Title of Invention

A MOLTEN STEEL LEVEL MEASURING DEVICE FOR A CONTINUOUS CASTING MACHINE MOLD

Abstract

Abstract A MOLTEN STEEL LEVEL MEASURING DEVICE WITH A LONG SCINTILLATOR A molten steel level measuring device for a continuous casting machine mold includes a receiver (101) mounted in a receiver mounting box (102) within a mold water chamber (107), a gamma Y radioactive source (103a) with shadow shielding mounted in a source mounting box (104), and a signal processor and so on. A detector (10If) in the receiver (101) is a long scintillator of end-window type or a long scintillator of side-window type. The long scintillator of end-window type is mounted vertically in its long axis and equipped with turning light guides (lOlh, lOli), and magnesia is used as a reflective layer. The long scintillator of side-window is mounted vertically in its long axis and magnesia is mainly used as a reflective layer and a glass window is provided on one side wall. And the long scintillator is connected to a photo-multiplier (1011) whose axis is horizontal orientation.

Full Text

A MOLTEN STEEL LEVEL MEASURING DEVICE WITH A LONG SCINTILLATOR Field of the Invention The present invention relates to a molten steel level measuring device for a continuous casting machine mold. Background of the Invention A molten steel level measuring device for a continuous casting machine mold usually adopts a sodium iodide scintillation crystal (scintillator) as a receiver. Generally, the sodium iodide scintillator is a cylinder of end-window type. Specifically, the cylindrical sodium iodide scintillator has magnesia powder which is applied on the cylindrical surface and one end of the cylinder as a photon reflective layer, and has a metal casing sheltering the cylindrical surface and the one end. On the other end of the cylinder, silicon gel or a gel sheet is applied and a glass enclosure is installed thereon as an emission window (i.e. end window) for the photons generated by the scintillator. The scintillator is connected to a light guide outside the end-window, a photo-multiplier and an electronic circuit board in tandem within the shell of a receiver to form the receiver. Generally, the receiver is a cylinder and is installed in the mold water chamber with the axis of the cylinder in approximately horizontal orientation. In order to improve the sensitivity and measurement range of the measurement of the molten steel level in the mold, in document US5564487A, a large naked sodium iodide scintillation crystal whose long axis is vertically mounted in a mold water chamber is used as a detector, where the crystal has gel applied on the surface as light transmission and shock absorption materials; the interior of a metal housing is used as a reflective layer, where the metal housing is a part of the receiver shell; the photon emission window also uses gel as light transmission and shock absorption materials. However, there are disadvantages including: the interior of the metal housing shows poor efficiency in reflecting photons, the surface of the gel light guide can be contaminated easily and. difficult to be cleaned, the structure and assembly of the receiver is relatively complicated and thus hard to be applied in wide range. Summary of the Invention The objective of the present invention is to provide a molten steel level measuring device for a continuous casting machine mold. The molten steel level measuring device, which can be mounted comfortably within the limited interior space of the mold water chamber, adopts a long scintillator of high photon collection efficiency as the detector and is easy to be manufactured and assembled. Hence the measurement sensitivity can be enhanced and the full molten steel level measurement range can be covered. The objective of the present invention is achieved by adopting a long scintillator of end-window type as a detector in a receiver, wherein a long axis of the long scintillator is mounted vertically and the long scintillator is equipped with turning light guides and a reflective layer of magnesia. The objective of the present invention is also achieved by adopting a long scintillator of side-window type as a detector in a receiver, wherein a long axis of the long scintillator is mounted vertically and the long scintillator is equipped with a reflective layer including magnesia mainly and a glass window on one side wall. The long scintillator of side-window type can be divided into two sections along the side window. For the longer section without the side window and the two ends of the long scintillator, magnesia is used as the reflective layer; for the shorter section with the side window, fluorine plastic is used as the reflective layer of the cylindrical surface. According to a conventional approach, the space between the metal housing of the receiver and the large naked sodium iodide scintillation crystal whose long axis is mounted vertically in the mold water chamber is filled