EVALUATION ON USE OF INDUSTRIAL RADIOGRAPHY FOR WELD JOINTS INSPECTION IN TANZANIA

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 5, May 2017, pp , Article ID: IJMET_08_05_008 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed EVALUATION ON USE OF INDUSTRIAL RADIOGRAPHY FOR WELD JOINTS INSPECTION IN TANZANIA Christopher T. Mgonja, (PhD) Department of Mechanical Engineering, Dar es Salaam Institute of Technology, Tanzania ABSTRACT The use of Industrial Radiography for examining the quality of Weld joints is very popular worldwide. In Tanzania, many welding activities like construction and laying the huge pipelines for gas and water transportation and distribution as well construction of storage tanks are performed. The objects are working under high pressure and therefore, it is important to produce the weld beads with high quality. Industrial radiography uses ionizing radiation to view objects in a way that cannot be seen otherwise. The method has grown out of engineering, and is a major element of non-destructive testing (NDT) to inspect materials for hidden flaws. The radiation caused by these facilities is very dangerous however, with the use of new technologies and proper protection, risks of injury and death associated with radiation can be greatly reduced. Applying different works conducted by other researchers, this paper gives the general overview on the use of radiation devices, effects of ionizing radiations, the consequences of misusing the devices and the safety precautions taken. It highlights the efforts taken by Tanzania Atomic Energy Commission (TAEC) on registration of radiation devices. Further, it presents the challenges faced during the weld joints inspections. It has been shown that, out of 470 registered facilities until 2010, the registered industrial radiography owned by companies executing welding works were 4 (1%). Also, it has been revealed that the people around the weld joints inspection area are exposed to ionizing radiation. Lack of awareness is one of the contributing factors. The paper recommends to abide with protective measures when using radiation devices. Key words: NDT, TAEC, Ionizing Radiation, Radiographic Inspection, Radiation Devices Register, Safety, Weld defects Cite this Article: Christopher T. Mgonja, Evaluation on Use of Industrial Radiography for Weld Joints Inspection in Tanzania. International Journal of Mechanical Engineering and Technology, 8(5), 2017, pp editor@iaeme.com

2 Evaluation on Use of Industrial Radiography for Weld Joints Inspection in Tanzania 1. INTRODUCTION In the last five decades, non-destructive testing (NDT) methods have gone from being a simple laboratory curiosity to an essential tool in industry [1]. The inspection of welds is a very important task for assuring safety and reliability in several industrial sectors, e.g., ship and aircraft industry. For this purpose NDT techniques have been employed to test a material for surface or internal flaws without interfering in any way with its suitability for service. Such methods are the acoustic emission, magnetic particle inspection, eddy current, ultrasonic testing, thermal inspection and several others. These techniques are based on the observation that weld defects cause some sort of discontinuity to the test signal, which allows for recognition. However, each method is appropriate only for specific types of defects. On the contrary, radiography (X-rays or sometimes gamma rays) seems to be the most effective method and the experts are able to identify most types of defects in the images produced by this method. The method is based on the fact that the defective areas absorb more energy and thus the defects appear darker in the image [2]. Furthermore, the method is widely used as an inspection tool for detecting flaws inside welded structures, pressure vessels, structural members and pipelines. Among the advantages of this method compared to other methods, such as ultrasound tests, is the formation of an internal photograph of the material, which no other method is able to achieve [3, 4, 5, 6]. The use of ionizing radiation in the form of medical X-rays only was introduced in the United Republic of Tanzania (URT) as early as 1938 without any legislation to control its use. In subsequent years there has been an increasing proliferation in the application of nuclear techniques in fields of human activities such as health, industries, agriculture, mining, research and teaching. In recognition of that statutory deficiency, the parliament of the URT enacted the Protection from Radiation Act No.5 in 1983 [7,8], which established the Regulatory body namely the National Radiation Commission (NRC) to regulate the safe use of ionizing radiation and protect people and environment against its danger in the country. The revision was also made in order to be consistent with the International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources (BSS) that was published in 1996 [7]. Furthermore, the revision of the Act was made in order to expand the scope of supervisions in order to include provisions for promotion of safe and peaceful utilizations of atomic energy and nuclear technology. As such, the Parliament of the URT enacted the Atomic Energy Act No.7 of 2003 with mandate to control the use of radiation sources and facilitate the promotion of safe and peaceful utilizations of atomic energy and nuclear technology, the law became effective from 2004 [7]. The benefits of ionizing radiation during the construction of gas pipelines for Songas and Mnazi bay gas projects in Tanzania where Radiation devices were used to control the quality of welded joints have been seen. However, the use of industrial radiography is harmful to mankind due to its effects during exposure if precautions are not followed. These radiation devices emit ionizing radiation which destroys the cells of human beings and may results to the following effects to human: cancer, infertility, death, loss of appetite, loss of hair, vomiting and diarrhea etc. [9, 10]. It is observed that apart from radiographers, the following public may be exposed to radiation during the use of radiation devices [9, 10]: People who work in or visit facilities where radiation sources are used. Persons living near locations where radiation sources are used e.g. along the pipelines during construction editor@iaeme.com

