Design approval defense: High-pressure vessels

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Case 1: I. Drawing design parameters: Design pressure of 20 MPa, design temperature of 60°C. Medium: Hydrogen, which is explosive. Specifications: DN500, cylinder wall thickness 38mm. Material: Q345R (normalized). Overall post-weld heat treatment of the equipment. II. Drawing issues: 1. The head steel plates must be ultrasonically inspected one by one, with a grade of II being considered acceptable. 2. The equipment has no manholes or inspection openings; the technical requirements only specify that thickness measurement is required. It has been added that “the calculated thickness must be indicated, along with requirements for periodic inspections during use.” ” 3. The purchased Grade IV forgings need to be re-inspected. 4. The hydrostatic test pressure is increased to 25.04 MPa for horizontal vessels. 5. The RT-III grade requirement for Class A and B welds of Equipment A and B is changed to Grade II as acceptable. 6. The technical requirements specify that a heat treatment for restoring properties is necessary after the cylinder is formed; therefore, a weld test plate should be provided along with the product. 7. The cylinder and head may not require heat treatment, provided that it is specified that preheating to 100°C is carried out before welding. 8. There is no indication regarding the inside and outside of the safety valve outlet; this should be specified in the technical requirements: Safety valves or overpressure relief devices must be taken into account in the process system. III. Teacher’s questions 1: How should unevenly thick welded joints be considered? 2. What are the differences in material selection between medium and low pressure vessels and high pressure vessels? For example, high-pressure vessels can use Q345R with a thickness of 38 mm; vessels for low and medium pressures with large diameters can also use Q345R. Why? Answer from the perspective of material selection. 3. Which devices require dehydrogenation treatment? 4. Which equipment requires post-weld heat treatment? 5. Stress analysis of horizontal vessels? (Nine forces) 6. How do welding stresses form and what are their hazards? 7. How many failure criteria are there for pressure vessels? 8. Under what circumstances is it necessary to use a burst disc device? 9. What are the types of container instability? What are elastic instability and inelastic instability? Case 2
I. Design parameters on the drawings
Design pressure: 17.9 MPa; Design temperature: 60°C. Medium: high-pressure nitrogen. Specifications: DN1400 mm, wall thickness: 110 mm. Material: Q345R (normalized). Post-weld heat treatment is required for the entire equipment.
II. Issues with the drawings
1. The technical characteristics table indicates 100% RT, but there is no specification of technical grade AB.
2. Tensile and impact tests must be conducted on each steel plate individually.
3. Each steel plate must undergo ultrasonic testing. (Important issues) 4. The insertion type is used for welding the small nozzles to the shell. 5. The technical specifications table lacks information on the material and standards of the main pressure-bearing components. 6. The technical specifications table does not include details regarding the properties of the medium. 7. Welding test plates are required for the product, but this is not indicated in the drawings. III. Questions posed by the instructor: 1. Why is the same formula used for calculating thin-walled and thick-walled structures? 2. What forces act on the edges reinforced due to openings in the shell? 3. What are the different types of reinforcement specified in GB150, and in what situations are they used? 4. What are the various connection methods between nozzles and the shell, and what are their respective advantages and disadvantages? 5. What considerations should be taken into account when designing the structure of horizontal containers? 6. How is pressure handled when the pressure on the shell side of a heat exchanger is lower than that on the tube side? 7. How to adjust cases where the stress calculation for fixed tube sheets is unsatisfactory? 8. What is the purpose of post-weld heat treatment? 9. What should be noted when performing post-weld heat treatment on composite plate containers? 10. Under what circumstances is it necessary to conduct pressure testing on equipment, and how is it carried out?