with a layer of gel as light transmission and shock absorption materials, and the interior of the metal housing is used as the photon reflective layer. However, the interior of the metal housing shows low efficiency in reflecting photons, especially for large scintillation crystal in which photons shall impinge on the interior of the metal housing for multiple times before reaching the photon emission window. Besides, the gel layer needs to fully cover the large sodium iodide scintillation crystal and be integrated with light guides of the same material, which makes the structure and assembly process of the receiver very complicated. In addition, the gel light guides tend to attract contaminant on the surface and are difficult to clean, which in turn affects the light transmission efficiency. According to the present invention, a well enclosed long scintillator (e.g. a sodium iodide scintillator) of end-window type is mounted as the detector in the mold water chamber in its long axis, and magnesia is normally used as the reflective layer of the long scintillator. Further, photons emitted from the end window are coupled by turning light guides to a photo-multiplier whose axis is in horizontal orientation. In addition, the electronic circuit boards including the high-voltage power source circuit and the amplifying and shaping circuit are connected in tandem behind the photo-multiplier. In this way, the overall height of the receiver is shortened so that the limited interior space of the mold water chamber may accommodate a long sodium iodide scintillator covering the fill molten steel level measurement range and that the measurement sensitivity can be enhanced. Furthermore, the photon reflection efficiency of the reflective layer of magnesia is higher than that of the interior of receiver housing which photons should travel through the gel layer to reach, especially for the long scintillator in which photons should impinge on side walls for multiple times before reaching the emission window. And it is easy to purchase the merchandise of an enclosed scintillator (e.g. a sodium iodide scintillator) of end-window type with magnesia as the reflective layer, easy to maintain the transparency of the glass end window of the scintillator, and also easy to transport and store the scintillator and to mount the scintillator in the receiver. The structure of the receiver is also relatively simply with such kind of scintillator. According to another aspect of the present invention, a long axis of the long scintillator of side-window type is mounted vertically in the mold water chamber, magnesia is mainly used as the reflective layer of the long scintillator and a glass window is provided on one side wall. The photon emission window of the long scintillator of side-window type is connected to a photo-multiplier whose axis is in horizontal orientation. Therefore, the turning light guides can be omitted and the overall height of the receiver mounted vertically in the mold water chamber can be further shortened. For the longer section without the side window and the two ends of the long scintillator of side-window type, magnesia is used as the reflective layer, hence the photon collection efficiency of the main serf of the long scintillator can be significantly improved; for the rest of the long scintillator, fluorine plastic, which provides better photon reflection efficiency than metal surface, is used as the reflective layer, and the space between the fluorine plastic and the long scintillator is filled with silicone grease as the optical coupling material, hence a higher overall photon collection efficiency can be guaranteed for the long scintillator. The assembly manner of the enclosed long scintillator of end-window type with magnesia as the reflective layer, as well as the assembly manner of the long scintillator of side-window type with magnesia mainly as the reflective layer and a glass window on one side wall, as described in the preceding description, can be applied to sodium iodide, cesium iodide, BGO and all kinds of organic scintillators. Brief Description of the Drawings Figures 1 to 3 illustrate the present invention. Figure 1 is a schematic diagram illustrating the installation of a molten steel level measuring system for a mold in which a long sodium iodide scintillator of end-window type and turning light guides are adopted. Figure 2 is a schematic diagram illustrating the installation of a molten steel level measuring system for a mold in which a long sodium iodide scintillator of side-window type is adopted. Figure 3 is a schematic diagram illustrating a structure of a long sodium iodide scintillator of side-window type. Detailed Description of the Invention A first embodiment of the present invention is shown in Figure 1. In Figure 1, a receiver 101 is pushed into a receiver mounting box 102 within a mold water chamber 107 on one side of the mold 105. A cylindrical source box 103 is mounted