01362 691484
info@corrolesseastern.co.uk

Polyurea Aquaculture Tank Linings, Scotland

THE PROBLEM

The new aquaculture farm had 10 pre cast concrete tanks that required a polyurea tank lining in order to provide protection to the fish that would be contained within them.

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Our client had previously suffered from poor polyurea application at other facilities in their estate that had caused ongoing issues with remedial works being required once in operation

THE SOLUTION

We proposed the application of a WRAS approved polyurea from VIP Coatings

As part of our tender we conducted preparation and adhesion tests on the pre cast concrete panels that the tanks were constructed from.

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This confirmed that due to the quality of the concrete preparation of the walls by method of high pressure washing would be sufficient, thus avoiding risking the opening of the concrete matrix and subsequent making good that might be required.

The tank walls were prepared by 3,000psi pressure washing using a spinning jet attachment to remove loose laitance and contaminants in order to provide a clean and stable surface for the tank lining primer to adhere to.

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The tank bases being site cast and having more surface laitance were prepared by method of vacuum controlled diamond grinding.

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The central outlet required a very flat surface to ensure an effective seal. We were therefore requested to level this area using an epoxy self smoother.

The fixings and perimeter of this area were first masked, and a foam tape installed around the outlet pipe to form a termination point for the subsequent polyurea tank lining to ‘toe’ into.

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Prior to any coating materials being applied and throughout the project the concrete moisture content and climatic conditions were tested and recorded as part of our tank lining quality assurance.

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The epoxy self smoother was then applied by trowel to smooth this area.

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Once cured this epoxy was diamond ground to create the smoothest transition possible to the surrounding concrete and also provide a mechanical key for subsequent coats to adhere to as the overcoat window would be exceeded.

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The vertical panel joints were then primed using a damp tolerant epoxy primer applied by brush.

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These were then filled using a polyurethane jointing compound to provide a smoother finished surface and create a simpler profile to apply the polyurea tank lining to. Due to the fast gel time and application equipment small recesses such as these are more challenging to apply polyurea coatings to.

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The first coat of damp tolerant epoxy primer was then applied throughout the tanks by method of brush and roller.

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To minimise pin holing during the polyurea application a second coat of damp tolerant epoxy primer was applied as part of our standard polyurea application process.

Whilst wet this second coat of epoxy primer was fully blinded using a quartz aggregate to provide an excellent mechanical profile for the polyurea tank lining to adhere to. This also meant that if the overcoat window of the primer was exceeded adhesion would still be obtained.

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Loose and unbound quartz aggregate was removed using soft brooms and vacuums so as not to disrupt the adhesion of the polyurea lining.

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The interface between the floor and the walls was isolated as per best lining practice using a polyurethane jointing compound applied using mastic guns.

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Items not to be coated with polyurea were masked to prevent overspray damage.

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VIP Quickspray Industrial was then spray applied to a nominal thickness of 2mm.

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Within the overcoat window of the polyurea lining (the same shift) the applied polyurea was tested for pin holing using a DC holiday spark tester.

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Any pin holes identified were marked prior to filling using a polyurethane mastic.

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A final continuous application of the same polyurea was applied throughout the tanks achieve as smooth a finish as possible as desired by our client.

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Following completion of polyurea spraying all masking was removed and previously cut termination points sealed using a polyurethane sealant to protect the edges of the polyurea tank lining from creeping.

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The top edge to the polyurea on the tank walls was protected by the installation of a plastic trim around the tanks circumference, bonded in place using a polyurethane sealant.

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Once complete the tanks were returned to the client and the fitment of the outlet pipes checked to ensure that a sufficient seal had been obtained between the pipe and the finished polyurea tank lining.

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By adhering to polyurea application best practice and implementing a stringent quality assurance regime we are confident that the issues with polyurea that our client had previously experienced will be avoided and an excellent solution for the prevention of damage to their fish found.