Value selection for jacket seal plate thickness
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In Note 3 of Figure D.23 in GB/T150 p309, δc is equal to 2δj. Is this δj the nominal thickness or the design thickness?
It is generally based on the nominal thickness
The jacket originally required a thickness of 3 mm to be strong enough; for some reason, 4 mm thick steel plate was used (perhaps due to leftover material in the warehouse). So, must the sealing plate also be 8 mm thick, or is 6 mm sufficient?
8 mm is already thin enough; it also depends on the width of your shoulder strap – you can’t simply use a standard size
You say that it’s not possible to simply apply standards, but then what is the reason you say that 8mm is already too thin? The width of the jacket shoulder (as I use it) is generally less than or equal to 50 mm.
δj refers to the nominal thickness, which is calculated in accordance with the notes provided in Figure D.23 of GB/T150.3-2011 (on pages P309 or P310). Since δn represents the nominal thickness of the shell, δj should be the nominal thickness of the sleeve shell.
What you say makes sense. I just think the rule is a bit absurd; no matter how thick the jacket actually needs to be, as long as the nominal thickness is known, the cover plate thickness is set to twice that value.
Sometimes I’m also confused; for example, if the thickness to be calculated is only 6 mm while the nominal thickness is 12 mm, should the double of this thickness be 12 or 20? Is 20 a waste of space?