For local non-destructive testing equipment, the default value for the coefficient SW6 in the case of opening reinforcement is 1; the inspection level within the reinforcement area is determined through coordination between design and inspection processes
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This post was last edited by Claymore2000 on 2025-3-7 at 15:32. Dear teachers, for equipment with a grade of 0.85–20%, Grade III, when using the reinforcement calculation module for SW6 openings, the software defaults to a welding joint coefficient of 1 for the openings and also 1 for the pipe connections (see Figures 1-a, 1-b, 1-c). In other words, for equipment in the 20%–0.85 range, the reinforcement calculation assumes a value of 1 throughout the effective range of the pipe connection openings. However, if the reinforcement is calculated using this value of 1, then the flaw detection within the 2DOP range of the pipe connections will be rated as Grade II, rather than Grade III. For non-destructive testing personnel, it was found on site that the nozzle pressed against the main weld or enclosed the main weld within a range equal to twice the diameter of the nozzle’s opening; in such cases, the 2DOP value was still determined according to Level III. They did not know how the value SW6 was calculated (in fact, non-destructive testing personnel are not interested in the calculation details either; the testing level is determined based on standards and the technical specifications in the drawings). In sections 150.4 (Figure 3) and 150.3 (Figure 2), it is specified that no defects exceeding the allowed limits should be present in the area covered by the 2DOP range of the nozzle openings, but no specific testing level was given. The testing personnel assumed that the level should be 100%, provided that it matched the level required for the main structure. Regarding this matter, how is coordination achieved among manufacturers, designers, and flaw detectors? For the weld joint at the default opening of SW6, a value of 1 is used; when performing calculations, account is taken of the inspector’s knowledge – should 0.85 or 1 be used, depending on whether the inspector has been informed? I have discussed this matter with non-destructive testing personnel before; GB/T150.3 -8.1.5 (Figure 2) only specifies that there should be no defects exceeding the specified limits within the reinforcement area B=2dop for openings, but it does not state the required grade. When 20% of the structure is involved, non-destructive testing is generally carried out according to Grade III for the main structure ； 150.4 That one too (Figure 3), with the major premise based on the premise of local non-destructive testing in 10.3.2. Moreover, the effective reinforcement range is determined by two parameters: width B=2dop and height h=sqrt(Dop, δnt). There must be no defects exceeding the specified limits within B=2dop, and the same applies to the height h=sqrt(Dop, δnt); hence, in addition to the inspection criteria for shells of types A and B within 2dop, there is also an inspection criterion related to the height of the longitudinal seams in the fittings themselves, namely h=sqrt(Dop, δnt). For example, for DN500 manhole fittings with longitudinal seams of type AM, grades A and B require 20% inspection at level III; by default, inspectors for manhole AM fittings also use a 20% inspection rate at level III. However, for SW6 fittings, a higher inspection rate is applied, with 100% inspection at level II required for AM fittings. Inspectors are not aware of this information. Therefore, I believe that the requirement that \"grades A and B within a range twice the diameter of the fitting opening should be inspected 100% and deemed acceptable at level II\" should always be indicated on the drawings related to the local inspection procedures
This post was last edited by zjq1962 on 2025-3-7 at 14:51. In such cases, it is even more difficult to maintain control when the design unit and the manufacturing unit are not the same entity. When calculating the reinforcement for openings, the joint coefficient at those openings in the shell should be taken as the one specified in the technical specifications. For pipes, if they are seamless, the joint coefficient is 1.0; if they are made from sheet metal, they are treated in the same way as the shell. If it is the same company, the welding technicians will check whether there are any welds within the reinforcement area. If there are, they will use the joint coefficient specified in the design calculations for hole reinforcement, or decide on the quality level for non-destructive testing after consulting with the designers. The inspection department will then issue a non-destructive testing order, which the testing personnel simply need to carry out.
Regarding open-hole reinforcement and flaw detection levels, adequate communication should be ensured among the manufacturing plant, the design department, and the flaw detection department. When using the SW6 calculation module for hole reinforcement calculations, the design department defaults to using a welding joint coefficient of 1; however, the actual inspection grade should be determined in accordance with specific standards and technical requirements. Although 1 is the default value in terms of design, it is still necessary to take into account the awareness of the inspection personnel; it may be required to clarify during the briefing whether the inspection level should be determined based on 0.85 or 1. In flaw detection work, non-destructive testing personnel usually follow the drawings and technical specifications; if the flaw detection level is not specified in the design documents, it is assumed to be the same as that of the main equipment. For special areas such as connection openings, if the inspection requirements for these areas differ from those of the main structure, the design department should specify this clearly in the design drawings or technical documents, and emphasize it during the production briefing to avoid confusion during on-site implementation. In summary, the design, production, and testing teams should enhance communication to ensure that design intentions are accurately conveyed and properly implemented. The design documents should clearly specify all special requirements, including the inspection level and scope, to ensure product quality and safety. .
When I do the calculations, I manually change SW6 to 0.85. (The U-tube heat exchanger in SW2011 V5.0 will have a value of 0.85 based on the cylinder size, but this is not the case in SW2024.)
