Claims:WE CLAIM:
1. A method for non-destructive testing to determine a location, and an axial length of a shallow defect in a tie rod (103) encased within a steel buckstay, the method comprising:
generating, by a transmitter (306), an ultrasonic pulse wherein a wavelength for the ultrasonic pulse is greater than three times of a diameter of the tie rod (103);
receiving, by a receiver (304), a reflected wave;
generating, by a processor (302), a time domain signal based on the reflected wave, wherein the processor (302) is coupled to the receiver (304) and the transmitter (306); and
determining, by the processor (302), using the time domain signal, the location of the shallow defect in the tie rod (103) based on a time of arrival of a first defect echo (ti) and an axial length of the shallow defect in the tie rod (103) based on time between the first defect echo (ti) and a second defect echo (te).
2. The method as claimed in claim 1, wherein the axial length and a maximum defect amplitude is plotted on a defect sizing chart to compute a % cross section of the defect.

3. The method as claimed in claim 1, wherein the transmitter (306) is mounted coaxially at one end of the tie rod (103) and generates square wave pulses.

4. The method as claimed in claim 1, wherein the receiver (304) is mounted perpendicular to the axis of the tie rod (103) on a circumferential surface of the tie rod.

5. The method as claimed in claim 1, wherein the spacing between the transmitter (306) and the receiver (304) is kept to a minimum.

6. A system for non-destructive testing to determine a location, and an axial length of a shallow defect in a tie rod (103) encased within a steel buckstay, the system comprising:
a transmitter, wherein the transmitter (306) is configured to generate an ultrasonic pulse, wherein a wavelength for the ultrasonic pulse is greater than three times of a diameter of the tie rod (103);
a receiver (304) is configured to receive a reflected wave; and
a processor (302) coupled to the transmitter (306) and the receiver (304), wherein the processor (302) is configured to:
generate a time domain signal based on the reflected wave; and determine using the time domain signal, the location of the shallow defect in the tie rod (103) based on a time of arrival of a first defect echo (ti) and an axial length of the shallow defect in the tie rod (103) based on time between the first defect echo (ti) and the second defect echo (te).
7. The system as claimed in claim 6, wherein the axial length and a maximum defect amplitude is plotted on a defect sizing chart to compute a % cross section of the defect.

8. The system as claimed in claim 6, wherein a transmitter (306) is mounted coaxially at one end of the tie rod (103) and generates square wave pulses.

9. The system as claimed in claim 6, wherein the receiver (304) is mounted perpendicular to the axis of the tie rod (103) on a circumferential surface of the tie rod.

10. The system as claimed in claim 6, wherein the spacing between the transmitter (306) and the receiver (304) is kept to a minimum.
, Description:TECHNICAL FIELD
[001] The present disclosure in general relates to the field of non-destructive testing. More particularly, the present subject matter relates to a system and method for non-destructive testing to determine a location, and an axial length of a shallow defect in a tie rod encased within a steel buckstay.
BACKGROUND
[002] Generally, coal is processed into coke in coke ovens through the process of destructive distillation. The coal is fed into the coke ovens in the form of stamped cakes of dimension slightly smaller than that of the ovens. During the coke making process, the coal cakes experience swelling which exert pressure on the side walls of the ovens. The sidewalls of the coke ovens experience buckling loads due to this. The walls of coke ovens are civil structures are made of refractory bricks. It is well known that civil structures tend to have poor tensile load bearing capacity. Tie rods are used in coke oven batteries as post tensioning members for the refractory side-walls. This process enhances the tensile strength of the side walls of the coke oven. Tie rods are approx. about the same length as that of the coke oven (15m long and 40mm diameter). The coking process results in release of highly corrosive gasses which may cause corrosion attack to the tie rods. The tie rods are thus made of corrosion resistant materials such as 42CrMo4 steel grade. In addition, the tie rods may be susceptible to water ingress through the walls of the ovens. The tie rods are thus encased within a steel buckstay which is a hollow steel channel of square cross-section. The buckstay generally experiences cracks or erosion over its service life and this consequently causes water ingress: which in conjunction with the corrosive gasses from the coking process result in corrosion of the tie rods. The corrosion of the tie rod poses a threat of in-service failure of the tie rods through necking at the corroded regions.
