Duplex system

Alternative 2 consists of preliminary treatment followed by dual-media pressure filtration, and two-stage air stripping (Figure 8.4). The preliminary treatment step for iron removal would be exactly the same as specified under Alternative 1. The filters would be recommended to remove suspended matter and particulate iron prior to the air strippers. The required filtration capacity could be provided with either a duplex system of two 60-in.-diameter filters or a triplex system of three 42-in-diameter filters. 

The sodium softener selected to treat this water is a duplex, 150-gpm system with 54-inch diameter by 72-inch side sheet vessels. Each vessel contains 50ft3 of resin. Since the duplex system operates with one vessel on line and one vessel in stand-by, the total system regenerates 2.4 times per day. At a salt dosage of 15 pounds per cubic foot, the system uses about 1,800 pounds (820 kg) of salt per day or 27.4 tons per month, assuming a 100% operating factor. At a salt cost of 80 per ton, the total month cost for salt is about 2,200.3... 

Heimann, R.B., Schurmann, N., and Muller, R.T. (2004) In vitro and in vivo performance of Ti6A14V implants with plasma-sprayed osteoconductive hydroxylapatite-bioinert titania coat duplex systems an experimental study in sheep. J. Mater. Sci. Mater. Med., 15, 1945-1952. 

Extensive work on titania bond coat/hydroxyapatite top coat duplex systems has been performed by one of the authors and his co-workers during the last two decades (Heimann and Vu, 1996, 1997 Vu and Heimann, 1997 Heimann,... 

Clearly, these prochiral and prostereotopic descriptors for paired ligands in molecules i-xv constitute a duplex system and, in any case, do not indicate the stereotopic relationships of the ligands in question. We propose an alternate, unified notation that specifies the concise stereotopicity of paired ligands on the one hand, and paired faces, on the other. The notation is further extended to accommodate the chirality of the molecular field (chirotopicity). 

Paint and galvanized steel (steel coated with zinc) can be used together to provide superior corrosion control than either method used alone. This technique, known as a duplex system, ccmsists of painting steel that has been hot-dip galvanized after fabrication [12], The paint serves as a barrier protecting the galvanized steel from the atmosphere. It slows down the rate at which zinc is consumed and therefore extends the life of the galvanized steel. 

A duplex system uses two filter housings so that one filter is constantly on-line. When the pressure drop becomes excessive, and the filter requires changing, the flow is... 

If laboratory tests using a disc of the filter membrane indicate that the filter will have insufficient throughput or life then prefiltration ould be considered. Ideally both filters should come to the end of their service life together, i.e. the dirt holding capacity of both filters should be exhausted at the same time. This enables both filters to be replaced together. A duplex system switching over both prefilter and fine filter is available. 

Exposed parts of bolts require supplementary protection. Goodwin and Piessen (1988) in 10-year tests in an industrial atmosphere showed that the best duplex systems were galvanized plus either 80 20 zinc dust/zinc oxide paint, polyurethane paint, or anodizing. 

Table 1.7 Comparative Costs of Galvanizing, Painting, and Duplex Systems Netherlands...

However, it is desirable (especially for paint systems and duplex systems) to carry out corrosion tests in the atmosphere on panels on other specimens, which are exposed in spring and another series in autumn. 

Also, corrosion on galvanized steel poles and fences in the coastal area of Simonstown and Muizenberg (Indian Ocean, Cape Province) is pronounced. At a distance of 10-20 m from the ocean spray, severe corrosion occurs after 3-5 years. Only duplex systems offer sufficiently long protection against rust. Unprotected steel is perforated within only a few years, but this knowledge led to successful trials of galvanized rails for the railway track. 

The cathodic protection on damaged galvanized items depends on (a) the coating thickness, the width of the bared area or scratch, and (c) the local climate. Allowance must be made for any extra loss of zinc due to cathodic protection effects or due to exposure of more zinc surfaces to the environment. It also has been shown that coatings of Al/Zn alloys alone offer no or only poor cathodic protection. More or less the same applies to duplex systems, where the paint coat covers the zinc (-q) layer, thus preventing or retarding the liberation of the necessary ions. 

Table 2.31 Evaluation of Anticorrosion Performances of Duplex Systems After 7 Years... 

Two television/radio towers in the Netherlands were built and galvanized in 1959. After 13 years they were painted with a polyurethane-based system. In 1984, when both towers were inspected, there was still no need to recondition this duplex system. One tower stands near Utrecht in a mildly industrial atmosphere. The other stands near Groningen, in the northern part of the country, in a light marine-industrial climate. 

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