【JST-047】One-on-one assistance office for heat exchanger technology

Since there are no issues with the heat exchanger, I’ll first upload some animation materials on heat exchangers that I found from other sources; I hope fellow enthusiasts will like them. Friends who download it can simply remove the .rar extension.

This post was last edited by ztr1118 on 2012-5-26 09:35. In shell-and-tube heat exchangers, when single-strength expansion jointing is used for the tubes and tube sheets (without seal welding), how can the sealing performance of the joints be ensured? During the swaging process qualification tests, a pull-out stress of 4 MPa is easily achievable, but it does not necessarily ensure satisfactory sealing performance. In product manufacturing, the traditional methods for checking and verifying the expansion rate of tubes are not only time-consuming and labor-intensive but also result in scattered data. GB151-1998 does not provide corresponding provisions on this in its manufacturing section. The expansion joining techniques described in some literature focus primarily on theoretical analysis and experimental research. The manufacturer is confused by this. Are there any mature and easy-to-control methods for inspecting and accepting products in this industry?

This post was last edited by Gu Tongjiu on 2012-5-27 at 17:03. In shell-and-tube heat exchangers, when a single-strength expansion joint is used between the tubes and the tube sheet, ensuring the sealing performance of such joints can be achieved by controlling the quality of the grooves made in the tube sheet. Additionally, the choice of expansion tool is also crucial; we have been using imported hydraulic expansion tools, which yield very good results； Advantages of hydraulic expansion: It offers better reliability compared to traditional expansion methods ； No crimping gap, eliminating gap corrosion ； Low expansion backforce ； It is not prone to over-inflation ； Reduce damage to the surface of the heat exchange tubes ； The stress distribution is uniform ； It offers advantages such as reducing the stress generated by crimping, minimizing the risk of leakage, and extending service life. Before performing the expansion joining on the equipment, a simulated expansion joining test is carried out first, and the simulated components are inspected in order to determine the actual expansion joining parameters and ensure the quality of this process. Traditional testing methods can only be used to test conventional operating condition designs, and there are still no other good alternatives available to date. For special operating conditions, such as high corrosivity or flammability and explosiveness, helium detection must be used.

Thank you, Teacher Gu, for your generous help. Creating expansion grooves through the tube sheet holes has a significant effect on increasing the pulling stress between the tubes and the tube sheet. For the relatively important heat exchangers in our production, hydraulic expansion joining is also widely used. We often encounter this problem: when conducting pressure tests on simulated crimped specimens, there is no leakage at the pipe ends. After crimping the products using the same crimping parameters, leakage may occur sometimes. The reason for this is that, although the pulling stress between the simulated test piece and the tube sheet of the product after expansion bonding is roughly the same, the pulling force exerted on the heat exchange tubes during pressure testing is not identical; it is very likely that the pulling force on the heat exchange tubes in the actual product is much greater, which leads to leakage. Sometimes, as a last resort, it is an empirical practice to increase the crimping parameters obtained from the simulation specimens before applying them to the actual product crimping. Some manufacturers still use the tube expansion rate for control. However, due to the varying sizes of the pipe holes and pipes, testing is not only time-consuming and labor-intensive but also results in scattered data. We hope to find a simple method to control only the expansion joint pressure in order to meet the pull-out force and sealing requirements of the pipes. ……

I’m not sure if those upstairs have paid close attention to this, but when we drill holes in the tube sheets at present, in order to meet deadlines we often focus only on the quantity of holes drilled, without considering how many times the drills need to be repaired. As a result, it’s difficult to ensure that the quality of the holes meets the required standards. This is why the test pieces turn out to be satisfactory, yet there are problems with the actual drilling process. When the diameter of the hole is too large or the verticality deviation is too great, the setting for expansion joining becomes ineffective. Fundamentally, if you want to obtain a good product, it is necessary to produce it in strict accordance with the production process; there is no room for carelessness

This post was last edited by awangyong1 on 2012-6-9 at 21:25. Hello, experts: I am currently dealing with a set of heat exchangers as shown in the diagram. I’m not sure how to design the middle part of the saddles used for overlapping these heat exchangers, nor how to carry out strength calculations. The upper heat exchanger has a diameter of DN500, while the lower one has a diameter of DN600. If I use the standards JB/T4712 to determine the dimensions of the saddles for the upper heat exchanger and increase their height by removing the intermediate support structures, then the height of such saddles would be 535 mm. I tried to use the specifications outlined in SH/T3418-2007 for three-overlapping saddles in my calculations, but there is an issue related to the \"total equivalent load acting on the equipment\". The seismic bending moment Meql – I don’t know which letter in the calculations for saddle supports of steel horizontal vessels as specified in JB/T4731-2005 corresponds to this symbol Meql; I’ve spent a lot of time reading the relevant documents but was unable to find it. I’m not sure what good calculation methods experts have for checking the saddles of this type of stacked heat exchanger; I would appreciate any guidance you can provide. Thank you very much

Sorry, I’m just getting back to your question. I have reviewed your question. Regarding the calculation of the frontward offset of the saddle, our company has not had any reliable criteria to rely on; we have always followed JB/T4712 for such calculations. When it is necessary to increase certain dimensions, we resolve this by increasing the thickness or adding reinforcing ribs based on experience, and so far no problems have arisen. Therefore, it is suggested that the original poster could also adopt this approach: when designing, we should meet strength requirements without being rigid in our thinking. I’m not sure if my explanation will be helpful to the original poster; if not, you can ask Haiyou from the design institute for assistance.

May I ask the expert: in the calculation of the triple overlapping saddle as specified in SH/T3418-2007, there is a concept of \"total equivalent force acting on the equipment.\" The seismic bending moment Meql – I’m not sure which letter in the calculations for saddle supports of steel horizontal vessels as specified in JB/T4731-2005 corresponds to this symbol Meql. Could experts please help explain this?

This post was last edited by Gu Tongjiu on 2012-6-12 08:20. Our company has never used the SH/T3418-2007 standard for triple lap saddles to calculate or manufacture heat exchangers, so we have no experience to share with you. I have also looked up a lot of information these days, but I couldn’t find any indication of the relationship between the \"seismic bending moment Meql\" you mentioned and the standards specified in JB/T4731-2005 for saddle supports of steel horizontal vessels. I’m sorry, I don’t know the answer to this question either; I can’t help you. One more thing: Nowadays, manufacturers of heat exchangers do not calculate the saddle supports in the way you mentioned; instead, they estimate them based on JB/T4731-2005 and practical experience, preferring to make them thicker rather than thinner. After all, a slightly greater thickness has little impact on the overall cost of the device.

This post was last edited by awangyong1 on 2012-6-13 at 17:23. Experts, I have a device whose baffle plates cannot be arranged evenly; no matter how I try to adjust them, they still can’t be arranged properly. The problem lies in the CAD file. Please have the experts take a look and offer some advice