In storage tank design for petroleum or liquid fuels: for tanks with capacity greater than 45 kilolitres, what is the recommended safe upper limit on the height-to-diameter ratio (h/d)?

Introduction / Context:
For above-ground petroleum and liquid fuel storage tanks, geometric proportions directly affect stability, seismic/wind response, sloshing, and shell stresses. A common siting and design practice is to keep the tank squat (i.e., height not greatly exceeding diameter) to improve stability and minimize overturning moments. Hence, designers often specify a safe limit for the height-to-diameter ratio (h/d) for larger capacities (> 45 kilolitres).

Given Data / Assumptions:

• Tank stores petroleum or similar liquid fuels.
• Capacity is greater than 45 kilolitres.
• Typical atmospheric, fixed or floating roof tank design; standard wind and seismic considerations.

Concept / Approach:
The h/d ratio controls the center of gravity location and shell buckling susceptibility. Lower h/d provides a broader base and lower overturning lever arm, which reduces risk under wind and seismic loads. For common field-erected tanks, conservative guidance places a practical upper limit on h/d around unity (i.e., less than 1) for large-capacity tanks to maintain stability and manageable shell courses.

Step-by-Step Solution:

Verification / Alternative check:
Qualitative checks from stability equations show that overturning moment from wind scales with projected height; reducing h/d reduces base shear and foundation demands. Shell buckling margins also improve with squat geometries.

Why Other Options Are Wrong:

• 2, 3, 3.5: These imply relatively tall, slender tanks, which are less stable and more demanding structurally for large capacities.

Common Pitfalls:
Ignoring local codes; not accounting for seismic zone; overlooking roof type (fixed vs. floating) that may change sloshing and freeboard needs; using tall narrow tanks merely to save plot area.

Final Answer:
1