As fiberglass reinforced plastic (FRP) continues to grow as a material of construction in applications such as tanks, packed bed scrubbers, piping, ductwork, and specialty equipment, the number of FRP structures which require repair or which have in some way lost their utility as they were initially designed will continue to grow. In some instances, damaged or obsolete FRP structures may be modified or repaired to a condition which can provide extended service lifetimes; this may result in lower life cycle costs than wholesale replacement. A number of factors must be assessed prior to design of repairs or modifications, such as the current condition of the structure, the material used in the initial fabrication, and the goals of the project. A thorough examination of these factors will help assess the plausibility and type of modification(s) required. A procedure for surface preparation and laminate application is provided.
The use of FRP as a viable material for applications where chemical resistance, high strength-to- weight ratio, and low life cycle costs are important continues to grow in a variety of industries. FRP is the material of choice in storage tanks, corrosion resistant grating, safety appurtenances (ladders and safety cages), packed bed scrubbers, piping, ductwork, and specialty equipment.
As the growing number of existing FRP structures age or degrade, it will become common for FRP structures to require repair. A repair may be needed where a defect (such as a blister, inclusion, worm hole, or pit) or an area cracked due to impact, overloading, thermal shock, etc. would affect the structural stability or corrosion resistance of an FRP laminate. Localized abrasion damage may also require repairs. Chemical degradation can be repaired by replacing affected resin rich or structural layers, although this is much less common due to the expense involved.
In some cases, the original design of the structure may not be suitable for the current or future service in its current form. This could be due to the geometry of the structure, a new service environment, a new operating temperature, a change in the operating loads, or degradation of the mechanical properties of the laminate. Loss of properties can be caused by penetration of a material which degrades the laminate or from long term exposure to elevated temperatures.
Some of the means of assessing the condition of the structure and the procedures required to upgrade or repair the structure are described below.
