Preliminary piping and instrumentation

Devise a control system for this reactor, and draw up a preliminary piping and instrument diagram. The follow points need to be considered ... 

The layout can only be started after a process flow diagram is available. The process flow diagram includes information such as the principal equipment items and order of the process flow. A sized equipment list is also useful from the standpoint of knowing what spaces are required to fit the equipment. Availability of a preliminary piping and instrumentation drawing (P ID) provides more information to aid in spacing equipment and thinking about piperack requirements. 

In the detailed design stage, everything must be specified. Each phase of the preliminary design must now be done in much more detail. The flow sheets develop into piping and instrument diagrams. The duty requirements for a piece of equipment become a specification sheet. The layout drawings may be replaced by a scale model, and a construction bid or detailed cost estimate is obtained to verify the previous cost estimate. 

After preliminary design is completed. Piping and instrument diagram. 

Since P ID s and Equipment Arrangement drawings are not available yet, piping and instrumentation information must be estimated with the preliminary procedures in Chapter 19. Painting and insulation can be estimated using a Lang Factor. ... 

As mentioned in Section H.l the activity breakdown for this example is based on the preliminary estimate in Appendix L that was prepared without the benefit of P ID s and arrangement drawings. This breakdown would be barely adequate for tracking the civil work - site, concrete, and steel erection. However, it is not detailed enough for use for tracking electromechanical work - equipment erection, piping, electrical, and instrumentation. 

The preliminary equipment cost for the two PTA (12 MGD RO WTP) with blowers was estimated to be 450,000, with an estimated total construction cost of 1 million. Included in the total construction cost are costs for 20 and 30 in. diameter stainless-steel inlet and discharge piping and valving, 30 and 42 in. diameter reinforced fiber glass ducts, 6 in. diameter PVC drain pipes, 2-14 ft diameter concrete pad for the vessels, electrical, instrumentation, and controls. The preliminary equipment cost for the four PTA (20 MGD LS WTP) without fans is 825,000 and the estimated total construction... 

Prepare/supervise preparation of piping or mechanical flow diagram (or P and ID), with necessary preliminary sizing of all pipe lines, distillation equipment, pumps, compressors, etc., and representation of all instrumentation for detailing by instrument engineers. 

Electrical This item consists of transformers, wiring, switching gear, as well as instrumentation and control wiring. The installed costs of the electrical items may be estimated as 20 to 40 percent of the delivered equipment costs or 5 to 10 percent of the fixed capital investment for preliminary estimates. As with piping estimation, the process design must be well along toward completion before detailed electrical takeoffs can be made. 

Since fluid shear rates vary enormously across the radius of a capillary tube, this type of instrument is perhaps not well suited to the quantitative study of thixotropy. For this purpose, rotational instruments with a very small clearance between the cup and bob are usually excellent. They enable the determination of hysteresis loops on a shear-stress-shear-rate diagram, the shapes of which may be taken as quantitative measures of the degree of thixotropy (G3). Since the applicability of such loops to equipment design has not yet been shown, and since even their theoretical value is disputed by other rheologists (L4), they are not discussed here. These factors tend to indicate that the experimental study of flow of thixotropic materials in pipes might constitute the most direct approach to this problem, since theoretical work on thixotropy appears to be reasonably far from application. Preliminary estimates of the experimental approach may be taken from the one paper available on flow of thixotropic fluids in pipes (A4). In addition, a recent contribution by Schultz-Grunow (S6) has presented an empirical procedure for correlation of unsteady state flow phenomena in rotational viscometers which can perhaps be extended to this problem in pipe lines. 

Estimation of column costs for preliminary process evaluations requires consideration not only of the basic type of internals but also of their effect on overall system cost. For a distillation system, for example, the overall system can include the vessel (column), attendant structures, supports, and foundations auxiliaries such as reboiler, condenser, feed neater, and control instruments and connecting piping. The choice of internals influences all these costs, but other factors influence them as well. A complete optimization of the system requires a full-process simulation model that can cover all pertinent variables influencing economics. 

A feasibility scoping study enabled by process simulation is the preliminary evaluation of improvement ideas in the context of overall process with the main objectives to perform cost and benefit analysis and determine if major equipment can accommodate the improvement ideas. The major equipment includes furnaces, reactors, main fractionators and separators, compressors, special pumps, and major heat exchangers. Usually, the scoping study is not concerned with relative ancillary equipment such as receivers, drums, heat exchangers, pumps, piping, instruments, relief valves, and so on. 

Vendor data Ail purchased equipment and specialty bulk items (e.g., pumps, compressors, air coolers, furnaces, control and safety v ves, level instruments, strainers, and silencers) require preliminary vendor drawings for the development of piping layouts. Final tonified drawings are usually not required until the detail phase. 

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