FRP liners

Figure 48-3 Concrete chimney with shell supported steel or FRP liner (shown as tension supported).

The wet lay-up is the most basic method for repair of pipes. As with all repair techniques, the surface of the pipe must be cleaned and prepared. Most designs assume that after the repair is completed the stresses in the pipe will be resisted jointly by the steel pipe and the FRP liner. This requires proper bonding between the FRP and the host pipe. A typical surface preparation for such pipes includes sandblasting of the pipe to white metal condition. The surface of the pipe must be cleaned by air pressure to remove any loose materials. If the resin system is moisture sensitive, care must be taken to avoid moisture buildup on the pipe surface. In most cases, forced airflow will provide ventilation for the crew working inside the pipe. The temperature of this air can be adjusted to ensure a dry pipe surface during the repair. 

Fig. 19.3 was developed to estimate the thickness of FRP Furan tanks. It is based on 500 psi allowable stress and includes a 1/4-in. liner. The wall thickness in FRP tanks normally tapers down from bottom to top for estimating purposes, the thickness should be calculated for the pressure at one-third of the tank height. 

Dual Laminate (Fluoropolymer-lined FRP) Same as Adhesive-bonded Fabricate liner first on a mandrel (hand and machine welding) and build FRP laminate over the liner. Use carbon cloth for spark testing Shop and Field Pressure OK (RTP-1 Dual lam) Vacuum OK for FRP/fluoropolymer bond. Design FRP for vacuum 33 dia max Visual Spark AE CRBBD Possible Testing recommended... 

The principle of dual laminate construction is to line an FRP vessel or column with a fluoropolymer lining. However, the sequence of construction is to first make the liner out of fabric-backed sheets the same as in the adhesively bonded construction. The FRP structure is then laminated on the liner to pro-... 

Eining for the heads are thermoformed afterpieces are welded. Carbon cloth is first laid using the resin. FRP is then laminated by contact molding (hand layup). The edge of the liner is left uncovered for subsequent welding. 

In the construction industries, UPE-based FRP has been replacing aluminium, stainless steel and wood because of its low cost, and ease of cleaning and working. The examples for such applications are solar panels, wall liners, automobile components, liners for truck trailers and railroad cars. UPE-FRP products are used to make sanitary ware as replacements for conventional materials such as porcelainised cast iron due to their obvious advantages of lower cost and easier installation. The other related applications are bath tubs, showers, toilets and sinks. 

Thermoflex tubes with diameter of 1.75" were used to form the gathering line in an operation in North-western West Virginia (PolyHow, 2012). The lines, produced by PolyFlow Inc. of Oaks, PA, accommodate 200 bbl/day capacity flow with no brine content. Dne to the hilly area, the line had to accommodate an operating pressure up to 500 psi. These tubes incorporated a Fortron liner to eliminate the potential for paraffin build-up in the pipe and were rated for 1000 psi operating pressnre. Since these pipes were connected to steel lines, it was found that appropriate measures should be taken to protect the FRP section in the transition region, so that the weld temperature propagation would not exceed 120°C. 

The performance criteria that usually determine the choice of one or more FRP resins over another include chemical resistance, mechanical strength, heat resistance, and (for the manufacturer) processability. A qualitative summary of FRP resin performance is presented in Table 5.48. For the final choice of the appropriate FRP resin(s) and liner combination for a given service (chemical environment, weathering exposure, abrasion resistance, etc.) more detailed information, including case history data, should be obtained. 

Stack Liner 316L,317LMN, 625, C276, C22 FRP, Plastic Lined CS Bororflicate Block... 

CFRP liner systems are typically specified to be functional and made with durable CFRP materials based on performance-based specification. Like with other eonstinc-tion materials, inappropriate and unsuitable FRP materials may lead to a substantial reduction in the service life of CFRP repairs. 

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