What is a Capsule Storage Tank?
A capsule storage tank is a pressure vessel comprising a central cylindrical body joined to two hemispherical end caps. The rounded capsule shape provides exceptional resistance against high internal pressures without stress concentrations.
For pressure vessel codes, see Pressure Vessel Design Standards (Wikipedia).
Capsule Tank Volume Formulas
Capsule Volume (Cylinder Body + Full Sphere):
Total Volume (V) = π × r² × L + (4 / 3) × π × r³Where r is radius and L is cylinder body length.
How to Calculate Capsule Tank Volume
- Measure Tank Diameter & Body Length: Record internal cylinder radius
rand body lengthL. - Calculate Cylinder Volume: Multiply π × r² × L.
- Calculate Sphere Volume (2 Hemispheres): Multiply (4/3) × π × r³.
- Add Volumes Together: Sum cylinder body and sphere volume.
Capsule Tank Numerical Example
For a capsule tank with 4 ft diameter (r = 2 ft) and 10 ft cylinder length:
Cylinder Volume = 3.14159 × (2)² × 10 = 125.66 ft³Sphere Caps Volume = (4/3) × 3.14159 × (2)³ = 33.51 ft³Total Volume = 125.66 + 33.51 = 159.17 ft³ ≈ 1,190.68 US Gallons
Standard Capsule Tank Capacity Chart
| Capsule Sizing | Dimensions (Diameter × Cylinder Length) | US Gallons | Litres |
|---|---|---|---|
| Small Pressure Receiver | 30" × 60" (0.76m × 1.52m) | 235 gal | 890 L |
| Medium Chemical Tank | 48" × 96" (1.22m × 2.44m) | 895 gal | 3,388 L |
| Large Transport Tank | 72" × 180" (1.83m × 4.57m) | 3,750 gal | 14,195 L |
Pressure Distribution in Capsule Vessels
Hemispherical end caps eliminate sharp corner seams, providing maximum structural strength for high-pressure pneumatic and hydraulic liquids.
Engineering Applications & Pressure Vessel Dynamics
Capsule-shaped storage vessels combine a central cylindrical shell with two hemispherical ends to optimize structural strength against internal hydrostatic and pneumatic pressure. Because spherical surfaces distribute mechanical stress equally across their entire geometry, capsule tanks eliminate high-stress concentrations typically found at sharp rectangular corners or flat end-plates.
When selecting materials and sizing capsule storage tanks for industrial facilities, engineers must account for both internal working volume and total external footprint.