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Industrial Applications of FRP Process Equipment
2013-08-04 16:03:29

Corrosion costs Industry billions of dollars each year and an important task of the design engineer is to seek ways of eliminating or reducing corrosion of industrial equipment. Much of the corrosive attack to industrial equipment comes from chlorides. The Figure shows the range of suitability for many important metals in the presence of chlorides. The ranges are limited to narrow bands above which more and more exotic materials are required. FRP, however, is suitable across the entire spectrum of chloride concentration and pH.

FRP process equipment is used in many industrial applications. A few include:

 

Chemical Storage Tanks
Carbon steel, stainless steel, rubber-lined steel, and premium alloys, once standard materials of construction for chemical storage tanks, are more and more being replaced by fiber reinforced plastics (FRP) as engineers begin to realize the advantages of FRP, e.g. increased corrosion resistance, light weight, higher strength to weight ratio, low life cycle costs, etc.

Underground Fuel Storage Tanks
The same advantages of FRP for chemical storage tanks apply to underground fuel storage tanks with the corrosion resistance of FRP taking particular prominence. Highly cross-linked terephthalic resins are particularly successful in containing gasoline and gasoline blends and resisting the corrosion that results from water condensation inside the tank and corrosion from ground water on the exterior of the tank. Secondary containment systems are easily incorporated into the fabrication of FRP tank shells.

Pickling and Plating Tanks
Among the best applications for FRP are pickling tanks or electrowinning tanks in minerals processing plants. These applications illustrate the advantage of FRP in an environment typified by high concentrations of chlorides. Metal alloys have limited practicality in acidic brine environments in contrast to FRP, which is applicable across this entire range of conditions.
 
Chemical Piping Systems
FRP piping is used extensively in process piping systems, stock and effluent piping in pulp bleach plants, chemical waste and municipal waste sewer piping, cooling tower piping, leach field acid piping, irrigation piping, etc.
 
Sewer Pipe
The formation of hydrogen sulfide and its successor, sulfuric acid, in sewer pipe aggressively attacks concrete sewer piping leading to reduced service life and degraded hydraulic performance when compared with FRP. The light weight of FRP is a special advantage in installing large diameter piping. A smaller capacity crane can be used in most cases, and, in the case of smaller diameter piping, a crane can be eliminated by two laborers handling pipe spools.
 
Fume Ducts and Scrubbers
The Clean Air Act has created increasing demand for scrubbers and collection ductwork systems that will resist the corrosive effects of industrial fumes drawn from process streams. Duct and scrubbers for pulp bleach plants, ducting from clean rooms in semiconductor fabrication plants, odor control ducts, carbon absorbers, and scrubbers in municipal waste water treatment plants: all use FRP as a key material of construction to combat corrosion. The smooth inside surface of FRP piping also greatly reduces the accumulation of biomass in duct systems transporting organo-chemical fumes.
 
Chimney Stacks and Stack Liners
As the demand for electrical generation capacity increases, new coal and natural gas-fired generating plants come on line, flue gas desulfurization systems will be needed to scrub NOx and SOx gases. Large diameter FRP stack liners and transport ducting for power generation stations are already a proven technology for this growing application.
 
Fans, Blowers, and Hoods
FRP impellers and fan housings are used in municipal waste water treatment plants. Hoods are used to capture chlorine dioxide fumes coming off pulp washers in bleach plants. And FRP pump housings are used to protect submersible sump pumps in industrial applications.
 
Pulp Washer Drums and Up-flow Tubes
FRP has long been a material of construction for pulp washer drums used to extract residual chlorine dioxide or caustic chemical carryover from pulp. FRP is also used in large diameter up-flow tubes and retention towers where digested wood chips are first chlorinated and then bleached in the pulping process.
 
Secondary Containment Systems
The process of FRP fabrication lends itself to the creation of outer skins, or secondary containment systems, separated from the inner wall by three dimensional glass fabrics. These interstitial spaces can then be incorporated with sensors to detect and locate leaks or drain to a sump where discharge can be detected.
 
Grating and Structural Shapes
Steel gratings used in catwalks around industrial process equipment provide a lot of surface area vulnerable to corrosion and small openings which make painting difficult. Likewise, carbon steel structural shapes are quickly attacked by corrosive fumes rising from process vessels, etc. In each case, FRP resists the corrosive attack and extends the service life of the structure by a significant time.
 
Cooling Tower Elements
The moisture and oxygen rich environment of cooling towers creates a corrosion-prone environment for louvers, structural elements, distributors, sumps, and piping. FRP has long been used in these applications to extend the life of the cooling towers. Similarly, large diameter steel cooling water intake and discharge piping systems are often clogged by zebra shells. The use of FRP piping decreases, and in some instances, eliminates this severe maintenance problem.
 
Highway Bridge Deck Overlays
Highways in the northern climes are subject to chloride attack from deicing salts used in the winter, roadways in coastal areas are subject to chloride attack from ocean spray, and highways in large metropolitan areas become “political lighting rods” when lanes are taken out of service for any reason. The use of polyester polymer concrete to overlay deteriorated wearing surfaces has become the method of choice where chloride attack is severe and traffic delays are not an option. Polymer concrete will allow a traffic lane to be returned to service in 2 to 4 hours, instead of the 1 to 4 days required for the more traditional concrete. Friction values remain high and chloride permeability is now zero.
 
Floor Coatings and Mortars
FDA regulations require that many food processing plants keep their floors clean. Polymer floor coatings and mortars seal the surface and prevent the accumulation of biomass, which is often present in the pores of Portland cement concrete.
 
Pulp Washer Drums and Up-flow Tubes
FRP has long been a material of construction for pulp washer drums used to extract residual chlorine dioxide or caustic chemical carryover from pulp. FRP is also used in large diameter up-flow tubes and retention towers where digested wood chips are first chlorinated and then bleached in the pulping process.
Chlorine Cell Covers and Collectors
The chlor-alkali industry is one of the most important, albeit, toxic and corrosive environments in industry. Chlorine gas, sodium hydroxide, and sodium chlorate are chemicals found in this process. Cell covers and headers capture and transport highly corrosive (and dangerous) chlorine gas, and FRP is used for the storage of highly flammable sodium chlorate. The corrosion potential is so great in cell headers, for example, that special thick corrosion barriers are specified to extend the service life of the equipment.

 

Chemical Storage Tanks
Carbon steel, stainless steel, rubber-lined steel, and premium alloys, once standard materials of construction for chemical storage tanks, are more and more being replaced by fiber reinforced plastics (FRP) as engineers begin to realize the advantages of FRP, e.g. increased corrosion resistance, light weight, higher strength to weight ratio, low life cycle costs, etc.
Carbon steel, stainless steel, rubber-lined steel, and premium alloys, once standard materials of construction for chemical storage tanks, are more and more being replaced by fiber reinforced plastics (FRP) as engineers begin to realize the advantages of FRP, e.g. increased corrosion resistance, light weight, higher strength to weight ratio, low life cycle costs, etc.

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