Questions from the first pressure vessel design review exam in 2015 (drawing selection and defense) for reference
Thread Content
I. Drawing selection: T218 (Class A high-pressure tower). 1. Design conditions: Equipment category: Class III; Design pressure: 7.15 MPa (G); Operating pressure: ≤6.3 MPa (G); Design temperature: 280°C; Operating temperature: 260°C–270°C; Medium: Syngas, quench liquid; Medium characteristics: Moderately hazardous/explosive; Main material: 13MnNiMoR + 316 (62 + 6 mm); Tower diameter: φ2600 × (62 + 6); Tower structure: Upper head (hemispherical) / Lower head (conical) / Skirt; Safety relief device: None; Tower volume: 77.5 cubic meters; Non-destructive testing requirements: For weld types A and B: 100% + 20% RT + UT, Grade II acceptable; For weld types C and D: 100% MT, Grade I acceptable. II. Errors in the drawing as estimated from visual inspection: (1) For the hydrostatic test, the pressure required for this test when the tower is in a horizontal position is not specified. (2) Heat treatment: no technical requirements. (3) The tower lacks the overall height dimension. (4) No non-destructive testing requirements are specified for the fillet welds of the tower’s lifting lugs. (My estimation is incorrect.) (5) The assembly drawing does not specify the standards for the composite panel material nor the relevant technical requirements. (My estimation was incorrect.) (6) Flange sealing surface type: The table shows RF for the pipe ends, with only two connections being RJ; I believe RJ could be replaced with RF. III. Defense: Teacher’s questions (1) What is the significance of the hydrostatic pressure of a liquid column? At which height is the hydrostatic pressure of a liquid column determined? (2) What are the advantages and disadvantages of a 150° and 120° saddle angle for horizontal containers? And stress analysis? (3) How are high-pressure studs processed? And what non-destructive testing is required? (4) How to prevent cracks from appearing in materials prone to delayed cracking? And how to detect it? (5) What other tasks need to be carried out on site after replacing the outlet pipe at the bottom of the tower? Is a hydrostatic test required? (6) What should be done if a high-pressure stud is found to be seized during maintenance? What measures can be taken to prevent being bitten to death? Are high-pressure studs fine-threaded or coarse-threaded? (7) How to inspect and accept composite panels?
Sofa, OP, how did the exam go? How did your defense go?
For A, B welding methods: 100% + 20% RT + UT – is grade II acceptable?
Reply: yong001 (No. 145515) The exam felt average; the defense also seemed average. I didn’t manage to show my usual level of performance – I could only do my best!
Reply: yong001 (No. 145515) The exam felt average; the defense also seemed average. I didn’t manage to show my usual level of performance – I could only do my best!
Reply: gjyzb (No. 753927) Well, the senior has examined it carefully; UT should be rated as grade I compliant.
Thank you for sharing, but the drawing information you provided isn’t very complete.
This post was last edited by Rose from YPES on 2015-7-23 at 10:03. 20% UT should be at least at level II to be considered qualified; there must be a mistake! ! I think RF should be changed to RJ; after all, 7.15 MPa is a fairly high pressure, and RF is used in applications with lower pressures. Choosing a textured surface is better than RF.
Mine is a liquid chlorine storage tank; it is highly toxic, with an operating pressure of around 1.4 MPa and a design pressure of 2.5 MPa； The operating temperature is 20 degrees, and the design temperature is -40 degrees. The estimated major error is the design temperature. I think the design temperature should be higher than the operating temperature, and it should be specified in the manufacturing requirements that low-temperature impact testing at -40 degrees Celsius is required. One of the technical errors is the failure to specify the maximum allowable operating pressure, which is a specific requirement for integrity tests ； Secondly, the material is Q345R; it should be changed to 16MnDR, and the value for low-temperature impact energy must also be modified ； Thirdly, there is no requirement to prepare welded test pieces. Another error is the set pressure of the safety valve (indicated as 2.5 MPa in the diagram). Due to the leak testing, the lower limit of the safety valve’s set pressure should be higher than the design pressure; the allowable deviation for this set pressure is generally Max(±3%Pz, 0.015 MPa). Based on calculations, the set pressure Pz should be no less than 2.5/0.97 MPa = 2.577 MPa, so Pz can be set at 2.6 MPa ； The maximum allowable operating pressure Pmax should be calculated based on the effective thickness, and it must not be less than 2.6×1.03 MPa = 2.678 MPa; if this requirement is not met, the wall thickness of the pressure-bearing components needs to be adjusted. Due to time constraints, I didn’t examine the general layout and material list in detail, so I’m not sure if there are any errors. When reviewing the drawings, focus on identifying major errors (1) and technical errors (3); 50 points will be awarded once all of them are found ； And all the general mistakes combined amount to only 10 points. The time available for reviewing the questions is really tight – only 30 minutes. Don’t waste time on areas that carry few points; it’s just an exam after all. As for the defense, luck plays a big role; if it happens to be questions you are familiar with, then everything is fine. Even if you’re not entirely sure, you should still mention what you know – that will get you another 20 points and help you pass.
I don’t dare; I’m just an elementary school student, let alone take an examiner exam. . . However, judging from the questions for defense posted by the original poster, they indeed cover a wide range of topics: horizontal containers, high-pressure containers, welding, inspection, hydrostatic testing, equipment operation, maintenance, and composite panels. . . Without extensive experience in design and proofreading, or without familiarity with the standards, it’s really difficult to answer many of the questions. I can only feel admiration. Thank you to the original poster for the generous sharing.
I am very grateful for the joint efforts of my colleagues; I also realize that I haven’t done enough work in this area. The design and manufacture of pressure vessels are inherently a reflection of comprehensive knowledge. I have only been working on pressure vessel design for a short time; previously I was involved in manufacturing and maintenance, so I paid little attention to the design aspect. It was only when I actually started doing design work that I realized it was the root cause of the problems I encountered over the years in my job. I recalled the information from memory after taking the exam; due to the tight schedule, I didn’t have time to read all the diagrams, so my description isn’t entirely comprehensive. Please understand.