Design Code for Buried Tanks – UL-58 or ASME VIII?

[Muhammad@ZEL]

Hello all,
I’m working as a junior design engineer at a consultancy firm, and currently involved in the design of horizontal underground (buried) storage tanks for these products :

• Methanol
• Bio-Naphtha

Basic Info

• 5.1 m dia × 20 m long and 6.1 m dia × 20 m long
• Orientation: Horizontal
• Installation: Fully buried underground

Submersible pumps will be used, during operation. Both liquids have notable vapor pressure

In addition to that, external pressure due to burial depth will also need to be considered (final depth is to be confirmed).
Also, the site is located in a rice-growing region, which typically has a high water table, so groundwater pressure acting on the tank is expected to be a significant factor in the design.

The tanks were buried due to:

• Local regulations regarding boundary/fire distances
• Safety requirements in line with NFPA 30
• Limited plot space for aboveground layout

When I spoke with my seniors, they advised going with ASME Section VIII. I reviewed older projects and also found ASME VIII Div. 1 specified as the governing design code. I was unsure about this from a pressure range perspective, since I understood ASME Section VIII to apply mainly to pressurized vessels. But as I searched further, I learned that UL-58 is intended specifically for underground tanks storing flammable and combustible liquids at atmospheric pressure.

We typically use PV Elite for detailed analysis, which is based on ASME Section VIII Division 1

If space wasn't a constraint and the tanks were installed aboveground, we would probably go for API 650

My Question

• In this case, is it acceptable engineering practice to use ASME Section VIII instead of UL-58 for buried tanks — even when formal internal pressure is very low or close to atmospheric?
• Is this just an overdesign, or are there regulatory/compliance issues in using ASME VIII in place of UL-58?
• If there were no burial requirement, these tanks would likely be vertical, aboveground, and designed per API 650 — do others agree with that assumption?
• Do you have any references or experience with similar buried tanks for flammable liquids where ASME Section VIII was used intentionally over UL-58?

Looking forward to your experience and input.

Thanks!

​

 

[JStephen]

UL-58 is commonly used for underground tanks, but they are usually considerably smaller than the tanks you're proposing.
If you can contact some UL-58 tank suppliers, their input might be helpful
I'd say use of ASME is reasonable, it may or may not be required.
External pressure from water and soil will be a major consideration.
Flotation of the tanks would be a major consideration, there will need to be a lot of concrete holding these down.
Many of the underground tanks are double-wall for environmental/ leak-detection, check if that's applicable here.
External coatings, cathodic, corrosion protection will be critical.
Consult with fabricators in the area to confirm that they can shop-fabricate ASME tanks of that size and can also ship them to the jobsite. It may be more economical to use more tanks of smaller size.

 

[Muhammad@ZEL]

UL-58 is commonly used for underground tanks, but they are usually considerably smaller than the tanks you're proposing.
If you can contact some UL-58 tank suppliers, their input might be helpful
I'd say use of ASME is reasonable, it may or may not be required.
External pressure from water and soil will be a major consideration.
Flotation of the tanks would be a major consideration, there will need to be a lot of concrete holding these down.
Many of the underground tanks are double-wall for environmental/ leak-detection, check if that's applicable here.
External coatings, cathodic, corrosion protection will be critical.
Consult with fabricators in the area to confirm that they can shop-fabricate ASME tanks of that size and can also ship them to the jobsite. It may be more economical to use more tanks of smaller size

Thank you for your input.

Your point about fabrication and transport is spot on, especially since we’re designing a total of five tanks of this size. Shop fabrication and delivery logistics are definitely a major concern in this case. Additionally, external pressure from soil and flotation due to the high water table will require a significantly heavy civil foundation.

Appreciate your practical insights — very useful.