3 Christopher T. Mgonja Contractors (other than authorized service agents) e.g. electricians, painters, plumbers etc. who may be required to carry out work in supervised or controlled areas. 2. INDUSTRIAL RADIOGRAPHY 2.1. Background Nowadays, in times of globalisation and with the considerable increase in competition among industries, the quality control of equipment and materials becomes a fundamental tool in a company s survival. Non-destructive inspection techniques are a theme of research and development in industries and universities. Although it is one of the oldest techniques of nondestructive inspection, radiographic testing is still widely used in evaluating the structural integrity of equipment and materials [11]. The reliable detection of defects is one of the most important tasks in non-destructive testing, mainly in the radiographic testing, since the human factor still has a decisive influence on the evaluation of defects on the film. An incorrect classification may disapprove a piece in good conditions or approve a piece with discontinuities exceeding the limit established by the applicable standards [11, 12, 13]. Beam of x-rays or gamma rays is pointed at the item being tested. A detector is lined up with the beam on the other side of the item. The detector records x-rays or gamma rays that pass through the material. The thicker the material, the fewer x-rays or gamma rays can pass through. Because the material is thinner where there is a crack or flaw, more rays pass through that area [14, 15]. The thickness of material in welding process, weld type, weld position and radiographic methods play an important role in image quality [16]. The detector captures the rays that pass through, which form a picture of the crack or flaw. A special camera, called a radiography camera, is used to capture radiography pictures. The pictures from these cameras are called radiographs [14]. TheX-ray and gamma ray devices are different and used for different purposes. X-ray radiography devices are powered by electricity. When the device is turned off, x-rays are not produced. X-ray radiography generally creates very clear pictures. The devices are large and good for use in factories. The gamma rays used in radiography come from radioactive material inside the radiography device. Gamma ray devices do not need electricity. They are smaller than x-ray devices. Their small size makes them useful for checking inside pipes, ships and other small spaces. However, they cannot be turned off like an x-ray device. The radionuclides in the device always produce gamma rays. The only way to turn off a gamma ray radiography device is to interrupt the beam by covering the opening with a heavy metal plate. Workers must be careful to close the opening when the gamma device is not in use to avoid exposure [14]. The internal discontinuities, detected by industrial radiography method in welded joints are worm holes (worm-like cavities), slag inclusion (slag or other foreign matter entrapped during welding),gas pores or porosity/gas cavities (spherical cavities due to entrapped gas), lack of fusion (lack of union between weld and parent metal), crack (discontinuity by fracture in the metal), linear porosity (linear cavities due to entrapped gas), lack of penetration (weld bead not start at the root of the weld), Undercut (crater that occurs near the toe of the weld) [2], Hence, the method has played an important role in the quality assurance of the piece or component, in conformity with the requirements of the standards, specifications and codes of manufacturing [2, 11, 9, 10, 16, 17, 18]. Fig. 1 shows some examples of defect patterns editor@iaeme.com

