Bio-Ethanol and Bio-Methanol tanks move into focus in tank farms with the introduction of E5 and E10 blended fuels. Bulk storage tanks for alcohols in tank farms or refineries are not only exposed to severe steel corrosion but conventional coating and corrosion protection products are also not chemically resistant to exposure to these products. These steel tanks face internal corrosion which is caused by both the medium and its vapour.
This case study is about a storage tank with 20 m diameter in Central Europe which is intended to be used for a bulk storage of ethanol. Wolftank Adisa decided to apply the system Epoflex® 6N which is resistant to 100 % bio-ethanol and approved as tank lining system for ethanol tanks by Germany’s national technical approval, DIBt.
The customer specified application of a 2-layer laminate system which is covered by a final Epoflex® 6n layer and an antistatic top layer. A wet on wet laminate application made the project very challenging. As attested by the German TÜV, this lining system exhibits structural properties and can be considered up to a certain extend a double floor lining (steel floor plus fiberglass floor).
The customer’s expectation is not to have any tank openings due to floor inspection for a period of 15-20 years. This was a basic requirement in the design of the layer system.
The Solution / Timing
The Epoflex® 6N lining system comprises the following:
- Epoflex® 6N lamination resin + bi-woven fiber glass fabric
- Epoflex® 6N resin
- Adapox® L conductive resin
For a proper long-lasting coating system, a clean subsurface is highly recommended. The surface was sand-blasted to achieve the proper adhesion (SA 3).
After surface preparation, the welding joints at the bottom of tank were levelled with mortar (Epoflex® Klebmoertel N) in order to get a smooth and even surface. Using the same material, a corner radius was created between shell and annular ring. The next day application of the laminate layer started. This reinforcement was applied in two layers, wet on wet, since the final, dried layer thickness of the lamination must reach 2,6 mm. This was the most challenging part of the implementation of the lining system since obtaining the appropriate amount of resin was very difficult: too much resin would result in the second sheet of fiber glass floating on the first one; not enough resin would result in inadequate thickness. Subsequently, Epoflex® 6N two component epoxy-based resin was applied on the cured and sanded subsurface with an airless spraying machine.
As the top layer, the conductive layer was rolled on quite thinly.
The whole application was carried out in a period of 20 days leading to a minimum downtime related to the upgrade to a new storage media. As no hot works and no hydraulic testing is necessary after this installation, these aspects result in a significant cost saving.
The Outcome / Benefit
The project was completed on time and according to the customer’s required standards (quality and safety). Since ethanol storage is increasing in Europe and other countries, this application is a great Wolftank Adisa reference for future projects.
With more than 20 years of expected lifetime extension of the lining system no additional floor maintenance is a major benefit next to the low installation down time. Due to the long term chemical resistance of the Epoflex lining even after 20 years no significant maintenance cost is to be expected as this type of lining is not subject to corrosive deterioriation.