vertically into a source mounting box 104 within the mold water chamber 107 through the fiange 106 of the mold 105. When the molten steel level measuring device for the mold is working, the cesium-137 dot source 103a in the source box 103 is close to one side of a copper tube 108 in the mold 105, and irradiates a long sodium iodide scintillator lOlf mounted vertically in the receiver 101 which is close to the opposite side of the copper tube 108a. The sodium iodide scintillator lOlf is an enclosed long scintillator of end-window type with magnesia as the reflective layer, the photons generated by the interaction between the gamma y ray from the cesium-137 dot source 103a and the sodium iodide scintillator lOlf are emitted into the turning light guides through a silicone gel sheet 10 Ig on the end-window of the sodium iodide scintillator lOlf. The silicone gel sheet lOlg is used as the optical coupling material. The turning light guides include a piece of transparent glass lOlh and a polytetrafluoroethene (PTFE) reflector lOli, each of which has a bevel surface whose normal line meets the vertical at an angle of 45°, and the two bevel surfaces are bonded with silicone grease which is used as the optical coupling material. The photons are turned by the bevel surfaces, and are transmitted, through a silicone gel sheet lOlk which is used as the optical coupling material, into a photo-multiplier 1011 whose axis is in horizontal orientation. The electronic signals generated from the photons in the photo-multiplier 1011 are amplified and shaped by an electronic circuit board 10In connected to the photo-multiplier 1011 in tandem, and are transmitted to a signal processor (not shown in the figure) via sockets lOlo and lOlp and signal cable 101s. The signal processor processes the amplified and shaped electronic signals, and provides a height value indicating the level 110 of molten steel 109. The use of turning light guides lOlh and 101 i enables horizontal positioning of the photo-multiplier 1011, the electronic circuit board 10In and the sockets 101 o and lOlp within the receiver 101. The overall height of the receiver 101 is therefore shortened and a comparatively long sodium iodide scintillator can be adopted to cover the full molten steel level measurement range R in the mold as well as to enhance the measurement sensitivity. The main body of the housing of the receiver 101 includes a vertical cylinder lOle and a horizontal cylinder 101 q which are welded together. The receiver 101 is assembled by: embedding the protruding part of the transparent glass lOlh into the recess in the PTFE reflector so as to form the turning light guides, attaching the silicone gel sheets with silicone grease lOlg and 101k to the two transparent surfaces of the light guides, putting the light guides onto an elastic pad lOlj in the vertical cylinder 101 e; putting the scintillator 10If with a shock absorbing ring 101c into the vertical cylinder lOle, screwing an upper lid 101a onto the vertical cylinder lOle with a seal ring 10Id after mounting a thrust bearing 101b on the scintillator lOlf to prevent the scintillator 10If from rotating, and then mounting the photo-multiplier 1011 with a shock absorbing "O" shape ring 101m, the electronic circuit board lOln, the socket lOlo and the socket lOlp with cable 101s into the horizontal cylinder lOlq. The receiver 101 is simple in structure and easy to be assembled. The receiver 101 is positioned in the receiver mounting box 102 via a handle lOlr. The shadow lead shield 103b in the cylindrical source box 103 shields the cesium-137 dot source 103a. The installation and removal of the source box 103 can be realized quickly by using a handle 103 c of the source box 103, and the operation distance from the dot source 103a is also thereby increased. The source box 103 can be rotated by 180° in the source mounting box 104 by using the handle 103c, thereby placing the cesium-137 dot source 103a between the lead shield 103b in the source box 103 and an additional shield 111 in the mold 105, and thus reducing the radiation dose rate when operators' hands reach into the copper tube of the mold before pouring starts. A second embodiment of the present invention is shown in Figure 2. In Figure 2, a receiver 201 is pushed into a receiver mounting box 202 within a mold water chamber 207 on one side of the mold 205. A cylindrical source box 203 is mounted vertically into a source mounting box 204 within the mold water chamber 207 through the flange 206 of the mold 205. When the molten steel level measuring device for the mold is working, the cesium-137 dot source 203a in the source box 203 is close to one side of a copper tube 208 in the mold 205, and irradiates a long sodium iodide scintillator 20If mounted vertically in the receiver 201 which is close to the opposite side of the copper tube 208a. The reflective layer of the scintillator 20If is mainly made of magnesia and the length of the