Questions regarding corrosion margin
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In GB150 and various petrochemical standards, requirements are set for the corrosion margin of heat exchange tubes made of different materials. If the surface of my heat exchange tubes is coated with an anti-corrosion coating, can the corrosion margin be designed to be smaller? I’ve searched for a long time but haven’t found any requirements regarding the corrosion margin after applying anti-corrosion coatings. I would be grateful if those who are knowledgeable could offer some guidance! Thank you!
The corrosion allowance is determined based on the corrosion rate; can a coupon test be conducted to determine the corrosion allowance? Or should it be determined by the ability of this coating to resist certain media?
According to GB/T151 4.4.5.4, corrosion allowance is generally not considered for heat exchange tubes; therefore, coating these tubes serves the purpose of preventing corrosion. If a larger corrosion allowance was considered initially, it may not be necessary to take it into account after coating.
What about the shell side? Under the condition that the design stress requirements are met, can corrosion allowance be disregarded after applying the anti-corrosion coating?
Heat exchange tubes do not require a corrosion margin; the choice of material and wall thickness are determined based on experience. Just a reminder: in the field specifying the service life of the equipment on the drawing, it should be written as 10 years (excluding the heat exchange tubes)