Materials
Fig. 5. FRP tanks in a typical tank farm in industrial areas.
material of choice for sodium hypochlorite storage tanks is FRP constructed from brominated epoxy vinyl ester resin. When these tanks are fabricated properly, they have lasted for more than 20 years. The reasons that FRP is the material of choice are primarily its low initial cost, low maintenance costs and the long life of the tanks. Other materials of construction will either not last as long or are more that twice the cost of an FRP tank. The odour abatement systems at waste water treatment plants are also made from epoxy vinyl ester-based FRP. Scrubbers, absorber towers, ducting, grating and piping have all been made out of FRP. To ensure a successful FRP application there are key
several things that need to be considered. The first step is to determine if there is a resin appropriate for the service. Proper resin selection is very important to long service life. Information
and structural wall construction. The third step is to write detailed specifications for the fabricator to follow. The fourth step is having the equipment fabricated. The quality of the fabricated equipment is important. An equipment fabricator should be evaluated and approved on their ability to meet the desired quality requirements in the specification. The next step is inspection of the fabricated equipment. Inspecting the equipment should be done while it is being made, when it is shipped, after it is received at the site and before it is put into service. These inspections will help insure that the equipment was made with the proper materials and that it meets the desired quality. An experienced FRP inspector is essential. An experienced inspector knows what to look for during the fabrication of FRP equipment. It is also advised to have the equipment inspected on a regular basis once it is in service to verify that it is performing they way it was intended.
Fig. 6. Composite cooling towers at 750MW Midwest Power Plant designed for 50-plus years service life.
required to make resin selection includes the chemicals in service, minimum and maximum concentrations, maximum temperatures, any upset conditions, abrasion requirements and any fire retardant requirements. With this information, the proper resin can be selected for the application. Most of the major resin suppliers can give assistance on resin selection through consultation with their technical personnel or by using their published resin selection guides. The next step is proper equipment design. This will include the proper corrosion liner
Conclusion
FRP equipment has been used successfully to mitigate corrosion in difficult environments since the early 1950s. When the proper resin is chosen, and the equipment is designed and fabricated properly, a long, maintenance-free service life can be expected. Numerous case histories are available demonstrating that FRP equipment can give very long service life. There are many applications where carbon steel and stainless steel simply cannot handle corrosive chemical environments. Currently, many corrosion engineers only consider FRP if they cannot find appropriate metals for a given application. In many of these applications FRP equipment can be used very successfully. FRP equipment should be considered as a viable material option when looking at materials of construction for new
equipment. ❒
Enter 35 or ✔ at
www.engineerlive.com/ece
Michael G Stevens is Senior Staff Scientist, Ashland Inc, Covington, Kentucky, USA.
www.ashland.com
www.engineerlive.com 35
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