AUTOMATED ULTRASONIC EXAMINATION SYSTEM FOR HEAT TRANSFER TUBES IN A BOILER

Abstract: A novel automated ultrasonic examination system for heat transfer tubes (2) in a boiler is disclosed herein, which makes it possible to perform ultrasonic examination from the inside of the heat transfer tubes (2) without neces­ sitating removal of scale from the outer surfaces of the boiler tubes (2) by polishing nor necessitating measurements in restricted places where manual measurements are dif­ ficult or impossible. The disclosed novel system comprises an insert tube (1) adapted to be inserted into a cylindrical header (3) to which one end of the heat transfer tubes (2) are connected, an insert tube moving device (5) for moving the insert tube (1) in the axial direction of the header (3) and revolving it about its own axis, an ejection nozzle (6) pro­ vided on the insert tube (1), a water pump for feeding pres­ surized water to the ejection nozzle (6), a cable (13) adapted to be inserted from the ejection nozzle (6) into the heat transfer tube (2) as passed through the insert tube (1) by the pressurized water fed from the water pump, a cable (13) accommodation tank (10a) for accommodating the cable (13), a revolving submerged ultrasonic probe (14) mounted at the tip end of the cable (13), and an ultrasonic examination unit (21) for processing signals sent from the probe (14) and displaying the results of examination. Preferably, means for detecting a length of the cable (13) inserted into the heat transfer tube (2), is provided in the automated ultrasonic examination system.

Description: BACKGROUND OF THE INVENTION: Field of the Invention: The present invention relates to an automated ultrasonic examination system for heat transfer tubes in a boiler of the kind defined by the precharacterizing features of claim 1. Description of the Prior Art: Heretofore, in the case of performing ultrasonic examination for heater tubes or reheater tubes in a boiler, as shown in Fig. 7 a worker entered in a narrow space within a boiler, and after he had removed dust and scale adhered onto surfaces of tubes 01, he performed ultrasonic examination from the outside of the tubes 01. However, since the heater tubes or reheater tubes in a boiler are normally located at a high position, in order to perform ultrasonic examination it is necessary to erect a scaffolding within the boiler. In addition, the heater tubes or reheater tubes are arrayed densely for enhancing a thermal efficiency, and hence there are many narrow places where a worker cannot make access to the tubes. Furthermore, as the ultrasonic examination is performed from the outside, it is necessary to remove dust and scale deposited on the outer surfaces of the tubes, prior to examination. An automated ultrasonic examination system of the kind defined at the preamble is known from the JP-A-60 161 515. Correct positioning of the insert tube vis-à-vis the end opening of the tube to be examined as well as the examination of the complete inner wall of the tube to be examined by means of the submerged ultrasonic probe can not be easily attained by means of this known system. Further, the handling of the nozzle and the nozzle neck of this known system by means of the control wire, which is only adapted for an erection of the nozzle, also is complicated. SUMMARY OF THE INVENTION It is the object of the present invention to provide an automated ultrasonic examination system of the kind in question which allows easy and safe handling of the insert tube as well as the nozzle and the nozzle neck and which further allows complete examination of the tube to be examined by means of the submerged ultrasonic probe in an easy manner. This object is attained by the characterizing features of claim 1. An advantageous development of the invention is given by the features of claim 2. The above-mentioned object and the advantages of the present invention will become more apparent by reference to the following description of a preferred embodiment of the present invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: In the accompanying drawings: Fig. 1 is a perspective view showing a general layout of an automated ultrasonic examination system for heat transfer tubes in a boiler according to one preferred embodiment of the present invention; Fig. 2 is a front view partly in cross-section showing the state where an insert tube has been inserted into a header; Fig. 3 is a front view showing a revolving submerged ultrasonic probe; Fig. 4 is a front view showing a cable accommodating apparatus; Fig. 5 is a piping diagram showing flows of pressurized water upon examination; Fig. 6 is a detailed construction view partly in cross-section showing one example of an insert tube and a pressurized water ejection nozzle in an automated ultrasonic examination system according to the present invention; and Fig. 7 is a perspective view showing a working condition of ultrasonic examination for heat transfer tubes in a boiler in the prior art. DESCRIPTION OF THE PREFERRED EMBODIMENT: Now description will be made on one preferred embodiment of the present invention illustrated in Figs. 1 through 6. At first, referring to Fig. 