Pressure vessel design 5

[Kulsummohd]

Hello everyone,

I am a newbie civil design engineer but my employer wants me to design a diesel tank of 100000 litres. It is a cylindrical horizontal tank with length 17.2 mtrs and dia 2.8 mtrs. Kindly help me clear the following doubts -

1. Design pressure is given as "full of water". what does this mean ?

2. Design temperature is given as "black body temperature". What does this mean ?

3. How will the internal gauge pressure be calculated ? I need to find the internal pressure in mpa and using hydrostatic pressure formula (i.e pressure = density × g × height) the value comes very less in mpa and i am not able to get any value for thickness.

Please help me to calculate thr internal pressure so that i can calculate the thickness using asme sec 8 formulas.

 

[LittleInch]

Don't design it, buy it from a tank vendor. You don't know enough and can't design it from the web.

Remember - More details = better answers
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[LittleInch]

Also, am atmospheric storage tank is not a pressure vessel so ASME VIII does not apply.

Please search for "design of horizontal cylindrical storage tanks" first.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Kulsummohd]

Appreciate your help. Thanks

 

[JStephen]

For a horizontal atmospheric tank, the thickness based on internal pressure calculates very small. Actual thickness will be based on code minimum requirements, practical fabrication limitations, and consideration of saddle/support design and associated stresses. If the tank is buried, external pressure may govern the design.

In the US, an above-ground diesel tank of those dimensions would most often be furnished built to UL-142. That might vary in other parts of the world. In the US, local fire and building codes would specify what codes a tank had to meet.

If there is not a specific need for those dimension, I'd suggest to let the tank suppler pick exact dimensions for best economy.

 

[racookpe1978]

I am surprised you do not recognize the term "full of water" ... What part of that do you not understand?

A black body temperature means "heated by the sun" (implying towards a radiation equilibrium temperature ) but that is NOT a design criteria, because minimum temperature will control cracking limits, and maximum equilibrium will not realistically be reached. (Better to ask for specifics, or "What region will it be fabricated in, what region will it be used in?" or the explicit "What temperatures are required?"

 

[JStephen]

"Black body" is a term in radiation heat transfer, but I have never heard it used in that context in tank design. It COULD mean the lowest temperature that a blackbody dropped to under a clear dark sky, but that's not how the lowest design temperature is normally set. Generally, carbon steel tanks are adequate (per the codes) for use up to 200 degrees F without any modifications to allowable stresses, etc. And stainless steels up to 100 degrees F. I don't remember if UL 142 specifies a minimum design temperature. In API-659, for larger tanks, the lowest design temperature is based on lowest atmospheric temperature plus some allowance for the thermal mass of the tank.

 

[Kulsummohd]

I understood the term full of water but i did not know about ul-142 so i was using the design pressure to calculate the thickness and hence the value was coming very very less.now i have read ul-142 and found the appropriate thickness for the tank.

Regarding the black body temperature, the tank is to be designed to be used in oman (middle east) and it is being fabricated in dubai, so i guess i need to ask for the maximum and minimum operating temperatures from the client ?

 

[racookpe1978]

Well, minimum temperatures (built locally, operated locally in the MidEast) will not be the potential problem of low temperature carbon steel cracking that I questioned.

Max temperatures should be explicitly stated by the client: If sunlight (desert environment) "only" (no process fluid heat entering the system, then that condition should be explicitly confirmed by the client. If they do confirm that condition, max steel temperature for an empty tank in the full sunlight will be less than 150 deg F, but don't just assume that. (The water inside a full tank will absorb heat from the sunlit tank walls, and so the full tank temperature will be less than that guess/estimate.

 

[LittleInch]

However from a thermal expansion point of view you need to think about all conditions, full, empty, half full.

Black body temps used in the ME for empty condition are commonly 70C.

If you search in the "storage tank forum" instead of the pressure vessel forum, you will find out a lot more about such tanks

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.