Kaynaklı konstrüksiyonlarda kalite güvenilirliği ve radyografik muayenenin kullanımına yönelik öneriler
Quality assurance of welded construction and suggestions for the use of radiographic inspection for quality control in production system
- Tez No: 19378
- Danışmanlar: DOÇ.DR. YILMAZ TAPTIK
- Tez Türü: Yüksek Lisans
- Konular: Metalurji Mühendisliği, Metallurgical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1991
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 102
Özet
ÖZET Kaynak kompleks bir teknolojidir ve özellikle şantiye koşulların da imalatı gerçekleştirilen konstrüksiyonlarda, çok farklı özellikte kaynakların yapılması gerekmektedir. Bu denli çeşitliliğin söz konusu olduğu kaynaklı konstrüksiyonla- rın imalinde elde edilecek kaliteye güvenmek, tasarım aşamasından başlıyarak kaynak işlerinin yürütülmesi ve kalite kontrolünü da kapsayan uygulamalı çalışmaların doğruluk derecelerine bağlıdır. Kaynaklı konstrüksiyonlarm imalinde tasarımın temel teorik bilgiler ışığında hazırlanması ve hangi işi kimlerin yapabileceği şeklindeki bir görevlendirmeyi de kapsaması durumunda kalitenin optimum maliyet ve güvenilirlik sınırlarında elde edilmesi olasıdır. Bu amaçla ka3'nakh konstrüksiyonlarda kalite güvenilirliği sisteminin oluşturulmasında temel alınacak yaklaşımlar, tasarım aşama sından başlayarak son üretime kadar'olan süreç itibariyle değerlendiril miş ve firma bazında bu tür sistemin oluşturulmasına yönelik bir model önerilmiştir. Çalışmanın genel kapsamı içerisinde kaynaklı konstrüksiyonlarda kalite kontrol uygulamaları arasında Önemli yer tutan radyografik yöntem uygulamalı olarak ele alınmış ve sistem içerisindeki entegras yonu önemli parametreler itibariyle gerçekleştirilmiştir. Deneysel çalışmalar sonucunda firma bazında oluşturulabilecek ve hata değerlendirmede yanılgıları en alt düzeye indirebilecek referans formlara örnekler verilmiştir. VI
Özet (Çeviri)
QUALITY ASSURANCE of WELDED CONSTRUCTION and SUGGESTIONS for the USE of RADIOGRAPHIC INSPECTION for QUALITY CONTROL in PRODUCTION SYSTEM SUMMARY Quality assurance concepts aroused as a result of the need of better quality in many industries after the Second World War, and now it is a unrenouncable necessity in a vast majority of industries. In the case of welded constructions concept and reliability of quality requires to deal with assurance of quality in a larger scale. Weld quality is affected by many factors such as welded and welding materials, environmental conditions, design, operator, etc. This complicated structure of weld quality, requires control of all these factors and this constitutes the concept of quality assurance. Identification and elimination of defects by quality control, reduces the failure costs which may be caused by defects. The incentive for manufacturers to reduce defects, and therefore costs, led to extensive development of quality control concepts. Generally, concept of quality assurance includes all activities to obtain desired quality of the product. This includes suitability studies of all possible applications to standards by using plans and previous service experience. It is especially important to select suitable material and qualified operator to achieve quality assurance of welded constructions. Following factors also shows (explains) the necessity of quality assurance of welded construction: 1. It may not be possible to eliminate failures occurred during service conditions by quality control tests and inspections. 2. It is necessary to design or constitute quality. 3. Defects can be identified in inspected specimens but non- inspected specimens may include defects too. 4. It is more expensive to repair defected welds to produce sound welds. Quality forms the base of quality assurance, and more effective control of quality may be done by people who are familiar to product or production. The responsibility of the product belongs to the vi lproducer. This approach has been developed especially after 1980 at many countries and industries. Thus responsibility of defects caused from design and production is attributed to producer. Assuming that top management is committed to a quality^ policy and all of its obligations, certain initial steps would be sensible. A supplier must first determine where quality problems are occurring (using parieto analysis), e.g. design and specification, procurement, material, manufacture, inspection, site construction. Following Table illustrates an analysis of problem areas and presents the approximate situation by one of UK pressure vessel manufacturers. Discussions with other manufacturers in other industries around the world confirm this general picture. The significance of the individual must be considered. Welding introduces particular