According to NBT47014-2023, how should the evaluation of heat exchanger tube sheets be carried out?

I asked the people in charge of making these specifications, and their answers were also vague; they said it should be determined based on the heat exchangers that the company has previously used. That response seems like it means nothing at all – how can the previous evaluation standards based on 20mm be adjusted? How should one choose the thickness for future evaluations?

In accordance with the requirements of NB/T 47014-2023, the thickness of the test pieces used for welding evaluation of tube sheets is specified as follows: 1. The thickness of the test pieces “shall be not less than the thickness of the thinnest tube sheet used in the actual products, and may not exceed 50 mm”. This means that if the thickness of the tube sheets in the heat exchangers produced by a company is typically above 30 mm (for example, between 30 mm and 50 mm), then an evaluation must be carried out using a test piece whose thickness is at least equal to the thickness of the thinnest tube sheets actually used in that company’s products. The method previously used for evaluating 20 mm thickness is no longer applicable to tube sheet thicknesses of 30 mm or more according to the new standards. 2. When the typical tube sheets currently produced by enterprises are 30 mm thick or thicker, it is recommended to choose typical dimensions that match or are similar to those of the actual products (such as 30 mm–40 mm) for evaluation; this way, a single evaluation can cover the actual conditions of the enterprise’s main products. 3. In previous versions, the old NBT47014 allowed the use of relatively thin tube sheets (such as 20 mm) for evaluation in order to cover thicker tube sheets, but this approach is clearly no longer feasible nowadays. Companies must now, in accordance with the explicit requirements of the new standards, reschedule the evaluation tests and select an appropriate tube sheet thickness. Currently, the industry tends to choose for weld procedure qualification typical thicknesses of tube sheet thicknesses found in standard product designs – such as 30 mm – or even thicker values like 35 mm or 40 mm. This approach not only meets the requirements specified in the latest standards but also offers good flexibility, reduces the number of procedure qualifications needed, and lowers subsequent management risks. .