Does rolling a cylinder from steel plate thin it?
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This post was last edited by SDHZZXM on 2017-9-13 08:26. As the title suggests: Does rolling steel plates into cylinders result in thinning? In other words: the designed thickness of the cylinder shell is 9.7 mm; can it be manufactured using steel plates with a thickness of 10 mm? (Negative deviation of steel plate: 0.3)
Cold rolling or medium-temperature rolling generally poses no problems, so there is no need to consider thinning.
This post was last edited by SDHZZXM on 2017-9-13 09:13. We have a container with a similar issue, and the inspection personnel disagree. It is mainly considered from two aspects: one is that the measuring tools have measurement errors, and the other is that scratches and dents are inevitable during the manufacturing process... The container has been manufactured; what should be done in such a situation?
For cold-rolled cylinders, thinning is not taken into account; therefore, it is not necessary to specify a minimum forming thickness
If the degree of dents and scratches exceeds the allowable limits, repairs can be carried out in accordance with the relevant requirements of GB150.4. As for measuring tools, it can only be said that the inspection personnel there are quite strange
Whether rolling a cylinder from steel plate will result in thinning depends on the specific forming process. For 10mm thin cold-rolled sheets, the pressure in the thickness direction is not sufficient to cause yield deformation in that direction, so thinning is unlikely to occur. Scrapes and scratches occurred during the manufacturing process; thickness measurement is required, followed by a determination of whether repair welding or simple grinding is needed. If inspection personnel have objections to the design, they should raise them during the review and signing of the design documents prior to the start of manufacturing (see ASME Section 6.2.1.1). Manufacturing is complete; only the manufacturing quality documents need to be reviewed. The design thickness is 9.7 mm, with a nominal thickness of 10 mm; this does not violate the standard requirements, but engineering design should not be so frugal. The process tolerances required for typical pressure vessel manufacturing processes such as cylinder rolling and head forming should be taken into account during the design phase. The thickness of the steel plates purchased should be equal to the nominal thickness specified in the drawings; any increase in thickness requires approval from the original designer.
It’s unlikely that the 10mm thickness will decrease, but as you said, for a 10mm thick plate the negative deviation is 0.3; so the actual thickness could be 9.7 mm, with little margin left. What the person above said is right – there’s no need to be so stingy; using 12mm will eliminate all problems
The actual thickness of the plate for 10mm pressure vessels should be 10.1mm. I’m not sure if your company has conducted any measurements. If you don’t believe it, you can measure the finished container. No problem.
It’s fine as long as the calculated thickness isn’t 9.7; to be precise, there are always deviations in the nominal thickness of steel plates – after all, those deviations aren’t taken into account
The calculated thickness is 9.7, the corrosion margin is 0, and the design thickness is also 9.7