D/L preferred ratios for horizontal tanks?

[DavidCR]

Hello everybody.
Are there preferred proportions for horizontal pressure vessels.
We need to define a preliminary size for a horizontal vessel that would be used for the storage-process of fuels with thorispherical heads. The required capacity is 48m3 (12682gal). Is there such a criteria for L/D (lenght/diam) ratios for horizontal tanks? Could somebody please provide values, formulas or tables.

 

[JStephen]

Here in the US, a tank like that would likely be 96" OD by whatever length was required. Typically, diameters in 6" increments or so, shell lengths (seam to seam) in 8' or 6' increments will be easiest, but they can be made to whatever dimensions you need. I see one catalog where they figure 6', 8', and 10' diameters.

If not in the US, check with local fabricators to see what works best for them.

 

[MJCronin]

DavidCR..

You say that these tanks will be used to store "fuel".???

You are aware that flat bottomed API-650 style tanks are usually cheaper on a $/gallon basis.....right ??

Horizontal tanks (sometimes called drums)are preferred when the tank is located on concrete piers or up in a structure.

Most atmospheric horizontal tanks have shell lengths from 3D to around 6D.

Horizontal pressure vessels are different and may have much longer shells fo a given diameter.

What are the volumes stored and specifically what are the contents ?

-MJC

 

[DavidCR]

The tank is a process equipment of 48m3 as mentioned, it is for a geothermal power plant that uses n-pentane as working fluid, the tank is designed as an ASME pressure vessel.

The design is not ours and will be defined in the future by a contractor, but we need to have a preliminary idea of the possible area that will be used by the tank (for lay-out purposes).

 

[Shmulik]

Pressure Vessel Design Manual (Dennis Moss, 3ed Ed.)
Procedure 2-19: Optimum Vessel Proportions.

 

[DavidCR]

Shmulik. I´m sorry. I have a previous edition (1987) of the "Moss". Looks like it does not include this 2.19 procedure. Could you please mention some numbers or attach some data.

 

[Shmulik]

David,
As you haven't mention your vessel's design press, material of construction, joint efficiency and corrosion allowance, the optimum L/D ratio can't be worked out precisely.
It seems that for pressure range of 0-250 PSIG, L/D ratio around 3 makes sense.
You may slightly modify this ratio acc. to standard plates dimensions available for you.
Vessel's dia. Is:
D={(4*V)/[PI*(0.3333+L/D)]}^1/3

I hope this helps.

 

[MJCronin]

david..

Since we have established that an ASME type pressure vessel is required, it is reasonable to say that having a longer vessel may be somewhat cheaper.

Pressure vessel heads are purchased in 6 inch ID increments(as stated above)

Some candidates to consider are:

Dia: 9'-0" Straight shell: 24'- 9"
Dia: 8'-6" Straight shell: 28'- 0"
Dia: 8'-0" Straight shell: 32'- 0"
Dia: 7'-6" Straight shell: 36'- 9"
Dia: 7'-0" Straight shell: 45'- 6"

Much beyond 45 feet and you will find delivery very expensive.

All dimensions are STRAIGHT SHELL not OAL..!!
All dimensions are approximate

Does this help ?

MJC

 

[DavidCR]

Thanks a lot and blessings to you, all your input is very useful.

I love eng-tips.