steel plate thickness for box supporting 4psi difference

[matlark]

Hello all,

I originally was thinking of making this from plywood but 4psi is too much for plywood. I have access to 4x8 sheets of steel 1/4 and 3/8". I would like to know which one I can get away with using for a 20"h x 13"w x 66"d box. There will be a 4psi difference inside the box vs. the outside. I am an electrical guy not structural so any help would be appreciated. I will be making a small altitude chamber for testing products.

Thanks

 

[ztengguy]

are you just going to weld this all together, or are you going to have a internal frame

 

[fegenbush]

You will need to look at Roark's Table 11.4 Case 1 (pressure on a rectangular flat plate with all edges simply supported). That should get you the stress and deflection of the walls. From that, you can determine the required thickness.

Hint: It will be much easier if you reinforce all 12 plate intersections with angle, since that will be where the problems are going to occur.

 

[matlark]

I was planning on having the box welded together, so it would appear like a large steel rectangle tube. Then weld a plate over one end and leave the other open so I could access the inside. I am not familiar with Roark's table.

 

[fegenbush]

Roark's Formulas for Stress and Strain. Available from many sources. If you would like, I can let you know the result from my copy. However, the plate thickness should be the least of your concern. I would be worried about the closure.

Really, the cheapest way for you to make this would be to use a piece of 24" Std Wt pipe with a pipe cap on one end. Then, you would only have one circumferential weld, it would hold the pressure with no problem, and you could still fit that size box in it (assuming the dimensions of your container were outside dimensions).

 

[matlark]

If you could let me know the result from your copy that would be a big help, just so I know. I will look into the 24" std wt pipe too. You wouldn't happen to have a general idea of price for the pipe would you, maybe a link?
Thanks for the help

 

[ztengguy]

can you just get a steel pipe that will allow what you want to test to fit into it??

 

[matlark]

A steel pipe might work, but I am trying to keep the cost down.

 

[ztengguy]

So engineering it, buying plate, cutting it, welding it all together, is cheaper than a section of pipe? I would have never guessed that.

 

[matlark]

Steel pipe is not something we have in stock or access to, so I am not familiar with the cost. why don't you enlighten me to the cost of a 6ft section of 24" diameter pipe.

 

[ztengguy]

Oh, ok. didnt know you had a stock of plate.

24" 3/8 scrap I can get for about $50/ft at a local scrap yard, varying lengths.