Sophisticated Internal tank lining systems protect both the tanks and stored materials.
Linings are generally used in situations where either the stored material needs protection from the tank steel, or the tank steel from the stored material.
Correctly specified tank lining systems enable cost effective carbon steel tanks to hold fluids that could not otherwise be stored in steel tanks. These linings can be used in situations where more robust materials such as stainless steel prove unsuitable for a variety of corrosive chemicals.
With the ever-increasing use of bio fuels and as a consequence the potential for more water contamination partially lined tanks are becoming more common. These tanks have a lining applied to the bottom of the tank to protect the carbon steel from any possible corrosion due to the presence of water in the bottom of the tank, an example of protecting the tank from the contents.
On the other hand, while aviation fuel does not corrode carbon steel tanks the desire to have the least possibility of any contamination of the fuel from the tank has led to the standard for aviation fuel storage tanks to always be lined. An example of protecting the contents from the tanks!
The most common linings for low level corrosive fluids are epoxy resin systems which provide excellent protection for chemicals.
For the more corrosive fluids or where abrasion is an issue, rubber, glass and resin type linings can be used. Rubber linings are applied to grit blasted surfaces and the tank is pressurised with steam to vulcanise the lining.
Where abrasion is an issue, rubber linings are common. Different colour rubber lining are built up in layers, any changes in colours can be used to gauge the wear level.
Epoxy vinyl ester resin linings such as Derakane are applied in multiple layers normally with fibre reinforcement to suit the contents such as Hydrochloric Acid (HCL).
Glass lined tanks are commonly used in the food and cosmetic industries.
In all cases, the lining is tested to ensure complete coverage typically using high voltage (up to 10,000V) spark (holiday) testing.
Consideration is given to the connecting pipework and fittings where large diameters can be lined as the tank and smaller diameters need to be made from a suitable material such as stainless steel or more resistant materials like Inconel.
A lined carbon steel tank can offer as good or better protection at a lower cost than a typical 304L stainless steel tank. Linings can be inspected and if necessary repaired to increase the life of the tank almost indefinitely.
Cookson & Zinn are a leader in this field.