13x13x4″ square pressure tank

[George GladwinParticipant @georgegladwin67002]

Ok so i underatand circle pressure tanks are normally used, but was wondering if i could have a small square one built safely, dimensions would be 13x13x4″ and would like it to have a useable pressure rating up to 80 psi.

Does anyone with the correct knowledge know if this is do able (im clueless with the technical calculations needed) and obviously i would have this welded by a proffesional

Thanks

[George GladwinParticipant @georgegladwin67002]

[michael darbyParticipant @michaeldarby61557]

Yes, its possible. but if the public are anywhere near it, get it built and certified.

[vintagengineerParticipant @vintagengineer]

Will probably need some internal stays.

[John ReeseParticipant @johnreese12848]

80 psi over a 13 x 13 square is a distributed load of 13,520 lbf. Either it has to be very thick to resist the bending or have a lot of stays. There is a reason that most pressure tanks are made with round shells and domed heads.

[Paul LousickParticipant @paullousick59116]

The same reason that you cannot find information about the pressure rating of square and rectangular tube.

 

 

Edited By Paul Lousick on 20/02/2017 21:27:46

[Mark RandParticipant @markrand96270]

If you can build it to withstand 15 (long) tons without deflection of the 13×13" faces then you may be in the right ballpark.

Edited By Mark Rand on 20/02/2017 21:31:30

[vintagengineerParticipant @vintagengineer]

Why can you not make a doughnut shaped tank inside a square tank?

[Nicholas FarrParticipant @nicholasfarr14254]

Hi George, yes I agree, very thick metal, which will reduce it's volume for your given size and will be quite heavy if made from steel. As said, alternatively lots of internal stays, six sides, that's stays in three directions. It's not a practical design for a pressure vessel in my view.

Regards Nick.

[JAParticipant @ja]

Not a good idea.

I did a quick few sums on this. Simplifying the 13" long face to a 13" long 1" wide beam gave the following for a steel. To reach a stress of 15 tons/in^2 (typical lower yield point for EN1) if the beam was built in at both ends the thickness would have to be about 3/8" and the maximum deflection would be about 0.061". For a freely supported beam these become 5/8" thick and 0.068".

Obviously the beam is only an approximation to a plate and the actual thickness and deflections would be less but it shows one of the difficulties. How the supports, fixed or free, approximates to the vessel's corners is anyone's guess. If the corners were welded the weld would be a fillet weld which at the best of times is a bit suspect. Things would get complex if you tried using good butt welds.

I should add I mistakenly used 14" instead of 13" for my sums but that is of little consequence.

I am not a boiler inspector and this is the first time I have done such sums for thirty years.

JA

[Robert Turner 1Participant @robertturner1]

How about three 4" diameter by 13" long tanks laid side by side, connected together?

[duncan webster 1Participant @duncanwebster1]

get hold of copy of BS5500. It will tell you all about stay spacing. As others have said, round tanks with domed ends are a lot easier

Edited By duncan webster on 21/02/2017 00:33:53

[JasonBModerator @jasonb]

Its basically just a thick firebox side so quite doable and you may not even need that many stays on the 13x 13 face.

I think the Aussy code would give you just 9 stays over that area if made from 8mm plate and that would be good for 100psi. The 13 x 4 sides would only need 3-4 stays each. as the stay pitch works out at 4.7"

This is based on a recently redesigned traction engine boiler which originally had 90 firebox stays all round and now has jusy 10, plate size was the same for both.

Edited By JasonB on 21/02/2017 07:58:54

[old AlParticipant @oldal]

Anybody considered it might be 13mm x 13 mm to fit a model

[Michael GilliganParticipant @michaelgilligan61133]

Posted by George Gladwin on 20/02/2017 19:15:33:
Ok so i underatand circle pressure tanks are normally used, but was wondering if i could have a small square one built safely, dimensions would be 13x13x4" and would like it to have a useable pressure rating up to 80 psi.

.

Nice try, 'old Al'

… but I think there was a reasonable clue in that opening post ^^^

MichaelG.

[David JuppParticipant @davidjupp51506]

Perfectly possible as others have already covered. I was recently involved in checking stresses in some rectangular section heat exchanger designs, manufactured from extruded profile with stays added.

For information BS5500, now goes by the name PD5500 (still maintained & published by BSI but not strictly a standard, still useful). BS EN 13445-3 also covers pressure vessels of rectangular section (in clauses 15).

[duncan webster 1Participant @duncanwebster1]

Posted by JasonB on 21/02/2017 07:42:02:

Its basically just a thick firebox side so quite doable and you may not even need that many stays on the 13x 13 face.

I think the Aussy code would give you just 9 stays over that area if made from 8mm plate and that would be good for 100psi. The 13 x 4 sides would only need 3-4 stays each. as the stay pitch works out at 4.7"

This is based on a recently redesigned traction engine boiler which originally had 90 firebox stays all round and now has jusy 10, plate size was the same for both.

Edited By JasonB on 21/02/2017 07:58:54

as stay pitch is greater than height of sides (take Jason's word for it), I don't think you need any stays in the sides

[JasonBModerator @jasonb]

Well spotted duncan and would make it a lot easier than trying to weave stays in three directions.

I also thought that the steel thickness could possibly be reduced if the "pressure tank" was not a boiler as then you would not need an allowance for wasteage if it were for say a gas.

Might also be able to bend a 3" wide strip to go all round and just have the one joint in that which would save on welding costs.

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