scintillator 20If covers the full molten steel level measurement range R. The scintillator 20 If has a glass photon emission window on one side wall. The photons generated by the interaction between y ray and the scintillator 20If are emitted, through the emission window and a silicone gel sheet 20Ih, into a photo-multiplier 20Ij whose axis is in horizontal orientation. The silicone gel sheet 201h is used as the optical coupling material. And the photo-multiplier 20 Ij is equipped with a shock absorbing "O" shape ring 20li. The electronic signals generated from the photons in the photo-multiplier 20 Ij are amplified and shaped by an electronic circuit board 201k connected to the photo-multiplier 201j in tandem, and are then transmitted to a signal processor (not shown in the figure) via sockets 2011 and 201m and a signal cable 201 p. The signal processor processes the amplified and shaped electronic signals, and provides a height value indicating the level 210 of molten steel 209. The parts mentioned above from the scintillator 201 f to the electronic circuit board 201k are mounted in the receiver housing which includes a vertical cylinder 201e and a horizontal cylinder 201n welded together, a seal ring 20Id, an upper lid 201a and a socket 2011; meanwhile, a thrust bearing 201b that prevents the scintillator 20If from rotating, a shock absorbing "O" shape ring 201c and an elastic pad 20 Ig are also mounted in the receiver housing. The receiver 201 is simple in structure and easy to be assembled. The receiver 201 is positioned in the receiver mounting box 202 via a handle 20lo. The shadow lead shield 203b in the cylindrical source box 203 shields the cesium-137 dot source 203a. The installation and removal of the source box 203 can be realized quickly by using a handle 203c of the source box 203, and the operation distance from the dot source 203a is also increased. The source box 203 can be rotated by 180° in the source mounting box 204 by using the handle 203c, thereby placing the cesium-137 dot source 203a between the lead shield 203b in the source box 203 and an additional shield 211 in the mold 205, and thus reducing the radiation dose rate when operators' hands reach into the copper tube of the mold before pouring starts. Compared with the first embodiment, the second embodiment omits the turning light guides and further shortens the overall height of the receiver, and therefore, an even longer sodium iodide scintillator can be adopted to further enhance the measurement sensitivity of the molten steel level measurement in the mold and to expand the measurement range of the molten steel level measurement in the mold. A scintillator of side-window type in accordance with the present invention is shown in Figure 3. The crystal 300 in the Figure 3 is divided into a longer upper sectiont and a shorter lower section with a glass side window 308 by a PTFE raw material ring 303 which coils around the cylindrical surface of the sodium iodide scintillator 306 for positioning and separation. The upper section uses magnesia 302 as the reflective layer, and the lower sectionuses a PTFE board 304 and a PTFE tube 309 as the reflective layer. The space between the PTFE board 304, the PTFE tube 309, the glass window 308 and the sodium iodide scintillator 306 is filled with transparent silicone gel 307 as the optical coupling material. The surface of the sodium iodide scintillator 306 is polished in the area facing the glass window 308 and rubbed rough in the remaining area. In the assembly procedure of the crystal 300, the glass window 308 with a protruding part shall be embedded from the inside of a metal housing 301 into an opening on the side wall of the metal housing 301 and attached tightly to the metal housing 301 with epoxy glue 305. The use of the protruding part is to prevent the glass window 308 from being forced apart from the metal housing 301 when the crystal 300 expands in an environment of high temperature. When the side window 308 is attached tightly to the metal housing, the PFTE board 304 shall also be mounted within the metal housing. After that, the sodium iodide scintillator 306 with the PTFE raw material ring 303 is placed into the metal housing 301 through the upper end of the metal housing and the magnesia 302 is filled. A plane pad 311b and an elastic pad 310b are then mounted on the upper end, and an upper lid 301b is screwed and glued onto the metal housing 301. After that, the crystal 300 shall be turned upside-down, the space between the metal housing 301, the glass side window 308, the PTFE board 304 and the sodium iodide scintillator 306 shall be filled with transparent silicone gel 307 and the PTFE tube 309 shall be mounted. After eliminating air from the transparent silicone gel 307and allowing the transparent silicone gel 307 to solidify by applying high temperature, a magnesia reflective layer 302 shall be applied to the end of the silicone gel 307 and an end lid 301a shall be