Piping functions

Figure 10-32 shows the schematic of a pump, moving a fluid from tank A to tank B, both of which are at the same level. Tne only force that the pump has to overcome in this case is the pipe function, variation of which with fluid flow rate is also shown in the figure. On the other for the use shown in Figure 10-33, the pump in addition to pipe friction should overcome head due to difference in elevation between tanks A and B. In this case, elevation head is constant, whereas the head required to overcome fric tiou depends on the flow rate. Figure 10-34 shows the pump performance requirement of a valve opening and closing. 

Polymer type Pipe Function Diameter mm Thickness mm Cross Section Area m Nominal Pressure PN MPa Price per Metre /m Mass per Metre kg/m Price per Mass /kg Price per Capacity /(PN)m Price per Area /m ... 

The factors fp and fj have not been applied to installation costs because installation costs are not a simple function of purchase cost. Although process piping and fittings made for the same unusual conditions are proportionally more expensive, labor, foundations, insulation, etc. are not. Furthermore, only about 70 percent of piping is directly exposed to process fluid. The balance is auxiliary or utility piping made of conventional materials. 

The surface facilities used to perform these functions are discussed in Section 10.1, and are installed as a sequence or train of vessels, valves, pipes, tanks etc. This section... 

In fig. 2 an ideal profile across a pipe is simulated. The unsharpness of the exposure rounds the edges. To detect these edges normally a differentiation is used. Edges are extrema in the second derivative. But a twofold numerical differentiation reduces the signal to noise ratio (SNR) of experimental data considerably. To avoid this a special filter procedure is used as known from Computerised Tomography (CT) /4/. This filter based on Fast Fourier transforms (1 dimensional FFT s) calculates a function like a second derivative based on the first derivative of the profile P (r) ... 

The scope of the directive covers the design, manufacture and conformity assessment of pressure equipment and assemblies with a maximum allowable pressure greater than 0,5 bar. A pressure equipment in the sense of the directive is any vessel, piping, safety accessory or pressure accessory. An assembly means several pieces of pressure equipment assembled by a manufacturer to constitute an integrated and functional whole. It is important to be aware that the directive relates exclusively to the pressure risk and that therefore other directives, such as for machinery, low voltage may be applicable to the equipment concerned. 

Directions are provided for preparing and using a simple coring device using PVC pipe. This experiment also details a procedure for determining the weight percent of organic material in sediments as a function of depth. 

As a vessel is loaded, it moves downward because of deflection of the load cells and support stmcture. Pipes rigidly attached to a vessel restrict its free movement and assume some portion of the load that cannot be measured by the load cells. This is very detrimental to scale accuracy. Deflection of the load cell is unavoidable deflection of the vessel support stmcture should be minimized. Anything which increases vessel deflection, eg, mbber pads used for shock protection, must be avoided. The total number of pipes should be minimized and be of the smallest diameter, thinnest wall possible. Pipe mns to weigh vessels must be horizontal and the first pipe support should be as far as possible from the vessel. Alternatively, a section of mbber hose or flexible bellows should be used to make the final connection to the vessel. The scale should be caUbrated using weights, not by means of an electrical simulation method, which cannot account for the effects of the piping or test the correct functioning of the scale. 

Head-Area Meters. The Bernoulli principle, the basis of closed-pipe differential-pressure flow measurement, can also be appHed to open-channel Hquid flows. When an obstmction is placed in an open channel, the flowing Hquid backs up and, by means of the Bernoulli equation, the flow rate can be shown to be proportional to the head, the exact relationship being a function of the obstmction shape. 

As velocity continues to rise, the thicknesses of the laminar sublayer and buffer layers decrease, almost in inverse proportion to the velocity. The shear stress becomes almost proportional to the momentum flux (pk ) and is only a modest function of fluid viscosity. Heat and mass transfer (qv) to the wall, which formerly were limited by diffusion throughout the pipe, now are limited mostly by the thin layers at the wall. Both the heat- and mass-transfer rates are increased by the onset of turbulence and continue to rise almost in proportion to the velocity. 