1 which shows a general layout of the automated ultrasonic examination system for heat transfer tubes in a boiler according to the present invention, reference numeral 1 designates an insert tube adapted to be inserted into a header (cylindrical body) 3 to which heating tubes (tubes to be examined) 2 are connected. This insert tube 1 is inserted through an inspection hole 4 provided in an end wall of the header 3, and an insert tube moving device 5 for moving the insert tube 1 in the axial direction of the header 3 and revolving the insert tube 1 about its own axis, is disposed in the proximity of the inspection hole 4. The above-described insert tube 1 is formed by successively jointing generally a plurality of insert tube units each having a length of, for example, about 1 m, and inserted into the header 3, and as best seen in Fig. 6 at the tip end portion of the foremost insert tube unit is pivotably mounted a pressurized water ejection nozzle 6. While this pressurized water ejection nozzle 6 is accommodated within the insert tube 1 when the insert tube 1 is inserted through the inspection hole 4, after the insert tube 1 has been inserted into the header 3, the pressurized water ejection nozzle 6 is erected at a right angle to the insert tube 1 by means of a wire 7a as shown in Fig. 2, and a nozzle neck 6a at the tip end of the ejection nozzle 6 is opposed to an end opening of the heater tube 2. And when another wire 7b is drawn, the above-mentioned nozzle neck 6a would project from the tip end of the nozzle 6 to be pressed against the tube end opening of the heater tube 2. One example of the structure of the above-described insert tube 1 and pressurized water ejection nozzle 6 will be explained with reference to Fig. 6. The hollow insert tube 1 is provided with a forwardly opened portion at its front end, and at this portion are integrally formed support members 1a. The pressurized water ejection nozzle 6 is pivotably supported from these support members 1a by means of a support pin 25. A wire 7a and another wire 7c are connected to the pressurized water ejection nozzle 6 at different positions on the opposite sides of the support pin 25, and these wires are passed through the above-mentioned insert tube 1 and respectively connected to a wire controller (not shown). By drawing the wire 7a by means of the wire controller, the pressurized water ejection nozzle 6 is rotated up to the position perpendicular to the insert tube 1 as shown by a solid line arrow, but on the contrary by drawing the wire 7c the pressurized water ejection nozzle 6 is rotated in the direction shown by a dash-dot line arrow and becomes parallel to the insert tube 1. In Fig. 6, reference numeral 28 designates a guide wheel, which is composed of a small guide wheel 28a and a large guide wheel 28b, and the above-mentioned wire 7a is wound around the large guide wheel 28b. To the pressurized water ejection nozzle 6 is mounted a nozzle neck 6a. This nozzle neck 6a would rotate jointly with the pressurized water ejection nozzle 6 when the latter is rotated via the wires 7a and 7c, and also it would be pushed up towards the tube end opening of the heater tube 2 by the intermediary of an L-shaped lever 29, a push-up lever 30 and a wire 7b to be pressed against the tube end opening. The above-mentioned dire 7b is wound around the small guide wheel 28a of the guide wheel 28, then passed through the insert tube 1, and like the wires 7a and 7c, connected to the wire controller. A hose 23 disposed within the insert tube 1 is connected to the nozzle neck 6a, and as shown in Fig. 6, this hose 23 extends through the pressurized water ejection nozzle 6 and is connected, on the opposite side, to a pressurized water feed hose 9 as will be described later. Provision is made such that pressurized water may be introduced into this hose 23 and a cable 13 (Fig. 3) having a revolving submerged ultrasonic probe at its tip end portion may be inserted into the heater tube 2 through the nozzle neck 6a by the action of the pressurized water as will be described later. It is to be noted that Fig. 6 illustrates merely one example of the structure of the insert tube 1 and the pressurized water ejection nozzle 6 and it is possible to employ different structures for these members. For instance, a modified structure in which the hose 23 is omitted and the insert tube 1 itself is given the function of a hose, could be employed. To the rear end of the above-described insert tube 1 is connected a pressurized water feed hose 9 to feed pressurized water to the above-described pressurized water feed nozzle 6 through a pressurized water passageway formed within the insert tube 1 (for instance, the hose 23 in the example shown in Fig. 6). The other end of this pressurized water feed hose 9 is connected to a delivery port of a pressurized water feed pump 11 via a cable accommodating apparatus 10, and at the delivery port of the pressurized water feed pump 11 is provided a pressurized water flow rate regulating and flow direction control device 12 for controlling a flow rate and direction of flow of pressurized water. Within the above-mentioned cable accommodating apparatus 10 is accommodated