Our client needed to expand the amount of rapeseed oil that they could store on site. Their primary storage vessel was a stainless steel tank, but in addition to this they had a mild steel tank which they wished to repurpose.
We proposed the application of a solvent free glass flake reinforced epoxy lining from Chemco International as a suitable lining, given that it has FDA approval for direct food contact.
The tank was thoroughly cleaned and degreased prior to handover to ourselves.
Grit blasting the surfaces
All surfaces to be coated were prepared by method of grit blasting, using expendable iron silicate media (Copper Slag). Grit blasting is still widely recognized as the best form of surface preparation as it both cleans the surface and raises an excellent mechanical profile to ensure good adhesion of the new tank lining.
Following grit blasting all surfaces were vacuumed clean and surface cleanliness and soluble salt tests conducted as per best tank lining practice. During and following grit blasting the atmosphere within the tank was maintained below 50% relative humidity in order to maintain the blast standard.
The surface profile from grit blasting was checked and recorded using a surface profile needle gauge.
Applying the stripe coat
As per best tank lining practice all angles, edges, nuts and bolts received a heavy stripe coat of Chemco RA500M to ensure full film thickness in these areas where paint pulls thin through gravity and surface tension.
Applying Chemco RA500M
Chemco RA500M was then applied in two coats of contrasting colour using our heated plural component spray machine. We elected for this method of application to reduce the quantities of solvent used in cleaning and flushing operations, in order to minimise the risk of solvent contamination of the tank lining given its use for storage of food products.
As per our standard quality assurance the new tank lining was tested for porosity using a DC holiday spark tester. Where pin holes were found these were marked with chalk prior to touching in using the same material.
Cleaning the tank
In order to comply with the materials food safety certification, following post curing the tank lining was cleaned using warm water and a mild food safe detergent.