Long-distance applications

CVD yields fibers with low loss (< 0.5 dB/km) which are suitable for both mono- and multimode long-distance applications. It has emerged as the strongest technology for high-volume, low- cost production. ]... 

These developments have resulted in a much more reliable and efficient blow tank feeding system, especially for long-distance applications, as shown in Fig. 8. Such systems now have been used successfully in many installations throughout Australia to meet the increasingly demanding requirements of conveying capacity and distance. 

From Table 3 it can be seen that by optimizing the configuration of pipeline, it is possible to reduce pressure loss, air flow, transport velocity, and hence, pipe/bend wear. Depending on hardware requirements and reliability, which would to some extent govern the maximum operating pressure of the system (e g., say, 400 or 500 kPag), Pipeline Nos. 5 or 6 could be selected for this long-distance application. However, if diverter valves are required at the end of the pipeline, it may be more convenient to select Pipeline No 5 (i.e., D1 = 154 mm instead of 203 mm). 

For the general purpose of minimizing air flow, transport velocity, wear and power, the fluidized dense-phase mode of flow is preferred for long-distance applications. Efficient blow tank feeders, rotary-screw compressors, refrigerated dryers and stepped-diameter pipelines also are recommended. For products that are not suited to fluidized dense-phase, the possible modes of flow include dilute-phase (suspension flow) or bypass conveying (Wypych, 1995a). 

Shirayev et al. have obtained minimum optical losses of 0.04 dB/m at 6.7 pm for a core-only Te2oAs3oSeso glass fiber [144]. Even though these losses are still too high for long-distance applications, they permit optical sensing on short and medium distances. 

Waveguide Compositions. Currently, commercial low-loss optical fibers for long-distance applications are based on silica compositions where losses of 0.2 dB/km are found for 1.55-fim operation. Extensive research has been done on finding other compositions and processes that produce low-loss optical fibers. However, none of these efforts produced results anywhere near the low losses obtained with silica compositions made by vapor deposition processes. A brief review of these processes as used for fiber fabrication will be given in Sec. 7.1.2. 

This spread in velocity is called modal dispersion and is the principle limit to the use of multimode fibres for long-distance transmissive applications. 

For some applications, either steam or electricity is simply not available and this makes the decision. It is rarely economic to install a steam boiler just for tracing. Steam tracing is generally considered only when a boiler already exists or is going to be installed for some other primary purpose. Additional electric capacity can be provided in most situations for reasonable costs. It is considerably more expensive to supply steam from a long distance than it is to provide electricity. Unless steam is available close to the pipes being traced, the automatic choice is usually electric tracing. 

The use of corrosion-resistant materials and the application of corrosion protection measures are in many cases the reason that industrial plants and structures can be built at all. This is particularly so in pipeline technology. Without cathodic protection and without suitable coating as a precondition for the efficiency of cathodic protection, long-distance transport of oil and gas under high pressures would not be possible. Furthermore, anodic protection was the only protective measure to make possible the safe operation of alkali solution evaporators (see Section 21.5). 

In this chapter, applications of the calculation methods used to predict the hazards of BLEVEs, as described in Chapter 6, are demonstrated in the solution of sample problems. Fire-induced BLEVEs are often accompanied by fireballs hence, problems include calculation of radiation effects. A BLEVE may also produce blast waves and propel vessel fragments for long distances. The problems include calculations for estimating these effects as well. Calculation methods for addressing each of these hazards will be demonstrated separately in the following order radiation, blast effects, and fragmentation effects. 

L. Botz, Sz. Nyiredy and O. Sticher, Applicability of long distance oveipressured layer cltromatography , 7. Planar Chromatogr. 4 115-122(1991). 

Hydrogen onboard storage systems for vehicles are bulkier, heavier, and costlier than those for liquid fuels or compressed natural gas, but are less bulky and less hca than presently envisaged electric batteries. Even with these constraints, it appears that hydrogen could be stored at acceptable cost, weight, and volume for vehicle applications. This is true because hydrogen can be used so efficiently that relatively little fuel is needed onboard to travel a long distance. 

Excessive belt whip Excessive belt whip is usually more common on long-center applications (applications where the distance between the two pulley shafts is great). Pulsating loads in the drive system can produce this... 

Since MPC dynamics yields the hydrodynamic equations on long distance and time scales, it provides a mesoscopic simulation algorithm for investigation of fluid flow that complements other mesoscopic methods. Since it is a particle-based scheme it incorporates fluctuations, which are essential in many applications. For macroscopic fluid flow averaging is required to obtain the deterministic flow fields. In spite of the additional averaging that is required the method has the advantage that it is numerically stable, does not suffer from lattice artifacts in the structure of the Navier-Stokes equations, and boundary conditions are easily implemented. 

A significant number of developments have occurred over the past decade to address these important issues of pneumatic conveying (Wypych, 1995a). This chapter summarizes some of the major design considerations that have resulted from this work in relation to long-distance and pipe branching applications. 

However, this section pursues particle size measurement and evaluates its importance (as well as density) for the purpose of classifying the suitability of powders for long-distance pneumatic conveying applications. Initially, an appreciation of the fundamentals and the existing powder classification techniques is required. 

Application to Long-Distance Pneumatic Conveying. From the above three classifications, there is sufficient evidence to suggest that powder classification (i.e., to select ultimately the most suitable mode of conveying for a given product and its behavioral properties) depends on the following properties ... 

Most existing models are suited only to pure dilute-phase or dense-phase (high m ) applications, whereas the possible modes of flow over long distances occur between these two extremes (e.g., dune-flow, sliding beds, irregular slugging, etc.—usually at moderate m ). 

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