Piping System Variations

The design of a piping system will be very site-specific. Factors that must be considered include 

Regardless of the needs dictated by these factors, the piping system itself will fall into a few general variations as shown in Fig. 4. Dead-head style piping systems are unusual and can only be used with a very well-suspended slurry. This type of system can minimize the loss of volatile components, such as ammonia from a slurry like Rodel Klebosol, since there is no circulation through a daytank or any other head space that would permit ammonia evaporation. It can also be attractive to minimize slurry turnovers to a shear- or gelling-sensitive slurry. Cabot SS-25 is well-suspended, but if 

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The number of cycles (or variations) shall not exceed 7000 during the life of the piping system. 

A general appreciation of some of the effect of gas pulsation on the performance and impact on the compressor pulsation drums, their nozzles, the piping system, and the cylinder valve performance, as well as possible other effects in some unique systems or items of equipment, can be discovered by examining the cylinder performance using an indicator card. This examination (see Chapter 12) can reveal acceptable and unacceptable performance in terms of pressure variations within the cylinder as the piston passes through its cycle. Hicks presents a helpful analysis see Figures 13-3 and 13M. 

Metallic pipe systems comprise the majority of applications. Metallic pipe, tubing, and pipe fittings are divided into two main categories seamless and welded. Both have advantages and disadvantages in terms of economy and function. Specifications governing the production of these products dictate the permissible mechanical and dimensional variations, and code design calculations account for these variations. 

Techniques, used by the gas and water industries to join and repair pipelines, include butt fusion, electrofusion socket welding and socket jointing (309). The study of bond strength testing for solvent joints in piping systems has noted extreme sensitivity to minor variations in sample preparation (259). 

Nonuniform fluid velocity This condition can induce local anodic and cathodic regions, causing variations at the surface in the concentration of cathodic species supporting corrosion and by removing corrosion products. This condition is frequently found in piping systems and pumps. 

Figure 17.4 Pressure control by vapor rate variations, (a) Product rate variation, superatmospheric columns (6) vapor spillback variation, vacuum columns (c) product rate variation, with internal condenser, (d) product rate variation, poorly piped system. (Part d from Tfnusual Operating Histories of Gas Processing and Olefins Plant Columns, H. Z. Kister and T. C. Hower, Jr., Plant/C rations Progress, vol. 6, no. 3, p. 163 (July 1987). Reproduced by permission of the American Institute of Chemical Engineers.)...

There are two different types of water sprinkler systems, wet-pipe and dry-pipe. The lines leading to the sprinkler heads are full of water in a wet-pipe system so that water will be discharged immediately from an open sprinkler head, while in a dry-pipe system, the lines are full of air under pressure instead of water. This latter type of unit should be used where the temperature is not maintained above freezing at aU times. Both types of systems include a main control valve which is designed not only to supply water to the sprinkler heads but also to provide a mechanism to cause an alarm to sound. The valves also usually provide a visual indication of whether they are open or closed. Except during maintenance, they should be in the open position. There are a number of design features for these valves which are beyond the scope of this document, except to note that some are intended to avoid false alarms due to surges or variations in the water supply pressure to the system. 

A variation of the dry-pipe system is the deluge system. The sprinkler heads are continuously open and water is prevented from entering the system by a deluge valve. When a fire is detected the valve to the water supply opens and water flows into the system and out of aU the sprinkler heads. This not only wets the immediate area of a small fire, but the entire area to which the fire may spread. This type of system is usually chosen when the contents of the space are unusually hazardous. A variation on this system is the pre-action system in which the sprinkler heads are not open, but when a fire is detected the deluge valve opens and water is supplied to the sprinkler heads. The water entering the system causes an alarm to be sounded. When the heat causes the sprinkler heads to fuse, or open, water is discharged onto the fire. 

Except for the influence of viscosity variation (which is not very important in many in-plant pumping systems), the head required to pump a given volumetric flowrate of liquid (0 through a piping system is independent of the fluid pumped, and in particular its density, as is the head generated by a centrifugal pump. Hence for such systems the head/flow characteristics are practically independent of the composition of the fluid pumped. 

Variations of pipe fittings, catch basins, sewer boxes, trenches, sumps, and lift stations are only a sample of what a plant layout designer encounters in the development of an underground piping system. Available vendor data for fittings, catch basins, and sewer boxes must be used as a reference. Typical cast iron fittings are shown in Exhibit 13-39. The list of labels for these... 

The service life of materials contained in any equipment, even when correlated with corrosion test data, should be primarily weighed in the light of the actual cost. Both the damage and the cost of external and internal corrosion should be considered for evaluation of the service life of hollow equipment and pipe systems. The effect of occasional and periodic variations of internal and external environmental conditions should also be evaluated for the true extent of service life of relevant equipment. 

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