SUMMARY
[003] Before the present a system and method for non-destructive testing of a tie rod encased within a steel buckstay are described, it is to be understood that this application is not limited to a particular system and method for non-destructive testing of a tie rod encased within a steel buckstay, as there may be multiple possible embodiments, which are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular implementations, versions, or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to a system and method for non-destructive testing of a tie rod encased within a steel buckstay. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.
[004] In one embodiment, a system for non-destructive testing of a tie rod encased within a steel buckstay. The system comprises, a transmitter, a receiver and a processor. In one embodiment, the transmitter is configured to generate an ultrasonic pulse and the receiver is configure is to receive a reflected wave. In one example, a wavelength for the ultrasonic pulse is greater than three times of a diameter of the tie rod. Further, the processor is configured to generate a time domain signal based on the reflected wave and determine using the time domain signal, the location of the shallow defect in the tie rod based on a time of arrival of a first defect echo and an axial length of the shallow defect in the tie rod based on time between the first defect echo and the second defect echo.
[005] In one embodiment, a method for non-destructive testing of a tie rod encased within a steel buckstay. The method comprising generating, by an a transmitter, an ultrasonic pulse wherein a wavelength for the ultrasonic pulse is greater than three times of a diameter of the tie rod. Upon generating, the method comprises receiving, by a receiver, a reflected wave. Further to receiving, the method comprises generating, by a processor, a time domain signal based on the reflected wave, wherein the processor is coupled to the receiver and the transmitter. Subsequent to generating, the method comprises determining, by the processor, using the time domain signal, the location of the shallow defect in the tie rod based on a time of arrival of a first defect echo and an axial length of the shallow defect in the tie rod based on time between the first defect echo and a second defect echo.
BRIEF DESCRIPTION OF DRAWINGS
[006] The foregoing detailed description of embodiments is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present subject matter, an example of construction of the present subject matter is provided as figures; however, the present subject matter is not limited to the specific a system and method for non-destructive testing of a tie rod encased within a steel buckstay disclosed in the document and the figures.
[007] The present subject matter is described in detail with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer various features of the present subject matter.
[008] Figure 1 illustrates a coke oven battery, in accordance with an embodiment of the present subject matter.
[009] Figure 2 illustrates shallow defects in rod-like structures, in accordance with an embodiment of the present subject matter.
[0010] Figure 3 illustrates a system for non-destructive testing of a tie rod encased within a steel buckstay, in accordance with an embodiment of the present subject matter.
[0011] Figure 4 illustrates a raw guided wave signal from a defect free rod sample, in accordance with an embodiment of the present subject matter.
[0012] Figure 5 illustrates envelope of filtered signals, in accordance with an embodiment of the present subject matter.
[0013] Figure 6 illustrates methodology used for calculation of the axial location of defect and its length, in accordance with an embodiment of the present subject matter.
[0014] Figure 7 illustrates a defect sizing curve, in accordance with an embodiment of the present subject matter.
[0015] Figure 8 illustrates a method for non-destructive testing of a tie rod encased within a steel buckstay, in accordance with an embodiment of the present subject matter.
DETAILED DESCRIPTION
[0016] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any a system and method for non-destructive testing of a tie rod encased within a steel buckstay and, similar or equivalent to those described herein may be used in the practice or testing of embodiments of the present disclosure, the exemplary, a system and method for non-destructive testing of a tie rod encased within a steel buckstay and are now described.
[0017] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments described, but is to be accorded the widest scope consist in this regard, in a generic sense.