4 Evaluation on Use of Industrial Radiography for Weld Joints Inspection in Tanzania Figure 1 Examples of Radiographic Defect Patterns 2.2. Hazards Caused by Ionizing Radiation Radiation exposure is defined by the number of ionization events in air that are produced by X-ray or gamma ray photons. Radiation dose is the amount of radiation energy deposited in a person s body by X-ray or gamma ray photons [20].Radiation sources used for industrial radiography purposes have high radiation outputs and are potentially very hazardous. Incidents have occurred mainly as a result of operator error or equipment failure, and have resulted in workers and members of the public receiving high radiation doses [21]. The exposure of persons to radiation is divided into three classes: (a) exposures from natural sources; (b) exposures from man-made sources other than environmental sources; and (c) exposures from environmental contamination [22]. Although industrial radiography is in widespread use, but it has a high hazard potential as follows [23]: The health effects of ionizing radiation which include [24, 25,26]: Death due to damage with the Central Nervous System, Radiation skin burns, Cancer (Borne cancer, Thyroid cancer, lung cancer, Leukemia), Cell mutations and other genetic effects (abortions/miscarriage, impotence, still birth, malformation of genes (disability), Cataracts and Life shortening. Environmental contamination due to the presence of radioactive nuclides/materials. The Embryo/fetus is rapidly developing and so is more sensitive to a possible radiation effect than an adult. Such effects vary with amount of radiation and stage of development. Principal effects can be loss of pregnancy (miscarriage), malformations (disability), and mental retardation. Pregnant women should thus not be allowed in areas with radiation Protection from Ionizing Radiation Radiation protection is the science and art of protecting people and the environment from the harmful effects of ionising radiation. It is also described as all activities directed towards minimising radiation exposure of patients and personnel during radiation exposure. The objective of radiation protection is to define how one can protect individuals, their descendants and the human race against the potential risks of ionising radiation. Fundamental principles of radiation protection are justification, optimisation and time/limitation. Based on the understanding of these fundamental principles, exposing only an individual(s) who should derive maximum benefits from such exposures to ionising radiation (justification), making sure that radiation doses as result of medical exposures are only enough to achieve needed diagnoses (optimisation)and reducing the time of exposure to sources of ionising radiation or 68 editor@iaeme.com

5 Christopher T. Mgonja the exposures to individuals shall not exceed the limits recommended. These are means of achieving radiation protection [20, 26]. Consequently, uses of immobilisers, positioning aids, beam size (ray field) limiting devices, the type and state of radiography device are important factors in radiation protection. Furthermore, availability of installed radiation protection instruments such as area radiation monitors, air borne contamination monitors and personnel exit monitors; and portable instruments such as survey meters, lead rubber shields and personnel dosimeters for staff and work place monitoring are also essential. Radiation protection measures also include periodic quality assurance checks on the radiography device(s) [26, 27]. 3. REGISTRATION OF RADIATION SOURCES IN THE URT 3.1. The National System of Notification and Register of Radiation Sources The Atomic Energy Regulations, 2004 clearly state that any person intending to initiate a practice or to possess a radiation source, shall submit a prior notification to the Commission of such an intention. The Act further requires that every radiation user, radiation generating device and mobile radioactive apparatus be registered. It can be revealed that, there has been an increase in the number of registered radiation facilities from 22 in 1985 to 436 in 2008 as shown in Fig. 2. In view of the above, it is clear that there is significant increase in use of radiation sources in the country and hence there is a need to strengthen the radiological protection infrastructure in order to keep the potential radiation exposures as low as reasonably achievable [7]. Out of 436 registered facilities, 70% were from medical applications, while 11%, 5%, and 14% were from industry and construction applications; research and teaching applications; and other applications, respectively as shown in Fig. 2. On the other hand, a total of 709 radiation sources were registered by the Commission, out of these, 60% were from medical diagnostic imaging practices, while 18%, 6%, and 16% were industry and construction applications, research and teaching applications and other applications, respectively. Figure 2 Trend of Registration of Radiation Facilities from 1985 to 2008[7] 69 editor@iaeme.com

