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TRANSMISSION OF FLUIDS
Piping is manufactured in many sizes, materials and thicknesses.
The size of a pipeline normally refers to its Inside Diameter (ID), and this factor depends upon the maximum expected VOLUME of Fluid to be transported.
The material of construction of a pipeline depends upon various factors such as :
- The type of fluid to be carried - Its Temperature, Pressure, Corrosive and Erosive Properties and the life expectancy of the Pipeline … etc.
- The Thickness of pipe material depends upon the maximum expected Pressure of the transported fluid and, again, its corrosive and erosive properties and the life expectancy of the Pipeline … etc.
Some examples of piping materials are: - Cast iron, mild steel, carbon steel, stainless steel, aluminium, copper, plastic, fibre-glass and concrete. Other special substances are used depending upon the nature of the fluids.
An important factor in material selection is, of course, the COST. However, the selection should put safety before cost.
Other factors to be considered in pipeline construction are; - the weight of the pipe with its contents and the fittings, the thermal expansion due to internal and external temperatures and the erosive and corrosive conditions of the environment through which the pipeline is passing - i.e. whether it is above or under the ground or in water ..etc. Factors of this nature also govern the protection of the pipe material - coating types, wrapping, lagging and Corrosion Protection methods (CP). In many cases, a Corrosion Inhibitor is injected into the fluid as it enters the pipeline.
Where a pipeline is carrying very hot or very cold materials, it will be lagged with a suitable material which prevents heat loss or heat gain and help to protect personnel from burns - (a cold burn can be just as painful as a heat burn). Also, liquids which have a high viscosity are usually transported in lagged piping and may also have steam or electrical 'tracing' running inside the lagging to maintain the liquid fluidity.
Also in hot or cold systems, such as steam or cryogenic fluids, the pipeline is constructed with 'Expansion Loops' which allow the length of the pipeline to vary as the temperature varies. The pipe will also be supported by 'rolling' type devices which will allow the expansion and contraction to take place with little or no friction between the support and the pipe - thus preventing external wear.
These aspects of piping are discussed later.
Figure : 1