AUXILIARY EQUIPMENT AND SECONDARY OPERATIONS

The SPI kit covers the primary processing machine communication protocol with chillers, blenders, dryers, water systems, discrete mold-temperature controllers, and the like. The protocol provides for centralized setup and monitoring of auxiliaries by the primary machine. The test simulation software that is a key part of the kit ensures uniform interpretation of technical specifications. It is a combination of a detailed technical specification of hardware requirements such as the type of cable, the connector and electrical interface, and software requirements. The kit protocol shows how electronic information moves through the system. 

The SPI standard references the standards of the Electronics Industry Association, American National Standards Institute, and Institute of Electrical and Electronics Engineers. 

Any large-scale resin-handling system has three basic subsystems, for unloading, storage, and transfer. For a complete system to work at peak efficiency, processors need to write specifications that fiilly account for the unique requirements of each subsystem. The least efficient component, no matter how inconsequential it may seem, will limit the overall efficiency of the entire system. 

As emphasized throughout this book, many different types of auxiliary equipment and secondary operations can be used to maximize overall processing plant productivity and efficiency. Their proper selection, use, and maintenance are as important as the selection of the processing machines (injection molder, extruder, etc.). The processor must determine what is needed, from upstream to downstream, based on what the equipment has to accomplish, what controls are required, ease of operation and maintenance, safety devices, energy requirements, compatibility with existing equipment, and so on. This chapter provides examples of this selection procedure and its importance in evaluating all the equipment required in a processing line. Details on all the equipment that is available can be obtained from plastics industry trade publications, usually compiled in an annual issue. These and other pertinent publications are included in the reference section (1-4, 33, 271-289). 

In most processes, for either small or large production runs, the cost of the plastics used compared to the total cost of production in the plant may be at least 60 percent. The proportion might be only 30 percent, but it is more likely to exceed 60 percent so it is important to handle material with care and to eliminate unnecessary production problems and waste. Where small-quantity users or expensive engineering resins are concerned, containers such as bags and gaylords are acceptable but for large commercial and custom processors, these delivery methods are bulky and costly. Resin storage in this form is also expensive. 

Any large-scale resin handling system has three basic subsystems un- 

The easiest method of unloading uses a vacuum pump/dust collector, which can be located in the silo skirt. The pump induces a vacuum in the line, drawing resin from the railcar into a vacuum loader. When the vacuum loader fills, the pump stops, and the resin dumps into the silo. This on-off batching effect keeps transfer rates relatively low, typically 6,000 to 7,000 Ib/h. If the manifold pickup is far from the silo, the transfer rates will drop. 

A two-blower system times purging to virtually eliminate any line blockages. With this arrangement, the pressure blower continues operating to ensure complete transfer to silos, while the vacuum blower remains out of the transfer loop. 

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AUXILIARY EQUIPMENT AND SECONDARY OPERATIONS 725 Table 8-6. Materials for Plastics Hardware... 

The TM-2 accident was initiated by a sudden stop of some pumps in the secondary system. Some erroneous operations and the inferiority of some equipment enhanced the accident. About three hours after the initial incident, the primary water overflowed onto the floor of the auxiliary building, and the radioactivity in the primary water, especially xenon, krypton and iodine, were released into the atmosphere. In total, 10 Ci of noble gases were released into the atmosphere, whereas the total amount of the iodine release was 17 Ci. 

Further considerations include skimmers and weir overflow rates. Skimmers should be provided on all units since even secondary effluents contain some floatable solids and grease. Overflow rates and sludge scraper design should conform to the requirements of other clarification units. The reader may refer to Chapter 9 for examples of typical flow sheets and auxiliary filtration equipment schematics, including process flow sheets for chemical feeding operations described above. 

In this work, a Motor-Operated Valve (MOV) of the Auxiliary Feed Water System (AFWS) has been selected based on several arguments. First, the basic event representing MOV fails to remain open is one of the most important contributors to the CDF based on the standard PSA available. Second, equipment aging, preventive maintenance and surveillance requirements are meaningful for this MOV. This basic event is modelled as a standby-related failure. This valve is normally open and its function is to control the flow from AFWS until Steam Generators on the secondary of a typical Pressurized Water Reactor (PWR) NPP. 

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