[0018] As described above, there is always a threat of in-service failure of the tie rods through necking at the corroded regions and hence need to be monitered. Conventional ultrasonic guided wave based technique has been described in M. D. Beard, Guided Wave Inspection of Embedded Cylindrical Structures, PhD dissertation, Dept. of Mech. Eng., Imperial College of Sci. Tech. and Med., London (2002) and B. J. Buys, Rock Bolt Condition Monitoring using Ultrasonic Guided Waces, MEng. Dissertation, Dept. of Mech. and Aero. Eng., Univ. Pretoria, South Africa (2008) for detection of corrosion defects in rock bolts which are used as reinforcing members in underground mines. The typical type of defects experienced in rock bolts are thinning and reduction in length of the end tips of the rock which in effect reduce the length of the rock bolt. In addition, the typical length of the rock bolts are in the range of about 3 to 4 meters. The technique described in these disclosures fail when the length of the rod increases beyond 5 meters as reported in M. D. Beard, Guided Wave Inspection of Embedded Cylindrical Structures, PhD dissertation, Dept. of Mech. Eng., Imperial College of Sci. Tech. and Med., London (2002).
[0019] Further, GB201702166D0, US4092868A describes a low frequency guided wave method utilizing SH modes with a central frequency of about 250 kHz for detecting corrosion defects in pipes. Although the geometry of the object in this invention is different from that of rods which are the object of the present disclosure; the limitations of the invention are evident in the sense that the technique is sensitive for corrosion defects with very small dimensions extending up to only a few millimeters in both lateral and depth.
[0020] In the present subject matter, embodiments of a system and method for non-destructive testing of a tie rod encased within a steel buckstay, is disclosed. In other words, the present subject matter discloses a system and method for in-situ non-destructive detection of shallow defects in long rod-like members using ultrasonic guided wave. Further, the present subject matter also relates to in-situ detection of reduced cross-section area of shallow nature on tie rods of coke oven batteries of an integrated steel plant.
[0021] Now referring to the figures, Figure 1 illustrates a coke oven battery (101) consisting of a series of coke ovens (102) and each coke oven (102) having a pair of tie rods (103) for reinforcing the lateral walls of the coke oven. The length of the tie rods (103) being slightly longer than that of the coke ovens (102). The tie rods contained within a metallic buckstay (104) which is a hollow channel which protects the tie rods within from water seepage which may cause corrosion of the tie rods.
[0022] Referring next figure, Figure 2 illustrates shallow defects in rod-like structures. In one example a defect may be understood as shallow defect when a defect length/diameter of the defect region > 20 & defect slope <20 degree. Further, the shallow defect can be characterized with four major dimensions as shown in figure. L being the total length of the rod having original diameter ?. The defect region being characterized by the total defect length Ld, neck length Ln, reduction slope length Ls, and the average neck diameter dn.
[0023] Referring now to Figure 3, a system for non-destructive testing of a tie rod encased within a steel buckstay, in accordance with an embodiment of the present subject matter may be described. Figure 4 illustrates a raw guided wave signal from a defect free rod sample, in accordance with an embodiment of the present subject matter. Figure 5 illustrates envelope of filtered signals, in accordance with an embodiment of the present subject matter. Figure 6 illustrates methodology used for calculation of the axial location of defect and its length, in accordance with an embodiment of the present subject matter. In the subsequent, the present subject matter is explained with reference to the figures 3-6.
[0024] In one example the system may be implemented as a standalone system or connected to a network. Furthermore, the system may be communicatively coupled to a database for storing data and a display system for displaying data.
[0025] In one embodiment the system comprises a processor (302) connected to a transmitter (306) and receiver (304). Further, the transmitter (306) is mounted coaxially at one end of the tie rod (103) and generates square wave pulses. Furthermore, the receiver (304) is mounted perpendicular to the axis of the tie rod (103) on a circumferential surface of the tie rod and comprises 24 kHz P-wave probes. Additionally, the spacing between the transmitter (306) and the receiver (304) is kept to a minimum. In one embodiment the processor (302) may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and/or any devices that manipulate signals based on operational instructions. Among other capabilities, the at least one processor 202 may be configured to fetch and execute computer-readable instructions stored in the memory.
