Values for the corrosion allowance of bolts and hook rings at the floating head end of floating head heat exchangers
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Regarding the values for the corrosion allowance of bolts and hook rings at the floating head end of floating head heat exchangers, there are two approaches: 1. Clause 5.14.4 of GB151-1999 specifies that the corrosivity of the fluid in the shell side must be taken into account, but it does not specify how to determine these values； 2. TEMA -1999, 8th edition, RCB-1.517 states that “Tubes, bolting and floating head backing devices are not required to have corrosion allowance.” In other words, there is no need to take corrosion allowance into account. Personally, I think a corrosion margin should be adopted, but as for the specific value to use, especially for bolts, should it be the root diameter plus CA or the root diameter plus 2CA?
It depends on the criteria used to design the heat exchanger. If national standards are followed, I think it’s necessary to take 2 times the CA into consideration
If designed in accordance with GB151, a corrosion margin must be taken into account as required
Personally, I think it should be considered; since only the shell-side fluid is in contact, adding +CA will suffice.
I think no matter what criteria are used for design, it’s important to consider how things should actually be handled. The criterion for design is mainly a matter of determining responsibility. The examples in the standard interpretation of GB151-1999 do not take CA into account.
Double-sided corrosion should be taken into account for hooked rings, as clearly stipulated in GB151. Regarding bolts, I think according to clause 5.14.4 of GB151, the corrosivity of the fluid in the shell side must be taken into account. Should this mean that the corrosivity of the fluid should be considered when selecting the material for the bolts? It’s not entirely clear whether a corrosion margin should be taken into account in the calculations. I think in such a situation, the designer can choose whatever they want; what’s important is to have a reasonable basis for it. Refer to Table 7-6 of HG20580.
This post was last edited by lmq881825 on 2014-11-20 22:34. I think it’s convenient to replace the bolts, corrosion being ignored. During major equipment overhauls, the main bolts are generally replaced. For circular marks, consider 2CA; see the calculation example for floating-head heat exchangers in the explanation of GB151.