Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF : RANCHI (BIHAR)
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
STANDARD SPECIFICATION
TITLE WELDING OF ONSHORE GAS
SPECIFICATION NO. PAGE 8 OF 48
PIPELINES
MEC/S/05/62/02 REVISION
The internal line-up clamp shall not be released before the entire root pass has
been completed.
When as external line-up clamp is used, all spaces between bars or atleast 60%
of the first pass shall be welded before the clamp is released and the pipe
remaining adequately supported on each side of the joint.
Segments thus welded shall be equally spaced around the circumference of the
pipe. Slag, etc. shall be cleaned off and the ends of the segments shall be
prepared by grinding, so as to ensure continuity of the weld bead.
09. WEATHER CONDITIONS
10.0 WELDING
10.1 Root Pass
The parts being welded and the welding personnel shall be adequately protected
from rain and strong winds. In the absence of such a protection no welding shall
be carried out. The completed welds shall be suitably protected in case of bad
weather conditions.
a) Root pass shall be made with electrodes/ filler wires recommended in the
welding specification chart attached along with other project data sheets.
The size of the electrodes used shall be as per the approved welding
procedure.
b) Position or roll welding may be permitted. Separate procedures shall be
submitted and qualified for up hill, down hill, vertical down and roll welding.
The vertical up method of welding shall be sued for the root pass of the
tie-ins, special crossings, fittings and special parts, filled welds, repairs
and when an external line up clamp is used. The down hill welding may be
used for root run welding of tie-ins and special crossings when (a) the
edges are machined or have equivalent preparation (b) line up clamps are
used and the fit up is geometrically and mechanically similar to one of the
oridinary line welding without misalignment or uneveness.
c) The root pass of butt joints shall be executed properly so as to achieve full
penetration with complete fusion of the root edges. Weld projection inside
the pipe shall not exceed 3mm wherever not specified by the applicable
code.
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