The Client

The carbon steel tank was of standard vertical cylindrical design, 5m high and 4.5cm in diameter. The tank had been previously linked with a traditional vulcanised rubber system, which needed to be replaced in the lower half of the vessel. The company had installed a new rubber lining but it immediately failed so we were called upon to identify the cause and make suitable recommendations.

We found that although the tank had been thoroughly washed prior to the start of the work, small amounts of H2SO4 in crystalline form had remained on the upper areas of the existing tank lining. The rubber lining had begun to disintegrate before it had become resistant to the acid.

Challenges

• To provide a resin-based tank lining system for the storage of bulk sulphuric acid at concentrations of 25-85% at temperatures ranging from 35-50°C.

Solution

Our recommendation was to remove all the rubber completely and apply a liquid resin lining system. We were able to find the most suitable material for this application, which was a high-tech modified acid-resistant epoxy resin system.

We proposed and used a lining system that was resistant to sulphuric acid concentrations of up to 96% at elevated temperatures. After thorough grit blasting to remove all traces of the existing rubber and corrosion from within the tank, we applied the modified epoxy resin tank ling resin by hand in multiple coats to avoid wastage to ensure complete coverage. Following the application process, we tested the new lining for the absence of holes and micro-porosity in the coating and also the dry film thickness.

The Results

Although the materials for the project were quite expensive, when comparing the cost of applying a new rubber lining or changing the technology completely, our solution proved to be 45% cheaper than rubber lining. The lining was applied at the beginning of 1997 and the tank has been in constant use since then with a fully operational lining.