Posted by Sebastian Wiesner - 20 January, 2020
The accidental spillage of coffee from a cup, an event that often occurs in everyday life, shows the two major principles regarding the functionality of secondary containments: first, a hot liquid has to be contained; second, the liquid starts cooling down immediately after it leaves the primary containment. This is precisely what happens to stored hot chemicals, a standard situation for any chemical company, in which the appropriate secondary containment system is crucial for handling possible leakages and keeping refurbishment costs under control; the potential savings are up to 30%.
Calculating the real impact temperature in case of leakage of hot chemicals is essential for designing a secondary containment solution that is both functional and cost-effective. As explained in the article The calculation of concrete surface temperatures for secondary barriers, BASF developed a specific tool for such calculations in cooperation with the University of Kaiserslautern to do so. Sebastian Wiesner, Senior Civil Engineer at BASF the secondary containments competence center, presents a real example showing how he used the temperature calculation tool to design a functional, safe and economic repair solution for a production facility. Details are given below.
The current secondary containment is a reinforced concrete structure which has several deficiencies (cracks, surface damage etc.). Refurbishment is required to maintain the functionality of the containment. See figure 1. Isometric drawing of secondary containment
- Storage temperature inside the tank: 70°C.
- In case of a leakage, the chemical has to be retained in the containment.
- Secondary containments are usually made from concrete with a thickness of 30 cm for the wall and 70 cm for the base slab. This massive concrete volume presents very high energy potential and is heated up in case of a leakage.
- Standard epoxy coating systems are well established for this type of refurbishment.
- The glass transition temperature of a standard epoxy coating system is approximately 60 °C.
- In that case a resistance of 70°C for 72h could not be confirmed.
Detailed calculation of the real surface temperature or the exposure of the potential coating considering the heat flow into the concrete structure.
Result in this special case:
Considering the geometry and the real structure elements on one side and the individual product characteristics on the other the impact on the coating could be reduced significantly.
The relevant temperature to be considered in view of resistance could be reduced from 70 °C to 52 °C. As a result, economical coating with MasterTop 1278 AS, a standard epoxy coating system was possible and was preferred to the cost intensive alternative VE-Laminate, allowing a cost reduction of approximately 30%.
This example from a real life situation clearly demonstrates how important it is to evaluate the exact temperature impacting on the secondary containment surface in the case of a leakage from a hot storage tank, with the aim of selecting a safe and suitable solution avoiding unnecessary overperformance and expensive alternatives.