How should the corrosion margin for detachable internal extension tubes be determined?
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For this type of detachable internal extension tube, can it be designed by using 1/4 of the cylinder’s corrosion margin as specified in Table 7.3.2-3 of HG20580 for \"stress-bearing detachable internals\"? In that case, half of the cylinder’s corrosion margin would be used for each side of the fitting, which means half of the total cylinder corrosion margin would be applied to the entire fitting.
For this type of detachable extended tube, I don’t think it’s very meaningful to delve into the concept of corrosion margin. After all, it is a replaceable component; unless it is a lined device, special considerations are required for the inner extension tube, which is made of a different material.
It mainly relates to the issue of reinforcement through openings in the flange cover; if a small corrosion margin is adopted, the calculation for reinforcement via openings can be omitted. This device is designed for a pressure of 0.1 MPaG/FV at 100 degrees. If calculations are to be done for reinforcing a single hole in a flat cover, the thickness of the flange cover is 50% greater than what is specified in the standards, which seems excessive.
Looking at the diagram, the diameter of the inward-extending pipe isn’t large; does that mean the thickness of the flange cover needs to be increased by 50% for reinforcement through openings?
This post was last edited by *AOL_1 on 2018-3-9 at 08:46. 1. The reinforcement for the openings in the flange is not a removable internal component but rather a removable external component; its diameter is likely small. In my opinion, it can be handled according to the opening sizes specified in GB150, without the need for any reinforcement, just as with the other connections on the cylinder body (or the thickness of those connections can be increased slightly). 2. As per the calculations, for safety reasons, the external components are required to have a corrosion margin in accordance with standards; however, I personally believe that considering replaceability, the corrosion margin can be set to 0, and it would be more reasonable to apply a corrosion margin of 1/4 based on the stresses experienced by the detachable internal components. The inward-extending portion is not under stress, but it is advisable to consider double-sided corrosion of the detachable internal components based on the applied forces.