Finite Element Analysis of Pipe Bends under External Loads

Finite Element Analysis of Pipe Bends under External Loads

Sumesh S. (National Institute of Technology, Tiruchirappalli, India), A. R. Veerappan (National Institute of Technology, Tiruchirappalli, India) and S. Shanmugam (National Institute of Technology, Tiruchirappalli, India)
Copyright: © 2017 |Pages: 30
DOI: 10.4018/978-1-5225-0588-4.ch007
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Abstract

Pipelines are being used to convey different sorts of fluids from hazardous and toxic substances to high pressure steam. Piping systems are subjected to various external loads leading to major failures with gross plastic deformation. Pipe bends are incorporated into piping systems not only to change the direction of flow but also to provide flexibility, hence they are considered to be critical components and its safe design under various loads becomes important. Earlier studies of pipe bends utilized analytical methods to determine the plastic loads. The evolution of FEM and the advancements in computational capabilities have enabled analysts to generate large number of data which is expensive and time consuming with experimental investigations. In this chapter, the major studies on pipe bends by various researchers are explored. Different studies on pipe bends namely stress analysis and the influence of geometric shape imperfections are also presented.
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Introduction

Piping Systems

Within an industry, the term piping relates to a system of pipes used to convey fluids (liquids and gases) from one location to another. The engineering discipline of piping design studies the efficient transport of various fluids under varied loading conditions. In urban areas like in cities, piping systems are used to transport water from the sources of water supply to the points of distribution; convey waste from residential and commercial buildings and other civic facilities to the treatment facility or to the point of discharge. The fire protection piping networks in residential, commercial, industrial, and other buildings carry fire suppression fluids, such as water, gases, and chemicals to provide protection to life and property. Similarly, pipelines are also used to carry crude oil from oil wells to tank farms for storage or to refineries for processing. The natural gas transportation and distribution lines convey natural gas from the source and storage tank to points of utilization. In chemical plants, paper mills, food processing plants, and other similar industrial establishments, the piping systems are utilized to carry liquids, chemicals, mixtures, gases, vapors, and solids from one location to another. The piping systems in thermal power plants convey high-pressure and high-temperature steam to generate electricity. Other piping systems in a power plant, transport high and low pressure water, chemicals, low pressure steam and condensate. Sophisticated piping systems are used to process and carry hazardous and toxic substances.

In health facilities, piping systems are used to transport gases and fluids for medical purposes. The piping systems in laboratories carry gases, chemicals, vapors, and other fluids that are critical for conducting research and development. In short, the piping systems are an essential and an integral part of modern civilization. The design, construction, operation, and maintenance of various piping systems involve understanding of piping fundamentals, materials, generic and specific design considerations, fabrication and installation, examinations, and testing and inspection requirements, in addition to the local, state and federal regulations.

Piping includes pipe, flanges, fittings, bolting, gaskets, valves, and the pressure containing portions of other piping components. It also includes pipe hangers and supports and other items necessary to prevent over pressurization and overstressing of the pressure-containing components. Pipe sections when joined with fittings, valves, and other mechanical equipment and properly supported by hangers and supports, are called piping systems.

Piping for most process units represents the major item of investment. Typically, the total erected piping cost ranges from 25 to 50 percent of the total cost of a unit. Consequently, the piping engineer often faces the necessity of making careful and realistic compromises between design features and cost without sacrificing minimum safety standards (Figure 1).

Figure 1.

Industrial piping system

Materials

The material with which a pipe is manufactured often forms the basis for choosing any pipe. Materials that are used commonly for manufacturing pipes include:

  • Carbon steel.

  • ASTM A252 Spec Grade 1, Grade 2, Grade 3 Steel Pile Pipe.

  • Low temperature service carbon steel.

  • Stainless steel.

  • Nonferrous metals, e.g. cupro-nickel.

  • Nonmetallic, e.g. tempered glass.

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