Description

A spherical storage tank is what you build when a gas has to be held as a liquid under pressure at scale. Spheres store LPG, anhydrous ammonia, propylene, butadiene and LNG at refineries, petrochemical plants, import terminals and gas processing facilities, typically at below-ambient temperatures with -50°C (-58°F) as a practical lower limit. Built to the ASME Boiler and Pressure Vessel Code, Section VIII. Priced by specification; the figure shown is indicative for a complete engineered and fabricated vessel.

Why Engineers Choose a Sphere

Uniform stress: internal pressure loads a sphere evenly across the entire shell. There is no corner, no knuckle and no flat face to concentrate stress, so there is no obvious place for a vessel to fail first.
Minimum surface area per volume: a sphere encloses a given volume with less shell than any other shape. Less steel to buy, and less area for heat to leak through in cold service.
Thinner shell for the same pressure: the even stress distribution means a sphere needs roughly half the wall thickness of a cylinder of the same diameter at the same pressure.
Proven at scale: spheres are the standard for large pressurised inventories where a cylindrical vessel would become impractically heavy.

The Trade-Offs

Spheres cost more to fabricate than cylindrical vessels — the shell is built from formed petal plates welded on site, the support structure is a ring of columns with wind bracing, and the whole job is field work rather than shop work. And for a given plot footprint, a sphere holds less than a tall cylinder. You buy a sphere when the pressure and the inventory make it the only sensible option, not because it is cheap.

Insulation and Cold Service

Where the contents are stored below ambient — and most sphere duty is — the thermal insulation system is as critical as the pressure shell. Heat leaking in boils off product, raises pressure and eventually vents inventory you paid for. A well designed and correctly installed insulation system with a sound vapour barrier is what keeps the contents at a consistent temperature and keeps boil-off within the design case, particularly in hot and humid climates where the driving temperature difference is largest.

Design and Fabrication

Vessels are fully designed, fabricated and certified in accordance with ASME Boiler and Pressure Vessel Code Section VIII, Divisions I, II and III as appropriate to the duty, in sizes up to 120,000 gallons and beyond for related custom vessels. Associated equipment — pumps, compressors, valving, liquid transfer and metering systems, vaporisers and blending systems — can be supplied with the vessel.

Enquiries

Spheres are engineered to the project, not bought off a shelf. Tell us the product, the design pressure and temperature, the required volume and the site, and we will scope the vessel, the foundations, the insulation system and the delivery programme. For smaller pressurised storage, see our ASME propane tanks and NH3 vessels.