API 650 covers welded steel tanks for storage at near-atmospheric pressure. The decisions that shape cost and safety are shell thickness method, roof type, wind and seismic design, and the foundation, together with nozzles, appurtenances and the settlement the tank must tolerate.
Key Takeaways
- Shell thickness depends on liquid height, density and allowable stress.
- Roof type follows the product and vapour losses.
- Seismic design affects anchorage and freeboard.
- The foundation and settlement limits are part of the tank design.
Shell Design
Each shell course is sized for the liquid head it carries, using the design and hydrostatic test conditions and the allowable stresses for the chosen material.
Roof and Bottom
Fixed cone or dome roofs suit many products; floating roofs reduce vapour losses for volatile liquids. Bottom plates and the annular ring are designed for the loads at the shell junction.
Wind and Seismic
Wind governs stiffening and stability of the shell. Seismic design governs overturning, anchorage and the sloshing wave height, which sets freeboard.
Foundation and Settlement
Tank foundations are designed together with the tank. Our structural team designs the ring wall or slab from the same loads, with settlement limits the tank can accept.
How We Work
We use verified calculation workbooks for API 650 tanks, silos and chimneys, and coordinate nozzles and piping with the plant model.
Frequently Asked Questions
Do you design the tank foundation too?
Yes, through our steel structure and foundation design team.
Can you design silos and chimneys as well?
Yes, using verified calculation workbooks to the codes set in the design basis.
