Storage tanks coating systems

Based on past experience, it has been found that the protection current density for buried storage tanks coated with bitumen is over 100 fiA With coatings in very good condition, it can amount to a few tens of jUA m but for coatings in a very poor state, it can rise to a level of mA m". The protection current demand can be very different for storage tanks of the same size so that in the design of the protection system it cannot be estimated with sufficient accuracy as with pipelines. For this reason it is necessary to determine the protection current requirement by a drainage test. 

Common uses of the impressed current method of protection include long transmission pipelines, complex underground structures, marine structures, ship hulls, and replacement for dissipated galvanic systems, large condenser water boxes, reinforcing steel in concrete, bare or poorly coated structures, unisolated structures and water storage tank interiors. 

Example 3 A plant storage tank requires either (i) replacement to last 25 yr with no maintenance at a cost of 690 000 or (ii) a coating system with maintenance cost of 10% of installation costs, tax rate of 48%, interest rate of 10% and straight-line depreciation. 

There are solvent-free systems with 100% solids principally used as protective coatings for concrete or metal storage tanks. Such coatings are unpigmented, clear compositions. They are thixotropic and can be applied both on horizontal and on vertical surfaces. 

Figure 368. Diagram depicting schematically the flow sheet of a typical (film) coating facility. (a) PLC (programmable controller), (b) storage tanks for spray liquid(s) and metering/pumping system, (c) equipment for air supply and processing, (d) air cleaning and exhaust system...

Taric Qeanq The tank outlet is rarely located in the very bottom of the tank. Indeed, it is about 6 to 12 inches up the side. Why Operate the system for a while, then drain the tank and youTl have the answer The polite name for all of that gunk and muck coating the bottom of the tank is sediment. How did it get there An open tank or a poorly covered one will always allow dirt, leaves, insects, lizards, and mice into the water system. Also, the incoming water may carry its own sediment, held in suspension. In the tranquil waters of the tank, this will precipitate out. Some minerals in the water itself will, upon contact with air, precipitate out in a storage tank. Locating the outlet up the side of the tank a wee bit, then, will always result in this accumulated debris. 

Corrosion may also take place in systems for transportation or storage of oil, e.g. when the fluid for some reason has absorbed water that is precipitated afterwards. This is a known problem in various types of storage tanks. To prevent eorrosion, inhibitors and (particularly in larger tanks), coatings and/or cathodic protection are used. 

Corrosion of aboveground storage tanks for petroleum distillates and choice of coating systems for their protection from corrosion... 

Appiications cable insulation, capacitors, coatings (agitators, centrifuges, electroplating equipment, exhaust hoods, filters, piping systems, reactors, semiconductor storage tanks, vessels), films, fibers, hollow fiber membranes, pipes, printed circuits, rods, sheet, solar collectors ... 

---