This post was last edited by Claymore2000 on 2025-3-7 at 21:02. Manual adjustment is possible, but I don’t think it’s necessary; after all, it’s unlikely for Class A or B joints to be present in the area around the opening. Moreover, using a value of 1 allows for more margin in terms of thickness calculation for that area. It’s sufficient to add a sentence to the design drawings: “Class A and B joints within a range of 2 times the diameter of the opening must undergo 100% RT testing, with acceptance at level II.” This way, the inspection standard for the area around the opening is clearly specified as level II, and there will be no concerns if the design uses a value of 1. As for the effective reinforcement height, for pipes without seams, no consideration is needed; a value of 1 is sufficient. Consideration becomes necessary for pipes with seams and a DN of 500 or more (such as manholes). The wall thickness of such pipes is usually 20 mm or less; if it’s thicker, then forged pipes are used and there’s no need to consider any pipe coefficient. The diameter should be taken as 3000. sqrt(3000 x 20) = 245. The extension length of the pipe is generally between 150 and 200 mm, while for manholes it can reach 300 to 400 mm. The actual maximum value for the reinforcement height h can be determined by measuring from the surface of the shell to the back of the PL/SO flange or to the weld line of the WN flange – this distance is around 200 mm. One inspection sheet is sufficient for this purpose. For pipes with longitudinal seams (usually manholes), a 100% requirement applies, with grade II being sufficient. Since it’s just one inspection sheet, changing the grade from III to II isn’t an issue. This type of inspection doesn’t increase costs. If one is concerned that inspectors might notice a difference such as “20% for the main body and 100% – grade II for the longitudinal seams of manholes”, then remember to use a pipe coefficient of 0.85 for manholes. Since manholes with a DN of over 250 already use a coefficient of 0.85, it’s sufficient to include a statement indicating that this coefficient should be applied when calculating manholes. The joint coefficient at the openings in the shell for each pipe is assumed to be 1 by default, so no changes are needed. I think that’s sufficient
Thank you for sharing; it was very informative. Thanks!
This post was last edited by Buddha and Orchid on 2025-3-15 at 20:49. This issue actually relates to the principle of reinforcing with openings of equal area. Equal-area strengthening takes into account the principal stress value in the cross-section surrounding the opening; for containers with a regular design, 150 already serves as a fixed limit, and it is the cross-section parallel to the axis of the cylinder that is considered. In other words, as long as the hole is not located in Class A or Class B welds, then for the equal-area reinforcement method, the welds will not affect the strength of the reinforcement material. Since most designers will only make holes in Class A or Class B welds as a last resort, in most cases the welding joint factor for the shell at the location of the hole is 1.0. That is why SW6 is set to 1.0 by default in the software. The requirement that there should be no defects exceeding specified limits within a diameter of 2 times that of the opening has nothing to do with reinforcement at the opening. What the standard takes into account is that the local film stress in the area around the opening, within a range of sqrt RT, will be higher than in areas without openings; hence, additional non-destructive testing is required. Furthermore, I believe that the acceptance level for non-destructive testing is not determined by the testing ratio, but rather by the factors that determine that testing ratio. As an example, consider a container in which the medium is extremely hazardous; the standard requires 100% RT, and a level II rating is considered satisfactory. The qualified grade here is Grade II because the hazard level of the medium in the container is extremely hazardous, and it is not because 100% RT means that the qualified grade must be Grade II ； Another example: for a low-pressure air storage tank, the standard requires a testing rate of 20%, but the customer demands 100% testing. In this case, the testing requirement is higher than the standard; should the acceptance threshold also be raised as a result? Therefore, there is actually no causal relationship between the testing ratio and the qualified grade.
This post was last edited by Claymore2000 on 2025-3-19 09:01. Hello, regarding what you mentioned – that the local film stress within the range of “sqrt(RT)” is greater than that in areas without openings – could you recommend any detailed references or relevant books on this topic? Thank you. There are also ① the formula for calculating the reinforcement height in case of hole reinforcement: h=sqrt(dop*δnt), ② in the calculation of flanges, the length of the straight sides is given by h0=sqrt(Di*δ0), and ③ the length of the conical reinforcement section is L1=sqrt(2*Dis*δr/cosα). All three of these formulas follow a structure similar to sqrt(D*T). Why is the \"effective range\" for calculations in these three cases all of the form sqrt(D*T)? Do these three places share any commonalities in the essence of mechanical calculations?
Yes, indeed there is no causal relationship between proportion and grade. As you mentioned, aside from those special conditions such as extremely high levels of hazard or low temperatures of -40°C, which require a Grade II qualification with 100% coverage and a coefficient of 1, for other cases where the 100% requirement is not due to the harshness of the working conditions, it is still considered as Grade III with a coefficient of 0.85. For example, in manufacturing processes where panels are first assembled before the head is formed, 100% inspection corresponds to Grade III; similarly, when welds are covered by gaskets or reinforcement rings, it also falls under Grade III with 100% coverage.
Choose the higher standard; for local equipment inspections, prioritize 100% inspection of welds within the coverage area of the reinforcement rings