QUALITY OF SEAL DISCS-THROUGH NDT
S. P. Srivastava, A. Manjunatha, M. Jayandranath
Central Workshops, B. A. R. C., Bombay-85, India
Keywords: Seal disc, Diffusion bonding, Ni-SS, Bonding defects, NDT
ABSTRACT Quality of seal discs manufactured at Central Workshops, Bhabha Atomic Research Centre, is achieved by various Non-destructive Examinations at different stages. Seal disc is used to prevent the leakage of heavy water from coolant channel in a 235-MWe pressurised heavy water nuclear reactor. It consists of 1.05mm thick nickel annular ring having 97.03 mm outside diameter and 86.36 mm inside diameter. This ring is diffusion bonded with a disc made of precipitation hardened stainless steel forging grade 17-4 PH. Raw material is inspected by ultrasonic test for any internal defect. Fluorescent wet magnetic particle test is used for detecting any surface defect on the machined seal disc forging before diffusion bonding. It is also used for detecting any surface crack after face straightening operation, which is carried out to remove any distortion introduced by heat treatment. Lack of bonding at the edges and between the faces of nickel annular ring and SS 17-4-pH disc is detected by the liquid penetrant test and focused ultrasonic beam immersion technique, respectively. All the examinations are carried out under the stringent acceptance standards. Product reliability, process control and reduction in ultimate rejections are the chief advantages of using different NDT methods at different stages. This paper presents a brief description of different NDT techniques used for testing seal disc, their justifications and applicable acceptance standards.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 2, pages 961 - 966
Publisher: Ashgate Publishing Company
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