problems, e.g. whilst designer and engineers are professional qualified and trained, welders and operators rely more and personal skills. The results of these efforts are judged by others who may have inadequate training or experience to take the critical decisions required of them. Thus: Skills in successful weldments Designer Welding engineer Welder Welding inspector Nondestructive tester -Professional training -Professional training -Artisan skills -Decision maker -Decision maker Studies aimed to develop quality, requires obligatory sanctions for the purchaser and suppliers. This should result, purchasers and suppliers have to encourage developments and studies for obtaining better performance for products through its economic life. VlllIt is important to understand that a wrong documentation or specification prepared by the purchaser will result sooner in bad quality. The major cause of failures is not only the human (operator) errors. The most recurrent cause of failures with“lack of, or inadequate specification”a major factor along with“ poor planning and coordination ”- all areas of management responsibility, rather than the operative. It has been found as a result of statistical research performed in the UK“ human ”error problems are 12% whereas“ management ”deficiencies in planning, specification and proving stages amount to some 66% of cases. If we add“ bad inspection methods ”which is often a management responsibility we have 76% of the causes attributable to management. This general analysis is quite applicable to the case of welding problems. A prime function of management should therefore be“ root cause analysis ”and it should be the concern of management to deploy appropriate personnel to this aspect as well as troubleshooting. The list below indicates some root causes of poor supplier performance identified by 20 quality assurance managers, both purchasers and supplier: - Lack of planning - Overbooking of work - Pressure of production over quality - Lack of authority of quality control personal - Lack of clear quality control systems - Inadequate in-process/final inspection - Poor manufacturing equipment - Inadequate briefing on specification/Lack of understanding - Inadequate direction, poor management, poor control - Disinterested work force - Poor control of sub-contractors - Lack of day to day quality assurance implantation - Middle management apathy - Poor customer specifications and contractual requirements - Poor quality assurance staff - Belief that quality costs money Factors to define quality levels of welded constructs should be settled by co-operation of design engineers and quality controllers. To settle better quality than the service requirements may cause economic loss. Thus it is necessary to settle an optimum quality level due to service condition, and it can be done by optimization constructive and functional conditions. In this study, quality assurance concept have been explained and the rules of quality control and inspection studies under site conditions have been examined by using following steps: - Control of materials due to procedure or specification - Control of the operator - Control of the weld machine and attachments- Control of welding operations - Preparation to the welding. During welding. After welding - Control of inspection equipment and personal Following flow chart has been suggested as a result of these examinations for organisation and sub-organisations. Similar flow charts for“work procedures relevant to organisations”and“control and inspection”are developed and suggested too. TECHNICAL OFFICE/WORK PROCEDURE WELDING GROUPS WELDING ENGINEER ! QUALITY CONTROL ! CONTROL ENGINEER WELDING ON SITE (COMPLETION OF WELDING) j (RELATED PERSONNEL) ı r HEAT TREATMENT AND N.D.T. (RELATED PERSONNEL) WELDING FOREMEN APPLICATIONS (CONTROL PERSONNEL) APPLICATION (SUITABLE WELDING OPERATORS) EVALUATION At the second part of the study, suggestions has been given for the radiographic quality control of welded constructions. For this purpose quality assurance and sensitivity parameters were chosen according to DIN 54109 and CEN Draft PrEN 444 standards. xIn the radiographic experiments welded steel of 20 mm thickness test plate were used, photographic film densities were chosen as 2 on G2 class film. Radiographic exposure parameters were 200kV and 10.5 min. From the result of these exposure conditions, the necessary IQI wire number for each sample were observed to be 12 which is in accordance with the standards. Starting from the radiographic films and macro metallographic examinations, a relationship has been established between the weld defects seen on the film and its macroview. XI
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