Safety guidelines
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Tube to tubesheet welds are the most probable leak location and thus have a strong influence on the reliability of steam generators. State of the art welding techniques like internal bore weld, and joint configuration to permit heat treatment and volumetric examination are suitable options to overcome this drawback. Butt welds should be adopted at the hot end of the steam generator with the above objectives and to reduce stress concentration.
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Designs with tube configuration with significant cross flow through the tube bundle should be avoided to avoid the risk of tube failure by flow induced vibration.
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Design codes do provide rules for exemption of postweld heat treatment on Cr–Mo steels. These exemptions should be taken with caution as the codes do not consider environmental effects like stress corrosion cracking.