Should I use WRC107 or WRC297?
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This post was last edited by nancy8339 on 2015-12-30 at 17:28. The fittings on the cylindrical shell are seamless steel pipes, rather than solid round bars. When performing local stress calculations, should WRC107 or WRC297 be used? Does the WRC107 standard apply to solid fittings, while WRC297 applies to nozzles rather than fittings? If WRC107 is used, how should the wall thickness of this circular fitting be calculated?
I only know that 107 does not check the local stress at the joint. As for what the difference between the two of them is, I don’t understand…
Both WRC107 and WRC297 calculate the stress at the housing, without calculating the stress at the attachments.
WRC107 is completely unable to calculate the thickness of the takeover wall. If there are any special requirements that necessitate a cautious approach, the most conservative option is to calculate WRC107, WRC197, EN13345, and CSCBPV all at once; if they all pass, then it’s considered acceptable. The calculation is not complicated. In fact, most in the industry just use WRC107 for calculations to ensure compliance. The others are too conservative; their allowable values are often only one-third or half of those of WRC107. WRC107 has been around for almost 30 years and is still in use, which shows it’s effective; that means the other versions are too conservative. The requirements regarding the wall thickness of pipes are relatively easy to meet; if you look at the tables showing the maximum allowable external forces and moments for those types of fittings, you don’t need to use the pipe wall thickness as a parameter at all when checking them. As long as thin-walled tubes are not specifically chosen, there is no issue with the wall thickness.
Does taking over involve making holes in the column shell? What I’m asking about is the attachment – there are no holes in the column shell; they are simply welded together. Using WRC107, it’s possible to calculate the size of the attachment, but I’m not quite sure how to check the wall thickness. Are there any empirical formulas or something like that?
WRC107 seems to have no requirements for inward-extending and flush type fittings. What size is the attachment, and how do you plan to weld it? Weld it directly on? Is that okay? If welding is done like in the case of ear-type support pads, then what needs to be checked is not the cylinder or the attachments, but rather the weld seam. Personally, I think that kind of welding is not reliable at all.
If the main pipe is thickened overall and the fitting is welded directly to the main pipe without gaskets, can the minimum diameter of such fitting be determined by checking the allowable stress value of the weld?
Currently, WRC107 is still the standard method for calculating the take over load, but I think it would be more conservative to use WRC297 for such calculations, as 107 is based on a solid cylindrical model.