Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF : RANCHI (BIHAR)
Document6
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
TITLE MAINLINE CONSTRUCTION
(ONSHORE)
STANDARD SPECIFICATION
SPECIFICATION NO. PAGE 39 OF 53
MEC/S/05/62/01 REVISION A
10.14 Backfilling shall be preferably carried out at the highest ambient temperature.
11.0 TIEING-IN
11.1 The unconnected sections of the pipe line at various locations have to be tied in
after the sections are coated, lowered and backfilled. The sections to be
connected shall have at the ends, sections of over lapping, uncovered pipe of
sufficient length to absorb, without inducing excessive stresses in the steel,
small displacements necessary for perfect alignment and connection of the
ends.
11.2 Tie-in shall preferably be carried out at ambient temperatures corresponding to
the average operating temperature in the case of a pipeline conveying fluids at
normal temperatures and at the maximum ambient temperature in the case
where the pipeline is carrying fluids at high temperature.
11.3 CONTRACTOR shall carry out tie-in-welding (including necessary cutting,
bevelling, grinding of pipe weld seams and line-up etc.) cleaning, priming,
coating and backfilling for the tie-in portion as per relevant specifications.
CONTRACTOR shall also excavate the required bell-holes for the connection.
Bell-holes made to facilitate welding shall provide adequate clearance to enable
the welders to exercise normal welding ability and skill. All tie-in welds shall be
radiographically examined.
11.4 The tie-in should be done in such a way as to leave a minimum of strain in the
pipe. If necessary, with respect to the trench, realigning of the pipe shall be done
to eliminate force or strain in the pipe by the CONTRACTOR at no extra cost to
COMPANY.
11.5 If a pup end cannot be avoided for tie-in, the minimum length that shall be
added is 1.0 meters and two or more such pups shall not be welded together. All
cut-off lengths greater than 1.0 meters shall be moved ahead in order to be
welded into the pipeline at a suitable location. Tie-in with two or more pups may
be used provided that they each have minimum length of 1.0 meter and are
separated by an entire length of pipe. In no case more than three (3) welds shall
be permitted on a 10 meter length of pipeline.