Battery-powered FPGA-based embedded system for ultrasonic pipe inspection and gauging systems.

A water-immersible battery-powered field programmable gate array (FPGA)-based embedded system is a most suitable tool required to check the health of the pipe operating under harsh conditions. A novel, water-immersible, battery-powered, compact, stand-alone and FPGA-based embedded system has been designed and developed, which is suitable for ultrasonic pipe inspection and gauging systems useful for major applications in the petrochemical and nuclear industries. The developed FPGA-based embedded system is operated with lithium-ion batteries for more than five hours, and the IP67-grade system modules are capable of floating inside the pipe along with the flow of oil or water. Such applications require a system that is capable of acquiring large data under water-immersed conditions of battery-operated instrumentation. The onboard Double Data Rate (DDR) RAM of the FPGA module has been utilized for the storage of the 256 MBytes streams of A-scan data during evaluation for more than five hours. The experimentation of the battery-powered embedded system was carried out inside two samples of SS and MS pipes with the help of the in-house developed nylon inspection-head installed with two sets of spring-loaded eight Teflon balls and two 5 MHz focused immersion transducers placed along the circumference at 180° apart. This paper provides brief details of the design, development, and evaluation phases of the battery-powered water-immersible embedded system suitable for ultrasonic pipe inspection and gauging, which can be expanded to 256 channels for demanding applications.

FPGA: Field programmable gate array-based four-channel embedded system for ultrasonic imaging of under-water concrete structures.

Non-destructive testing is needed for the evaluation of quality and safety of concrete structures in the field of civil engineering. The imaging of concrete/reinforced cement concrete structures (RCC) is a challenging task due to the non-homogeneous properties of the concrete material. To address this challenge, a novel real-time, re-configurable, four-channel embedded system has been designed and developed to image the internal details of the concrete samples using the water immersion pulse-echo (PE) mode under automation, which needs access from one side of the structure. The system performs data acquisition (DAQ) of the amplified echo signals under the control of the computer via a universal serial bus interface. A graphical user interface (GUI) has been developed using C# in a Visual environment, for image acquisition and control of the DAQ parameters. The performance of the system has been evaluated by acquiring B-Scan images of three types of concrete test blocks having side drilled holes (SDHs) and simulated inclusions embedded in concrete blocks of M20 grade using a linear array of 92 kHz water immersion transducers operating in under-water PE mode. The acquired B-Scan images revealed the internal details of the concrete test blocks with sizing of the SDHs and inclusions. Therefore, the developed four-channel ultrasonic imaging system can visualize the internal details of under-water concrete structures, such as bridges and sea links, with the help of corresponding 2-D cross-sectional images, acquired using the developed system.

Design and development of water-immersible two-channel high-voltage spike pulser for under-water inspection and gauging of pipes.

A water-immersible two-channel high-voltage (HV) spike pulser has been designed, developed, and mounted inside the IP 67 (Ingress Protection 67) grade enclosure, and it is suitable for the ultrasonic Pipe Inspection and Gauging (PIG) system utilized in the petrochemical industry. Such a critical and strategic application requires a portable, miniaturized, and water-immersible water-tight pulser module, which resides inside the pipe carrying water or liquid petrochemicals. The developed spike pulser printed circuit board (PCB) generates a HV negative spike pulse up to -300 V and 100 ns half-amplitude pulse width, required for the energization of ultrasonic immersion transducers of 5-10 MHz frequency. The water-immersible pulser is mounted inside the water-tight IP 67 grade enclosure, and it is operated through an external DC power supply/lithium batteries. The evaluation of the module was carried out using a two-channel water-immersible HV spike pulser, in-house developed preamplifier, and inspection head supported by four sets of spring-loaded Teflon balls for centering, and the inspection head carries two ultrasonic immersion transducers placed 180° apart and a sample SS pipe with a length of 400 mm, Inner Diameter of 200 mm, and Wall Thickness of 9 mm. The two-channel pulser module was evaluated in water to measure the dimensions of the sample SS pipe. This two-channel water-immersible novel spike pulser has dedicated circuitry, and each channel is a standalone PCB and it operates through external LV and HV DC supplies. The module can be scaled up to 256 channels for dimension measurement and flaw detection of long length pipes. In the absence of any literature available on the water-immersible pulser for PIG systems, the present two-channel pulser module has been designed and developed, and the module was evaluated by gauging of the SS pipe from inside. This paper provides the details of the water-immersible HV spike pulser module suitable for the gauging of metallic pipes.

Design and development of ultrasonic bipolar square-wave pulser for non-destructive testing of concrete structures.

This paper provides design and development details of the generation of bipolar High Voltage (HV) square wave pulses for the excitation of low frequency ultrasonic transducers. Such a circuit is required for the purpose of ultrasonic inspection of components, particularly where high energy is required to insonify the attenuative medium, such as concrete. A HV (±350 V) square wave pulse has been generated by an ultrafast complementary Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) pair, which is driven by high speed MOSFET drivers. The generated bipolar square wave pulse has been utilized to energize a 108 kHz ultrasonic transducer to operate in the pulse-echo mode for the evaluation of a concrete test block. The receiver amplifier filters the received low-amplitude echo signals, which are reflected back from a discontinuity, and amplifies further for signal to noise ratio enhancement. The pulser board designed has been tested and evaluated for its functionality to measure ultrasonic velocity in the highly attenuative concrete medium up to a depth of 1 m. The measured value of acoustic velocity was compared with the value obtained from the commercially available ultrasonic pulse velocity instrument, and the values obtained are within ±5%.

