Mechanical design piping systems

This part will discuss opportunities, primarily in the design of equipment, to make a plant inherently safer. This equipment includes mechanical equipment, piping systems, control systems, and electrical systems. There have been many developments in recent years that process designers can use to improve plant safety and make the plant inherently safer. 

The physical and mechanical properties of the principal thermoplastics of interest for process plant applications are listed in Table 3.42. Table 3.43 gives typical hydrostatic design stresses for different types of thermoplastic pipe. Plastics widely employed in piping systems are described briefly below. 

The mechanical design of thermosiphon reboiler piping must be carefully examined for (a) system pressures and (b) elevadon reladonship between the liquid level in the disdl-ladon column and the verdcal or horizontal reboiler. Kem provides an excellent presentadon on this topic, including the important hydraulics. AbboT also presents a computer program for this topic. 

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. 

Numerous developments in mechanical equipment, piping, control systems, and electrical systems have contributed to the design of safer chemical plants. However, they also have made the designer s job more difficult. With so many choices, how is the designer to choose the best one ... 

A major factor involved in the design of pumping and piping systems is the amount of power that is required for the particular operation. Mechanical power must be supplied by the pump to overcome frictional resistance, changes in elevation, changes in internal energy, and other resistances set up in the flow... 

Compute the size of the connection pipe. In usual vacuum-pump practice, the pressure drop in pipes serving mechanical pumps is not allowed to exceed 20 percent of the inlet pressure prevailing under steady operating conditions. A correctly designed vacuum system, where this pressure loss is not exceeded, will have a pump-down time which closely approximates that obtained under ideal conditions. 

MECHANICAL DESIGN OF PIPING SYSTEMS 5.5.1. Wall thickness pipe schedule... 

Many chemical and petroleum companies are now using Process Industry Practices (PIP) criteria for the development of P IDs. These criteria include symbols and nomenclature for typical equipment, instrumentation, and piping. They are compatible with industry codes of the American National Standards Institute (ANSI), American Society of Mechanical Engineers (ASME), Instrument Society of America (ISA), and Tubular Exchanger Manufacturers Association (TEMA). The PIP criteria can be applied irrespective of whatever Computer Assisted Design (CAD) system is used to develop P IDs. Process Industries Practice (1998) may be obtained from the Construction Industry Institute mentioned in the References. 

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