NDT system

1.    Introduction

NDT system is electronic device used to detect defects in products from a variety of metal and non-metallic materials by non-destructive testing. By defects means discontinuity or homogeneity of the structure, areas of corrosion damage. Flaw detectors are used in various fields of mechanical engineering, chemical industry, oil and gas, energy, construction, research laboratories to determine the properties of solids and molecular properties and in other industries are used to control parts and pieces, welded, soldered and glued joints.

 

1.1 Overview:

Nowadays, in our world we have several million kilometers of different type of pipes. Pipes are used to transport various types of liquid like oil, water for heating premises, isolated and buried under the ground or water. Moreover metal pipe is widely used in construction as a structural profile. Pipes are commonly joined by welding, using threaded pipe and fittings. And during the installation and joining the pipes, we cannot provide the information about the any leakage and welding defects from these pipelines. After a few years by detecting the spillage and corrosion in the metal pipes it can be environmentally hazardous and expensive to maintain, therefore preventive measures are taken to detect the any flaw in pipelines before they come of. Non-destructive testing system takes a significant role in the all type of construction and, oil and gas area. The damages that occur inside the pipeline it is not only about waste of oil or gas, it also can be result of pollution of our environment. That can seriously affect to human nature. Non-destructive testing system detects the flaw or any leakage inside the pipeline without any disrupting and destroying which will be very costly and time consuming, NDT system which is use ultrasonic waves is very convenient; the system is very easy in use, and cheap versus with other ways.

Ultrasonic uses high frequency for transmitting the signal into a material to detect any corrosion or to locate changes into material properties. The most common used ultrasonic testing technique is pulse echo. Where the sound wave transmitted into the pipeline or any material and reflected back to the receiver switch.

From block diagram that shown above, we learned that power supply which we will use in this project has to supply +/-150 DC voltage. We supply the circuit with small DC voltge which is converted to AC and back to high DC voltage using boost converter. Power Amplifier is needed to the signal that is generated from tone burst generator. The amplified signal is needed to excite the transducers. And the signal go to the  transceiver switch that transmits the signal to ultrasonic sensor throw PIC controlled switch  than pulse echo goes back to transceiver switch  reflected by the flaw inside the pipeline. Echo amplifier is very interesting and important stage in the system. The reflected signal leaving the transceiver switch is very low, so it needs to be amplified by echo amplifier using op-amp circuitry. Band pass filter is needed to propagate the frequencies in range between 20-125Khz. Therefore the obtained signal will be analyzed using MATLab program.

1.2 Objectives and Aims:

The main objectives of this project to elaborate the Non-destructive testing system by making the system portable. Common non-destructive system works with conventional AC Power Supply. Thus the common NDT system is stationary and it has lack of mobility. Portability of the NDT system is very big advantage, because now the most of the pipelines located in areas where there is no conventional AC power supply. Thus big accent will be given to develop the power supply using battery. We need to built two circuits which will supply +/- 150 volts from battery and second circuit should give +/- 15 volts to power the band pass filter, transceiver and echo amplifier.

• To understand the long range Ultrasonic testing method
• To analyze the each component of the entire system
• To investigate various methods to perform and finish the project
• To develop the hardware prototype for the complete design.

 

Moreover it should be able to detect the defects and test the joints between the pipes using ultrasonic waves. The pipeline is divided into four quadrants and by sending the signals the system should identify the exact status of the damage. PIC controlled mode selector has to be designed and built, this circuit will enable the system to work in different modes. Four different channels will give us more accurate position of defect.  The project also concentrates on improvements of the non-destructive testing system aside from portability.

Before the hardware part, the project will focus firstly on the design and building the circuits , using preferable software program. All the circuits will be simulated and built until the desired results have taken.

1.2  Deliverables

• To obtain the power supply circuit that will consist of rectifier, inverter.
• To develop circuit which will include the transceiver switch, power amplifier, echo amplifier and band pass filter.
• To develop PIC controlled Mode Switch
• To join all the circuits and obtain one portable system

2       Methodology

One of the first non-destructive testing method came into industrial application was X-ray. In this project ultrasonic signal will be used, which came latest into industrial use. The method of exciting ultrasound waves were discovered in nineteen’s century by James Prescott and by Pierre Curie and his brother Paul Jacques. In 1912 the first application of NDT system was proposed after “Titanic” had sunk. The Englishman Richardson claimed the identification of icebergs by ultrasound in his patent applications. During World War I   two French researchers started their development to detect submarines by ultrasound. In 1929 the Russian Sokolov proposed to use ultrasound for testing castings. Today more than 50 companies are active in industrial NDT. They are still working under strong competition to the benefit of their customers on their way to improve the quality of industrially produced parts.

The reason why I am using the ultrasonic testing, that it has some advantages that other methods do not have. The Ultrasonic testing it is very sensitive to surface and subsurface discontinuities. Only single sided access is needed when pulse-echo method is used in the system. It has high accuracy in determining reflector position and estimating size and shape. Therefore, the ultrasonic inspection has several limitations which includes, Linear defects oriented parallel to the sound beam may go undetected. Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise.

2.1 Design and Testing:

All the design will be done using Pspice program. Firstly, the information about each component will be collected, to choose an appropriate components that have good efficiency and low cost. PCB will be designed in manner that all components of the system compact, using less space. Because major goal of our project to make the system portable that it will be easy to carry it from one point to another.

During the development process, unit testing will be done to ensure all modules are built correctly. System integration testing will be done after we have built all the components and combined them into the application.

2.2 Evaluation:

After we will finish all the testing, we will evaluate the application to check whether it fulfills our objectives or not.

The Evaluation Phase will be carried out at every milestone of our project. We will look to this project from different sides to determine and justify the success. There are basically several aspects that we going to use in our project:

·         Reliability

·         Feedbacks from supervisor, moderator.

·         Consistency with the stated objectives

·         Comparison with other similar projects

We will also use the data to analyze the overall performance and the effects of each smaller part on the whole.