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SPC-AL Inner Floating Roof

Reduces product evaporation loss by over 95%, preventing air pollution and enhancing storage efficiency

SPC-AL Inner Floating Roof

The annual evaporation loss from a cone tank that stores volatile liquids, such as crude oil, petrochemicals or aromatic solvents, is over 8% of the tank capacity (for gasoline) due to breathing and filling loss, if performing standard withdrawal operations.
The SPC-AL Inner Floating Roof uses a float made of aluminum alloy or stainless steel to block contact with the air, greatly reducing breathing loss from the evaporation of stored liquids.


The inner float consists of a pontoon, aluminum channel, joint, aluminum sheet and wiper seal. Each of these metal pieces is fabricated in advance at the Isogo Factory.

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Absence of pontoon chamber allows more liquid to be stored and provides safety even when sloshing occurs

The SPC-AL Inner Floating Roof does not have a pontoon chamber like conventional floating roof tanks, providing sufficient space if sloshing occurs. This allows the height of the stored liquid to be set higher than pontoon types, thereby increasing storage capacity.

    • Absence of pontoon chamber allows more liquid to be stored and provides safety even when sloshing occurs

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  • The upper space of the SPC-AL Inner Floating Roof features an air scoop vent for compliance with JIS, API and HPI hydrocarbon concentration standards. This ensures levels are well below the explosive limit.
  • The SPC-AL Inner Floating Roof was designed with a buoyancy force to exceed normal requirements by 100% and uses aluminum alloy materials that are highly corrosion-resistant. The float is extremely reliable and has a long working life.
  • The inner wall of the tank is sealed with a wiper seal that completely affixes and slides smoothly, even if the tank changes shape or becomes distorted.


  • Can be manufactured and installed in less time than conventional steel floating roofs.
  • All materials can be delivered into the tank through a 500 mm manhole. Installation can be completed in a short period of time.

High Quality

  • All parts are made from stainless steel, aluminum or rust-resistant alloys, eliminating corrosion or contamination concerns.
  • Each structural component is fabricated in advance at the Isogo Factory, ensuring high quality standardized components. This process is based on our integrated management of materials procurement to completion inspection.


  • Can be easily installed in existing problem-free tanks. Retains high value added nature and wide adaptability as it can be used when changing oil types and tank usage, etc.


  • The structure was designed with maintenance, work processes and cost in mind, and can easily be serviced for maintenance, part changes or legally required tank cleaning.

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Tank Annual Evaporative Loss Comparison Chart

Tank volume content
Annual evaporative loss by tank (KL)
Normal cone roof tank SPC-AL-modified into an inner floating roof tank
Breathing loss (KL) Filling loss (KL) Storage loss + Withdrawal loss (KL)
500 KL 23 30 2.0
1,000 KL 32 58 2.4
2,000 KL 53 116 3.3
3,000 KL 78 175 4.4
4,000 KL 91 350 4.9
5,000 KL 130 525 7.0

For example, if a 2,000 KL tank were filled completely 36 times over a one year period, a total of 23.4 KL of stored liquid would be lost due to evaporation. Under the same conditions, the SPC-AL Inner Floating Roof reduces this product loss to only 0.4 KL. (Source: API MPMS Chapter 19, Section 1 & 2)
Compared to the cost for a conventionally built new tank or modification, the cost of installing the SPC-AL Inner Floating Roof in an existing or new storage tank can be recovered in a short period of time as it can cut evaporation losses by up to 95%.

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