A SYSTEM FOR ANALYZING HEALTH OF A PIPE CARRYING HOT FLUID VIA FBG SENSORS

TECHNICAL FIELD

[001] The invention relates to a system for health monitoring of pipes carrying hot fluid.
BACKGROUND
[002] Blast furnaces are used to smelt iron ore from iron in steel industries. It operates large volume of iron ore, fuel and limestone simultaneously. Hence the structure involved are massive. As the raw material descends from the top of the furnace towards the hearth, it experiences increase in temperature upto 1600°C during extraction process.
[003] In blast furnaces the raw materials are charged from the top of and hot blast is blown through tuyeres from the bottom level. These tuyeres draw the hot blast from bustle pipe through blowpipe and then they inject it into the blast furnace. Therefore, the blowpipe and tuyere are exposed to high temperature flowing fluid directly. This makes them the more vulnerable components in furnace. In addition, blow pipe carries pulverized coal particles in it and any failure can lead to leakage of coal and hot gas outside.
[004] On its way from bottom to top, the hot blast enables the chemical reaction of smelting iron ore into iron. This hot blast is injected by tuyeres is drawn from bustle pipe through blowpipes as shown in Fig.1.
[005] The blowpipe feeds the tuyere with pulverized coal also. As these hot blast and pulverized coal are injected, they make the blowpipe more vulnerable for wear and thermal cracking. Such failures not only affect the productivity in terms of breakdown, but it also causes safety threats as it is carrying flammable pulverized coal and hot blast together. Hence there is a need to monitor the condition of the blowpipe on a continuous basis to avoid such unexpected failures.
[006] Thermographic camera cannot be used as it cannot capture the region of interest (nose of the blowpipe), as there is very limited space. Also, the space is normally engulfed by dust. The blowpipe monitoring is more essential not only in terms of productivity, but also to ensure safe operation of blast furnace.
Blow pipe experiences failures majorly in gradual thinning and rupture and thermal cracking and leakage.
[007] In the patent US5481247A, a sensor system to detect any blockage in coal and hot blast injection unit in blast furnaces is claimed. The patent photosensitive sensor to detect and monitor the blockage in coal and hot blast injection in system, in particular it is focused to monitor the tuyere on a continuous basis. The system claimed in the patent employs a camera to obtain real time images of the tuyere pathway, despite the temperature constraint.
[008] In the patent EP3256610B1, an optical system with light deflection components for monitoring the tuyere nose and raceway. The optical system is enabled by light defecting units and light carrier. In an article, Fiber Bragg Grating sensor was used as an effective tool for monitoring strain in the structure.
[009] In United States Patent 5397108, a peepsight for a blast furnace tuyere sensor system comprises a housing in which is mounted a colored glass viewing window and one end of a fiber optic cable directed toward a tuyere so that an operator can view the interior of the furnace and the cable can receive light energy emitted at the tuyere for transmittal of such light energy to an optical sensor.
[0010] Hot blast and pulverized coal injection system is one of the most vulnerable element in blast furnaces. Hence, there are many inventions intended to monitor the condition of the tuyere in real time but none of them disclose real time health condition of blow pipes.
OBJECTS
[0011] An object of the invention is to assess the online health of a pipe carrying hot fluid.
[0012] Another object of the is to determine the various pipes location with corresponding temperature in real time.
[0013] For a better understanding of the invention and to show how the same may be performed, a preferred embodiment thereof will now be described, by way of non-limiting example only, with reference to accompanying drawings.
[0014] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY
[0015] The present invention provides a system for determining health of a pipe carrying hot fluid, the system (100) comprising:
a plurality of FBG sensors located at various locations of the pipe to sense temperature signal and transmit temperature signal to a processor;
the processor being coupled to the plurality of FBG sensors to receive and process the temperature signal in a form of location and temperature data of the pipe and send the location and temperature data to a display unit; and
the display unit being coupled to the processor to display location and temperature data.
[0016] The plurality of FBG sensors located at various locations of the pipe senses temperature signal and transmit the temperature signal with location to a processor. The processor receives and process the temperature signal with location in the form of location and temperature data of the pipe. Such data is displayed so that operator comes to know in case of any abnormality.
[0017] The processor comprises an analyzing unit to analyze the location and temperature data to alarm in case of temperature nearing or surpassing the threshold.
