Pipes for natural gas distribution

Part of system Gas pressure (bar) Requirement Material (old material) 

National grid 7-70 Maximum flow high hoop strength High strength steel 

Local distribution 0.075-4 See later Plastic (cast iron/steel) 

Inside house 0.075 Safe durable connections Copper (lead) 

Individual housing estates take their gas supplies via pressure governors which reduce the gas pressure to 40 mbar. 

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As experience with creep rupture testing of polyolefins has been gained, elevated temperature tests have been used for quality control purposes, and standards set using such tests, i.e. the creep rupture time for pipes for natural gas distribution must exceed 170 h at 80 °C and a hoop stress of 3 MPa. Care must, however, be exercised if a polyethylene made by a different process is introduced, because the use temperature is close to 10 °C when the pipe is buried in the ground the slope of the Arrhenius plot varies between different polyethylenes. 

FIGURE 13.1 Plastic pipe as a percentage of all piping used in gas distribution. (Source Duvall, D.E., Polyethylene Pipe for Natural Gas Distribution, presented at the Transportation Safety Institute s Pipeline Failure Investigation course, 1997. Data from Pipeline Gas Journal surveys)... 

Defects and welding faults in 6 mm thick PE pipes for natural gas and water distribution may also be examined by Se y-ray radiography [733]. 

Reference has been made to injection moulding, which is a fair market for HDPE. Extruded pipe from HDPE and a tougher variant of lower density is widely used for natural gas distribution, particularly in cold climates where some failures of PVC (Chapter 8) have been encountered. HDPE has also been formed into mudguards for commercial vehicles, where the non-corroding... 

The monomers used to make an addition polymer need not be identical. When two or more different monomers are polymerized into the same chain, the product is a copolymer. For instance, we routinely copolymerize ethylene with small percentages of other monomers such as a-olefins (e.g., 1-butene and 1-hexene) and vinyl acetate. We call the products of these reactions linear low density polyethylenes and ethylene-vinyl acetate copolymer, respectively. We encounter these copolymers in such diverse applications as cling film, food storage containers, natural gas distribution pipes, and shoe insoles. 

Bottled gas was sold as early as 1810 in England, but propane was discovered at the start of the 20th century with the development of the natural gas industry. Problems in natural gas distribution were attributed to condensation of particular fractions of natural gas in pipes. This led to the removal of these higher boiling point gases and a search for applications for these gases. Concurrent with the development of the natural gas industry, society s... 

This work is aimed to predict the hydrate formation throughout the discharge of trapped natural gas in the north super block of Tehran natural gas distribution system. A well known software is used to construct the numerical model of the north super block and the developed model is employed to predict the hydrate formation. Furthermore, the results of a field experiment carried out in a part of Tehran gas network are used to calibrate the numerical model. Simulations indicate that the hydrate formation potential for pipes ended with a closed valve is high. It is also found that hydrate formation is sensitive to the soil temperature. 

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