Galvanizing tanks

Galvanizing Hot-dip-galvanizing-tank kettle Fumes, particulates (liquid), vapors Close-fitting hoods with high in-draft... 

Hot-dip-galvanizing-tank kettle dipping material into the molten zinc dusting flux onto the surface of the molten zinc... 

Fig. 3. 21. Sectional view through a galvanizing tank or kettle.

Fig. 3.28. Galvanizing tank rebuilt with high-velocity end firing replacing side firing for better tank...

S.3.5.2. Losses from Exposed Bath Surfaces. (See also sections 3.8.3 and 3.8.9 relative to galvanizing tanks and pp. 125 to 126 of reference 51 for water... 

After 4 years of use, all insides of the ungalvanized tanks showed large formations of rust in the lower third of the interior. All galvanized tanks remained completely free from rust, and there was no blocking of oil filters or burner nozzles. 

BNFMRA. (1964). Guidance on the Use of Galvanized Tanks and Cisterns. BNFMRA, London, 8 pp. 

Materials of Construction Suitable materials of constmction are steel, stainless steel, and aluminum 3003. Galvanized steel should not be used. Plastic tanks and lines are not recommended. 

Handling Temperatures. Optimum temperature for pumping is in 37—48°C range. Piping should be stainless steel, aluminum, or galvanized iron. Valves and pumps should be bronze, cast-iron with bronze trim, or stainless steel. A pump of 3.15-L/s (50-gal/min) capacity unloads a tank car of warm glycerol in ca 4 h. 

In spite of a low driving voltage of about 0.2 V, about 90% of all galvanic anodes for the external protection of seagoing ships are zinc anodes (see Section 17.3.2). Zinc alloys are the only anode materials permitted without restrictions for the internal protection of exchange tanks on tankers [16] (see Section 17.4). 

Materials for metal tanks and installations include plain carbon steel, hot-dipped galvanized steel, stainless steel [e.g., steel No. 1.4571 (AISI 316Ti)], copper and its alloys. The corrosion resistance of these materials in water is very variable and can... 

Tanks that are enamelled or that have other high-resistance coatings with volumes below 4 m do not require automatic exhausts if they are equipped with galvanic anodes in which the surface area does not exceed 5 dm per square meter of surface to be protected, or with controlled impressed current anodes with a low current output of 150 mA. 

The electrolysis protection process using impressed current aluminum anodes allows uncoated and hot-dipped galvanized ferrous materials in domestic installations to be protected from corrosion. If impressed current aluminum anodes are installed in water tanks, the pipework is protected by the formation of a film without affecting the potability of the water. With domestic galvanized steel pipes, a marked retardation of the cathodic partial reaction occurs [15]. Electrolytic treatment alters the electrolytic characteristics of the water, as well as internal cathodic protection of the tank and its inserts (e.g., heating elements). The pipe protection relies on colloidal chemical processes and is applied only to new installations and not to old ones already attacked by corrosion. 

The impressed current method with metal oxide-coated niobium anodes is usually employed for internal protection (see Section 7.2.3). In smaller tanks, galvanic anodes of zinc can also be used. Potential control should be provided to avoid unacceptably negative potentials. Pure zinc electrodes serve as monitoring and control electrodes in exposed areas which have to be anodically cleaned in the course of operation. Ag-AgCl electrodes are used to check these reference electrodes. 

Further chapters cover in detail the characteristics and applications of galvanic anodes and of cathodic protection rectifiers, including specialized instruments for stray current protection and impressed current anodes. The fields of application discussed are buried pipelines storage tanks tank farms telephone, power and gas-pressurized cables ships harbor installations and the internal protection of water tanks and industrial plants. A separate chapter deals with the problems of high-tension effects on pipelines and cables. A study of costs and economic factors concludes the discussion. The appendix contains those tables and mathematical derivations which appeared appropriate for practical purposes and for rounding off the subject. 

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