the rule of thumb in inches was "pi spacing, rounded up to the next multiple of 4"
[i.e., 16 bolts on a 16" bolt circle; 20 bolts on an 18" BCD] so ~ 3-1/8" [80mm} between bolts
the ABS has design rules for high speed craft:
http://www.eagle.org/eagleExternalPortalWEB/appmanager/absEagle/absEagleDesktop?_nfpb=true&_pageLabel=abs_eagle_portal_rules_guides_download_page&nodePath=%2FBEA+Repository%2FRules%26Guides%2FCurrent%2F61_HighSpeedCraft
sometimes they'll scribe a line 1" back on the pipe from the fitting end @ full insertion depth, so that after it's welded they can verify the gap from the outside
is it possible to have a link or stabiliser tie rod from one end to a base plate or foundation to prevent moments? Or does attachment to the compressor accomplish this?
Look in the old Taylor Forge Bolt Data Chart - it gives edge didtances & other dims by bolt size. for 3/4 bolts, they have 13/16" cL-edge. If you're really tight on space, check out Graylocs: http://www.grayloc.com/grayloc/
Could you just stand it up when complete, seal the bottom & fill with water? that would give you ~880x the pressure from the column of air. just made sure it can take the "Full of Water" weight
Hydro before PWHT would tend to relieve the favorable stresses induced by the hydrotest at concentrated stress areas, so you'd want to do it again afterwards anyway
Look up A.E.Blach, "Bolted Flanged Connections for Non-Circular Pressure Vessels,"
There were some Rectangular Flange articles ~20 years back in the ASME Transactions or the PVP booklets
Did you guys see that Ladish has the Good Old #55 Fittings book on their Website:
http://www.hackneyladish.com/Catalog.aspx
[Mucho megabytes, but they don’t make ‘em like this any more! - From 1954]