[0018] In another embodiment, the plurality of the FBG sensors are coupled to the processor via a one or more fiber optic cable.
[0019] In still another embodiment the pipe carrying hot fluid is blow pipe carrying blast.
[0020] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
[0021] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0022] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0023] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
Fig. 1 illustrates cross section of a blast furnace with a blowpipe.
Fig. 2 illustrates Layout of a system for determining health of a pipe carrying hot fluid in accordance with an embodiment of the invention.
Fig. 3 illustrates Temperature Calibration of FBG Sensor in accordance with an embodiment of the invention.
Fig. 4 illustrates Temperature Profiling Exercise in accordance with an embodiment of the invention.
[0024] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENTS
[0025] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0026] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0028] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0029] Shown in Figs. 2 is a system (100) for determining temperature of various locations of a pipe (104) carrying hot fluid. This temperature determination will further ascertain health of the pipe. In an embodiment, the pipe (104) disclosed here is a blow pipe carrying hot blasts.
[0030] The system (100) comprises a plurality of FBG sensors (108, 1-4) located at various locations of the blow pipe (104) to sense temperature signal and transmit the temperature signal with location to a processor (112). The processor (112) is coupled to the plurality of FBG sensors (108, 1-4) to receive and process the temperature signal with location in the form of location and temperature data of the blow pipe (104).
[0031] The plurality of the FBG sensors (108, 1-4) are coupled to the processor (112) via a one or more fiber optic cable (116). The one or more fibre optic cable (116) acts as the carrier of input broad band light as well as the characteristic reflected light (rest of the light gets transmitted). The processor (112) sends the input light) through fibre optic cable (116) and at the FBG sensors (108, 1-4) wavelength of light, which matches the grating in the FBG gets reflected. The processor (112) receives the reflected light. The processor (112) analyses the wavelength (?) of the reflected light. The wavelength of the reflected light tends to shift proportionally as the temperature changes. Hence, the processor monitors the shift in wavelength for temperature in real time. Also, the processor (112) processes the temperature signal and location of the sensor with respect to time, in form of location and temperature data and the processor send the location and temperature data to a display unit (120) which is coupled to the processor for displaying the temperature and location date it in real time.
[0032] Such location and temperature data can be in the form of trend of temperature profile overtime. Such location and temperature data helps operator to know the status of temperatures of the blow pipe at various locations.
[0033] High temperature and dust pose the challenge the implementation of FBG sensors in blowpipe. To avoid dust the one or more fibre optic cable (116) is spliced directly, instead of connector joints. To avoid temperature the fibre is carried in a conduit (118), which is capable of withstanding high temperature.
[0034] In some embodiments, the processor (112) may further include an analyzing unit (124) to analyze the location and temperature data to alarm in case of temperature in blow pipe nearing or surpassing the threshold. The alarming can be done via the display unit (120) or in a form of a beacon.
[0035] The FBGs are configured to sense temperature signal and transmit the temperature signal to with location a processor (112) on a real-time basis hence the system (100) displays temperature of various locations of a pipe (104) on a continuous basis. This enables the online or real time continuous monitoring of the condition of pipes (104) of blowpipes in the hostile environment such as blast furnace.
TEMPERATURE PROFILING BY FBG SENSOR:
[0036] The FBG sensors can carry many sensors in a single fibre. The sensing portion will be a small portion only and measurement can be done from all the sensors simultaneously. Another unique feature of FBG is that it is tiny and works irrespective of hazardous environment.

[0037] Fibre Bragg Grating (FBG) sensor works on the principles of Bragg’s Grating. The sensor is a special structure in the fibre with periodic perturbation in refractive index. The periodic perturbation of refractive index makes that portion of fibre, a filter for a frequency of light whose wavelength matches with the periodicity of the perturbation in the fibre.
Bragg Wavelength (?b) = 2*neff *?
[0038] Where, neff: Refractive Index, ?: spacing of gratings.
[0039] This property of Bragg grating and thermal expansion property of objects together makes the FBG a very sensitive sensor of temperature. Under heating, the spacing between the perturbation will change, hence it will result in reflection of different wavelength. The shift in wavelength of reflection is the measure of temperature.
