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Area for Reinforcement
3

Area for Reinforcement

Area for Reinforcement

(OP)
I have a flat stayed plate with multiple openings that will be attached to a Section I vessel.  The plate has thru-hole openings for flanged connections to be bolted directly to the plate as well as the accompanying bolt holes (not thru).  The thru -hole openings happen to be closer than 2*Diameter and therefore need to be reinforced.

I was designing the plate to have the reinforcement within its material thickness (see attachment).  When I examine a cross section that is normal to the plate and intersects the centers of two adjacent thru holes (Plane 1), there is plenty of material within the area available for reinforcement.  The complication comes with the bolt holes.  If I look at a cross section that goes from one thru hole to a bolt hole (Plane 2), the hole intersects the allowable area for compensation I determined earlier.  However, this 2nd plane does not intersect any other thru-holes.

Do I need to subtract out the bolt hole area found in Plane 2 from the area used for compensation in Plane 1?  Additionally, can I use the material from the bolted flange as compensation?  Looking at all this in terms of area is somewhat confusing because it seems what I should be concerned with is volume of material within the allowable area for reinforcement.

I hope I explained this well enough to understand.  Any help would be greatly appreciated!

Best,
Steris

RE: Area for Reinforcement

Do I need to subtract out the bolt hole area found in Plane 2 from the area used for compensation in Plane 1? ->No
Additionally, can I use the material from the bolted flange as compensation? ->No
The compensation has to be done on all planes containing the CL for each opening. So for the single openings you'll subtract the bolt hole from the available area (and of course this won't be limiting). When your plane intersects a close by opening (and of course worst case is when the plane passes through the CL of the other opening), there are no bolt holes so you just take the available area midway of the two (for equal diameters).

prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides
http://www.levitans.com : Air bearing pads

RE: Area for Reinforcement

(OP)
Thanks for the help!  That really clears up my questions.  That article was really informative as well.  Thanks again!

-Steris

RE: Area for Reinforcement

Be careful of the stress risers.

If the "bolt holes" are not through holes - which is how I understand your commnet above - then the studs (not bolts!) are creating additional stress risers on the plate at each place where they are attached.

See, a real bolt hole penetrates the plate, and is "filled" by a bolt going through the plate, creating a clamping force between inside and outside (or between the two flanges) of the PV.   The bolt is transmitting the force on the handhole or manway, but that force is being pulled through the plate by the inside bolt, washer, and nut.  The the steel around the hole is ablwe to "spread" out the extra load compared to a threaded stud.

A stud is screwed into female threads inside a hole in the plate, but the entire load on the stud is going through those threads.  This is a somewhat smaller area than that under a bolt, nut, and washer - so each hole is a stress riser.  

Also, the stud will be threaded deep enough to carry the load.    

RE: Area for Reinforcement

racookpe,
Normally you wouldn't use any bolts/studs directly in any vessel shell. Where direct bolting is require to a vessel one would normally use studding outlets were any additional stress with resulting stress risers are taken care of by the outlet.  

RE: Area for Reinforcement

I agree with your observation - in this case, it did appear he was using studs in the pressure wall itself.

RE: Area for Reinforcement

(OP)
Thank you for the help.  I did mis-phrase my original question.  The flanged connections will made by threaded studs (not bolts) as per PG-39.4.

I will check into the studding outlets.  Thanks for all the help!

-Steris

RE: Area for Reinforcement

Prex and racookpe1978,

This site has a lot of good information under the heading technical inforamtion.  

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