with a friction member 59 which is mounted on and keyed to the shaft portion 57a of the pinion gear 57 through a sleeve 60. The friction member 59 is free to move axially within a limited area so that, upon energizing of the coil 61, the friction members 58 and 59 will be drawn together to provide rotation of the rack pinion 57 in response to rotation of the worm 47. If a malfunction in controls occurs, the coil 61 is de-energized, as will be more fully explained hereinafter, to release the frictional engagement between the members 58 and 59, and the spring 51 returns the source into the shield 29.

With the clutch 49 activated, the motor 46 will drive the rack 45 along its guideway 62 to extend or retract the source. At the limits of its movement in each direction, the rack activates micro-switches 40 or 50, depending on the direction of movement, to shut off motor 46, as will be more fully explained hereinafter.

Reference is now made to FIGS. 7, 8 and 9 which show a control system.

A signal-generating means is provided which includes an electro-magnet signal generator 42 (FIGS. 4 and 7). The electro-magnet is energized by a suitable source of 110-volt current by closing of the switch 63. As previously explained, this electro-magnet 42 is placed on the pipe relative to the crawler so that a signal from the electro-magnet will be picked up by the receiving coil 43 carried on the crawler. After the crawler has been started, the electro-magnet is moved to a position in which it is desired to stop the crawler, and, when the crawler moves to a position where the next signal is picked up by the receiving coil coming into proximity with the sending coil, a second signal will be received which will stop the crawler as shown in FIG. 4.

It will be appreciated that the electro-magnet will generate a field which will extend out a foot or two from the electro-magnet inside the pipe. By adjusting the gain on the receiving system, the receiving coil 43 will pick up a signal at a selected proximity to the sending coil 42. Preferably the gain is selected so that an operative signal is received when the pickup coil is immediately below the signal-generating coil as shown in FIG. 4.

The signal received from the pickup coil 43 is amplified in the amplifier A and operates the relay 64 to step the stepping relay indicated generally at 65 one step. Stepping relay 65 is a lockout relay which will not step again until after the previous signal has been reversed. Alternate positions are dead. It will be noted that when the relay 64 is closed, a current from a suitable source indicated generally at 67 passes through the coil 68 to activate the stepping relay one step. If it be assumed that at the beginning of operations the stepping switch 66 was at the one position, no output signal would be present as the position is dead. Upon the signal generator 42 being brought into proximity with the receiving coil 43 and the switch 64 closed to generate a signal, the stepping coil will step to position 2.

Forward motion of the crawler is provided by stepping relay 65 to position 2. With the relay in position 2, current flows from the source 67 through line 69 to contact 2 of the relay and thence through line 71 to the forward relay 72. Upon closing of forward relay 72, current flows through the second forward relay 73 through lines 74, 75 and 76 to activate the second relay. Line 76 is connected to the negative terminal of the power source 67.

It might be noted that throughout the control system multiple relays are used for convenience and to permit stepping up the current so that only a small current will pass through the stepping relay 65 to increase its useful life.

In FIG. 9 the main power source (12 -volt batteries) is shown at 77, and the power source 67 of FIG. 7 will be connected to this 12 -volt battery. It might be noted that this battery is separate from the battery 78 which drives the amplifier A. A separate battery is provided for the amplifier so that a constant power will be available for the amplifier. It will be appreciated that the main battery 77 operates all of the various motors and its available power will vary substantially between charges.

Upon closing of the second forward relay 73, current flows from the battery 77 through relay 73, line 78, and line 79 through the closed contact 81 of the reverse relay 80, and thence to the motor 16. From motor 16 current flows through line 82, closed contact 83 of the reverse relay 80 and line 84 to the motor shunt 85 and thence through line 86 to the battery 77. Thus, with the stepping relay 65 in the number 2 position, the crawler motor is operating to drive the crawler in a forward direction through the pipe.

Stopping of the crawler is provided for by moving stepping relay 65 to position 3. The signal-generating electro-magnet 42 is positioned relative to a weld 41 as shown in FIG. 4, and the switch 63 closed. By moving the electro-magnet away from the pickup coil 43, the relay 64 is de-energized and the stepping relay 65 is now in condition to step to contact 3 upon receiving the next signal, which it will do when the pickup coil 43 comes into proximity with the sending coil 42. This disconnects the control current to the forward relay 72 and opens this relay to stop the motor 16.

The operator then opens the switch 63 to de-energize the sending coil and the stepping relay is now ready to receive a third signal.

Advancing stepping relay to position 4 extends source 28. Upon the third signal being sent by closing of the switch 63, the relay steps to position 4. Current passes through position 4 and line 87 to the source relay 88. Upon source relay 88 being closed, current flows through lines 75 and 89 to a second source relay 90. Current also passes simultaneously through lines 91 and 92 to clutch relay 93. Closing of the source relay 90 provides a current through line 100, the forward limit switch 40 which is now closed as the source is retracted and in the shield, through switch contact 94, line 95, to the source motor 46. Current returns to battery through line 95a, contact 96 which is in its up position and line 97. This activates the source motor in a direction to extend the source.

In the meanwhile, the clutch relay 93 has been activated to shift the contacts to their up position and current flows from the battery 77 through line 98, contact 99, and line 101 to the clutch 49, thence through line 103 and the time-delay 104 which is in closed position, to midpoint of the coil 105 (clutch 49 requires 6 volts) and returns to the battery through line 106, contact 107 and line 108. Thus, with the source motor operating and the clutch 49 energized, the rack 45 will move rearwardly of the crawler until it strikes the forward limit switch 40 to open the switch and break the circuit to stop the motor.

