I am currently in Kunming attending training for examiners. Could someone help me with the following questions, which are from last year’s exam?
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4. For a fixed-tube-sheet heat exchanger, when the shell is made of Q245R with a thickness of 8 mm, the calculations yield satisfactory results; later, 10 mm thick plates of the same material are used instead. Is it necessary to redo the calculations? Why? 6. The cylinder of one equipment is made of a composite plate of S31603+Q345R, with a thickness of 3+100. A DN200 pipe connection is provided on the cylinder, and the reinforcement tubes are made of S31603 forgings, to be welded in place. What are the potential risks during manufacturing? Comprehensive Question 1: (High-neck flange design issue) (15 points) 1. What are the criteria for checking axial stress? 2. Where is the maximum radial stress? 3. Draw the distribution diagram of circumferential stress. 4. There is a leak at the flange sealing surface. What are the possible causes, and how should it be adjusted? One of the sub-questions in Comprehensive Question 2 is: 2. What is the difference between the equal-area reinforcement calculation method and the analytical reinforcement calculation method, and what are the differences in their calculation results? I’m not very good at any of these; please help answer them
This post was last edited by fzujunru on 2015-7-11 at 21:18. The answers to 4 questions are here. 4. There is a fixed-tube-sheet heat exchanger; when the shell is made of Q245R with a thickness of 8 mm, the calculations show it is acceptable, but later the same material was used in sheets with a thickness of 10 mm... http://bbs.hcbbs.com/thread-1323576-1-1.html Recalculations are necessary because an increase in the shell thickness has an impact on the tube sheet.
For flanged tube sheets used in combination or welded tube sheets: it affects the stiffness of the supports surrounding the tube sheet, thereby influencing the calculated thickness of the tube sheet； In addition, it affects the axial stiffness of the shell-side cylinder, thereby influencing the calculation of temperature difference stress. For other types of tube sheets: they affect the axial stiffness of the shell-side cylinder, thereby influencing the calculation of temperature difference stresses.
I think it’s not appropriate to ask for the actual exam questions directly online in this way. The expert who issues the certificate will take this into account when forming an opinion about you, which will increase the difficulty of your defense and the likelihood of you failing.
Let’s discuss last year’s exam questions; I think they are quite good
What is the difference between the equal-area reinforcement calculation method and the analytical reinforcement calculation method, and how do their calculation results differ? Answer: The equal area method is based on static equilibrium; it is a calculation approach that relies on the principle of balancing the load-bearing capacity of the metal area within the effective reinforcement range of the opening (including the shell, nozzles, reinforcement materials, etc.) with the internal pressure load. The analysis method is based on plastic limit and stability analysis; it ensures the safety of the openings by guaranteeing sufficient plastic bearing capacity during single loading and the stability requirements under repeated loading. The calculation result shows that C＞1 indicates that the analysis method requires a reinforcement area that is larger than or equal to the equivalent area for reinforcement ； C<1 indicates that the analysis method requires a reinforcement area that is smaller than or equal to the equivalent area reinforcement. Note: The C value represents the reinforcement coefficient for the nozzles required to design the corresponding cylinder reinforcement according to the analytical method, under the given opening ratio and D/T (where D is the diameter of the midplane of the cylinder and T is the effective thickness of the cylinder); or it represents the ratio of the corresponding reinforcement area calculated based on the effective reinforcement areas of the cylinder and nozzles as specified by the equal-area reinforcement method, to the reinforcement area required by that method.
1. What are the checking conditions for axial stress? For σH≤1.5 ft, the maximum radial stress in the flange occurs at the inner edge of the junction surface between the flange ring and the cone neck.
The circumferential stress distribution diagram is at the bottom of page 221 in the \"Training Manual for Pressure Vessel Design Engineers\"; just draw it according to that. There is a leak at the flange sealing surface. What are the possible causes, and how should it be adjusted? Page 214 of the “Training Manual for Pressure Vessel Design Engineers”, clause 12.1.2, which consists of 5 sub-clauses; you can summarize it accordingly.
There is a device whose cylinder is made of S31603+Q345R composite steel, with a thickness of 3+100 mm. A DN200 pipe opening is provided on the cylinder, and the reinforcement tubes are made of S31603 forgings, to be welded in place. What are the potential risks during manufacturing? In my opinion, the thicker the steel, the deeper the weld will be, and the greater the tendency for the weld to contract after cooling ； Moreover, as the rigidity increases, the ability to resist local contraction deformation grows, thereby resulting in greater welding residual stresses. Furthermore, the linear expansion coefficient of stainless steel differs from that of carbon steel; as a result, the cooling and contraction rates after welding are different, leading to greater deformation inconsistencies and higher stress levels. Excessive welding stress can easily cause welding cracks, or even complete failure of the weld.
People use pseudonyms online; how can experts know who you are, haha.