CSC Services Managing Director Mark Lemon looks at some of the key factors to be considered when specifying tank coating systems.
In the UK tanks holding drinking water will need to be lined with products approved by the Drinking Water Inspectorate. Regulation 31 ensures that products and substances do not cause any detrimental effects to the safety or quality of the drinking water. Products used externally on drinking water sites need to be WRAS approved.
Temperature will impact upon the curing ability of the coating. Cold-weather and very humid conditions may have an adverse effect upon a lining. A cold-weather coating which permits curing in temperatures as low as -40ºC may be required depending on the time of year the programme is scheduled to take place. Polyurea can be applied at sub-zero temperatures. It is however pending DWI approval.
Similarly the temperature range of the coating will need to be considered if the tank is to store heated materials. Coatings can be permanently damaged by exposure to heat above the stated range.
If the tank experiences extreme expansion and contraction due to atmospheric conditions, then a lining with good flexibility or elongation properties should be specified.
Most lining failures relate to poor surface preparation and/or a lack of understanding about the relationship between the substrate, primer and membrane. The primer’s role is to form a mechanical bond with the substrate and a chemical bond with the top coat. There are a range of solvent free and solvent based primers on the market, and the environment in which they are to be applied is very important as solvent based primers are very flammable.
Chemicals and reagents that come into contact with the coating need to be considered. The product’s data sheet will outline what the coating has resistance to. A chemical chart will often be included.
If the tank contents form a unique mixture that hasn’t been tested you should arrange to send a sample to the manufacturers laboratories for testing or request a sample of the coating to test yourself. Most coating manufacturers have a technical department who can offer advice on this, and can advise if the contents of the tank when mixed with the coating will affect chemical resistance.
Return to service
The length of time the job will take is a key consideration. It may need to be scheduled for shut-down periods or when production is not occurring. Time is usually of the essence as shut-downs are costly to any organisation. Different coatings have different setting times and the amount of preparation required can vary which can also impact the programme of work.
Another key advantage of Polyurea technology is that it has very fast setting times (5-20 seconds) and can be applied to any thickness in one hit, removing the need for a primer, or second coat. Both factors can enable rapid return to service.
The coating’s ability to be repaired should be considered. If the coating can be repaired this can drastically reduce costs in the future. Some coatings cannot be repaired which mean there will be significant costs in removing the coating (through abrasive blasting or similar) and recoating the entire tank. Once a coating has been installed an appropriate after care programme should always be scheduled.
As the above list shows there are many factors to consider when selecting a suitable coating for a tank refurbishment. This list is not exhaustive, but includes some of the key considerations which should be taken in to account to maximise chances of a successful project.
CSC Services have been refurbishing corroded and damaged water storage and chemical storage tanks since 2002. This can be done in situ and at the fraction of the cost of replacing and installing a new tank. Tank coating systems can address leakage issues, control corrosion and protect the structure from chemical attack and abrasion.
From epoxy and polyurethane tanks linings to the latest polyurea technology there are a full range of protective coatings on the market. CSC Services work with a range of manufacturers, undertaking relevant application training to be able to specify the best solution for clients.
If you have any questions, or would like any help with a project please call CSC Services on 0191 410 3444.