·Table of Contents
Restoration of real-Time Radiographic System for industry in Indonesia
Gede B. Suparta
Department of Physics, Gadjah Mada University, Yogyakarta - 55281, Indonesia
Riil Isaris, Ardianto A. Moenir, Mairing M. Pongtuluran
Center for Management and Guidance for Industry, BATAN, Puspitek, Serpong,
Tangerang - 15310, Indonesia
The work on modification of a real-time industrial radiographic system based on x-ray image intensifier (XRII) for inspecting aluminum wheel in Indonesia has been completed. The built-in imported plant was initially installed at the one factory in Jakarta in 1992. However, it was unexpected collapsed since 1997. Some main parts were either broken or gone. The system was re-built and innovated (some parts are modified) using some different components available in the domestic market. Some test, calibrations and certifications have been carried out upon the modified system, and those results were compared to the results of the associated original system. The system has been operated for monitoring the production process in a real-time mode. On-going maintenance and further modification have been put on the plan to optimize the system capabilities.
Keywords: real-time radiography, NDT, product inspection
As the economic crisis exposed Indonesia in the last two years, some industries and manufacturers had serious financial problem as their products were mainly supported by imported components. Some products and goods were fortunately manufactured for export so the impact can be compensated. However, for those products being exported, there was a strong requirement that all products should fulfill certain standards and certifications for quality of products achieved . Therefore nondestructive testing (NDT) facilities in the manufacturing process were considered important. The work described in this paper reports the work of three parties dealing with this issue.
One project described in this paper was based at the Pakoakuina Pty. Ltd. located at Sunter, North of Jakarta, Indonesia. Currently, the company supplies aluminum (Al) wheels for domestic manufacturers and Proton Saga in Malaysia. It also supplies for OEM market, such as for Mercy and some Japanese cars. It contributes 17,000 pieces/month for export in which 10,000 pieces supplied by the company, while the rest supplied by its partners. This is one-eighth of the total product capacity. The demand tends to increase and the company plans to double the product capacity to 160.000 pieces per year to fulfill the market. To ensure the quality of Al wheel being exported is fulfilled, one real-time radiographic plant for Al wheel inspection has been installed.
The impact of the economic crisis showed the industries and manufacturers in Indonesia are very volatile due to its dependence to technology, massive import components and some expertise. This situation also happened at the Pakoakuina as the only one real-time radiographic facility had broken unexpectedly in 1997 after 5 years in service since it was firstly installed in 1992 . Restoring the facility need substantial finance if the original performance was set and the initial developer was invited. Therefore, it was a strong recommendation to acquire more local technology, reduce import components by local components and use more local experts. Concerning this recommendation, a joint project was established between the Pakoakuina with the Center for Management and Guidance for Industry, BATAN Indonesia in October to December 1999, involving the Department of Physics, Gadjah Mada University, Yogyakarta. The work of this project is reported in this paper.
The next section introduces the system arrangements, the approach of the restoration and the methods of assessments. Then, results and discussion are presented in the following section. The concluding remarks are presented in the last section.
2. Restoration of Real-Time Radiographic Plant
Basically the real-time radiographic facility set-up in the Pakoakuina (Figure 1) consists of an x-ray generator with water-cooled circulation system, an imaging system based on XRII , an object stage completed with a railway system for upload and download specimen being inspected and a unified control unit. The critical units, i.e. x-ray tube, object stage and XRII are in a close-protected room to minimize the radiation exposure to both the operators and the environment.
Fig 1: Basic principle of real-time radiographic facility installed at Pakoakuina.|
The monitoring process is basically a process of generating radiographic images of a specimen i.e. Al wheel upon an image intensifier, XRII. The images are then captured by video camera and then transmitted and displayed onto a TV monitor. The process is considered to be a real-time inspection as the inspection process and the justification on the quality of the product can be determined during the process. The process is applied to every Al-wheel product after it came from the furnace, just before further machinery process being carried out.
As mentioned above, the facility was broken and a joint project to restoring the plant was established. At the first step, a set of individual testing on the parts of the system was carried out. The purpose of this individual testing was to distinguish problems so that a summary of the work was able to set. However, the project was far from simple due to several problems. First, incompatibility in the electricity, in which the PLN (National Electric Company) actually supplied 220 volt rather than a 100 volt as it was required by the plant. Second, the plant was complicated in the form of an integrated system so that each unit module seemed connected each other. These major problems led to a major change on the system and required a certain degree of innovation to suit with the recommendations and the standard requirement being intended. Therefore, the restoration was carried out in the following steps. First, the plant was separated into module units, and parts by parts were marked. Second, the work and inspection during the work is carried out parts by parts. Once all partial units have been fixed, an integrated inspection was done to see the performance and the capability of the system as a whole. It was highly recommended that the performance of the system should more alike the original set-up. The following section shows the results followed by a brief discussion.
