An Introduction to the Different Types of Storage Tanks

04 December 2019

Storage tanks are used as containers for liquids, non organic liquids and vapours in industries such as petroleum producing and refining; petrochemical and chemical manufacturing, bulk storage and transfer operations; other industries consuming or producing liquids and vapours. There are eight different types of storage tanks that are commonly used in the abovementioned industries.

Fixed-Roof Tanks

The fixed-roof tank is a cylindrical steel shell with a cone or dome-shaped roof that is permanently affixed to the tank shell. Among all commonly-used types of storage tanks, fixed roof tanks are considered the least expensive to construct. It is also deemed as the minimum acceptable equipment for storing liquids. Fixed-roof storage tanks are usually fully welded and designed for both liquid and vapour tight, while older tanks are often have a riveted or bolted construction and are not vapour tight.

External Floating Roof Tanks

From the name itself, an external floating roof tank consists of an open-topped cylindrical steel shell with a roof that floats on the surface of the stored liquid. The floating roof rises and falls with the liquid level. It is also comprised of a deck, fittings, and a rim seal system. Floating roof decks are constructed of welded steel plates and are of three general types namely pan, pontoon, and double deck.

Internal Floating Roof Tanks

Internal floating roof tanks are the type of storage tanks that have a permanent fixed roof and a floating roof inside. Basically, there are two types of internal floating roof tanks – those tanks in which the fixed roof is supported by vertical columns within the tank and those with a self-supporting fixed roof and no internal support columns.

Domed External Floating Roof Tanks

Domed external floating roof tanks are more commonly known as the retrofitted version of an external floating roof tank with a fixed roof. These tanks have the heavier type of deck used in external floating roof tanks as well as a fixed roof at the top of the shell like internal floating roof tanks.

Horizontal Tanks

Horizontal tanks are usually constructed with either steel only or steel with a fibreglass overlay, or fibreglass-reinforced polyester. They are generally small storage tanks constructed for both above-ground and underground service. These tanks have pressure-vacuum vents, gauge hatches and sample wells, as well as manholes to provide accessibility to these tanks.

Pressure Tanks

Pressure tanks are often shaped in sections of spheres, cylinders, and cones. Their common design is a cylinder with end caps called heads that are frequently either hemispherical or dished. More complicated shapes have historically been much harder to analyse for safe operation and are usually far more difficult to construct. They are often used in industries such as industrial compressed air receivers and domestic hot water storage tanks.

Variable Vapour Space Tanks

Variable vapour space tanks have expandable vapour reservoirs to hold vapour volume fluctuations brought by temperature and barometric pressure changes. The two most common types of variable vapour space tanks are lifter roof tanks and flexible diaphragm tanks. Lifter roof tanks have a telescoping roof that fits loosely around the outside of the main tank wall, while flexible diaphragm tanks have flexible membranes to provide expandable volume.

Liquefied Natural Gas (LNG) Storage Tanks

A liquefied natural gas storage tank or LNG storage tank is a specialized type of storage tank used for the storage of Liquefied Natural Gas. LNG storage tanks can be found in ground, above ground or in LNG carriers. The common characteristic of LNG Storage tanks is the ability to store LNG at the very low temperature of -162°C.

Know more about the different types of storage tanks from Sureweld Engineering. We provide a 24/7 break down – mechanical and maintenance support. We are here to service your business any time of the day or night. Our welders are certified coded welder and supervisors.