Best Practices of FRP and Elastomeric Linings for Steel and Concrete Tanks Abstract:

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1 1 Best Practices of FRP and Elastomeric Linings for Steel and Concrete Tanks Abstract: Since case studies have demonstrated that achieving a service life of years in harsh environments is the norm, a number of projects continue to utilize FRP and elastomeric liners. However, in order to have an adequate service life, many factors including, material choice, training and inspection are required. This paper will examine the use of polymeric linings, the common lining problems, the NACE/SSPC standards and the industry practices necessary to produce a lining that will fulfill its expected service life.

2 2 Author Biography: Michael P. Yee The Managing Partner of RT Consults who also controls an engineering and 3 rd -party inspection company for the FRP and coatings industry. Has over 10 years of experience in the nonmetallic industry and is a NACE Level III Certified Coating Inspector with a background in chemical engineering and construction management. He is actively involved in the nonmetallic technical committees at NACE and also ICRI. Presenter for a number of professional organizations over the years who continues to strive for excellence in providing technical services and support for many leading petrochemical companies in chlorine and sulfuric acid, in addition to the offshore oil industry. Richard Taraborelli, P.E. The owner of RT Consultants with over 35 years of experience in the protective coatings and nonmetallic industry. He is a registered professional engineer in the state of Texas. Performed over 2,000 failure analysis and other projects in his career and continues to provide technical services and support to many leading petrochemical Fortune 500 companies.

3 3 Table of Contents Introduction... 4 Material Selection... 4 Resins... 4 Fiber-Reinforced Polymers (FRPs)... 5 Flake Glass Liners... 7 Rubber Linings Application and Quality Issues Quality Inspection Program Conclusion References

4 4 Introduction Chemical facilities face a number of issues when dealing with corrosion and harsh chemicals. The conventional method of addressing these issues is to adequatelyprepare the steel surface and then apply the proper coating to protect it from the elements. However, in chemical facilities, harsh chemicals are essential to the process and require adequate containment and reliable service in order to keep the facilities operational. This paper will address the issues that these facilities face when dealing with severe chemical exposure and protection; namely, with respect to the nonmetallic linings and construction materials where high-priced alloys and thin coatings are not strong enough to withstand the constant thermocycling and harsh facility operations. Material Selection Material selection determination is made based on existing tanks and secondary containment areas that are primarily made out of steel and concrete. The chemicals that require special attention include, but are not limited to, sulfuric acid, chlorine, phosphoric acid, hydrochloric acid, sodium hydroxide, sodium hypochlorite (bleach), potassium hydroxide, brine, white and black liquor, hydrocarbon solvents and alcohols. The containment of these chemicals requires materials that are considered unique, but continue to be rigorously used around the world, like fiberglass-reinforced polymers (FRP), rubber linings and resin-rich flake glass liners.

5 5 Resins While there are many resins on the market, the primary resin used in linings is the thermosetting resin. Thermosetting resins cure to produce an infusible solid material that does not melt when heated. The most commonly-used thermoset resin system is epoxy vinyl ester with a chemically-resistant glass as the corrosionprotection layer for caustic service. For stronger acids, the novalac epoxy vinyl ester is commonly-used due to its chemical resistance. These combinations can also be used as the liners for steel tanks, though a solid FRP-construction will traditionally see a longer service life and lower installed cost due to the labor reductions associated with automation in fabrication shops. Additionally, there is limit to the vessel size and logistics costs when the vessels grow past the 30 - diameter mark. Fiber-Reinforced Polymers (FRPs) FRPs are used daily in hostile environments. While the majority of FRP applications and uses are located in Asia, it is equally-matched to the demand in the United States, Canada and Europe. The use of chemically-resistant resins with glass has been around since its introduction in the 1950 s by Dow Chemical, as well as several other Japanese companies that have been incorporating composites. FRP was created for its use in hostile, chemical environments and thus, different product lines were created to address different services for each environment. Today, a lot of these resins are being added to coatings to provide a similar level of chemical protection to steel and concrete surfaces. Technology has not changed much since the 1970 s and there are numerous case studies that show that a properly-designed FRP vessel and lining with excellent quality, properly maintained, inspected, and operated can reliably last for over 20 years.

