B31.8, AGA XR0104 and 49 CFR 192. Abandoning existing gas piping shall be
done in accordance with ASME B31.8. Pipe shall be cut without damaging the
pipe. Unless otherwise authorized, cutting shall be done by an approved
type of mechanical cutter. Wheel cutters shall be used where practicable.
On steel pipe 150 mm (6 inches 6 inches and larger, an approved
gas-cutting-and-beveling machine may be used. Cutting of plastic pipe
shall be in accordance with AGA XR0104. Valve installation in plastic pipe
shall be designed to protect the plastic pipe against excessive torsional
or shearing loads when the valve is operated and from other stresses which
may be exerted through the valve or valve box.[ Polyethylene mains and
service lines for LPG shall only be installed below ground in accordance
with NFPA 58.]
3.6.1
Installing Pipe Underground
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NOTE: Indicate profile of gas lines on the drawing.
If it is impractical to comply with the minimum
cover specified for pipe, and necessary to prevent
damage from external loads, the pipe will be
installed in a casing. The locations of all casings
and details of the installation will be indicated.
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Gas mains and service lines shall be graded as indicated. Joints in steel
pipe shall be welded except as otherwise permitted for installation of
valves. Mains shall have 600 mm 24 inch minimum cover; service lines shall
have 485 mm 18 inch minimum cover; and both mains and service lines shall
be placed on firmly compacted select material for the full length. Where
indicated, the main shall be encased, bridged, or designed to withstand any
anticipated external loads as specified in ASME B31.8. The encasement
material shall be standard weight black steel pipe with a protective
coating as specified. The pipe shall be separated from the casing by
insulating spacers and sealed at the ends with casing bushings. Trench
shall be excavated below pipe grade, bedded with bank sand, and compacted
to provide full-length bearing. Laying the pipe on blocks to produce
uniform grade will not be permitted. The pipe shall be clean inside before
it is lowered into the trench and shall be kept free of water, soil, and
all other foreign matter that might damage or obstruct the operation of the
valves, regulators, meters, or other equipment. When work is not in
progress, open ends of pipe or fittings shall be securely closed by
expandable plugs or other suitable means. Minor changes in line or
gradient of pipe that can be accomplished through the natural flexibility
of the pipe material without producing permanent deformation and without
overstressing joints may be made when approved. Changes in line or
gradient that exceed the limitations specified shall be made with fittings.
When cathodic protection is furnished, electrically insulated joints or
flanges shall be provided. When polyethylene or fiberglass piping is
installed underground, foil backed magnetic tape shall be placed above the
pipe to permit locating with a magnetic detector. After laying of pipe and
testing, trench shall be backfilled in accordance with Section 02300
EARTHWORK.
3.6.2
Installing Pipe Aboveground
Aboveground piping shall be protected against dirt and other foreign matter
as specified for underground piping. Joints in steel pipe shall be welded;
however, joints in pipe 40 mm (1-1/2 inches) 1-1/2 inches in diameter and
smaller may be threaded; joints may also be threaded to accommodate the
SECTION 02556A
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