Page 246 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

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Distribution Systems

1. Background assessment system to measure pipeline risks with a focus
on transmission systems. Distribution systems present some
There are many similarities between transmission and distribu- different issues for the risk evaluator, as are discussed in this
tion systems, but there are also critical differences from a chapter.
risk standpoint. A transmission pipeline system is normally For purposes of this chapter, a distribution pipeline system
designed to transport product to large end-users such as a distri- will be considered to be the piping network that delivers prod-
bution system, which in turn delivers that product to all users in uct from the transmission pipeline to the final user (i.e., the
towns and cities (e.g., natural gas for cooking and heating or consumer). This includes the low-pressure segments that oper-
water for multiple uses is delivered to homes and other build- ate at pressures close to those of the customers’ appliances as
ings by the distribution system within a municipality). The sim- well as the higher pressure segments that require pressure regu-
ilarities between transmission and distribution systems arise lation to control the pressure to the customer. The most com-
because a pressurized pipeline installed underground will mon distribution systems transport water and natural gas,
experience threats common to all such systems. Differences although steam and other product systems are also in use.
arise due to varying material types, pipe connection designs, An easy way to picture a distribution system is as a network
interconnectivity of components, pressure ranges, leak toler- or grid of mains, service lines, and connections to customers
ance, and other factors. Chapters 3 through 7 detail a risk (see Figure 1 1.1). This grid can then be envisioned as overlaying