ABSTRACT Proper surface preparation is essential in obtaining adequate adhesion of fiberglass reinforced plastic (FRP) during laminate repairs on existing FRP substrates. In order to reduce the time required for the surface preparation of large areas, abrasive blasting was considered as an alternative to traditional power tool techniques. A pilot test was performed on a damaged hydrochloric acid FRP storage tank. Based upon the results, an operating pickling solution tank was repaired during a time- sensitive outage. This paper provides an overview of FRP materials and the types of damage that can occur, and presents a case history involving the use of abrasive blast cleaning as an innovative surface preparation technique for repairing this material of construction.
INTRODUCTION The use of fiberglass reinforced plastic (FRP) as a viable material of construction continues to grow for applications where chemical resistance, high strength-to-weight ratio, and low life cycle cost are important. FRP is the material of choice in many chemical environments for storage tanks, piping, ductwork and other specialty equipment.
Reinforced plastic is used in a wide variety of industries. FRP is used in the aerospace and aeronautics industries because of its strength and lightweight properties. FRP is used in sculptures and architectural applications as a readily formed, atmospherically stable building material. FRP is used in boats, drop-in pools, and spas as a custom built material suitable for long term, low maintenance service.
FRP is also widely used in the chemical process industry as a corrosion resistant alternative to expensive alloys. The current uses for FRP in this industry include chemical storage tanks, wet and packed bed scrubber towers, piping, ductwork and hoods, fans and housings, pumps, valve bodies, agitator shafts and blades, vessel and tank linings, secondary containment linings and structural support members.
FRP equipment can be fabricated using several different types of resin systems. Isophthalic polyester resins are frequently used in FRP fabrication because of their low cost and adequate mechanical properties, particularly when reinforced with fiberglass. They are used in applications involving weak acids or bases with temperatures up to 150 degrees Fahrenheit. Vinyl ester resins are used when superior corrosion resistance, superior mechanical properties and elevated service temperatures are required, but at a higher cost as compared to isophthalic polyesters.
Vinyl ester resins include Bisphenol-A and Bisphenol F (Novalac). Vinyl esters are formulated by reacting an epoxy resin with acrylic acid to form the polymer.
Other types of resin systems, such as epoxies, chlorendic anhydrides and furans, are available, but their use in chemical handling varies according to the type of equipment being fabricated.
Damage to FRP equipment can occur for a wide variety of reasons. Typical types of damage include cracking due to mechanical impact, improper handling during shipping and installation, chemical degradation, thermal degradation and chemical permeation leading to blistering and cracking due to thermal shock.
As indicated, cracking of FRP equipment can be caused by a number of items. One of these items includes mechanical damage. Mechanical damage includes physically hitting the equipment with an object such as a forklift or truck, dropping a tool(s) onto the FRP, or hitting objects with the equipment during installation. Cracking caused by these types of scenarios is known as impact cracking.
Thermal shock can cause cracking of FRP equipment. This occurs when a considerable change in temperature is applied to