a cable 13 shown in Fig. 3 as wound around a rotary drum not shown. This cable 13 has flexibility so that it may be conveyed by the pressurized water through the insert tube 1 and the pressurized water ejection nozzle 6 up to the interior of the heater tube 2. The rotary drum is disposed within a pressure tank 10a (See Fig. 4) of the cable accommodating apparatus 10 with its axis directed in the axial direction of the pressure tank 10a, and it is either automatically rotated in accordance with the flow of the pressurized water or manually rotated. In addition, the rotary drum is adapted to be moved in the axial direction of the pressure tank 10a by one pitch of cable winding for every revolution thereof so that the position of the cable 13 being paid out from the rotary drum or wound up therearound may always oppose to a cable pay-out/wind-up port 10b provided at the center of the pressure tank 10a. On the other hand, as shown in Fig. 3, at the tip end of the cable 13 is mounted a revolving submerged ultrasonic probe 14. This revolving submerged ultrasonic probe 14 includes a probe main body 15, centering jigs 16 for holding the probe main body 15 along a center axis of the tube to be examined, and a motor 17 for revolving the probe main body 15, and in order that the same probe can be applied to tubes having different diameters, the outer circumferential surfaces of the centering jigs 16 are studded with brushes 18 made of high molecular material. In addition, float members 19 are fixedly secured to the cable 13 at a fixed interval, and a propelling force for the cable 13 is generated by these float members. In Fig. 1, reference numeral 20 designates a cable insert length detector unit for detecting a rotational angle of the rotary drum in the cable accommodating apparatus 10 and calculating a feed length of the cable 13 on the basis of the rotational angle as well as the outer diameter of the rotary drum, and reference numeral 21 designates an ultrasonic examination unit which processes signals sent from the revolving submerged ultrasonic probe 14 and out-putting the results of examination to a printer 22 or the like. Now description will be made on the operation in the case of measuring a tube wall thickness of the heater tube 2 by making use of the automated ultrasonic examination system according to the present invention constructed in the above-described manner. At first, blind covers for the inspection holes 4,4 formed at the opposite ends of the header 3 are removed by melting to form openings, and thereafter an insert tube moving device 5 is set in the proximity of the inspection hole 4 outside thereof. In this case, as shown in Fig. 5, insert tube moving devices 5 are set in the proximities of the inspection holes 4 of the headers 3 on the inlet side as well as on the outlet side of the heater tubes 2 (inlet side means the side where the water enters into the tubes; outlet side means the side where the water flows out from the tubes). After the insert tube 1 has been set on the insert tube moving device 5, a fiberscope is inserted into the insert tube 1 from the disconnected end untile the tip end of the fiberscope comes to the nozzle neck 6a of the pressurized water ejection nozzle 6. Under this condition, while an operater is looking into the fiberscope, the insert tube 1 is moved in the axial direction of the header 3 and revolved about its own axis by the insert tube moving device 5, and thereby the tube end opening of the heater tube 2 is sought for. When the tube end opening of the heater tube 2 has been found through the above-mentioned process, the fiberscope is withdrawn from the insert tube 1. At one header on the inlet side or the outlet side through which the cable is inserted (In Fig. 5, such a header is shown as inlet side header 3-1.), the insert tube 1 and the cable accommodating apparatus 10 are connected with each other by means of the hose 9-1, and also the cable accommodating apparatus 10 and the pressurized water feed pump 11 which is connected to a cable tank 32 are connected with each other by means of another hose 9-2. At another header on the inlet side or the outlet side through which the cable is not inserted (In Fig. 5, such a header is shown as outlet side header 3-2.), the insert tube 1 is directly connected with the pressurized water feed pump 11 by means of hose 9-4 without providing the cable accommodating apparatus. In these hoses 9-2 and 9-4 Valves V₁, V₃ are provided as shown in Fig. 5. The above cable accommodating apparatus 10 on the cable insertion side and the insert tube 1 on the other side are also connected to the cable tank 32 by means of hoses 9-3 and 9-5, to each of which Valve 2 or Valve 4 is provided, respectively. In Fig. 5, numeral 11 shows a pump for feeding water from the cable tank 32 to cable accomodating apparatus 10. Under this condition, the nozzle neck 6a of the pressurized water ejection nozzle 6 of the insert tube 1 in each of the inlet side and outlet side headers is pressed against the tube opening of the header tube 2 by drawing the wire 7b by the action of the wire controller 8. Then, the Valves V₁ and V₄ are opened, the Valves V₂ and V₃ are