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Hydraulic press. Check with me this calculations

hydraulic press calculations

14 replies to this topic

#1 pyrosailor99

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Posted 17 October 2012 - 09:44 AM

Hi all!

i'm rebuilding my jack pres. it will have a new frame and i will mount a gauge on the hidraulic jack.

I'm doing some calculation to be sure the 5T jack is enough for my projects.
The most high pressure required for project i've seen is 7500PSI (for whistles) so i want to be sure that my press will be able to reach this value for tubes until 2,5cm ID.

as i'm more pratical with metrical system i will use Kg, square cm (or cm2), KSC (kilogram per square centimeter) , MPa (Mega-Pascal ), Square inch (sq-i)
You can use this table for conversions: http://en.wikipedia.org/wiki/Pressure

Well,
1 PSI= 0,06895 bar = 0,00689 MPa =0,07031 KSC
7500 PSI are equivalent to about 527 KSC = 517 bar = 51,71MPa [i have to reach this!]

The diameter of the larger *visible* part of the piston my jack is about 28mm, i suppose that when i will un-mount the jack to apply the gauge (as in this page: http://www.skylighte...ocket-press.asp) it will have a max diameter of 35mm (where oil will apply the force)...

with 35mm diameter i have an Area of 11,34cm2 (1,76sq-i) [bottom piston area]

now, if i want press a whistle of 2,5 cm ID i should apply a force over an Area=Pi * 1,25 * 1,25= 4,91 cm2 (0,75 square inch) [ram area]
To have 527KSC on 4,91cm2 i need 527 * 4,91 = 2587Kg (about 2,5Ton - 5703Pounds) [Force needed in the jack]
This mean that my 5Ton jack is enugh for this job also if the label lie of 1 Ton. (right?)

Now i calculate what i should read on the gauge to ensure i'm applying 7500PSI (or 527KSC) on the whistle comp (in the 2,5 cm ID tube)

2587Kg=5703Pounds, this mean i should apply 5703Pounds over the entire bottom piston area (see up for measures)
5703Pounds / 1,75sq-i= 3259 PSI (224,7 Bar | 22,47 MPa ) [Correct reading on the gauge to have 7500psi in 2,5cm ID tubes]

As the ratio between RAM diameter and piston bottom diameter is 0,75sq-i/1,75sq-i = 0,43 i can say that when i need X PSI of pressure on the composition in a tube 2,5cm ID i need to read on the gauge Y = X * 0,43 [generic formula to have correct read on the gauge in 2,5cm ID tubes]

A most generic formula to obtain the PSI value Y to read on the Gauge for
- tube of ID or Ram diameter (inches) = Z
- bottom piston diameter (inches) = W
- Needed PSI inside the tube = X

Y = X * ( Z^2 / W^2 )


Do you think is this all correct?

Edited by pyrosailor99, 17 October 2012 - 10:02 AM.


#2 Col

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Posted 17 October 2012 - 11:21 AM

If the jack can lift a 5 tonne weight, it can put 14,457psi on a 25mm rammer. If its only 4 tonne, it`ll still manage 11,566psi.
The math looks ok even though i prefer inches and lbs for pressure calculations, i make it 2595kg on a 25mm rammmer for 7500psi.
You only need to worry about the jack`s ram area if you plan to install a pressure guage directly into the jack.
I have a 10 tonne press, a bit of headroom is never a bad thing ;)

Edited by Col, 17 October 2012 - 11:23 AM.

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#3 pyrosailor99

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Posted 17 October 2012 - 11:26 AM

Thanks Col.
yes maybe some number lost some precision rounding between transcriptions...

Yes, actually i think to install the gauge directly in the Jack as in my location is impossible to find taht mini-jack to build an universal detachable cauge... and ordering over internet would cost me more i want to spend...

#4 Col

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Posted 17 October 2012 - 11:49 AM

If the jack ram diameter is 35mm, 7500psi on a 25mm rammer would read 3830psi on the pressure guage. The actual weight on the jack would be equivalent to 5709lbs or 2,595kg so your 5 tonne is ok for that job.

#5 pyrosailor99

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Posted 17 October 2012 - 01:19 PM

right, redoing calculations with my final formulae it comes up with 3826 PSI...
maybe i done some mistake or too much rounding in the various conversions between kg and pounds and other measure units...

#6 Col

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Posted 17 October 2012 - 03:38 PM

i rounded up/down, you`ll struggle to find a 5000psi pressure gauge with 10psi increments :)

#7 pyrosailor99

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Posted 18 October 2012 - 01:12 AM

never wanted to reach a so precise value. i was meaning that in my first post the result was 3259PSI that is too far from the final result of about 3830PSI ...

#8 Col

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Posted 18 October 2012 - 04:36 AM

The initial error was a mix up in the 35mm ram area (1.76 versus 1.49), its easily done when you`re working with several different ram diameters at the same time.

#9 dagabu

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Posted 18 October 2012 - 08:46 AM

Posted Image

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#10 Algenco

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Posted 18 October 2012 - 08:54 AM

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one more thing that makes PF worth the money

but APC is still my favorite forum

Edited by Algenco, 18 October 2012 - 08:55 AM.

Old Fart

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#11 Col

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Posted 18 October 2012 - 08:59 AM

Here`s a simple excel version, the ram and tooling diameters are entered in metric, output pressure is in psi.
http://www.datafileh...d-9612863b.html

#12 pyrosailor99

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Posted 18 October 2012 - 09:31 AM

Thank you very much both!
I don't know why the excel sheet is password protected (maybe only to avoid editing other cells).
I will build another excel file where I can also modify (input) the effective pressure on tool that i want to calculate the Gauge value to read.

thanks again!

#13 Col

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Posted 18 October 2012 - 10:08 AM

Force of habit to protect sheets, i`ve messed up a few that took days to make :) It only takes a few iterations of the gauge pressure to get the effective pressure on tool to match what you want ;)

Modded so you have the choice of entering the target force on the tool.
http://www.datafileh...d-2e21048c.html.

Edited by Col, 18 October 2012 - 10:30 AM.

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#14 dagabu

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Posted 18 October 2012 - 11:11 AM

one more thing that makes PF worth the money

but APC is still my favorite forum


Amen brother! I go to PF to watch the struggle between the egos and here to have relationships with other pyro friends. I would pay the entry fee to PF just for that calculator alone since I am so visual.

-dag

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#15 Algenco

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Posted 18 October 2012 - 05:26 PM

Amen brother! I go to PF to watch the struggle between the egos and here to have relationships with other pyro friends. I would pay the entry fee to PF just for that calculator alone since I am so visual.

-dag


I hadn't seen that calculater before, very helpful, thanks for posting

Egos? surely not :)

I was just thinking about a similar situation today, at this years PGI only builders were allowed in the "Large Shell manufacturing"
Suprising that only cylinders shells were being built there, and not all of them met the criteria of "large shells", hmm
Old Fart

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