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5

Design Pressure Of Gasoline Api 650 Tank

api650

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#1 Jay_

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Posted 13 August 2019 - 11:16 AM

hello all,

I'm new here but i have been reading posts from this forum, quite interesting stuff.

I'm in the design process of a large gasoline tank (25 meters dia x 18 meters ht), consisting of an internal floating roof and a fixed roof.

the client didn't give me any clue of what the design pressure/vacuum might be,

As a rule of thumb what might be the design pressure/vacuum be for this tank?

any advice would help.

thanks!



#2 fallah

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Posted 13 August 2019 - 12:33 PM

 

I'm in the design process of a large gasoline tank (25 meters dia x 18 meters ht), consisting of an internal floating roof and a fixed roof.

the client didn't give me any clue of what the design pressure/vacuum might be,

As a rule of thumb what might be the design pressure/vacuum be for this tank?

 

Hi,

 

As per API 650 the design pressure of the atmospheric storage tanks shall not be higher than 2.5 psig and design vacuum of the atmospheric storage tanks shall not be less than 0.25 kPa (equal to 1" WC or 0.577 OZ/in2).



#3 Jay_

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Posted 13 August 2019 - 01:02 PM

hello and thanks sir,

but this i already know,

designing a tank to a design pressure of 2,5psia will have a great additional cost on tank foundation, roof, structural elements, anchorage etc...

i am looking for an optimum yet logical design pressure for this size of tank that should contain gasoline as per api 650 (internal floating roof for the tank as a i said).

i don't wanna be designing a high cost tank if 2.5psia is a pressure the tank will never experience,

kindly advise,



#4 rikakose

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Posted 14 August 2019 - 04:40 AM

Quite often seen +/-50mbara, +50mbara/-25 mbara, +100mbara/-50mbara. for atm tanks 

 

It is also up to the process condition. 

The tank manufacture will also give you some indications. 



#5 PhilippM

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Posted 14 August 2019 - 12:20 PM

What do you mean by "a pressure the tank will never experience"?

 

In order to state what pressure the tank may or may not experience you should first do a proper HAZOP, PAAG or whatever they call it in your jurisdiction or what the client standards require.



#6 Jay_

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Posted 16 August 2019 - 02:15 PM

well,

as we all know gasoline will be lost in the atmosphere  if a p/v wasn't implemented and the tank was instead open to the atmosphere directly.

my question is......on which pressure (usually) the p/v is set to open for a gasoline tank that has an internal floating roof??

a consultant told me that 5mbar/-5mbar is enough but i'm not sure if this pressure would cause a lot of losses to the atmosphere or not,

can anyone help me so i can start initiate the design phase??



#7 Pilesar

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Posted 16 August 2019 - 02:58 PM

The liquid content in a floating roof tank is not open to the atmosphere directly. The roof floats on the liquid surface so that there is little or no vapor space. When liquid is added or removed from storage, the internal roof also moves. So the tank does not need to 'breathe' vapor and you do not get much loss to the atmosphere when compared to fixed roof storage. What is the weight of the internal floating roof? That will influence what design pressure you need and the setting of your pressure relief valve! You will set the pressure relief valve so that it relieves the pressure before the internal roof is pushed up by vapor.



#8 Jay_

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Posted 16 August 2019 - 03:06 PM

dear sir;

thank you for your above response!

so you are saying i need to design the IFR before designing the tank itself?

the design pressure is then simply the weight of the IFR? (kg/m2)



#9 Pilesar

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Posted 17 August 2019 - 12:11 AM

The design pressure must account for the weight of the floating roof. There may be reasons to use a higher design pressure for safety in 'non-normal' cases. Please do not interpret my comments as trying to encourage you to design this tank yourself. Maybe you can do it properly. But I would want someone experienced in floating roof tank design to take a leading role in my first attempt. When I have had storage tanks built, I determined the capacity, style, available footprint so I could then work with a reliable vendor who specializes in storage equipment for the details. This is large, expensive equipment and a design failure would be difficult to hide. 



#10 breizh

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Posted 17 August 2019 - 01:44 AM

Hi ,

Let you consider the resource attached and get some experienced engineer to support you .

Good luck

Breizh

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