3. Results and Discussion
Some modifications on the units by parts have been carried out. First, the separation system modules has been completed and the associated power suppliers such as for the chiller, the unit control, the specimen stage and railway, the interlocks and the imaging devices was changed to based on 220 volt.
Second, the water cooling system (chiller) has been modified as the pumping unit has burned and the system was partially broken including its connection to the critical interlocks. The pump was changed using a commercial pump provided in the local market. After the test, the pump gave flow-rate of 5.5 liters per minute, which was fulfill the requirement suggested by the original set-up, i.e 4-11 liters per minute. The chiller worked at the room temperature in the factory, i.e. 33o C, while the maximum temperature was set to 55o C. In order to keep the temperature stable at the room temperature, a circulating fan was used to blow the compressor to maintain the temperature of the water. For safety considerations, some inter-locks were installed to check flow-rate and ambient temperature.
Third, the x-ray generator was not changed, except the parts associated with the chiller. The operational voltage was set to 75 kV and beam current to 3 mA in fluoroscopic mode. However, due to the varieties of the thickness of Al-wheel specimens being inspected, the variation of voltage of the x-ray tube was set from 70 keV to 100 kV, with beam current of 3 mA . This set-up was able to inspect both the Al wheel for Mercy that equivalent to about 18 mm in thick and for Proton of about 14 mm in thick. Considering the age of the x-ray tube and the current defect on the anode, the system was suggested to be operated for 12 hours a day, which was divided into three shifts of 4 hours in continuous operation.
Fourth, the panel control was also restored and a better feature for display and convenience condition was achieved. A set of training to operators in order to master the new feature of the panel was established. The similar program was also established for the associated modules. Associated course and certification for the operator being involved was also established to ensure the radiation protection, safety work and environment are fulfilled.
Fifth, the XRII unit along with the imaging devices was replaced as it failed to produce visible image. The substitute of imaging device  has more simple features and much easier to operate rather than the original one. The resolution after replacement improved from 250 lines per inch to 600 lines per inch. The inspection time per wheel was estimated about 3 minutes per specimen. However, in practice about 400 units per day has been inspected instead of about 250 as suggested.
The last, the lead glass on the in-let has been replaced using 18 mm lead glass supplied by local market. To fulfill the standard requirement for work and environmental safety, the system has been audited by the authorized institution BAPETEN (Nuclear Power Inspection Agency). The results shows that the radiation leakage just outside the shielding was maximum 0.04 mR/h when the x-ray tube was operated at 120 kV, 3 mA. This was much lower than the IAEA standard of 0.75 mR/h for environment safety requirement and 2.5 mR/h for work safety requirement.
Fig 2: Image of test piece that shows the resolving ability of the restored system.|
|Fig 3: Image of imperfect Al wheel specimen. The bubbles are clearly shown as artifacts.
4. Concluding Remarks
After the work completed, significant achievement are gained by both the Pakoakuina Pty. Ltd. and the project team. Significant progresses on the way the company performs testing and evaluating the product are achieved. This achievement leads to commercial benefits. The team has better understanding with the set-up of the plant since the plant has been modified into a system comprises some independent modules. The modular system arrangement seems the best arrangement as the individual testing, maintenance and restoration process are far easier to be carried out. Further modification on the current plant is set to extend the capability and the life of service of the current plant. A new real-time radiographic plant is also set-up in the near future, involving the team.
The authors acknowledge that the work was able to be completed due to participation and collaboration with Mr. Bambang T. Wahyuadi, Mr. Ramlan Mamentu, Mr. Diam Keliat, Mr. Ganda T. Manalu, Mr. Suwandi and other CGMI staffs, and also to Mr. Waskito Nugroho of Gadjah Mada University. Thank you are also addressed to our colleagues from Pakoakuina Ltd. Mr. Hadi Kasim, Mr. Ismed D. Nasution and Mr. F. Christa Matita of Pakoakuina. Some pictures presented in this paper was provided by Mr. Bobby M. Sumarkho of Tawada Ltd., Jakarta.
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