Returning the source to the shield results from stepping relay 65 to position 5. After the film has been exposed, the control switch 63 is opened to take the signal off the relay 64, and then closed again to move the stepping relay 65 to contact 5. This de-energizes the three relays 88, 90 and 93, and returns the contacts 94 and 96 of relay 90, and 99 and 107 of relay 93 to the position shown in the drawings. In this position current flows in the clutch system through lines 98, contact 99, line 101, through clutch 49 to line 103, through the closed time-delay relay 104, coil 105, line 106, contact 107 and 108 to battery. Thus, the clutch is still energized.

The reverse limit switch was closed upon the rack 45 moving forward, and now a current may flow through line 100, the reverse limit switch 50, contact 96 and line 95 to source motor 46, and thence return to the battery through line 95, contact 94 and line 97 to operate the motor in the reverse direction to withdraw the source and return it to the camera.

If a malfunction occurs, time-delay 104 becomes operative to de-energize clutch 49 to permit spring 51 to return the source to the shield. It will be noted that when contact 107 is in its down position, current flows through the contact, the time-delay relay 104, line 109, reverse limit switch 50 and line 100, to the battery 77. Thus, upon the stepping switch being stepped to position 5, the time-delay 104 is energized. If for some reason there is a malfunction in the system and the rack 45 does not move into contact with the reverse limit switch 64 to break the circuit, the time-delay 104 will, after a selected time interval, open the contact 111 to break the circuit through clutch 49 and de-energize the clutch 49. If this occurs, the current is taken off the coil 61 (FIG. 6) to de-energize the clutch and the spring 51 will mechanically return the source to the shield.

Reverse movement of the crawler is provided by stepping relay 65 to position 6. After the source has been returned to the camera, the switch 63 is opened and then closed again to step the stepping relay to position 6. Current passes through line 112 through the time-delay 113, and line 114 to the reverse relay 115. The contact 116 of the time-delay 113 is normally open and does not close for a selective period of time. When the reverse relay 115 is activated, current flows through lines 75, 117, reversing relay 80 and line 76 to energize the reversing relay 80 and raise the contacts 81 and 83. In this position of the relay, current flows from battery 77 through line 118, contact 83, line 82, motor 16, line 79, contact 81, line 84, shunt 85, and line 86 to the battery 77 to run the motor 16 in the reverse direction and move the crawler in a reverse direction in the pipe.

While reverse movement is sometimes desirable, it is not normally desirable in successively inspecting welds, and for this reason the time-delay 113 is provided in the reverse circuit. Thus, if within the period allowed by the time-delay 113 which is normally open, the control switch 63 is opened and then again closed to step the stepping relay to position 7, the reverse circuit will not be energized. If the circuit is left at position 6 until the time-delay 113 is activated, then the crawler will be moved in the reverse direction.

It should be noted that forward relay 73 and reverse relay 80 are interlocked so that both relays cannot be simultaneously operated. With the stepping relay 65 in position 7, it will be appreciated that the normal cycle of operation has been completed and the pipeline inspected, the source returned to the shield, and the crawler is inactive in the pipeline. If a 6 -contact relay were used, the cycle could be repeated. In order to increase the life of the relay 65, a 12 -contact relay is utilized and the cycle above explained is repeated through contacts 7 through 12 in the exact manner herein above explained.

From the above it is apparent that in the event of a power failure, the clutch 49 is de-energized and the spring 51 returns the source to retracted position if it is not already in this position.

FIG. 10 shows an alternate safety system that may be used if desired. In this system, instead of line 89 connecting directly to the source relay 90 as shown in FIG. 8, connection to the source relay 90 is through line 119 and the closed contact 120 of a time-delay indicated generally at 121, and line 122. Current is provided to the time-delay 121 through line 123 and line 124. The time-delay 121 would normally be for a substantial time, say 5 minutes, and a timing motor would be included. Thus, if the source is extended, the weld inspected and the source returned to the shield within a normal period of time, the time-delay 121 would remain closed and would not affect operation of the circuit. However, if through some malfunction the source remained in extended position due to the source extending circuit remaining activated, then after a selected period of time, the time-delay 121 would open contact 120 to break the circuit to both the source relay 90 and the clutch relay 93 to de-energize the source-extend circuit and energize the source-return circuit.

From the above it will be seen that all of the objects of this invention have been attained. There has been provided a simple inexpensive control system for controlling the movement of a crawler through a pipe and for controlling the exposure of radio-active source to inspect a weld. It will be appreciated that if an X-ray tube were used that control of the X-ray tube would be carried out in the manner taught by this invention.

While the operator has positive control of the source, suitable safeguards are present which will insure that the source not remain extended through malfunction of the equipment.

The use of the shield narrows the direction of the high intensity rays to a 360° arc which will pass through the circumferential weld of the pipe. As the lead camera is in line with the tube 33 a complete shield in both directions along the pipe is provided. This will protect people along the pipeline in either direction and greatly simplify protection of personnel as it is only necessary to insure that personnel are not present in a direction perpendicular to the pipeline in the area of the weld.

While a simple stepping coil and relays are employed in the system shown, it will be appreciated that more sophisticated electronic stepping systems might be employed if desired.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.