[0040] In an embodiment the blowpipe temperature ranges from 300°C, hence the FBG should have stability in high temperature. In this maximum temperature of the FBG can measure is 700°C. In the embodiment shown in Fig. 2, copper coated fibre is used to make them capable of withstanding at 700°C.
[0041] The FBG sensors are calibrated against a thermocouple as shown in Fig. 3. The accuracy found is 99%. For various know temperature, the wavelength that is reflected by the FBG sensor is analysed by the processor (112). Shift in wavelength is plotted against the actual thermocouple temperature, where the maximum error is found to be only ±1%.
HOT SPOT EXERCISE:
[0042] Again, shown in Fig. 2 the FBGs sensor (108, 1-4) is embedded onto the blowpipe (104) surface by making a small groove of size 2 mm depth, which allows the fibre (116) to get seated properly. The FBG sensor (108) is then fixed permanently using high temperature Epoxy. During rise in surface temperature the Fibre tends to elongate, which results in Bragg wavelength shift. The Bragg wavelength shift is proportional to the surface temperature and thus, the temperature measurement is accomplished.
[0043] The sensors are located equidistantly. A hot spot is created deliberately by gas cutting torch, which is closer to the sensor 108-3 & 108-4. But the hot spot is made to be 300 mm away also has made significant change in the sensor 108-1 & 108-2 as shown in FIG. 4. The temperature result of the four sensors during the heating exercise. During this hot spot exercise, the hot spot of only 100°C was created to sense the effectiveness of the farthest and closest FBG sensor. The farthest (300 mm distance) sensor for the actual hotspot shows only a small rise (i.e. sensor 108-1 & 108-2) with respect to the exact hotspot location (sensors 108-3 & 108-4), whereas the closest one shows a sharp rise in temperature. The slope of rise in temperature is higher for the closest sensor. Hence the slope in rise of temperature can provide location information of the hot spot, qualitatively.
[0044] It is to be appreciated that the location of the processor (112) and the display (120) can be at remotely located from where the monitoring can be done. In case of any eventualities of abnormality displayed by the display unit in the blow pipe, the operator can address the issue such as crack propagation or seepage or decay on the blowpipe with near location.
[0045] The pipes such as blow pipes carrying hot gases have temperature at its surfaces one the pertinent attributes vis a vis health of such pipes is concerned. Hence the system (100) focuses on assessing the temperature of the pipe on its surface. Abnormal rise of the temperature of the pipe at some locations is result of crack or seepage or decay of the pipe. Hence such spots need to be identified and addressed for maintaining its health.
[0046] There may be other variations of pipes carrying hot fluids are where such system (100) can be deployed.
ADVANTAGES
[0047] The system (100) enables remotely monitoring temperature profile of blowpipe. In case of abnormalities blowpipe, the data can be utilized for immediate alarm or SMS communication to the operators.
[0048] The system helps in online health monitoring of blowpipe to avoid unexpected failure.
[0049] The system helps in online continuous temperature profiling of the blowpipe reflects the actual condition of the blowpipe on continuous basis.
[0050] The system can be retrofitted in existing blowpipes to enable online health monitoring, which helps in better predictive maintenance.
[0051] Furthermore, those skilled in the art can appreciate that the above description does not provide specific details of the manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art can choose suitable manufacturing and design details.
Further, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Claims:

1. A system (100) for determining health of a pipe (104) carrying hot fluid, the system (100) comprising:
a plurality of FBG sensors (108, 1-4) located at various locations of the pipe (104) to sense temperature signal and transmit temperature signal with location to a processor (112);
the processor (112) being coupled to the plurality of FBG sensors (108) to receive and process the temperature signal with location in a form of location and temperature data of the pipe (104) and send the location and temperature data to a display unit (120); and
the display unit (120) being coupled to the processor (112) to display location and temperature data.
2. The system (100) as claimed in claim 1, wherein the processor (112) further comprises an analyzing unit (124) to analyze the location and temperature data to alarm in case of temperature nearing or surpassing threshold.
3. The system (100) as claimed in claim 1, wherein the plurality of the FBG sensors (108, 1-4) are coupled to the processor (112) via a one or more fiber optic cable (116).
4. The system (100) as claimed in claim 1, wherein the pipe (104) carrying hot fluid is blow pipe carrying blast.