[0026] In one embodiment, the system may include an input/output (I/O) interface, and a memory.
[0027] In one embodiment, the I/O interface may include a variety of software and hardware interfaces, for example, a web interface, a graphical user interface, and the like. The I/O interface may allow the system to interact with the user directly or through the client devices. Further, the I/O interface may enable the system to communicate with other computing devices, such as web servers and external data servers (not shown). The I/O interface can facilitate multiple communications within a wide variety of networks and protocol types, including wired networks, for example, LAN, cable, etc., and wireless networks, such as WLAN, cellular, or satellite. The I/O interface may include one or more ports for connecting a number of devices to one another or to another server. In one implementation, at first, a user may use a device to access the system via the I/O interface. The user may register using the I/O interface in order to use the system. In one aspect, the user may access the I/O interface of the system and the device for obtaining information or providing input information such as monitoring. In one implementation the system may automatically provide information to the user through I/O interface, and the display device.
[0028] In embodiment, the memory may include any computer-readable medium or computer program product known in the art including, for example, volatile memory, such as static random access memory (SRAM) and dynamic random access memory (DRAM), and/or non-volatile memory, such as read only memory (ROM), erasable programmable ROM, flash memories, hard disks, optical disks, and magnetic tapes. The memory, amongst other things, serves as a repository for storing data processed, received, and generated by one or more of the modules. The memory may include data generated as a result of the execution of one or more instructions.
[0029] In one embodiment, during execution, the transmitter (306) generates an ultrasonic pulse, for example, a square wave pulse. In one example, a wavelength for the ultrasonic pulse is greater than three times of a diameter of the tie rod (103). Further to generation, the receiver (304) receives a reflected wave.
[0030] A raw reflected wave signal from a defect free rod sample is shown in figure 4. The direct received wave (402) has a time span of about 0.5 milliseconds. This is caused due to the reverberation of guided wave mode produced in the rod and will exist till it is attenuated and dies down. The direct received wave acts as a blind zone as reflection from any defects within that range will superimpose with the direct received wave and will be indistinguishable. For tie rods (103) of the present subject matter, made of 42CrMo4 steel, this blind zone works out to be about 1.2 meters. This is insignificant compared to the tie rods of length greater than 10 meters which are the scope of this disclosure. In addition, the initial 1.2meters of such long rod members would normally be visible to spot the presence of any defect in that range. The actual applicability of the disclosure being the defects which are further along the length of the rod and hidden from plain sight. The raw guided wave signal further consisting of the end reflection echo (404) and having travelled twice the length of the rod. Any defects would show up as additional peaks between the direct received wave (402) and the end reflection echo (404).
[0031] Thus upon receiving, the processor (302) generates a time domain signal based on the reflected wave. In one other example, the time domain signals generated to improve signal quality. In other example, generating may comprise a basic band pass FFT filter applied to the reflected wave with the filter limits set between 20 kHz and 40 kHz and the envelope of the filtered signals is shown in FIG. 5.
[0032] Further to generating, the processor (302) may determine using the time domain signal, the location of the shallow defect in the tie rod (103) based on a time of arrival of a first defect echo (ti) and an axial length of the shallow defect in the tie rod (103) based on time between the first defect echo (ti) and the second defect echo (te). Referring to figure 6, the time of arrival of the defect echoes (402-ti) can be used to pinpoint the position of the defect along the axial length of the rod. In addition, echoes are obtained from the start and end of the defect (first and second) can be used to determine the axial length of the defect (ti-te).
