FLUID TRANSPORT EQUIPMENT Piping

Ithough liquids particularly can be transported by operators carrying buckets, the usual mode of transport of fluids is through pipelines with pumps, blowers, compressors, or ejectors. Those categories of equipment will be considered in this chapter. A few statements will be made at the start about piping, fittings, and valves, although for the most part this is information best 

Standard pipe is made in a discrete number of sizes that are designated by nominal diameters in inches, as inches IPS (iron pipe size). Table A5 lists some of these sizes with dimensions in inches. Depending on the size, up to 14 different wall thicknesses are made with the same outside diameter. They are identified by schedule numbers, of which the most common is Schedule 40. Approximately, 

Tubing for heat exchangers, refrigeration, and general service is made with outside diameters measured in increments of 1/16 or 1/8 in. Standard size pipe is made of various metals, ceramics, glass, and plastics. 

More than 100 manufacturers in the United States make valves that may differ substantially from each other even for the same line size and pressure rating. There are, however, independent publications that list essentially equivalent valves of the several manufacturers, for example the books of Zappe (1981) and Lyons (1975). 

Control valves have orifices that can be adjusted to regulate the flow of fluids through them. Four features important to their use are capacity, characteristic, rangeability and recoveiy. 

---

Criteria for selection of equipment and components for commercial supercritical fluid processing plants for the food processing industry are listed and discussed. Unique features and designs for SCF food processing are specified. Requirements for vessels, heat exchangers, instrumentation, piping, fluid transport devices and typical ancillary equipment are reviewed. 

Dead time is also called transportation lag, because it is the time required for fresh heat transfer fluid to displace the contents of the exchanger and its associated piping. The dead time is the worst enemy of control, because until it has expired, a change in the heat transfer fluid flow (or temperature) will not even begin to have an observable effect. For a heat exchanger, the dead time is usually between 1 and 30 seconds. When the equipment is correctly designed, the dead time is much less than the time constant. 

Reynolds dye experiment on transition to turbulence in pipe flow and G. I. Taylor s experiments on axial dispersion in laminar flow represent the early use of tracers in flow visualization and transport parameters evaluation in chemical engineering. A more widespread use in chemical reactors dates to the work of Danckwerts (1). He realized that the performance of process equipment depends on the residence time distribution of process fluid, and that this information can be obtained by tracer methods. Residence time distributions are now discussed in standard chemical reaction engineering texts (2,3) and are well summarized in a recent excellent monograph by Nauman and Buffham (4). Tracer methods. 

---