Guest
does anybody know where to find formulae for designing rectangular flat covers for ASME vessels. Similar to air cooler box covers, what are they designed to???
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In ASME VIII, Div 1, UG-34 you find the rules for flat covers (circular and non circular).
The thickness required with the rules of UG-34 of course depends on the pressure and the diameter and with some "playing with the formulas" you may find why on most cases blind flanges are so thick or why formed heads is a good bussines.
I´ve seen cases where they, for some reason, want to use flat covers (even where they are not "practical" within the code philosophy), but aided with FEA analysis and/or the use of stiffners, a topic not covered by the code.
For bolted covers the type of gasket may affect a lot the design of the cover.
DavidCR
The thickness required with the rules of UG-34 of course depends on the pressure and the diameter and with some "playing with the formulas" you may find why on most cases blind flanges are so thick or why formed heads is a good bussines.
I´ve seen cases where they, for some reason, want to use flat covers (even where they are not "practical" within the code philosophy), but aided with FEA analysis and/or the use of stiffners, a topic not covered by the code.
For bolted covers the type of gasket may affect a lot the design of the cover.
DavidCR
You can design the bolted rectangular unstayed flat cover as used for cover plate type header boxes of Air Cooled Heat Exchangers as per ASME Sec VIII Div 1 UG 34 rules usinfg formula (5). Bolt load W to be computed correctly for rectangular configuration taking the guide lines from Appendix 2. This is an accepted practice. I have been designing this way since many years. This is also followed by all concerned designers of Air coolers. If you have a specific case please send me the data to my E-mail : dwarakakrishn@sify.com, I will provide the sizing to you.
V.Dwarakakrishna.
V.Dwarakakrishna.
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db80,
If this is your first attempt at rectangular flanges there are somethings to consider when designing rectangular chamber flanges that are to be used with rectangular covers.
Box flange distortion due to welding in the long sides of the rectangles can be considerable. It sometimes pays to leave a larger "Edge Distance" at bolt holes to accomadate bowing due to the bar-to-side-wall welds.
If your fitters and welders are also unfamilar with this configuration, a lot of time and expense may be required to straighten edges.
If configuration allows, bolt rectangular flange bars to cover before welding-out. If you don't intend to bolt together, Do NOT Drill until Header is completed.
Stiffeners between the inner box walls help, but residual stress may still bow in sides when these are removed.
Depending on materials of construction, and client requirements, it sometimes pays to leave extra material in flange width and mill off after welding, thus matching dimensions of the cover and preserving edge distance.
If you are in a fabrication shop, get some feed back from your floor people before you specify your materials to purchasing.
"Round things are better"
If this is your first attempt at rectangular flanges there are somethings to consider when designing rectangular chamber flanges that are to be used with rectangular covers.
Box flange distortion due to welding in the long sides of the rectangles can be considerable. It sometimes pays to leave a larger "Edge Distance" at bolt holes to accomadate bowing due to the bar-to-side-wall welds.
If your fitters and welders are also unfamilar with this configuration, a lot of time and expense may be required to straighten edges.
If configuration allows, bolt rectangular flange bars to cover before welding-out. If you don't intend to bolt together, Do NOT Drill until Header is completed.
Stiffeners between the inner box walls help, but residual stress may still bow in sides when these are removed.
Depending on materials of construction, and client requirements, it sometimes pays to leave extra material in flange width and mill off after welding, thus matching dimensions of the cover and preserving edge distance.
If you are in a fabrication shop, get some feed back from your floor people before you specify your materials to purchasing.
"Round things are better"
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