6 Figure 1: FRP Lined Steel tank with a BPO/DMA Cure 6

7 7 Figure 2: Hand-lay up method of application Flake Glass Linings Flake glass linings are relatively-new to the coatings industry and are seeing a lot of adoption by the petrochemical industry. They were developed in the 1960 s but never really started to take off until the 1980 s when they then branched into many different industries and companies. As in FRP, these resin-rich, flake glass linings use a significant quantity of resin in the formulation. They also use the same catalyst, benzo-peroxide, to fully-cure the system. Trowel methods are normally employed to both provide a high material-to-surface transfer and to minimize air bubble issues. These linings include glass flakes in the material and are reinforced with fiberglass that is woven for concrete linings and unreinforced for steel linings.

8 Figure 3: Sulfuric Acid Containment 8

9 9 Figure 4: Reinforced Mat Lining Application Figure 5: Trowel Method of Flakeglass Lining

10 10 Figure 6: Holiday Testing Rubber Linings Rubber lining has been around since the 1890 s when the autoclave method of curing was invented. Not much has changed, as evidenced by the steel linings of rail car tanks for mild chemical and brine storage. Rubber can be either natural or synthetic, but is a very robust material that handles impact and abrasion very well. The upfront cost is less than FRP and is an economical choice for mild chemical and brine service. On average, when properly installed, it will last longer than thin paint coatings and unreinforced linings. It is applied by first preparing the surface

11 11 and then applying a primer/adhesive that normally comes in sheets. Different systems may use natural rubber as a bonding interface with the synthetic rubber forming a composite. There are a number of things to observe when inspecting the surface as well as when repairing a rubber lining and it is important to note the difficulty of doing so in the field. Figure 7: Rubber Sheets cut and fitted together inside a tank roof

12 Figure 8: Issue with Stitching Quality 12

13 13 Application and Quality Issues: Lining systems are labor intensive and will typically involve 66-85% of a project s labor cost in the United States. This is the result of the surface preparation, application and quality, which encompass a successful project. Surface preparation is considered the foundation of the lining system. Steel and concrete require the most rigorous surface preparation because there is little allowable variation since almost all will call for a NACE 1/SSPC-SP5 white metal blast. Before the abrasive blast, a detergent pressure wash must be performed in order to remove salts, sulfites and nitrate contaminants from the surface. Concrete is a difficult material to achieve a proper surface profile since it is heterogeneous and very sensitive to moisture. When mechanically removing the surface, the laitance must be removed in order to reveal any small and large aggregates. The required and best-consensus standards available are either IRCI 300R8.1 or NACE 6/SSPC-13. Once surface preparation is complete, the application process soon follows in an effort to either protect the steel from flash rusting or to take advantage of the coating window. The substrate surface must be 5-degrees Fahrenheit higher than the dew point in order to prevent moisture from interfering with the cure and adhesion of the lining system. The application process must be initiated at temperatures in excess of 50-degrees Fahrenheit because it is almost impossible to obtain a complete resin cure without the application of external heat. Corners and edges must be reinforced through the use of putties or flashings. The tank must also have the radius filled-in with putty or reinforcement from the bottom to the shell in order to prevent the formation of air pockets. This holds true for weld seams and other metal deformities as well. A comprehensive guide to this practice is found in the standard NACE SP The surface preparation process is considered a critical quality control point. It must have a proper surface profile and be free of contaminates prior to application.

14 14 Figure 9. Steel Pits Found on a Relining Project Resin lining applications require an accurate gel time in order to provide sufficient working time to remove air bubbles from the laminate. A resilient wetting primer is recommended in order to provide an interface that will assist with expansion and thermal cycling performance. The primer must be applied with a thickness of no more than 4 mils in order to prevent detrimental effects on the adhesion. Following manufacturer product data sheets during the application process is important and training is needed for optimal lining performance. Quality inspections must be performed and evaluated in order to ensure proper application techniques are being used. Rubber application is normally done in sheets and requires the proper technique with respect to the seam-stitching. Curing with either autoclave or atmospheric steam must be performed within the time span specified by the manufacturer. Hardness should be inspected and verified in order to conform to manufacturer cure specifications prior to initiating chemical service.

