Piping loop design

S AND 8 r-NGINEERINC SERVICES PIPE LOOP DESIGN PROGRAM... 

The program is capable of expansion to handle naany piping loop design possibilities but used for... 

Thermal expansion and the resultant pipe stresses must be considered in any piping system design. For example, if the temperature changes from 50 to 600°F, the increase in length would be 4.9 in. per 100 ft for steel pipe and 7.3 in. per 100 ft for brass pipe. This amount of thermal expansion could easily cause a pipe or wall to buckle if the pipe were fastened firmly at each end with no allowances for expansion. The necessary flexibility for the piping system can be provided by the use of expansion loops, changes in direction, bellows joints, slip joints, and other devices. 

Shull, W.W. Bogel, G.N. A Simplified Computer Program for Pipe Expansion Loop Design. Hydrocarbon Processing, September 1967, p. 183. 

In the case of pipe loops it is sometimes possible to arrange all the hot pipes on one side of the rack, and to accept that all the hot pipes will be looped at the same point along the piperack, in which case the loop may be in the same plane as the rack pipes. Otherwise, and if there is any doubt about possibly conflicting design development or future needs, the loops should be stationed in a horizontal plane above the rack pipes, and the pipes connected vertically to the loops. 

Applicable design codes are found in Table 5.2-1. The reactor coolant loop piping is designed and analyzed for all transients specified in Section 3.9.1. In addition, those nozzles subjected to local thermal transients, caused by fluid entering the Reactor Coolant System from an auxiliary system, are analyzed to ensure that the nozzles can accommodate the additional transients. 

In airlift bioreactors the fluid volume of the vessel is divided into two interconnected zones by means of a baffle or draft-tube (Fig. 5). Only one of these zones is sparged with air or other gas. The sparged zone is known as the riser the zone that receives no gas is the downcomer (Fig. 5a-c). The bulk density of the gas-liquid dispersion in the gas-sparged riser tends to be less than the bulk density in the downcomer consequently, the dispersion flows up in the riser zone and downflow occurs in the downcomer. Sometimes the riser and the downcomer are two separate vertical pipes that are interconnected at the top and the bottom to form an external circulation loop (Fig. 5c). External-loop airlift reactors are less common in commercial processes compared to the internal-loop designs (Fig. 5a, b). The internal-loop configuration may be either a concentric draft-tube device or an split-cylinder (Fig. 5a, b). Airlift reactors have been successfully employed in nearly every kind of bioprocess—bacterial and yeast culture, fermentations of mycelial fungi, animal and plant cell culture, immobilized enzyme and cell biocatalysis, culture of microalgae, and wastewater treatment. 

Phillips Pilot PlantVertical Pipe-Loop Reactor Design... 

The first United States patent that described the vertical pipe-loop slurry polymerization reactor illustrated in Figure 5.11 was issued to Donald D. Norwood on April 26,1966, as U.S. Patent 3,248,179 and assigned to Phillips Petroleum Company. Earlier applications filed in 1959 were abandoned, thus explaining the relatively late issue date on the Norwood patent. Although Donald Norwood was the only name on the first United States patent issued to Phillips Petroleum, Philips Petroleum credits three process engineers, D. D. Norwood, S. J. Marwil and R G. Rohling, for the design of the vertical loop reactor [24]. 

The agitators necessary in the autoclave reactor were no longer required in the vertical pipe-loop system as a new design was disclosed in U.S. 

U.S. Patent 3,152,872 issued to J.S. Scoggin and Harvey S. Kimble on October 13, 1964, and assigned to Phillips Petroleum Company, provides a detailed description of the separation system used to isolate the solid polyethylene granular particles from the liquid diluent used in the vertical pipe-loop reactor. The contributions of Scoggin and Kimble were important in the design and start-up of the first commercial loop reactor in Pasadena, Texas, in 1961. It should be noted that the first vertical loop reactor used n-pentane as the slurry solvent, which was later changed to isopentane and then to isobutane in about 1970. 

The 95-gallon, pilot-plant, vertical pipe-loop reactor was designed to eliminate the problem of polymer build-up on reactor surfaces found in the stirred tank auoclave designs by circulation of the reacting slurry around a closed loop at a velocity sufficient to keep the polymer particles suspended. This design was the critical technical development that led to the introduction in 1961 of the Phillips vertical-loop, particle-form reactor on a commercial scale, which is illustrated in Figure 5.12. 

A detailed description of the Phillips pilot plant pipe-loop slurry reactor (Figure 5.11) is found in U.S. Patent 3,248,179. The design consisted of three 4.5 foot, 10 inch, inner-diameter sections and one 4.5 foot, 12 inch inner-diameter pipe which contained the reactor pumping unit as one of the two vertical sections of the design, with either n-pentane or n-hexane as the slurry solvent. 

The major process piping is made of 8-inch galvanized carbon steel from the pump discharge to the top of the loop seal and the remainder of the system is constructed of Type 304L SS. The piping was designed to the requirement of the ANSI B31.3 and seismically qualified as discussed earlier. 

Horizontal loops. Horizontal loop designs vary fi om a single, in-series pipe to multipipe parallel systems. Pipes are laid in trenches 4-6 ft deep, using a baddioe or trencher, and pressure tested, and then the trench is backfilled. See Fig. H-3. 

Seismic design basis for the main coolant loop piping and pumps, and for typical category I piping, e.g., the auxiliary feedwater line. 

The concrete block walls of the cell housing the generator tube and associated components are 1.7 meters thick. The facility also includes a Kaman Nuclear dual-axis rotator assembly for simultaneous transfer and irradiation of reference and unknown sample, and a dual Na iodide (Nal) scintillation detector system designed for simultaneous counting of activated samples. Automatic transfer of samples between load station to the rotator assembly in front of the target, and back to the count station, is accomplished pneumatically by means of two 1.2cm (i.d.) polyethylene tubes which loop down at both ends of the system and pass underneath the concrete shielding thru a pipe duct. Total one-way traverse distance for the samples is approx 9 meters. In performing quantitative analysis for a particular element by neutron activation, the usual approach is to compare the count rates of an unknown sample with that of a reference standard of known compn irradiated under identical conditions... 

Reaction occurs in the loop as well as in the stirred tank, and it is possible to eliminate the stirred tank so that the reactor volume consists of the heat exchanger and piping. This approach is used for very large reactors. In the limiting case where the loop becomes the CSTR without a separate agitated vessel, Equation (5.35) becomes q/Q > 10. This is similar to the rule-of-thumb discussed in Section 4.5.3 that a recycle loop reactor approximates a CSTR. The reader may wonder why the rule-of-thumb proposed a minimum recycle ratio of 8 in Chapter 4 but 10 here. Thumbs vary in size. More conservative designers have... 

As noted above, batch and semi-batch-based operations result in periodic high loads and subsequent over-design and increased capital cost. By destroying the hypochlorite in situ, within the scrubber recycle loop, the end of cycle concentration can be reduced and the load on the end-of-pipe hypochlorite destruction system lowered allowing an overall cost reduction. The reduced free chlorine concentration also leads to improved process safety, although increased heat removal is required. 

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