How Storage Tanks are Designed, Made, Installed
Atmospheric — Atmospheric pressure tanks are designed and equipped for storage of contents at atmospheric pressure. This category usually employs tanks of vertical cylindrical configuration that range in size from small shop welded to large field erected tanks. Bolted tanks, and occasionally rectangular welded tanks, are also used for atmospheric storage service.
Low Pressure (0 to 2.5 psig) — Low pressure tanks are normally used in applications for storage of intermediates and products that require an internal gas pressure from close to atmospheric up to a gas pressure of 2.5 psig. The shape is generally cylindrical with flat or dished bottoms and sloped or domed roofs. Low pressure storage tanks are usually of welded design. However, bolted tanks are often used for operating pressures near atmospheric. Many refrigerated storage tanks operate at approximately 0.5 psig.
Medium Pressure (2.5 to 15 psig) — Medium pressure tanks are normally used for the storage of higher volatility intermediates and products that cannot be stored in low pressure tanks. The shape may be cylindrical with flat or dished bottoms and sloped or domed roofs. Medium pressure tanks are usually of welded design. Welded spheres may also be used, particularly for pressures at or near 15 psig.
High Pressure (Above 15 psig) — High pressure tanks are generally used for storage of refined products or fractionated components at pressure above 15 psig. Tanks are of welded design and may be of cylindrical or spherical configuration.
Underground Gas processing industry liquids may be stored in underground, conventionally mined or solution mined caverns. No known standard procedures are available for this type storage; however, there are many publications and books covering the subject in detail.
1-ENGINEERING DATA BOOK by Gas Processors Suppliers Association
2-Process Technology - Equipment and Systems by Charles E. Thomas