Pressure acting upon sidewall of bottom housing (with 6 housings stacked above for transportation)

[pauldw2012]

I have been asked (by tomorrow) to calculate the pressure (in bar) acting upon the side wall of a conical housing. one Housing has 6 more housing sat upon it. the housings are spaced apart with 6 peices of wood.

Imagine if you will like 7 plastic cups stacked on top of one another. I need to ensure the side wall of the bottom cup will withstand the weight of the ones above it.

I have enclosed AutoCAD and PDF file of the sketch showing the stack of seven housings.

I know the maximum bar pressure each housing can withstand. I need to ensure that the bottom vessel will not be damaged by the 6 above.

Each housing weighs 2056kg
Therefore the 6 housings = 12336kg
The area of the pad between each housing is 0.134m squared. (243.5mm x 552.4mm)
There are 6 pads equi-spaced around the perimeter of each conical wall.

Can anyone help me out please?

 

[vpl]

Hopefully you've done more than just post on here hoping someone else will solve the problem for free that you're being paid to solve. Or are you willing to pay someone if they save your bacon?

Patricia Lougheed

******

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[dhengr]

Wow... “(by tomorrow),” that’s not very much time to get an engineering education and learn something about mechanical and structural design. You should know from sad experience that when you stack 7 plastic cups (any cups or glasses or vessels like yours) together, that way, that those pressures and friction can become very high, and make it almost impossible to get the vessels apart. The more so after this stack has vibrated down the road on a truck for a few hours. Why not redesign your lower shipping frame a bit to have four columns at the four corners, at the location of the four pad-eyes (lifting eyes/lugs) on the vessels? Then design a small vert. support fixture (actually 24 of them) which fits btwn. the flanges on your vessels, at the lifting lugs, 4 at each vessel flange; bolt these to the vessel flanges and the lifting lugs and maybe your shipping frame columns; to support the vessel stack vertically and laterally. This system would also hold the vessels apart, and maybe you would still want you wood blocking, but hang these off the top flange of each vessel so they don’t fall out.

 

[pauldw2012]

Wow, thanks for nothing vpl you sound rather miffed.

It is not saving my bacon, I worked out the problem the following morning. I only posted it in hope to have a second opinion.
Thanks for the ocmments dhengr, much appreciated.

 

[DRWeig]

pauldw2012,

In the future, please do not post the same question in multiple fora. Please read the forum policies, there is a link below my name.

Good on ya,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[vpl]

pauldw, Not miffed at all. I was giving you a reason why you might not be getting any answers. If you come back, (and I'd be surprised if you did) you'll find you get much more help if you say what steps you've taken yourself rather than just "I need an answer by tomorrow." You claim to be a mechanical engineer -- so show your work. If you're brand new out of college, then state that you don't know where to start.

This site can be a tremendous resource, but it can also be brutal. (and yes, this more complete answer comes only after your deadline has passed.)

Patricia Lougheed

******

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[pauldw2012]

Sure I will come back, I don't scare that easy I appreciate the comments and it was a little cheeky asking without delivering any answers.

I did a standard calculation of force in Y direction, knowing it would be more than the force acting perpendicular to the wall. it turned out to be 1.49 bar.

Our housings are tested to withstand 3 bar, so the bottom hjousing could hold the 12.3 ton load quite happily.

Kind regards,
Paul.

 

[MikeHalloran]

>>Our housings are tested to withstand 3 bar, so the bottom hjousing could hold the 12.3 ton load quite happily.<<

Well, yeah, except that the packing blocks convert the weight to 6 concentrated loads, not a uniform pressure, so your cones may suffer some distortion, especially if you don't control the angular location of the block sets relative to each other.





Mike Halloran
Pembroke Pines, FL, USA

 

[dhengr]

Paul:
Patricia and MikeH give good advice, and you would do well to reread/study their posts, for your own edification, if not for the betterment of this shipping scheme. Are you a Mech. Eng.? At what experience level? We all started on the lower rungs at beginning of our careers. So, starting out, and having to learn how to approach real world problems is nothing to be ashamed of. Remember, being able to draw something with a CAD program doesn’t mean it’ll work and is not the same as giving it thorough engineering attention in its details. You were asked the wrong question, or interpreted the question incorrectly if you think the result should be presented in bars of pressure. Just what standard calcs. did you do to get from 27.2 kips applied at six locations (~4.5 kips/wood block) on a shell/plate cone structure, to 1.49 bars pressure. Uniform pressure of 3 bars is quite different than compressive line loads perpendicular to the cone plate, which will cause buckling. I’ll bet the question was... ‘will this shipping arrangement work without screwing up our cone housings in transit?’ Or, design a shipping arrangement for these cone housings. As MikeH mentioned your 3 bar test pressure is quite different that six line loads on that lowest cone structure. Have you checked the 31.7 kip load on the lowest flange at four points on the shipping frame (~31.7/4= 7.9 kips) at the flange and up into the cone shell plate? That’s a compressive loading on the flange, a bearing load on the flange/cone plate welds, and akin to a web crippling problem in a plate girder. Did your CAD tell you that you probably can’t get into the shipping frame tube to make that bottom bolted connection to the lowest flange or to tack weld a nut in place? That’s about 15" into the tube. Did it tell you that lifting slings or chains might slip off the four lifting ends you show in your sketch. You at least have to prevent this potential slippage, or provide a lifting lug or some such at each corner.

Now, look at my last post again and reread it for its full meaning. I don’t think you should load those cone shells the way you show. I think you would have a better solution if you used about 9" long/high oak blocks btwn. the cone bottom flanges, at each level. They would keep the cones properly separated and provide a direct and continuous load path down to the shipping frame. These blocks would be about 3"x16" wide x 9" high, one on each side of each of your lifting lugs on the cones. On the four corner columns, I suggested above, I would have vert. slotted holes to bolt your lifting lugs to. But, more importantly when I put the cone down with its lifting lugs touching the column I would also be aligning the flange holes for some through bolts. The wood blocks would have a vert. kerf cut, at mid width, in their outer face to allow a full height through bolt. These wooden blocks would span 3 flange bolt holes; the middle one with the kerf for the through bolt; and the two side locations would be for locator dowels, top and bottom, to fit into the adjacent flange holes. I would also adjust the dimensions of your shipping frame so that the cone flange landed on both frame members at each corner to give you more bearing area at each corner.