6 Evaluation on Use of Industrial Radiography for Weld Joints Inspection in Tanzania Fig. 3 shows that the number of registered radiation facilities and sources by the year 2008 increased by 118% and 119%, respectively relative to the number of facilities and sources registered by the year 2000 [7, 28]. These include sealed sources, unsealed sources, nonmedical X-ray machines, and diagnostic X-ray generators. Over 70% of these national registers of ionizing radiation sources were migrated into one national register of radiation sources using the version of Regulatory Authority Information System (RAIS) 3.0 SQL provided by the International Atomic Energy Agency (IAEA) [7]. Figure 3 Number of radiation facilities and sources by practices as of June 2008 [7] Hence, till 2008, about 436 radiation work places and installations were registered; and their compliances with license requirements are satisfactory. The non-compliances with license requirements for majority of the radiation facilities are largely attributed by inadequate radiation shielding of the premises, poor performance of radiation generating equipment; lack of qualified operating personnel, and incomplete submission of license application forms [7]. However, apart from the fact that welding works were intensively practiced in the URT especially in the construction of dangerous objects like natural gas pipelines, gas and oil storage tanks as well water pipelines, it shows that in this period only one registered device was owned by a welding construction company. Fig. 4 indicates that, out of 260 registered radiation facilities as from 2003 to 2010, 3 (1.2%) facilities were registered in welding construction companies, 1 in 2009 and 2 in Other registered facilities were 66 (25.4%) in other industrial applications, 175 (67.3%) radiation sources in Medical sector and 16 (6.1%) sources of radiation in Research activities. The data still shows a small number of industrial radiography registered for welding activities. However, it is observed that, there were many welding activities which involved inspection of weld joints using industrial radiography. It was noted that, other welding construction companies did not own industrial radiography, but to conduct the tests they hired the equipment from other companies or research and training institutions [9, 10] editor@iaeme.com

7 Christopher T. Mgonja Figure 4Trend of Registration of Radiation Facilities from 2003 to Education and Training Occupationally Exposed Workers The TAEC regularly coordinate and undertake a training program to occupationally exposed workers, radiation safety officers and other stakeholders in the country in order to ensure that appropriate knowledge of radiation protection and safety is imparted to them. In addition, the training is provided to law enforcers such as customs control officials, clearing and forwarding agents, and police officers in order to assist the Commission in enforcing the law and regulations by controlling the movement of radioactive materials. The training is provided through regular annual national seminars and workshops and through the IAEA training programs. The Commission has basic training facilities for conducting national training courses using curriculum that conforms to IAEA standards. For the period from 2001 to 2007, a total of 422 persons attended various training courses, out of them 64% were occupationally radiation workers, while 20% and 16% were law enforcers and TAEC staff respectively as indicated in Fig. 5. On the other hand, following the increase in use of nuclear technology applications, the URT is facing a key challenge on general lack of personnel with the prerequisite knowledge and skills in nuclear science. A high demand for personnel with basic knowledge in nuclear science has arisen in the fields of health, safety, agriculture, livestock development, industry and research [7]. Figure 5 Radiation Workers and TAEC Staff trained on Radiation Protection for the period from 2001 to 2007 [7] 71 editor@iaeme.com

8 Evaluation on Use of Industrial Radiography for Weld Joints Inspection in Tanzania Despite the big efforts that have been taken by TAEC, it has been observed that the radiography testing exercise is carried out without any sign indicating the dangerous area as shown in Fig. 6 and Fig. 7. Fig. 8 and Fig. 9 show that many people are notaware on the effects of ionizing radiation. Radiographers conduct radiographic tests while people and car are passing freely through the dangerous area [9, 10]. Figure 6 Radiographic test on Mtwara gas pipeline Project in Tanzania Figure 7 Radiographic weld joint test on a fuel storage Tank Figure 8 People crossing near the location of radiation source in Tanzania 4. CONCLUSIONS AND RECOMMENDATIONS Figure 9 Car approaching to where radiographic testing is conducted 4.1. Conclusions Evaluation on use of industrial radiography for weld joints inspection has been conducted. The general overview on non-destructive testing of weld joints, ionizing radiation facilities in Tanzania, hazards caused by ionizing radiation was carried out. It has been revealed that ionizing radiation was first introduced in Tanzania for medical purposes in The application of this Technology including radiographic testing for weld joints was increasing in subsequent years. Furthermore, the hazards caused by ionizing radiation were pointed out which indicate that the exposure of ionizing radiation has high negative effects to human body if extra precautions are not taken. The registration status of radiation facilities, sources and organisations/companies that use these facilities in Tanzania was carried out. The efforts taken by Tanzania Atomic Energy Commission (TAEC) indicate that till 2008, 436 facilities of different applications were registered. The registration of manufacturing companies that own industrial radiography for weld joints inspection were 4 (1%) out of 470 registered facilities till It has been revealed further that TAEC conducted a number of training courses to occupationally exposed workers however it is noted that still many people are not aware on ionising radiation effects. It has been also observed that the welding manufacturing 72 editor@iaeme.com

