Dual Laminate Fabrication Association (DLFA) is a nonprofit organization established in 1993 to create a forum for engineers to promote the use of dual laminate equipment, which are composed of a corrosion resistant thermoplastic liner overwrapped with fiberglass reinforcement. DLFA members collaborate to bring design engineers the information and standards that make it easier to determine when dual laminate equipment is the best solution.
Dual Laminate equipment has found use in handling various types of corrosive and high-purity liquids and gases. Tanks, pipe, fittings, scrubbers, and various other process equipment are fabricated in this manner and provide a cost effective long-term solution.
Dual Laminate Equipment
Dual laminate construction incorporates a thermoplastic lining into a fiberglass reinforced plastic (FRP) structure. The thermoplastic lining functions as the primary corrosion barrier to protect the traditional FRP corrosion-resistant structure. Dual laminates combine the excellent chemical resistance of thermoplastics with the known structural advantages of FRP.
Why Use Dual Laminates?
Dual laminates are used when the corrosive service exceeds the limits of straight FRP or when cost restrictions prevent the use of high nickel alloys. In addition, dual laminates provide a low maintenance alternative to glass lined, rubber lined, and brick lined systems.
Advantages of Dual Laminates
Dual laminates have many benefits over traditional FRP or metallic construction:
- Lighter Weight
- Longer Service Life
- Lower Maintenance Cost
- Reduced Downtime
- Increased Productivity
- Interior / Exterior Corrosion Resistance
- No Geometric Restrictions
- No Size Restrictions
Secondary Corrosion Protection
Dual laminates are manufactured with a traditional FRP corrosion-resistant barrier that provides secondary corrosion protection behind the thermoplastic lining. The FRP corrosion barrier provides added protection in the unlikely event of a lining breach.
Dual Laminate Construction
Thermoplastic linings used in dual laminate construction are manufactured in roll or sheet form. The lining is formed and welded prior to integration with the FRP structure. Welding technologies include hot gas hand welding, flow fusion machine welding, and butt fusion machine welding. The thermoplastic lining is internally supported and the FRP is chemically or mechanically bonded to the lining. The FRP bond to the thermoplastic lining must have minimum climbing drum peel strength of 50 in.-lb/in. when tested per ASTM D 1781. The FRP structure is laminated using hand layup, filament winding, or vacuum infusion molding processes.
Conductive Spark Testing
A conductive carbon veil layer is integrated into the FRP corrosion barrier to facilitate high voltage spark testing of the lining. The conductive target should cover 100% of the lining.
Dual laminates are applicable to several ASME codes and standards related to FRP vessel design and fabrication. The ASME RTP-1 Standard for Reinforced Thermoset Plastic Corrosion Resistant Equipment provides comprehensive coverage of dual laminate construction. Dual laminate vessels can be stamped with the ASME RTP-1 mark. Vessels stamped per Section X of the ASME Boiler and Pressure Vessel Code are also available with dual laminate construction.
Dual laminates have applications in the following industries, and serve both aggressive chemical and high purity applications in these markets:
- Chemical Processing
- Oil & Gas
- Pollution Control
- Pulp and Paper