Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF : RANCHI (BIHAR)
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
STANDARD SPECIFICATION
TITLE PIPELINES CROSSING ROADS, SPECIFICATION NO. PAGE 7 OF 10
RAILROADS, MINOR WATER AND
OTHER CROSSINGS MEC/S/05/62/05 REVISION 0
3.7 The assembly of vent pipe units as approved by COMPANY shall be carried out
by direct insertion and welding to the ends of the casing pipe before introducing
the carrier pipe. The operation of assembling and extending the vent pipe shall
be carried out in such a way that there is no contact with the carrier pipe. The
painting/ coating of the vent pipes shall be applied before backfilling as per
relevant specifications.
3.8 The casing pipe shall be considered ready for installation of the carrier pipe,
after careful inspection and internal cleaning with the removal of soil, mud,
stones and other foreign materials.
3.9 Insulators, as approved by COMPANY, shall be securely fastened to the pipe
with all bolts and fixtures firmly tightened. The number of insulators and spacing
shall be as shown in the drawings or at 2.5m intervals (whichever is more
stringent). At the end of both sides of the casing, a double set of insulators shall
be installed.
3.10 Care must be taken in pushing or pulling carrier pipe into the casing so that the
pipe is aligned correctly in the casing and that the pushing or pulling force is
evenly and constantly applied to avoid damages to the insulators. A nose piece
having a diameter equal to that of the pipe shall be welded on the front and back
end of the carrier pipe to facilitate installation of the carrier pipe properly in the
casing and to keep it dry and clean.
3.11 After installation of the carrier pipe section, the casing and the appurtenances,
but prior to making tie-in welds and backfilling, an electrical test shall be
conducted by the CONTRACTOR in the presence of the COMPANY, to
determine the resistance between the casing and the carrier pipe or the carrier
pipe and the soil. These tests shall show at least a resistance of 100 kohm/m 2 .
After backfilling and compaction, additional tests shall be conducted to
determine if the casing is electrically shorted to the pipe. If the installation is
found to be shorted, CONTRACTOR shall make the necessary corrections and
repairs at his cost, until a test to the satisfaction of the COMPANY is obtained.
4.0 CROSSINGS OF BURIED SERVICES
4.1 The pipeline under construction may pass above or below the existing buried
facilities such as pipelines, cables, etc. Type of crossing shall be such that a
minimum depth of cover as required in the drawings and specifications are
guaranteed. The minimum clearance required between pipeline and the existing
facility shall be 500mm.
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