Laminates, dual

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- 

Fabrication of lining by welding and insertion in the steel vessels 

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Thermoplastics Thermoplastics are used in a numoer of ways. They may be freestanding vessels, pipe, and other equipment as linings in metallic vessels or as dual laminates in combination with thermoset... 

TABLE 25-20 Dual-Laminate Construction and Lining Properties... 

Dual laminate Same as adhesively bonded Fabricate liner first Pressure ok 33 diameter Visual Possible... 

Dual laminate (FRP)(vessel piping) - FEP, PFA, ETFE I— Rotolining (vessels piping) - ETFE, PFA... 

Preparation of the panels needs to be done in accordance with the shop practices that produce the lining or coating. For loose, bonded, and dual laminates, it is important to include a weld in the lining. A T-weld in the panel, as shown in Fig. 4.1c, best achieves this. Once prepared, the panels should be spark tested. 

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... 

Bonded FEP, TEFZEL, PFA Dual laminate FEP, PFA, TEFZEL (Note dual laminate and bonded linings have limited vacuum resistance check with expert)... 

Bonded TEFZEL Dual laminate TEFZEL (Note PFA or FEP are still options)... 

Bonded FEP, PFA Electrochemical Engineering Manufacturing Co. Dual laminate PFA, FEP RL Industries, DPF Dual Lam... 

Table 8.2. Fluoropolymers Used for Dual Laminate Structures...

Figure 8.25 shows an operator working on laminate fabrication. Figures 8.26 and 8.27 illustrate the fabrication technique and examples of dual laminate structures. The job sequence is as follows ... 

Figure 8.22 Machine butt welding of fluoropolymer prior to dual laminate construction. (Courtesy CPF Dualam, Montreal, Canada.)...

Figure 8.24 Supply chain and Job sequence for dual laminate construction.

Dual Laminate - FRP (fiberglass reinforced polyester) piping lined with fluoropolymer is manufactured by forming FRP over a fluoropolymer tube. The resulting stmcture is called adual laminate. 

The chlorine headers popular in Europe are dual laminate headers, which are preferred over FRP for environmental reasons. The dual laminate has an inner ring of less brittle PVC-C of 5-mm thickness for corrosion protection and an outer layer of 10-15 mm thickness of FRP for structural strength, the intermediate layer being 5 mm of resin-rich FRP 5 ION or 197-3. The outer layer contains a flame retardant and is added after the dual laminate is stress relieved. The chlorinated PVC (CPVC)/FRP dual laminate header is fabricated from CPVC tubing up to 60 cm in diameter. The dual laminate headers have a life of 8-10 years vs the 6-12 years of life of FRP, at a comparable cost. 

Vessels Carbon steel with a minimum 3.2 mm corrosion allowance, steel lined with 6.35 mm PVC-lined FRP dual laminate or PVC... 

Dual laminate structures are composed of fiber reinforced plastic (FRP) built with fiuoropolymer sheeting that serves as a lining. This lining is fabricated by machine and hand welding of fiber backed fiuoropolymer sheets, like those described above for adhesive bonded systems. The fabric aids in bonding the sheeting to the FRP. 

The dual laminate construction lessens the problem of permeation through liners. If there is permeation, it is believed to pass through the RTF structure at a rate equal to or greater than through the fluoropolymer itself, resulting in no potential for collection of permeate at the thermoplastic-thermoset interface. If delamination does not occur, permeation is not a problem. 

Unplasticized PVC cannot be bonded directly to a metal substrate, while plastisols (type 2 PVC) can be bonded directly. Because of this, many PVC sheet linings are dual laminates with an unplasticized PVC sheet bonded to a plastisol. This dual laminate can then be bonded to the metal substrate, leaving the unplasticized PVC sheet exposed to the eorrodent. 

Dual Laminate Specifications, published by Composites USA, Inc., North East, Maryland, www.compositesusa.com/duaFspecs. 

FRP piping lined with fluoropolymer is manufactured by forming FRP over a fluoropolymer tube. The resulting structure is a called a dual laminate. Typically, this tube is a thermoplastic fluoropolymer such as PFA or FEP so that glass fabric can be readily embedded in its outer wall. This fabric bonds with the FRP structure so that the lining is held firmly in place. 

Like piping, lined vessels can be constructed as dual laminates with FRP. In some uses, these are preferred to lined steel vessels because the FRP vessels often have sufficient chemical resistance to prevent damage by spills, and they do not require periodic painting to prevent rusting. Also, because they weigh less, they need less support so installations can cost less. 

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