Cost bilizers. In most cases the alkyl tin stabilizets ate particularly efficient heat stabilizers for PVC without the addition of costabilizers. Many of the traditional coadditives, such as antioxidants, epoxy compounds, and phosphites, used with the mixed metal stabilizer systems, afford only minimal benefits when used with the alkyl tin mercaptides. Mercaptans are quite effective costabilizets for some of the alkyl tin mercaptides, particularly those based on mercaptoethyl ester technology (23). Combinations of mercaptan and alkyl tin mercaptide ate currendy the most efficient stabilizers for PVC extmsion processes. The level of tin metal in the stabilizer composition can be reduced by up to 50% while maintaining equivalent performance. Figure 2 shows the two-roU mill performance of some methyl tin stabilizers in a PVC pipe formulation as a function of the tin content and the mercaptide groups at 200°C. 

Corrosion of reactors used for functionalization and ia pipes and valves along transferlines for sulfuric acid is a problem that results ia maintenance shutdowns. Sufficient agitation is needed to keep the resia beads fluidized duting sulfonation. As for copolymer kettles, transfer lines should be sufficiently large to allow reasonably rapid transfer of Hquids and resia slurries. 

Heat transfer in static mixers is intensified by turbulence causing inserts. For the Kenics mixer, the heat-transfer coefficient b is two to three times greater, whereas for Sulzer mixers it is five times greater, and for polymer appHcations it is 15 times greater than the coefficient for low viscosity flow in an open pipe. The heat-transfer coefficient is expressed in the form of Nusselt number Nu = hD /k as a function of system properties and flow conditions. 

Carbon—carbon composites are used in high temperature service for aerospace and aircraft appHcations as weU as for corrosion-resistant industrial pipes and housings. AppHcations include rocket nozzles and cases, aircraft brakes, and sateUite stmctures. Carbonized phenoHc resin with graphite fiber functioned effectively as the ablative shield in orbital re-entry vehicles for many years (92). 

Design parameters as a function of temperature and design temperature limits are set forth in the ANSI/ASME B31 Piping Codes for a very broad range of materials. These codes, and the additional information available from manufacturers, vendors, and technical societies such as the National Association of Corrosion Engineers provide ample data for the selection of materials for piping systems (1—13). 

Restraints ate provided to limit movements ia any number of directions (Fig. 7). For example, a siagle-directional arrangement uses a simple tie rod with pia connections (Fig. 7a). This type is favored because of low frictional resistance and positive action. Another simple arrangement utilizes a shoe and provides two functions at one poiat (Fig. 7b). Partial restraint along the pipe axis may be accompHshed as shown ia Figure 7c, and Figure 7d shows typical restraint perpendicular to the pipe axis. 

Insulation provides other functions in addition to energy conservation. A key role for insulation is safety. It protects personnel from bums and minimizes hot surfaces that could ignite inflammables. It also protects equipment, piping, and contents in event of fire. Thus materials such as mineral wool are sometimes used despite relatively poor thermal quaUties. 

For smooth pipe, the friction factor is a function only of the Reynolds number. In rough pipe, the relative roughness /D also affects the friction factor. Figure 6-9 plots/as a function of Re and /D. Values of for various materials are given in Table 6-1. The Fanning friction factor should not be confused with the Darcy friction fac tor used by Moody Trans. ASME, 66, 671 [1944]), which is four times greater. Using the momentum equation, the stress at the wall of the pipe may be expressed in terms of the friction factor ... 

For fully developed incompressible horizontal gas/hquid flow, a quick estimate for Ri may be obtained from Fig. 6-27, as a function of the Lockhart-MartineUi parameter X defined by Eq. (6-131). Indications are that liquid volume fractious may be overpredicled for liquids more viscous than water (Alves, Chem. Eng. Prog., 50, 449-4.56 [19.54]), and uuderpredicted for pipes larger than 25 mm diameter (Baker, Oil Gas]., 53[12], 185-190, 192-195 [1954]). 

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