15 15 Quality Control Program There are three motivating factors in completing a successful project: safety, productivity, and quality. Safety in chemical plants is non-negotiable and therefore the balance of productivity and quality is always at odds with one another. The reality that exists today is that there is a failure rate of at least one out of three in premature failures within 4-5 years. The expected life in proper service of these lining systems with excellent quality, properly maintained, inspected, and operated can reliably last for over 20 years. The main quality issues come from the inadequate surface preparation requirements for the lining system and also issues with application. In addition, testing and specifying the right system and material choice is just as crucial since low concentrations of impurities in the chemical stream will also result in premature failure. A lot of these lessons are imparted from experience and not recognized by material suppliers since it would be detrimental to the product line. An example of this happening is the issue of the recoating window for a lining system. A manufacturer stated on product data sheets that it could be recoated within 30 days. However, the coating cure was very sensitive to moisture and so it was revised after a technical meeting to be 3 days. After numerous adhesion failures, it was then finally revised to just one day which resulted in the project being terminated and reworked. Another example is the wrong curing mechanism and the lack of environmental conditions during application. Moisture was seen in the laminate and also the hypochlorite contained in the tank would have attacked the promoter used (Cobalt) for the FRP lining system resulting in failure. There are many examples but the lesson is always the same in the need of doing the project right the first time. There isn t much that can be done after failure has taken place, it normally results in total rework.

16 16 Conclusion With respect to each material, all waste and product streams must be accounted for in order to determine proper material selection. Chemical services have special requirements that demand respect for the chemicals being used as well as for the dangerous/lethal concentrations being created. As a result of the changing service conditions, one should not rely solely on the material service tables. Solution mixtures in a waste stream can wreak havoc on any system that was designed for only one concentration. Lower concentrations of certain chemicals as well as alkaline solutions can be detrimental to the material being used. Permeation and temperature changes can drastically-affect any laminate performance; therefore, quality assurance and technical specifications addressing these issues is of vital importance. There are many plants that had to close their doors due to chemical remediation fines and regulatory requirements after leaks and spills resulted from containment failures. There is an important need for nonmetallic engineering and for the quality inspections used to determine satisfactory results in a material s performance. While the best materials and methods can be used, the system won t provide reliable service if the quality is lacking. This is why 3 rd -party inspections are required, in order to ensure that details and issues are timely-addressed and corrected.

17 17 References 1. ACI Committee 440, Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures (ACI 440.2R-08), American Concrete Institute, Farmington Hills, MI, 2008, 80 pp. 2. ASME RTP , Reinforced Thermoset Plastic Corrosion-Resistant Equipment, American Society of Mechanical Engineers, New York, NY, SSPC-SP 13/NACE NO. 6, Surface Preparation of Concrete (2003), SSPC: The Society of Protective Coatings, Pittsburgh, PA. 4. ACI Concrete Repair Terminology, International, Farmington Hills, MI. ACI 5. ICRI CSP 4-5, ICRI Committee 310, Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, Polymer Overlays, and Concrete Repair (ICRI 310.2R-2013), International Concrete Repair Institute, St. Paul, MN, 48 pp. 6. ASTM C582, Standard Specification for Contact-Molded Reinforced Thermosetting Plastic (RTP) Laminates for Corrosion-Resistant Equipment, ASTM International, West Conshohocken, PA, 2009, 7 pp. 7. ASTM D7234, Standard Test Method for Pull-Off Adhesion Strength of Coatings on Concrete Using Portable Pull-Off Adhesion Testers, ASTM International, West Conshohocken, PA, 2012, 9 pp. 8. ASTM D4541, Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers, ASTM International, West Conshohocken, PA, ASTM D2583, Standard Test Method for Indentation Hardness of Rigid Plastics by Means of a Barcol Impressor, ASTM International, West Conshohocken, PA, 2001.