Carbon steel steam lines

Example 2. In the previous example, the curvature of the levee and railroad track aroxmd the tank area determined the circular arc for the 680 psi, 650°F steam line. This 8-inch schedule 80 carbon steel pipe line will be redesigned and recalculated with the idea of using the smallest possible rise with the maximum bending stress Emax and the resultant force, F at the fixed anchor ends so they will be within the allowable stress range. A rise of 10 feet above the straight line 508 feet d distance will be tried first. (See Figure 7-51) The pipe will be suspended from fi ee movement pipe supports similar to the elevation shown in Figure 7-50. 

Molten maleic anhydride is shipped in tank rail cars, tank tmcks, and isotanks (for overseas shipments). Tank rail cars are typically constmcted of lined carbon steel and are insulated and equipped with steam coHs. Tank rail cars containing as much as 80 m (20,000 gal) are used. Tank tmcks are typically constmcted of stainless steel [12597-68-1/, insulated, and equipped with steam coHs. Tank tmcks containing up to 17 m (4500 gal) are used. Isotanks are typically constmcted of stainless steel and are insulated and equipped with steam coHs. Isotanks containing up to 17 m are used. 

Apphcations requiring accurate temperature control are generally limited to electric tracing. For example chocolate lines cannot be exposed to steam temperatures or the product will degrade and if caustic soda is heated ove 150°F it becomes extremely corrosive to carbon steel pipes. 

Neutralizing amines are generally fed to the FW line but may be fed directly to the boiler or to the steam header. Day tanks may be polyethylene or carbon steel. 

The effluent from the reaction boiler is handled in type 310 (UNS S31000) SS above 800° F (425° C), type 321 or 347 (UNS S34700) SS above 500°F (260°C), and carbon steel below 500°F (260°C). Molten sulfur is handled in steam-traced steel or aluminum. At the discharge to the pits, oxygen causes severe attack on steel, so the discharge end of the steel line often contains a short piece of alloy 20. 

The secondary reformer in an ammonia plant is a carbon steel vessel with a dual layer refractory lining. Internal temperatures reach -2,000°F (1,090°C) from burning as a result of air added through a burner at the top of the vessel to the feed gas (hydrogen, carbon monoxide, carbon dioxide, and steam). The burner is a refractory-lined device that is subject to failure if not carefully designed. Quench steam generators have refractory-lined inlet channels and tube sheets. Tubes are often made of carbon steel because the heat transfer from the steam on the outside of the tube is markedly better than that from the synthesis gas inside the tube. As a result, the metal temperature closely approaches the temperature of the steam. The inlet ends of the tubes are protected from the inlet gas by ferrules, usually made of type 310 (UNS S31000) SS with insulation between the ferrule and the tube. The tube material should be selected... 

The main steam safety valves are direct acting, spring loaded, carbon steel valves. The valves are mounted on each of the main steam lines upstream of the steam line isolation valves, and outside containment. A schematic drawing of the main steam safety valves is given in Figure 5.4.13-2. The valve parameters are given in Table 5.4.13-2. For a description of overpressure protection equipment and components for the main steam system refer to Section 10.3.2. 

With a few exceptions, coatings and linings are not used on the water and steam sides. In an EPRI project, about 50 turbine blade coatings have been evaluated, but none of these are being routinely applied. To reduce steam side oxidation in reheaters and superheaters, chromizing and chromating have been developed but these treatments are also not routinely applied. There is little use of composite materials with the exception of condenser tube sheets, which could be made of explosively clad stainless steel or titanium on carbon steel, and of the surfaces in the primary cycles of nuclear units where carbon or low alloy steels are protected by weld-deposited stainless steels. In pulp mill black liquor recovery boilers, stainless steel clad boiler tubes are often used. 

Materials of construction for double alkali process plants are quite similar to those used for limestone/lime systems—stairdess steel (316L) venturis and scrubbers, rubbo -lined pumps and slurry lines, Hastelloy G tubes for direct steam tube gas rdieat, and fiberglass reinforced plastic or plastic-lined carbon steel tanks. 

The adsorbers are usually built of steel, and may be lagged or left unlagged the horizontal type is shown in Figure 28. The vapor-laden air is fed by the blower into one adsorber which contains a bed of 6- to 8-mesh activated carbon granules 12 to 30 inches thick. The air velocity through the bed is 40 to 90 feet per minute. The carbon particles retain the vapor only the denuded air reaches the exit, and then the exhaust line. The adsorption is allowed to continue until the carbon is saturated, when the vapor-laden air is diverted to the second adsorber, while the first adsorber receives low-pressure steam fed in below the carbon bed. The vapor is reformed and carried out by the steam. The two are condensed and if the solvent is not miscible with water, it may be decanted continuously while the water is run off similarly. After a period which may be approximately 30 or 60 minutes, all the vapor has been removed, the adsorbing power of the charcoal has been restored, and the adsorber is ready to function again, while adsorber No. 2 is steamed in turn. 

Condensate returns lines are often copper. Copper has good corrosion resistance to oxygen and carbon dioxide individually. When both gases are present in the condensate, copper is susceptible to corrosion. Copper picked up in the condensate system and returned to the boiler causes serious corrosion problems in the boiler and any steel feedwater and steam pipework. Boiler tubes should last for 25 years but can fail within one year in a mismanaged or ill-designed boiler system suffering from these faults. 

Oxygen is not the only noncondensable gas found in boiler circuits, Problems occur due to the presence of carbon dioxide (C02). Carbon dioxide is steam-volatile and reacts with condensing steam to produce carbonic acid, which attacks steel condensate return lines. 

Oxygen infiltration coupled with (steam volatile) carbon dioxide produces enhanced condensate line corrosion. The corrosion rate of steel in the system is particularly high when both gases are present. 

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