Equipment cleaning design characteristics

Clean and efficient heat exchangers are a prerequisite if the water treater wishes to retain business, and therefore some considerable effort must be made to properly understand not only the design characteristics of this equipment but also the current and previous water treatment history. 

Requirements for cleaning wiU vary with the type of equipment. The operating characteristics and design should be assessed before selecting a cleaning method. 

Typical new equipment design efficiencies are between 99 and 99.9%. Older existing equipment have a range of actual operating efficiencies of 95 to 99.9%. Several factors determine fabric filter collection efficiency. These include gas filtration velocity, particle characteristics, fabric characteristics, and cleaning mechanism. In general, collection efficiency increases with increasing filtration velocity and particle size. 

This discussion will address needs, applications, performance characteristics, and design considerations for LVHV exhaust ventilation. The applications are primarily for dust control. LVHV systems can be effective for protecting workers from dust exposures and for recovering valuable process materials. The equipment, excepting the nozzles, involves technology that is the same as for large central vacuum cleaning systems. 

The first essential step in the design of a fume control system and selection of gas-cleaning equipment is the characterization of the fume emission source. Design procedures which can be used for new and existing industrial plants follow. The characterization of fume emission sources includes parameters such as plume flow rates (mVs), plume geometry (m), source heat flux (J/s), physical and chemical characteristics of particulates, fume loadings (mg/m ), etc. 

In spite of the problems that are associated with this design, it is often applied, particularly in clean environments and for easily deformable materials which require small extrusion pressure. Tab. 8.2 lists the standard models offered by one manufacturer and summarizes their most important technical details. Among the medium-pressure agglomerators or pellet mills, the Alexanderwerk moist granulator represents equipment that operates with the lowest forces. In Fig. 8.48 three examples of products are shown. As can be easily seen, granules or pellets can be well formed (a and c) or somewhat crumbly (b). If the latter is not acceptable, the extrusion characteristics of the feed may be adjusted by changing (in this case increasing) the moisture, binder, and/or lubricant contents. 

As will be shown in the following sections 6.2.1, 6.2.2, and 6.2.3 all the main types of processes and techniques of size enlargement by agglomeration (Chapter 5) are being used in the pharmaceutical industry. Characteristic design features are based on what has been discussed above. The equipment is typically small, built from stainless steel, and can be cleaned easily inside and out to avoid cross-contamination. In addition, more and more installations are executed with a physical separation between the (dirty) drives and other mechanical parts that require technical maintenance and the containments that process the charge. Sophisticated control and recording devices are a common part of all systems, in part to satisfy the requirements of process validation. 

Dust is created, not only when solid material is worked on, but also whenever materials are moved or handled. A dust presents a higher fire risk than the solid because of its greater contact area with air with resultant lower ignition characteristics. A dust cloud has many of the fire characteristics of a gas. Accumulations of dust should be removed as quickly as possible by techniques which do not generate a dust cloud, i.e. damp sweeping or vacuum cleaning. The electrical equipment in areas where flammable solids and powders are handled or occur must be designed and maintained to the appropriate flameproof standard. 

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