Resistant Tank

As reviewed throughout this book part of the wide acceptance of plastics is from their relative compatibility to chemicals, particularly to moisture, as compared to that of other materials. Because plastics are largely immune to the electrochemical corrosion to which metals are susceptible, they can frequently be used in transportation and other markets successfully to contain water and corrosive chemicals that would attack metals. RP fabricators also have a major market for tanks as well as pipes, grating, and a variety of other structures used to withstand corrosive working environments that serve industrial customers. 

However, certain plastics are subject to attack by aggressive fluids and chemicals, although the same media attacks not all plastics. It is thus most practical to select a plastic to meet a particular design performance condition. For example, some plastics like HDPE are immune to almost all commonly found solvents. Polytetrafluoroethylene (PTFE) in particular is noted principally for its resistance to practically all-chemical substances. It includes what has been generally identified as the most inert material known worldwide. 

It is important to recognize that all materials will have problems in certain environments, whether they are plastics, metals, aluminum, or something else. For example, the corrosion of metal surfaces has a damaging effect on both the static and dynamic strength properties of metals because it ultimately creates a reduced cross-section that can lead to eventual failure. The combined effect of corrosion and stress on strength characteristics is called stress corrosion. When the load is variable, the combination of corrosion and the varying stress is called corrosion fetigue. 

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Parts with fiber volume fractions up to 60% can be fabricated by filament winding. The procedure is often used to manufacture composite rocket motors, corrosion-resistant tanks and storage containers, and piping for below-ground appHcations. 

Alums and many solution polymers, or polymers dissolved in water, are corrosive therefore, use corrosion-resistant tanks. 

Following are some examples of passive safety systems to reduce the likelihood of explosions in storage units. The use of baffles in a high-pressure storage vessel can cool the tank wall above the liquid surface via liquid pumped around by vapor bubbles, extending the time for fire fighting. Fire resistant tank insulation is also effective in delaying a BLEVE. 

U L 2080, Standard for Fire Resistant Tanks for Flammable and Combustible Liquids... 

Examples of products fireplaces, vanities, plaques, shower stalls, playground equipment, bowling balls, sewer pipe, pistol grips, corrosion resistant tanks... 

SwRI 97-04, Standard for Fire Resistant Tanks, includes tests to evaluate the performance of ASTs under fire and hose stream. This standard is similar to UL 2080 in that the construction is exposed to a 2-h hydrocarbon pool fire of 1093°C (2000°F). However, SwRI 97-04 is concerned only with the integrity of the tank after the 2-h test and not concerned with the temperature inside the tank due to the heat transfer. As a result, UL 142 tanks have been tested to the SwRI standard and passed. Secondary containment with insulation is not necessarily an integral component of the system. 

As stated earlier, shop-fabricated ASTs are often categorized according to the standards to which the tanks are fabricated, e.g., a UL 142 or UL 2085 tank. That said, however, there are defined categories such as diked tanks, protected tanks, fire-resistant tanks, and insulated tanks. It s critical, then, for the tank buyer or specifier to know precisely what is required or desired given the application, code requirements, and/or owner/operator preferences—and to discuss this with the tank contractor and/or manufacturer. 

An insulated tank can be a protected tank, built to third-party standards UL 2085 and/or SwRl 93-01, or a fire-resistant tank built to UL 2080 or SwRI 97-04. Protected tanks were developed in line with NFPA requirements and terminology, while fire-resistant ASTs were developed in line with Uniform Fire Code (now International Fire Code) requirements and terminology. Both protected tanks and fire-resistant tanks must pass a 1093°C (2000°F), 2-h fire test. 

Separation distance requirements may dictate whether a bmk buyer purchases a traditional steel UL 142 tank, a fire-resistant tank, or a tank in a vault. For example, NFPA 30, NFPA30A, and the IFC codes allow UL 2085 tanks to be installed closer to buildings and property lines, thereby reducing the real estate necessary to meet fire codes. 

Under NFPA 30A, dispensers may be installed directly over vaults or upon fire-resistant tanks at fleet-type installations, whereas a 7.6- to 15.2-m (25- to 50-ft) separation distance is required at retail-type service station installations. The IFC only allows gasoline and diesel to be dispensed from ASTs, designed with a 2-h fire rating. Non-2-h firerated UL 142 tanks dispensing diesel can be installed upon approval of the local authority. 

Boova, A.A. 1987. "Chemical Resistant Tanks and Linings." Metal Finishing Guidebook Directory 1987. Metals and Plastics Publications, Inc. Haekensack, NJ. Pp. 656-658. 

Standard specification for contact-molded FRP chemical-resistant tanks Standard specification for PTFE PFA FEP- and ETFE-lined piping Standard specification for PE and polypropylene (PP) plastic-lined ferrous metal pipe and fittings... 

Corrosive Store only in a corrosion-resistant tank. 

Coatings resistance to mineral acids resistance to a wide range of pH biological resistance Tank Unings Sewage-treatment plants... 

PTFE membranes are highly hydrophobic and, therefore, are used as air filters. Air filters have to be highly hydrophobic to avoid water blockage due to moisture or condensate, especially after steam sterilization of these filters. Water blockage could be detrimental, if the filter is, for example, used in a tank venting application to overcome condensation vacuum of a non-vacuum resistant tank. If the filter would not allow a free flow of air into the tank, it may implode. Therefore, vent filters for this application have to be chosen and sized with care. PTFE membranes are also highly mechanical and thermal resistant, which is required, because such filters are used over several... 

Fiiament Wound Giass Fiber Reinforced Thermoset Resin Chemical Resistant Tanks (ASTM D-3299-81)... 

If you are designing a corrosion-resistant tank of rolled (annealed) Hastelloy alloy C, the tensile strength needed for your calculations is 896 MN/m, which is... 

Typically, a low molecular weight solid epoxy resin and latent curing agent, such as dicyandiamide dissolved in an appropriate solvent, are widely used in dry lay-up formulations for electrical laminates for computers, aerospace applications, and communications equipment. Wet lay-up systems are almost exclusively based on low-viscosity resins cured with aliphatic amines. These ambient cure resin systems are used primarily for manufacture of large chemical-resistant tanks, ducting, and scrubbers. Filament winding is used... 

Although acid hydrolysis is most commonly used to prepare the starting sirup, the liquefying amylase from B. subtilis can be used to thin the initial starch paste without the need for add resistant tanks. The process then becomes an all-enzyme process. The all-enzyme process produces a smaller amount of reversion products than the acid-enzyme process. 

Uses Epoxy curing agent for two-pkg. air-dry coatings, e.g., industrial maintenance primers, midcoats, and topcoats, anticorrosive marine primers, zinc-rich primers, methanol-resist, tank coatings, concrete floor coatings... 

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