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Secondary Compression Plate Seal (CPI)

Secondary Compression Plate Seal (CPI)

The Secondary Seal is a rim mounted system suitable for floating roof tanks of all sizes storing all grades of crude and refined products. The CPI Seal is designed to be installed whilst the tank is in service. The seal incorporates a compression plate, synthetic rubber wiper and vapour barrier membrane. The compression plate can be made from either galvanised steel or stainless steel.

The vapour barrier membrane is normally manufactured from polyurethane-coated nylon fabric with very low vapour permeability properties. The seal design is such that all the fixings are on the outside of the seal; i.e. the tank shell side is completely smooth. The smooth outside surface of the seal ensures that the risk of damage is minimized if the roof is floating above the tank shell. The seal can be fixed to either a vertical upstand or horizontal angle. The dimensions of the compression plate can be varied to suit a wide range of nominal rim spaces.

The CPI Secondary Seal can be easily installed with the tank in service as no hot work is required and the seal is simply bolted in position on top of the roof rim.

For other designs, please head to our Floating Roof Storage Tank Seals page where you can find a range of internal and external tank seals.

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Material Specification:

Compression Plate and Clamp Channels:

Galvanised / Stainless Steel


Synthetic rubber

Vapour Barrier:

Teflon (Fiberglass) / Calcium Silicate / Urethane / Polyurethane


Stainless Steel

Typical Service Life:

10-20 years

Technical data:

Rim space:

200 mm ± 100 mm (standard)

Aromatic resistance:


Alternative designs and specifications for the Secondary Compression Plate Seal (CPI) are available on request