closed, and the pressurized water feed pump 11 is started. The pressurized water flows as shown by arrow A in Fig. 5 from the inlet side header 3-1 to the outlet side header 3-2, and the cable 13 is conveyed by the pressurized water through the insert tube 1 and the pressurized water ejection nozzle 6 into the heater tube 2. When the length of cable 13 in the heater tube 2 becomes to the predetermined value, the pressurized water feed pump 11 is stopped and the Valves V₁, V₄ are closed so that the flow of the pressurized water is stopped. Next, Valves V₂, V₃ are opened, Valves V₁, V₄ are kept closed, and the pressurized water feed pump 11 is started again. The pressurized water reversely flows from the outlet side header 3-2 to the inlet side header 3-1 as shown by arrow B in Fig. 5, and the cable 13 moves in the heater tube toward the inlet side header 3-1, and is wound by the cable accommodating apparatus 10. In this step, ultrasonic examination for the heater tube 2 is achieved from the inside of the heater tube. In this case, the position in the axial direction of the examination conducted by the probe can be detected by the cable insert length detector unit 20. As described in detail above, according to the present invention, since ultrasonic examination can be performed from the inside of tubes, erection of scaffoldings and removal of dust or scale deposited to the outside of the tubes would become unnecessary, and ultrasonic examination can be easily conducted even at narrow places where a worker cannot make access. According to experiments conducted by the inventors of the present invention, it was confirmed that a tube wall thickness of a heater tube of 40 m in total length could be examined in about 3 minutes. Since many changes and modifications can be made to the above-described construction and arrangement without departing from the spirit of the present invention, all matter contained in the above description and illustrated in the accompanying drawings shall be interpreted to be illustrative and not in a limiting sense.

Claims: An automated ultrasonic examination system for examining heat transfer tubes (2) in a boiler, which tubes (2) with one ends thereof are connected to the cylindrical wall of a cylindrical header (3), said system comprising an insert tube (1) adapted to be inserted into the header (3), an insert tube moving device (5) for moving said insert tube (1) in the axial direction of said header (3), a pressurized water ejection nozzle (6) provided at the front end of the insert tube (1) and being adapted to be erected at a right angle with respect to the insert tube (1) by means of a first wire (7a) under the control of a wire controller so that a nozzle neck (6a) at the tip end of said nozzle (6) is opposed to an end opening of the tube (2) to be examined, when the insert tube (1) is in position in the header (3), a pressurized water feed pump (11) for feeding pressurized water to said pressurized water ejection nozzle (6), a cable (13) for being inserted into the tube (2) to be examined via the insert tube (1) and the pressurized water ejection nozzle (6) by means of pressurized water, the said cable (13) being accommodated in a cable accommodation apparatus (10) which is connected to the pressurized water feed pump (11) and the rear end of the insert tube (1), a submerged ultrasonic probe (14) mounted at the tip end of said cable (13) and an ultrasonic examination unit for processing signals sent from said submerged ultrasonic probe (14) and displaying the results of examination, characterized in that the insert tube moving device (5) is adapted for revolving the insert tube (1) about its own axis to facilitate positioning of the erected ejection nozzle (6) vis-à-vis the end opening of the tube (2) to be examined, in that the pressurized water ejection nozzle (6) is pivotably supported at the front end of the insert tube (1), a second wire (7c) under control of the wire controller being connected to said nozzle (6) for rotating said nozzle (6) from its erected position to a position in parallel to said insert tube (1), said nozzle neck (6a) being axially displaceably mounted to said nozzle (6) by means of a third wire (7b) under control of said wire controller such that the nozzle (6) is pressed against the said end opening of the tube (2) to be examined and in that the submerged ultrasonic probe (14) is adapted for revolving to allow an examination of the tube (2) to be examined around the complete circumference thereof. The system according to claim 1, further comprising means (20) for detecting the actual length of the cable (13) which has been inserted into the tube (2) to be examined.

Inventors: ICHINARI, JOJI NAGASAKI SHIPYARD & ENGINE WORKS, IWAMOTO, KEIICHI C/O NAGASAKI TECHNICAL INSTITUTE, KANEKO, SHOZO NAGASAKI SHIPYARD & ENGINE WORKS, KOIZUMI, KIYOSHI, OKABE, YOSHIMI, TORICHIGAI, MASAAKI NAGASAKI TECHNICAL INSTITUTE, Ichinari, Joji Nagasaki Shipyard &amp; Engine Works, Kaneko, Shozo Nagasaki Shipyard &amp; Engine Works
Applicants: MITSUBISHI JUKOGYO KABUSHIKI KAISHA, TOKYO ELECTRIC POWER COMPANY
Application year: 1988
Main classification: G01N29
IPC codes: G01N29, F28G15, F22B37