Pressure tap pipe of the tower vessel
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In refinery units that use pressure tapping pipes for towers, there are welded pipelines on the towers; for example, in the atmospheric tower of a vacuum distillation unit, two issues arise: 1. What determines the material of the welded pipelines on the tower, such as the oil outlet pipelines and the pipelines for connecting instruments? I don’t know how thick it is? 2. Will corrosion occur over time with prolonged use? 3. After installing the equipment, we will need to work with oil from CNOOC that has a high acid value; therefore, modifications are necessary, with some of the equipment being replaced with 316L material resistant to corrosion. Is it also necessary to replace the pipelines welded to the tower with corrosion-resistant materials? We just measured the thickness of these pipelines; despite having been in use for several years, their thickness has changed hardly at all. Please give some advice, I’m learning!
It is mainly determined based on factors such as the nature of the process stream, temperature, pressure, and flow rate. Corrosion is generally quite severe in refineries; to ensure the safe operation of the facilities over extended periods, it is advisable to consider using materials that are resistant to corrosion.
1. The pipelines welded to the tower should, as much as possible, be made of the same material as the tower itself; they can also be of a higher grade. Their thickness is determined based on the pressure rating specified in the design specifications. The pressure transduction pipelines for instruments in atmospheric-pressure towers are typically 2 mm thick. 2. Over time, corrosion will definitely occur, though to varying degrees. 3. If, after several years of use, the thickness of these pipelines hasn’t changed much, then there’s no need to replace them with materials resistant to corrosion. If the equipment itself is replaced with corrosion-resistant materials, it’s also advisable to replace the pipelines as well, so that in case corrosive substances are encountered, there’s no need to repair the equipment just because of those pipelines. It’s sufficient to replace only the section that is welded to the equipment