Processing line downstream

Processing line, downstream The plastic discharge end of the fabricating equipment such as the auxiliary equipment in an extrusion pipe line after the extruder. 

Figure 10.11 Temperature plot of a thermocouple sensor moving downstream through a process line. The process noise occurred because the unshielded sensor wires were in the proximity of a motor and heaters...

You will often see workflows in which the simple sequence pattern runs into a task that has multiple lines downstream. This is an example where a clear understanding of workflow patterns is useful. This visual description might represent a parallel split, in which data clone themselves and pass to two or more parallel or independent sets of processes (fig. 19.3B). Alternatively, it might represent an exclusive choice, in which the data pass to just one of a number of downstream options (fig. 19.3C). Clearly, these are very different behaviors, and indeed, they are described by different patterns. 

When the valve switches from nitrogen to air, the flow of gas will change abruptly if the vent line and reactor line are inadequately equilibrated the pressure at both exits of the four-way valve must be equalized. This may be accomplished by a back pressure regulator. Whereas a pressure regulator reduces the supply pressure at the inlet to a lower pressure at the outlet, a back pressure regulator throttles the flow downstream to maintain the inlet pressure. A needle valve or a back pressure regulator is required at the vent line to match the pressure across the reactor, process lines, and analytical equipment. 

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). 

When fluid flows past objects or through orifices or similar restrictions, vortices may periodically be shed downstream. Objects such as smokestacks, chemical-processing columns, suspended pipehnes, and electrical transmission lines can be sul ected to damaging vibrations and forces due to the vortices, especially if the shedding frequency is close to a natural vibration frequency of the objecl. The shedding can also produce sound. See Krzywoblocki (Appl. Mech. Rev., 6, 39 397 [1953]) and Marris (J. Basic Eng., 86, 185-196 [1964]). 

Bends and tee-pieces in pipework often create locally turbulent flow. This enhances the corrosivity of the process liquid. These effects should be minimized by the use of flow straighteners, swept tees and gentle bends. Flow-induced corrosion downstream of control valves, orifice plates, etc. is sometimes so serious that pipework requires lining with resistant material for some twelve pipe diameters beyond the valve. 

Tolerance The penalty for having an unbalanced wall is the reduction of tolerance control. Tolerance limits are usually at least doubled. Also, with certain plastics it is more difficult to process them, such as those with low melt strength. Although the balanced wall is the ideal, having it is not always possible. Recognize that the unbalanced wall can be extruded with proper die design and control of the extruder line from upstream to downstream equipment. 

Where problems develop, there is always a cause-and-effect process. In this case, as oxygen infiltrates the CR system, enhanced condensate line corrosion results (i.e., corrosion over and above the level that may be caused by the carbonic acid formed during steam condensation). This enhanced corrosion, in turn, creates the potential for further downstream corrosion debris pickup by the returning condensate and transporting this material back to the FW system. 

Grandics, R, Szathmary, S., Szathmary, Z., and O Neill, T., Integration of cell culture with continuous, on-line sterile downstream processing, Ann. N. Y. Acad. Sci., 646, 322, 1991. 

It is easy to improperly design a steam trap. The design must work for two circumstances and often a designer will check only one of these. The circumstance often overlooked is as follows On startup or upset, the steam control valve can open wide so that the steam chest pressure (assume for this discussion that we are speaking of a reboiler) rises to full steam line pressure. At a time like this, the steam trap downstream pressure can be atmospheric due to process variations or the operators opening the trap discharge to atmosphere in an attempt to get it working. 

Overall, therefore, the routine manufacture of a biopharmaceutical product is initiated by large-scale culture of its producing cell line (upstream processing). Subsequent to this, the product is recovered, purified and formulated into final product format. These latter operations are collectively termed downstream processing and are described in Chapter 6. 

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