Problems encountered in the manufacturing of heat exchangers
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A set of 3-effect drawings was prepared, but some problems arose during manufacturing: 1. For the heat exchange tubes, I chose those in accordance with GB/T13296 standards; the first batch purchased were sealed tubes (with seams), and due to the corrosive nature of the medium, the second batch was those in accordance with GB/T14976 standards, and all of them were welded. 2. To save a few pipes, the spacing tubes were removed, and the tie rods and baffle plates were welded together. 3. When planning the material list, cancel a few baffle plates (inner diameter of the heat exchanger: 900 mm). I have some questions for everyone: 1. Why is it specified that 14976 cannot be used for heat exchange tubes at 1.150? Is the difference between 13296 and 14976 just in flaw detection? 2. Are there any “side effects” to removing the spacing tube? 3. Is it worth doing to save money?
First of all, the standard number mentioned by the original poster is incorrect; it’s not 13296 without a /T – it’s GB13296, which is a **mandatory standard**. Regarding your first question, you can refer to this post: https://bbs.hcbbs.com/thread-1388420-1-1.html
It’s correct for the poster to add /T; for details, please refer to Document No. 7 issued by the General Administration of Quality Supervision, Inspection and Quarantine in 2017. 1. Note that the heat exchange tubes referred to in this provision are those of shell-and-tube heat exchangers. The reason for the standard restrictions is that the requirements for diameter and wall thickness tolerances of 14976 are relatively low. 2. The spacing tube is used to fix the baffle; in addition to disrupting the flow, the baffle also serves to prevent vibrations caused by excessive span distances ； 3. Not worth it.
I also think it’s not worth it; I just can’t come up with any good reasons.
Yes, the standard number should be GB/T13296
Cutting corners – no wonder such companies never win bids
2. The spacing tube is removed; the tie rod and baffle are connected by welding. There are no significant negative effects, and in principle it is also a viable structure.
3. To save money, several baffle plates were removed…… It’s not a question of whether this is worth it or not; the heat exchange efficiency will be insufficient, and the equipment may end up needing to be discarded and rebuilt
Regarding the first point, there are differences in terms of precision level, testing grade, range of metal content, and smelting method. You can consider it as follows: the requirements set by 14976 are too low, which means that the safety performance of such tubes for use in heat exchange applications is not very good； Regarding the second point, it’s not that it can’t be done; it’s just that assembling the cage is rather troublesome, and the welding isn’t strong enough – during assembly the weld points are likely to come apart, rendering it useless. It’s not that cost-effective. Regarding point three, it’s not about saving money; it’s the case that decisions are made based on personal interests. In short, design involves taking on risks, and in the event of problems, whoever signs off is responsible, with the designer bearing primary responsibility.