9 Christopher T. Mgonja companies that did not have facilities were using the hired facilities from other companies or research and training institutions Recommendations The efforts of TAEC to report on the registration status of ionizing radiation facilities have been seen however, it is advised to release the current i.e. 2015/2016 registration situation, improvements, and current challenges. Furthermore, there is a need to improve and strengthen the safety measures on controlling and monitoring on the use of radiation equipment in welding field. This can be achieved by, providing sufficient training for all personnel dealing with these equipment, disseminate the information by using TV and radio programs and hence provide training on radiation effects and protection to general public. All protective measures should be followed during the application of ionizing radiation facilities. REFERENCES [1] Vilar, R., Zapata, J, and Ruiz, R. An Automatic System of Classification of Weld Defects in Radiographic Images. NDT & E International, Elsevier. 2009, 42. pp [2] Valavanis, I. and Kosmopoulos, D. Multiclass Defect Detection and Classification in Weld Radiographic Images Using Geometric and Texture Features. Journal of Expert Systems with Applications, Elsevier. 2010, pp [3] Carvalho, A. A., Rebello, J. M. A., Souza, M. P. V., Sagrilo, L. V. S. and Soares, S. D. Reliability of Non-Destructive Test Techniques in the Inspection of Pipelines used in the Oil Industry. International Journal of Pressure Vessels and Piping, Elsevier pp [4] Lim, T. Y., Ratnam, M. M. and Khalid, M. A. Automatic Classification of Weld Defects Using Simulated Data and an MLP Neural Network. Radiography.2007, 49 (3). pp [5] Da Silvaa, R. R., Caloˆbab, L. P., Siqueiraa, M. Joa o, H.S. and Rebelloa, M.A. Pattern recognition of weld defects detected by radiographic test.ndt & E International, Elsevier. 2004, 37. pp [6] Wang, G. and Liao, T. W. Automatic Identification of Different Types of Welding Defects in Radiographic Images.NDT&E International. Elsevier. 2002, 35. pp [7] Ngaile, J. E. Mompome, W. K. and Meza L. H. The Current Status of Radiological Protection Infrastructure in Tanzania. 12th Congress of the International Radiation Protection Association (IRPA12),Buenos Aires, Argentina, 2008, pp. 12. [8] Ngaile, J. E., Msaki, P. and Kazema, R. Current Status of Patient Radiation Doses from Computed Tomography Examinations in Tanzania. Radiation Protection Dosimetry, 2006, 121(2), pp [9] Mapunda, M. Investigation of Safety and Effects of Ionizing Radiation in Industrial Radiography, Dar es Salaam. Dar es Salaam Institute of Technology. Senior Project Report. Bachelor of Mechanical Engineering pp. 75. [10] Mgonja, C. T. Assessment of Safety and Hazards Caused By Ionizing Radiation in Industrial Radiography during Weld Joints Inspection. Proceedings of the Third Annual International Conference on Innovations for Advancement of Humanity. Eldoret Polytechnic, Kenya. 2013, pp [11] Da Silva, R. R., Siqueira, M. H. S., Calôba, L. P. and Rebello, J. M. A. Radiographic Pattern Recognition of Welding Defects using Linear Classifiers. Radiographic Interpretation, Authorized by IIW. 2001, 43(10). pp editor@iaeme.com

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