Pipe contractions

Mackay, M. E., Y. L. Yeow and D. V. Boger, Pressure Drop in Pipe Contractions—Experimental Measurements or Finite Element Simulation , Chem. Eng. Res. Des. 66 22-25 (1988). 

The validated numerical model can be used to predict optimum geometries in process equipment, such as cross-flow filters and shell and tube heat exchangers which reduce the eddy losses due to pipe contractions. Details of such a design procedure are given by Nassehi et. al [11]. 

Fester V.G., Mbiya B.M., Slatter P.T. (2008), Energy losses of non-Newtonian fluids in sudden pipe contractions. Chemical Engineering Journal, Vol.145, No.l, pp. 57-63, ISSN 1385-8947... 

Major items of equipment are normally procured by the EPCM contractor s head office. The EPCM contractor s procurement from the site office is generally limited to minor items purchased locally for speed and convenience. Items issued free by the owner may be special process equipment. For civil works and buildings, the construction contractors normally procure items such as pre-mixed concrete, reinforcing bars, doors, windows, and so forth. Concerning piping contracts, pipes, valves and fittings may be procured either by the... 

In Section 7.6 the principles of traceability are outlined and Appendix D shows in greater detail how these can be applied to welding. As far as piping is concerned the level of traceability must be defined contractually for each line class and clarified completely in detail at the outset of the piping contract. 

For laminar flow the losses in sudden contraction may be estimated for area ratios Ao A < 0.2 by an equivalent additional pipe length Lc given by... 

Thermal-expansion and -contraction loads occur when a piping system is prevented from free thermal expansion or contraction as a result of anchors and restraints or undergoes large, rapid temperature changes or unequal temperature distribution because of an injection of cold liquid striking the wall of a pipe cariying hot gas. 

The force required to overcome the static friction of the pipe in expanding or contracting on its supports, from installed to operating position. The length of pipe considered should be that located between the anchor and the expansion joint. 

Table 10-56 gives values for the modulus of elasticity for nonmetals however, no specific stress-limiting criteria or methods of stress analysis are presented. Stress-strain behavior of most nonmetals differs considerably from that of metals and is less well-defined for mathematic analysis. The piping system should be designed and laid out so that flexural stresses resulting from displacement due to expansion, contraction, and other movement are minimized. This concept requires special attention to supports, terminals, and other restraints. 

Displacement Strains The concepts of strain imposed by restraint of thermal expansion or contraction and by external movement described for metallic piping apply in principle to nonmetals. Nevertheless, the assumption that stresses throughout the piping system can be predic ted from these strains because of fully elastic behavior of the piping materials is not generally valid for nonmetals. 

A toller may need to use resources outside their company to measure physical properties, conduct safety or other testing, engineer changes to piping or other facilities and equipment. This need frequently occurs for products in the initial development or commercialization stage. The toller should maintain confidentiality agreements with their suppliers and subcontractors commensurate with the proprietary nature of their client companies processes. Provision to allow disclosure of information to third parties should be addressed in the contract between the toller and the client. It may be structured so that the client must approve the toller s release of information to third parties. 

Also in the long term, the equipment loses its eflicieney, and replacement parts are substituted in a maintenance function. Also, the plant goes through production expansions and contractions new equipment is added into the pipes. In short, the system and its elevations and pressures, its resistances and velocities, are very dynamic. The BEP of the pump is static. 

Open Tube Sections (Water cooled) Tubes require no shell, only end headers, usually long, water sprays over surface, sheds scales on outside tubes by expansion and contraction. Can also be used in water box. Condensing, relatively low heat loads on sensible transfer. Transfer coefficient is low, takes up less space than pipe coil. 0.8-1.1... 

Thermal contraction of piping must be allowed for, based on the lowest possible service temperature. 

When the pipe is cooled it will contract by an amount given by et = ci AT) and when this equals the fixed strain. Eg, the pipe would leak... 

Full consideration of the thermal expansion of the tubes is necessary, with adequate provision for expansion and contraction. It is a wise policy to fit thermometer wells in the pipes near the inlets and outlets of all airheating batteries, as these provide a useful means of checking the coil performance. 

Futures Prices Natural gas futures contracts began trading on April 3, 1990, on the New York Mercantile Exchange (NYMEX). Sabine Pipe Line Company s Heniy Hub near Erath,... 

For sudden pipe system contractions as represented in Figure 2-12A through 2-16, the values of the resistance coefficient, K, can be read from the charts. For more details for various angles of enlargements and contractions, see References [3] and [2]. 

The K coefficient values for each of the items of pipe, bends, valves, fittings, contractions, enlargements, entrance/exits into/from vessels are additive as long as they are on the same size basis (see Table 2-2 and Figures 2-12A through 2-16). Thus the resistance equation is applicable to calculate the head or pressure loss through the specific system when the combined Rvalue is used. 

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