Storage tanks are among the most essential structures in the industrial world. They stand quietly at refineries, factories, power plants, and even farms, yet they hold the lifeblood of modern civilization — oil, fuel, water, chemicals, and countless other liquids. Without storage tanks, energy production would stop, industries would collapse, and even basic city infrastructure could not function. But what exactly are these tanks? How are they designed? What materials are they made of? And how does the construction process ensure they remain safe for decades?

This article gives a deep, easy-to-understand explanation of storage tanks, exploring everything from their purpose and types to the engineering, manufacturing, and testing processes behind them.

What Are Storage Tanks?

A storage tank is a large engineered container used to store liquids or gases in bulk. They serve a simple purpose — to store material safely and reliably until it is needed — but achieving this purpose requires complex engineering, strict safety standards, and precise construction.

Storage tanks are used everywhere:

• Oil and gas refineries
• Power plants
• Airports
• Chemical processing facilities
• Agricultural and food industries
• Water treatment plants
• Municipal and firefighting systems

Most tanks are designed to last for decades, often 30–50 years, meaning they must resist corrosion, pressure, wind, seismic activity, and extreme temperatures. Their importance cannot be overstated; every country’s energy security depends on safe, reliable tank farms.

Why Are Storage Tanks So Important?

Storage tanks play a crucial role in industry and national infrastructure. They allow:

• Continuous availability of fuel and oil, even during supply interruptions
• Safe storage of chemicals and hazardous materials
• Firefighting water supply
• Long-term water storage for cities and agriculture
• Stable operation of refineries and processing plants
• Strategic reserves that protect national energy supply

Without them, industries would run out of raw materials every hour, and cities would quickly face shortages of fuel, water, and essential chemicals.

Types of Storage Tanks

1. Aboveground Storage Tanks (ASTs)

These are the most common. They include:

• Fixed roof tanks (cone roof, dome roof)
• Internal or external floating roof tanks (used for crude oil to reduce vapor loss)
• Open-top tanks
• Vertical cylindrical tanks

ASTs are typically designed according to API 650 standards, which specify requirements for welded steel tanks.

2. Underground Storage Tanks (USTs)

Used where space is limited, such as at fuel stations. They must resist:

• Soil pressure
• Moisture
• External corrosion

Many USTs are double-walled for extra safety.

3. Pressurized Tanks / Pressure Vessels

Used for storing LPG, ammonia, compressed gases, and chemicals that require pressure containment. These follow ASME BPVC Section VIII rules and are much stronger because they operate under internal pressure.

4. Specialized Tanks

Some industries require special materials or designs:

• Stainless steel tanks for food and pharmaceutical liquids
• Fiberglass (FRP/GRP) tanks for corrosive chemicals
• Concrete tanks for massive water reservoirs

What Materials Are Storage Tanks Made Of?

Most industrial tanks are constructed from steel, chosen for its strength, durability, and ability to be welded into large structures. Common materials include:

Carbon Steel (Most Common)

Examples: S235JR, S275JR, A36, A283, A516
Used for crude oil, diesel, gasoline, firewater, and general industrial liquids.

Stainless Steel (SS304/SS316L)

Used where corrosion resistance is critical:

• Chemicals
• Food products
• Pharmaceuticals
• High-purity water

Fiberglass (FRP/GRP)

Lightweight and corrosion-resistant. Used for:

• Chemical storage
• Water treatment plants
• Wastewater systems

Concrete

Used for extremely large water tanks or reservoirs.

Material selection depends on:

• Stored liquid
• Temperature
• Corrosion risks
• Required service life
• Applicable engineering code

How Engineers Design Storage Tanks

Designing a tank is a scientific and highly regulated process. Engineers must follow global standards such as:

• API 650 for aboveground tanks
• API 620 for low-pressure large-diameter tanks
• ASME BPVC for pressure vessels
• NFPA 22 for firewater tanks

1. Determining Size and Volume

Engineers calculate:

• Tank diameter
• Tank height
• Shell thickness
• Roof design
• Bottom plate arrangement

For example, a 5,000,000-liter diesel tank might have a diameter of 22 meters and a height of 14 meters.

2. Structural Analysis

The tank must withstand:

• Internal pressure
• Wind load
• Earthquake forces
• Liquid hydrostatic pressure
• Foundation settlement

Failure to consider these loads can lead to catastrophic tank collapse.

3. Foundation Design

Because tanks are extremely heavy, the foundation must be carefully engineered:

• Compacted soil
• Crushed stone ring wall
• Concrete ring beam
• Anchor bolts (for wind or seismic zones)

Good foundation design prevents settlement, cracking, or tilting of the tank.

How Storage Tanks Are Manufactured and Built

Manufacturing a storage tank is a multi-stage process involving both factory work and site construction.

1. Steel Plate Preparation

Large steel plates arrive from the mill. They are:

• Inspected
• Marked
• Cut with CNC plasma or laser
• Beveled for welding

2. Rolling the Shell Plates

Each plate is passed through a rolling machine to create the curved shape needed for the tank’s cylindrical shell.

3. Bottom Plate Installation

At the construction site:

• A sand or gravel pad is prepared
• Bottom plates are placed in a radial or annular pattern
• Welders join the plates using SMAW or MIG
• A vacuum box test checks for leaks

4. Building the Shell

The tank shell is built course by course:

• Placing the first shell course
• Aligning plates perfectly
• Welding vertical and horizontal seams
• Adding the second, third, and remaining courses

For tall tanks, scaffolding or jacks are used.

5. Roof Construction

The roof type depends on the product:

• Cone roof for diesel
• Dome roof for water
• Floating roof for crude oil to reduce vapor loss

6. Adding Nozzles and Accessories

These include:

• Manholes
• Inlet and outlet pipes
• Level indicators
• Pressure relief valves
• Ladders and handrails
• Platforms and walkways

7. Non-Destructive Testing (NDT)

Welds are inspected using:

• Radiography (X-ray)
• Ultrasonic testing
• Magnetic particle testing
• Dye penetrant testing

8. Hydrostatic Testing

The tank is filled with water up to the roof level.
This confirms:

• No leaks
• Structural stability
• Settlement within acceptable limits

9. Painting and Corrosion Protection

Tanks are coated with:

• Zinc-rich primer
• Epoxy intermediate layer
• Polyurethane final layer

This protects the tank for decades.

The Lifespan and Maintenance of Storage Tanks

A properly engineered and maintained tank can last 25–40 years, sometimes even longer. Regular maintenance includes:

• Annual inspections
• Ultrasonic thickness measurements
• Checking for corrosion
• Roof and floor inspections
• Repainting every 5–7 years

Good maintenance prevents product contamination and ensures environmental safety.

Conclusion: Why Storage Tanks Matter to the Modern World

Storage tanks are far more than steel cylinders standing in a field. They are the backbone of global industrial operations. Every car, airplane, business, city, and home depends on the materials stored inside them — fuels, water, chemicals, and essential products that keep life functioning.

The engineering behind storage tanks reflects precision, safety, and decades of technical evolution. From careful design and strict welding standards to advanced coatings and tests, each tank represents thousands of hours of work and expertise.

As countries develop their energy infrastructure, storage tanks remain one of the first and most important structures ever built. They symbolize growth, stability, and industrial capability.