Volatile Organic Compound (VOC) emissions from storage tanks pose a significant environmental and economic challenge for the fuel and chemical industries. The choice of appropriate emission reduction technology is crucial. Two most popular solutions are Internal Floating Roofs (IFR) and External Floating Roofs (EFR). How do they differ and which is more effective?

External Floating Roof (EFR)

EFR is a roof that floats directly on the surface of the stored liquid in a tank without a fixed roof. The main element limiting emissions here is the peripheral seal system, which minimizes the gap between the roof edge and the tank shell.

EFR Advantages:

  • Relatively simple concept for newly constructed tanks for products with low vapor pressure.
  • No vapor space above the product under ideal conditions.

EFR Disadvantages:

  • High sensitivity to atmospheric conditions (rain, snow, wind), which can load the roof and contaminate the product.
  • Need for complicated and expensive roof drainage systems.
  • Emission reduction efficiency strongly dependent on the quality and technical condition of peripheral seals (primary and secondary).
  • More difficult inspection and maintenance of seals.

Internal Floating Roof (IFR)

IFR is a lightweight structure (usually aluminum or steel) installed inside a tank with a fixed roof. Like EFR, it floats on the liquid surface, creating a vapor barrier.

IFR Advantages:

  • Very high emission reduction efficiency (often >98%), because the fixed roof protects the IFR from atmospheric conditions, and the cover itself minimizes evaporation surface.
  • No need for complicated drainage systems.
  • Product protection from external contamination.
  • Easier inspection and maintenance (in empty tank).
  • Possibility of effective modernization of existing fixed-roof tanks.
  • Lower risk associated with snow or wind loading.

IFR Disadvantages:

  • Requires existence or construction of a fixed roof on the tank.
  • Need to ensure proper ventilation of space between IFR and fixed roof.

Summary: IFR vs EFR

Although both solutions aim to reduce VOC emissions, Internal Floating Roofs (IFR) combined with fixed roofs are generally considered Best Available Technique (BAT) for storing most volatile products. They offer higher and more stable emission reduction efficiency, better product protection, and lower maintenance-related operating costs compared to EFR.

However, the choice of appropriate solution depends on specific conditions, product type, age and construction of the tank, and applicable local environmental regulations.

Techcom Serwis offers both modern seal systems for EFR roofs and complete Internal Floating Roofs IFR (steel and aluminum). Our experts will help select the optimal solution for your needs.

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