Internal Floating Roofs for Vertical Tanks: Types, Characteristics, Advantages and Recommendations

Introduction

Internal floating roofs are structures used in vertical storage tanks for products such as fuels and chemicals, with the aim of reducing evaporation, minimizing emissions into the atmosphere and improving operational safety.

The main types of internal floating roofs, their characteristics, as well as their advantages and disadvantages are described below. Key aspects related to safety, assembly and maintenance are also analyzed.

Difference Between Internal Floating Cover and Internal Floating Roofs

Although both terms are often used interchangeably, there is a functional and design difference:

• Internal Floating Covers:

  Lightweight structures that float directly on the surface of the liquid, eliminating or reducing vapor space. They are more compact and have less impact on the useful capacity of the tank. Examples: tubular pontoons and full contact (honeycomb).

• Internal Floating Roofs:

  More robust structures, commonly made of steel, that also float on top of liquid, but with greater height and weight, which can reduce the available storage volume. Examples: pontoon or double deck roofs.

Types of Internal Floating Roofs

1. Tubular Pontoon Roofs

Description: These roofs are formed by a roof supported on structural profiles that rest on tubular pontoons, which provide buoyancy and stability. They are usually made of aluminum, stainless steel, or hybrid (aluminum and stainless steel).

Advantages:

• Light weight → easy transport and installation.

• Low comparative cost.

• Modular prefabrication → faster installation.

Disadvantages:

• There is no total contact with the liquid → more vapor space and more emissions.

• In the event of a fire, it is necessary to apply foam to the entire surface of the liquid, which implies greater consumption of resources.

Tubular Pontoons Internal Floating Roofs

2. Full-Contact Internal Covers ("Honeycomb" Type)

Description:

They are in direct contact with the liquid, eliminating the vapor space. They are made up of honeycomb sandwich panels and are made of aluminum or stainless steel.

Advantages:

• Significant reduction of emissions due to total contact.

• High structural stability.

• In fire, only foam needs to be applied to the perimeter seal.

Disadvantages:

• Higher weight than tubular pontoon roofs.

• Higher cost per material and manufacturing complexity, compared to tubular pontoon roofs.

Full-Contact Internal Covers ("Honeycomb" Type)

3. Floating Steel Roofs (Pontoon Type or Double Deck)

Description:

Built in carbon steel, they can be of the pontoon type (with peripheral floats) or double deck (with internal air chamber). They are heavier and taller, which reduces the effective capacity of the tank.

Advantages:

• High mechanical strength and durability.

• Suitable for products with high vapor pressures.

Disadvantages:

• More complex installation due to its weight. They are heavier than tubular pontoon roofs and full-contact inner covers.

• They require additional support structures.

• Reduction of useful tank volume.

Steel Internal Floating Roof with Fixed Roof

Additional Technical Considerations

🔥 Fire Fighting Foam Requirements

Roof Type / Area to be covered with foam in fire

• Tubular pontoons: The entire surface of the liquid.

• Total contact (honeycomb): Only the perimeter seal.

• Steel (pontoon or double deck): Only the perimeter seal

Note: The need to cover the entire surface with foam, as in the case of tubular pontoons, can represent a critical contingency in large capacity tanks.

⚖️ Weights, Assembly and Prefabrication

• Tubular Pontoons: Very light. Easy prefabrication and modular assembly.

• Total Contact: Heavier than tubular pontoon roofs. They require additional support during installation.

• Steel: They are heavier and bulkier. Laborious installation, affects useful tank capacity.

🎨 Paint and Protection Requirements

• Aluminum/Stainless Steel: No painting required, high natural corrosion resistance.

• Carbon Steel: Requires specialized paint systems, which increases costs and installation times.

Practice Recommendations

Situation / Recommendation

• Existing tanks: Tubular pontoons (aluminum, stainless steel and/or hybrids).

• New tanks: Full contact + aluminum dome roof.

• High vapor pressure or charge: Steel Floating roofs.

✅ Conclusion

The choice of the type of internal floating roof should consider:

• Type of product stored

• Current environmental regulations

• Fire Protection Strategies

• Tank Operating Conditions

For existing tanks, tubular pontoon roofs in aluminum, stainless steel, and/or hybrids are a cost-effective and easy-to-install option.
For new tanks, the most efficient is to combine a full-contact cover with an aluminum dome roof, maximizing emissions reduction, minimizing risks and installation times.

This combination also allows you to meet more stringent environmental regulations and reduces long-term operating costs.