[0033] In one implementation of the present subject matter, few defect conditions were artificially recreated for experimental validation. Three samples: one without any defect (?=40mm), one with 20% reduction in cross section (dn=32mm) and one with 50% reduction in cross section (dn=20mm) are prepared. Further, the location and length of the defects as determined using the present subject matter as described above. Furthermore, the experimental results are detailed in Table 1. The measurement results are within an accuracy of ±5% of the actual values.
TABLE 1: Experimental results from lab scale tie rod samples.
Tie Rod Sample Axial position of defect from end Axial length of defect
Actual (mm) From GW signal (mm) %Error Actual (mm) From GW signal (mm) %Error
20% Defect 2300 2380 +3.47 450 439 -2.44
50% Defect 2350 2460 +4.68 470 450 -4.25
[0034] Conventionally, it is observed that for a constant total defect length, reduction slope length and neck length; the reflection amplitude from sub-wavelength defects tends to follow a linear increase with decreasing neck diameter. Such a curve is usually used in typical guided wave applications for defect sizing. In case of sub-wavelength defects however, such a curve can be misleading as the reflection amplitude is not just a function of the neck diameter but also its length.
[0035] Now referring to next figure, figure 7 illustrates a defect sizing curve generated by additional FEM studies. It can be seen in figure 7 that at neck length to wavelength ratios greater than 2.5: the conventional inference stands true. Things however get more complicated when the neck length to wavelength ratio falls below 2.5 and hence the need for a more elaborate defect sizing curve such as one disclosed in figure 7. In one embodiment, the axial length and a maximum defect amplitude is plotted on a defect sizing chart to compute a % cross section of the defect. In one example, if the % cross section of the defect is above a predetermined threshold, such as 60% then the tie rod is discarded
[0036] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include the following:
[0037] Some embodiments of the present subject matter disclose a system and method for detecting defects which are extremely shallow and having lateral dimensions over few hundred millimeters up to a couple of meters and depth in the range of a few millimeters in long rod-like structures having length in the range of 15-20 meters.
[0038] Some embodiments of the present subject matter disclose a system and method for sizing defects which are extremely shallow and having lateral dimensions over few hundred millimeters up to a couple of meters and depth in the range of a few millimeters in long rod-like structures having length in the range of 15-20 meters.
[0039] Some embodiments of the present subject matter disclose a system and method for online monitoring of the condition of long rods for detection and sizing of defects which are extremely shallow and having lateral dimensions over few hundred millimeters up to a couple of meters and depth in the range of a few millimeters in long rod-like structures having length in the range of 15-20 meters.
[0040] Referring now to Figure 8, a method for non-destructive testing to determine a location, and an axial length of a shallow defect in a tie rod (103) encased within a steel buckstay is shown, in accordance with an embodiment of the present subject matter.
[0041] The order in which the method 300 for non-destructive testing to determine a location, and an axial length of a shallow defect in a tie rod (103) encased within a steel buckstay as described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method or alternate methods. Additionally, individual blocks may be deleted from the method without departing from the spirit and scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof. However, for ease of explanation, in the embodiments described below, the method 300 may be considered to be implemented in the above described system.
[0042] At block 802, an ultrasonic pulse is generated by an a transmitter (306), In one example, a wavelength for the ultrasonic pulse is greater than three times of a diameter of the tie rod (103);
[0043] At block 802, a reflected wave is receiving, by a receiver (304).
[0044] At block 802, a time domain signal is generated by a processor (302) based on the reflected wave. In one example, the processor (302) is coupled to the receiver (304) and the transmitter (306).
[0045] At block 802, the location of the shallow defect in the tie rod (103) based on a time of arrival of a first defect echo (ti) and an axial length of the shallow defect in the tie rod (103) based on time between the first defect echo (ti) and a second defect echo (te) is determined by the processor (302) using the time domain signal,
[0046] Although implementations for s and a system and method for non-destructive testing of a tie rod encased within a steel buckstays have been described in language specific to structural features and/or system, it is to be understood that the appended claims are not necessarily limited to the specific features or described. Rather, the specific features are disclosed as examples of implementations.