Resistance of pipe

The flow resistance of pipe fittings (elbows, tees, etc) and valves is expressed in terms of either an equivalent length of straight pipe or velocity head loss (head loss = Kv /2g ). Most handbooks and manufacturers pubHcations dealing with fluid flow incorporate either tables of equivalent lengths for fittings and valves or K values for velocity head loss. Inasmuch as the velocity in the equipment is generally much lower than in the pipe, a pressure loss equal to at least one velocity head occurs when the fluid is accelerated to the pipe velocity. 

U being the total heat transfer coefficient, Ri the inside convective resistance, Rk the conductive resistance of pipe walls, and R0 the outside convective resistance. This result may be rearranged in terms of the characteristic length 1/m = JkAjVP for fins [recall Eq. (2.113)], the thermal diffiisivity,... 

Both E and Ea represent differences between polarized potential with current flowing and corrosion potential in absence of current, Rl is the resistance of pipe of radius r per unit length, k is a constant, and z is the resistance of pipe coating per unit area (for derivation, see Appendix, Section 29.4). This equation is derived by assuming that polarization of the cathodically protected surface is a linear function of current density. Note that E becomes zero at x = oo. 

Figure 29.6. Sketch of buried pipe cathodically protected by anodes distance a apart. /, is the current density at pipe surface at distance x from point of bonding /, is the total current in pipe at distance x E is the difference between measured and corrosion potentials of pipe r is the radius of pipe fit is the resistance of metaiiic pipe per unit iength and z is the resistance of pipe coating per unit area.

Buzdakov, A. P. (1966). Resistance of pipes with thetmodiffused zinc coatings in various media. Collect Sci. Pap. Mfr. Pipes with Anti-Corrosion Coatings, pp. 132-138 (in Russian). 

Proskurkin, E. V., Gorbunov, N. S., and Lavrenko, N. A. (1968). Corrosion resistance of pipes with a diffusion-coated zinc layer in welded and bent zones. Zashch. Metall. (special issue No. 6), 730-732 (in Russian). 

Proskurkin, E. V., Bakalyuk, Ya. K. L., Zholudev, M. D., et al. (1981). Problems associated with increasing the corrosion resistance of pipes of hot water supply systems. Water Supply Sanit. Technol. (10), 16-18 (in Russian). 

Fig. 24.16 Buckling resistance of pipes of Hostalen under external water pressure at 20 C. The curves show the beginning and end of buckling...

This overview of the various cases of repercussions of chemicals on HDPE materials justifies the conclusion already addressed several times that, though HDPE geomembranes are not entirely inert, they are extraordinarily resistant to a broad spectrum of high-concentration chemicals at normal temperatures. This can also be seen by the assessment of chemical resistance as described in DIN 8075-Attachment 1 1984 High Density Polyethylene (HDPE) Pipes Chemical Resistance of Pipes and Fittings. The standard classifies for a large number of chemicals whether HDPE materials are resistant, only conditionally resistant or are not resistant at all... 

DIN 8075 attachment 1 1984 High Density Polyethylene (HDPE) Pipes Chemical Resistance of Pipes and Fittings... 

Table 49 Distribution of resistance of pipe samples in Table 51 to Table 54 ...

Supplement 1 for DIN 8061 [465] Unplasticized polyvinylchloride pipes chemical resistance of pipes and fittings of (PVC-U)... 

DIN 8078 [467] Polypropylene (PP) pipes - PP-FI, PP-B, PP-R, PP-RCT - General quality requirements and testing Supplement chemical resistance of pipes and fittings... 

Environmental stress crack resistance of pipes ASTM F 1248... 

The thermal resistance of pipe insulation can be calculated from Equation 11.2 if the reciprocal of the thermal conductivity of the insulation is taken as the equivalent of the electrical resistance. The rate of energy loss from the pipe then is directly proportional to the temperature difference and inversely proportional to the thermal resistance. If a 6.0-cm-diameter pipe carries chilled water at an average velocity of 3.0 m/s over a distance of 1.50 km, what thickness of insulation (same k as in Problem 11.6) is needed to keep the temperature from rising more than 2.0°C when the inside temperature is 10°C and the outside is 65°C Neglect all resistance except that of the insulation. 

PLANE STRESS RAPID FRACTURE RESISTANCE OF PIPE GRADE PE ESTIMATION FROM TENSILE DRAWING DATA... 

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