Weld joint coefficients and non-destructive testing issues in the shell and tube sides of heat exchangers
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This post was last edited by jia717 on 2010-11-8 at 20:38. In a fixed-tube-sheet heat exchanger, both the tube side and shell side cylinders are made of seamless steel pipes. According to the regulations, the welding joint factor for the shell side is set at 1.0, and the same value of 1.0 is used for the tube side (assuming a cylinder length of 600 mm). In this case, should all the circumferential welds between the tube side end cap and the cylinder be inspected, or only some of them? In my understanding, according to Article 85 of the pressure vessel regulations: Article 85 states that for the butt joints of pressure vessels, full radiographic or ultrasonic testing is required when one of the following conditions applies: 1...... 2....... 3........ ....... 6. Pressure vessels for which a weld factor of 1.0 is specified in the design (except for seamless tube shells); 7. ...... Therefore, I believe that the circumferential welds between the tube end closure and the shell can be tested locally at RT-III level, even if the welding joint factor indicated in the drawings is 1.0.
The circumferential weld can be inspected locally; a grade of RT-III is sufficient. It is sufficient to indicate in the drawings that the joint coefficients for the longitudinal and circumferential welds are 1.0 and 0.85, respectively.