screwed and glued onto the metal housing 301 on this end after a plane pad 311a and an elastic pad 31 Oak are mounted. Industrial Applicability The present invention adopts the enclosed long scintillator of end-window type or of side-window type as the detector in the mold water chamber, the scintillator has a normal reflective layer of magnesia and is mounted vertically in its long axis in the water chamber, therefore the limited room within the mold water chamber may accommodate a long sodium iodide scintillator covering the full molten steel level measurement range and the measurement sensitivity can be enhanced. What is claimed is: 1. A molten steel level measuring device for a continuous casting machine mold, comprising: a receiver mounted in a receiver mounting box in a mold water chamber, the receiver being close to one side of a copper tube in the continuous casting machine mold; a gamma radioactive source mounted in a source mounting box in the mold water chamber, the gamma radioactive source being close to the opposite side of the copper tube; and a signal processor; wherein the receiver comprises: a detector which is a long scintillator of end-window type, a long axis of the long scintillator being mounted vertically and the long scintillator being equipped with turning light guides and a reflective layer of magnesia. 2. The device as claimed in claim 1, wherein the source mounting box comprises: a source box comprising the gamma radioactive source, a lead shield adapted to shield the gamma radioactive source and a handle by which the source box is installed, removed or rotated in the source mounting box. 3. The device as claimed in claim 1 or 2, wherein the receiver is positioned in the receiver mounting box via a handle. 4. A molten steel level measuring device for a continuous casting machine mold, comprising: a receiver mounted in a receiver mounting box in a mold water chamber, the receiver being close to one side of a copper tube in the continuous casting machine mold; a gamma radioactive source mounted in a source mounting box in the mold water chamber, the gamma radioactive source being close to the opposite side of the copper tube; and a signal processor; wherein the receiver comprises a detector which is a long scintillator of side-window type, and a long axis of the long scintillator being mounted vertically and the long scintillator being equipped with a reflective layer comprising magnesia mainly and a glass window on one side wall. 5. The detector as claimed in claim 4, wherein a longer section of the long scintillator without the glass side window and two ends of the long scintillator adopt magnesia as reflective layer; and a cylindrical surface of a shorter section of the long scintillator with the glass side window adopts fluorine plastic as the reflective layer; wherein the magnesia reflective layer and the fluorine plastic reflective layer are separated by a raw material ring which coils around the cylindrical surface of the long scintillator. 6. The device as claimed in claim 4 or 5, wherein the source mounting box comprises: a source box comprising the gamma radioactive source, a lead shield adapted to shield the gamma radioactive source and a handle by which the source box is installed, removed or rotated in the source mounting box. 7. The device as claimed in claim 4 or 5, wherein the receiver is positioned in the receiver mounting box via a handle. 8. A detector, characterized in that: the detector is a long scintillator of side-window type, and a long axis of the long scintillator is mounted vertically and the long scintillator is equipped with reflective layer comprising magnesia mainly and a glass window on one side wall. 9. The detector as claimed in claim 8, wherein a longer section of the long scintillator without the glass side window and two ends of the long scintillator adopt magnesia as reflective layer; and a cylindrical surface of a shorter section of the long scintillator with the glass side window adopts fluorine plastic as the reflective layer; wherein the magnesia reflective layer and the fluorine plastic reflective layer are separated by a raw material ring which coils around the cylindrical surface of the long scintillator.

Documents:

2788-CHENP-2008 CORRESPONDENCE OTHERS 02-05-2014.pdf

2788-CHENP-2008 AMENDED CLAIMS 22-08-2014.pdf

2788-CHENP-2008 AMENDED PAGES OF SPECIFICATION 22-08-2014.pdf

2788-CHENP-2008 ENGLISH TRANSLATION 22-08-2014.pdf

2788-CHENP-2008 EXAMINATION REPORT REPLY RECEIVED 22-08-2014.pdf

2788-CHENP-2008 FORM-1 22-08-2014.pdf

2788-CHENP-2008 FORM-3 22-08-2014.pdf

2788-CHENP-2008 POWER OF ATTORNEY 22-08-2014.pdf

2788-chenp-2008 abstract.pdf

2788-chenp-2008 claims.pdf

2788-chenp-2008 correspondence-others.pdf

2788-chenp-2008 desription-(complete).pdf

2788-chenp-2008 drawings.pdf

2788-chenp-2008 form-1.pdf

2788-chenp-2008 form-3.pdf

2788-chenp-2008 form-5.pdf

2788-chenp-2008 pct.pdf

2788-Chenp-2008-Form 13.pdf