Piping systems, cost comparison

A capital cost comparison of the two concepts appears to favor the pool primarily as a result of a smaller building for the more compact system and the less expensive primary piping 21). On the other hand, some items are more expensive such as the large vessel and neutron shield within the vessel. As the comparison is made in greater detail, additional tradeoffs become apparent with important areas of uncertainty revealed. The slight economic advantage of the pool concept therefore proves to be within the region of uncertainty. 

Although these units find initial application in areas of limited water, they have not been limited to this situation. In many instances they are more economical than cooling tower systems and have been successfully applied in combination with cooling towers (see Figure 10-184). Economic comparisons should include such items as tower costs, basin, make-up facilities, water treatment, pumps for circulation, power supply, blow down, piping, etc. For small installations of air-cooled units, they should be compared... 

It follows from economical comparison that coal-log pipeline is cheaper than truck transport for distances longer than 65 km and pipe diameter D = 200 mm. For D = 500 m even for distance over 25 km. Compared with railway, the transport cost is on the level of unit trains. For large quantity of coal it could be even less. Another advantage is given by fact that length of pipeline is usually at least about 30 % lower than that of the railway. From environmental protection point of view, capsule pipeline, similarly as slurry pipeline, is dust free and noiseless. In spite of these advantages the utilisation of coal-log pipeline system could expect only for transport of coal from new mines to power stations, especially in mountains areas without railways and highways or in heavy populated and industrial areas, where railway is overloaded. 

One of the advantages claimed for the technology in comparison with the sponge rubber ball system, is that it requires less maintenance. A major disadvantage perhaps in some situations more than others, is the momentary interruption in flow while the flow reversal is accomplished. The disruption of steady state conditions in the plant operation may be difficult to accommodate and could have implications for product quality. The cost of the complex piping arrangements and the control system could be expensive, particularly in a retrofit... 

Paper studies were first made to determine a basis for design work. This covered pipe sizes from 1/2 in. through 8 in. and included analysis of vacuum insulation systems using perlite, CS-5 opacified powder and two different grades of superinsulation, SI-12 and SI-4. BoA cost and performance were compared. Comparison was based on application in hydrogen service and return of investment over a two-year period based on both depreciation and the savings due to the reduction of evaporation losses. For the purposes of this study the arbitrarily assumed value of liquid hydrogen is. 50/lb. 

For pumped systems rapidly increasing energy costs have aroused considerable interest in designing for very low valve-pressure drops. This pushes us toward line-sized valves. If piping and equipment pressure drops are large in comparison with valve-pressure drops, valve turndown sui rs (becomes smaller). The installed flow characteristic also becomes very different ftom the inherent flow characteristic. A linear valve tends toward an installed square-root flow characteristic, while an equal-perccntJ e valve tends toward an installed linear characteristic. At the hi -flow, high-lift end of the plot, however, all curves, r ardless of y alve inherent characteristic, level off at a maximum flow. This is so because the valve has run out of pressure drop. 

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