construction specifications should be representative
of suitable practice for the geographic location and
service intended. It is intended however, that
steel pipe only be used for gas mains and services
wherever external loading conditions for the pipe
exceed the normal; i.e., corrosion, road, and
railroad crossings. In the event that unusual
conditions affect only a part of the gas line, that
part should be steel.
2. Pipe materials which are known to be unsuitable
for particular local conditions (i.e., corrosion,
deterioration) should not be permitted for the
project. However, consideration should be given to
the use of more effective protective coatings where
economically feasible.
3. When RTR or PE pipe or tubing is specified for
use in gas distribution piping, detailed
investigation should be made for assurance that the
material selected for use is suitable for the
service intended. Areas of investigation should
include: excessive external loading as a result of
heavily traveled roads, storage areas, ambient
temperature range, use of manufactured or mixed
gases, introduction of antifreeze solution and so
forth. PE pipe and fittings should not be allowed
for any project where the gas distributed is liquid
petroleum manufactured gas, or a mixture of
manufactured and natural gas.
4. Ductile-iron, RTR or PE and plastic pipe should
not be allowed if the project is located in an area
subject to seismic forces, erosion, or unstable
soils.
5. PE may be allowed for direct buried exterior gas
distribution mains and service lines only if
recommended by the local gas utility.
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NOTE: Pipe Design:
1. Equivalent pipe design for the project
conditions (using the applicable criteria for each
pipe material) should be specified for each pipe
material insofar as is practicable, in view of the
fact that design criteria differ for the standard
manufactured pipe of the different materials.
2. External loads, including earth loads, truck
loads, seismic loads, and impact, should be
investigated in the design stage of the project.
3. Where different classes, wall thicknesses, etc.,
of pipe are required for different sections of
pipelines due to significant differences in external
loading, the applicable paragraphs for the project
SECTION 02551N
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