Real-time imaging of immersed fuel-sub assemblies using multi-channel ultrasonic camera.

The novel circular-array based real-time ultrasonic imaging technique using an ultrasonic camera has been proposed in this paper for imaging of a fuel sub-assembly (FSA) of a fast breeder reactor. The developed ultrasonic camera-based system provides real-time images of the top-head region of the FSA in a high-temperature environment. For the circular-array based ultrasonic imaging, the entire circular-array has been divided into the various arcs, and the address-based analog multiplexing scheme has been proposed in such a way that all channels of the specific arc are selected concurrently (transducer excitation, data acquisition, and data processing and transferring). Various data processing algorithms are proposed and implemented for multi-channel ultrasonic data processing in real-time. For the experimentation, the complete 18-channel ultrasonic camera system has been designed, developed, and evaluated in the laboratory. The performance evaluation of the developed circular-array based ultrasonic camera has been shown by acquiring the real-time images of the water-immersed dummy FSA in elevated temperature. Furthermore, both qualitative visualization and quantitative measurements of growth and bowing of the FSA top-head are presented.

Reconfigurable hardware implementation of coherent averaging technique for ultrasonic NDT instruments.

The paper proposed a novel hardware (FPGA) implementation of the coherent averaging architecture for the reconfigurable ultrasonic NDT system. The proposed hardware architecture uses the addressing based shifting technique for the addition operation and Radix-2 non-restoring algorithm for the division operation. Since the amount of hardware required by the proposed averaging scheme is independent of the number of averages, it supports on-the-fly control on the number of averages. Compared to conventional architecture, it provides 96% reduction in memory storage, 98% reduction in the number of adders, and 32% reduction in the processing time for the case of 64 coherent averages. For the experimentation, the ultrasonic imaging system designed and developed by the authors has been utilized. The developed system further supports dynamic on-line reconfiguration of the analog front-end hardware, real-time data acquisition, real-time hardware based data processing, and data transfer operations. The performance of implemented coherent averaging has been presented by various applications such as removal of RF random false-echoes, smoothing of A-scan waveforms and speckle removal of B-scan images.

Mitigating artifacts by data driven identification & correction of rotational misalignment in gamma ray computed tomography.

Industrial Computed Tomography (ICT) is a radiation based cross sectional imaging technique that requires a sample to be manipulated precisely in a specific geometry to acquire analytically useful data. Unlike medical CT, industrial CT may require use of gamma radiation from radio-isotopes like Co60, Cs137 etc. having higher energy radiations for penetrating through higher density and thickness of material under inspection. Data acquisition in ICT involves use of a mechanical manipulator to rotate either the specimen or the source and detectors assembly in circular and linear geometry. Misalignment in mechanical set-up leads to significant artifacts in CT image. The effects may be even more pronounced in data acquired with discrete detector as against Linear Detector Array (LDA) because of certain built-in mechanical integrity associated with LDA. This paper discusses cross correlation based software correction method for combination of gamma ray source and NaI (Tl) scintillation detector based transmission ICT system in parallel beam CT geometry. The proposed correction does not require calibration of the set-up and any prior knowledge of the sample geometry or composition. This data driven correction yields improved CT reconstruction with limited data. The method is demonstrated with a mathematical simulation and applied to experimental data for validation.

Real time implementation of empirical mode decomposition algorithm for ultrasonic nondestructive testing applications.

A real time empirical mode decomposition (EMD) algorithm based ultrasonic imaging system has been developed for non-destructive testing (NDT) applications. It is difficult to implement the EMD based signal processing algorithm in real time because it is totally a data-driven process which comprises numerous sifting operations. In this paper, the EMD algorithm has been implemented in the visual software environment. The EMD implementation encompasses two types of interpolation methods: piecewise linear interpolation (PLI) and cubic spline interpolation (CSI). The cubic spline tridiagonal matrix has been solved by using the Thomas algorithm for real time processing. The total time complexity functions for both the implemented PLI and CSI based EMD methods have been computed. For the signal filtering, the partial reconstruction algorithm has been adopted. The baseline correction and noise filtering applications have been presented using an EMD based visual software. The real time practicability and the efficiency of this method have been validated through ultrasonic NDT experimentation for improvement in the time domain resolution of the ultrasonic A-scan raw data. The practical results show that in the noisy environment, it is possible to enhance the signal-to-noise ratio for the visualization and identification of ultrasonic pulse-echo signals in real time.

Ring artifact correction in gamma-ray process tomography imaging.

Ring artifacts have been studied for X-ray based Computed Tomography (CT) systems but not on γ-ray based in-situ applications. This paper discusses application of recently proposed automatic ring artifact reduction method (Yoon et al., 2016) on previously obtained experimental projection data from a γ-ray based Industrial Process Tomography (IPT) system for a prototype catalytic column. Studies include qualitative and quantitative evaluation of the method. It is observed that ring artifacts are suppressed without loss of significant information in γ-ray PT images.