Page 139 - CITS - Welder - Trade Theory

WELDER - CITS

Note for knowledge purpose only: Another restricted weld position called as “6GR” in which the
letter “R” indicated that 6G positioned test coupon fitted with a restriction ring to restrict the
welding holder movement / position. 6GR position qualification is mandatory for welder / procedure
qualification of TKY joints in tubular structural construction. The difference with the 6G and 6GR
position is the restriction ring. 6GR position is applicable only for welding tubular structures and
not for process / power or oil and gas piping.
Equipment and consumables requirement: Welding machine, grinding machine with grinding disc., welding
consumables (electrode in case of SMAW and “filler metal & shielding gas normally argon” in case of TIG (also
called as GTAW process) welding, try square / right angle, measuring tape / scale, chipping chisel, wire brush,
PPE including welding helmet.
Work instruction
1 Always comply to work instruction and relevant welding procedure specification (WPS) and all safety
requirements;
2 Verify based metal type and grade supplied as per WPS;
3 Verify consumable supplied as specified in WPS;
4 Check SMAW/TIG welding equipment and accessories functionality;
5 Cut the pipe and perform edge preparation of the pipe as per specification; normally, 32 to 38° for 6” MB pipe
with sch 60 or sch 80 thickness pipes. Edges shall be prepared as per WPS; normally with 2 to 3mm root face
and 2 to 3mm root gap.
6 Grind the edges to get smooth surface and clean & remove the mill scale up to 25mm from the joining edges
of the pipe.
7 Perform pipe to pipe butt joint the fit-up duly maintaining the specified root face root gap as per WPS. Pipe
edges misalignment shall not exceed 1.5mm.
8 Preheating is not required if atmospheric temperature is above 20°C. If WPS required preheat, joint shall be
preheated to the specified temperature using propane gas with rose bud torch. Otherwise, small warm up heat
(about 50°C) is enough; but not mandatory unless required by WPS.
9 Welding electrodes / Filler metal specification and grade will wary with respect to base material quality /
specification. Approved WPS shall be referred. Normally, E 6013 / E 7018 for low carbon steel base metal
welding with SMAW process and ER 70 - S2 / S6 series for GTAW weld process.

10 Tack welding can be performed; but preformed; but preferred bridge tacking.
11 Whenever you start and stop pipe welding, always do so no the side wall - never in the root gap. Start the
arc, wait for the weld pool to form, then slowly and gently move across the open root to the other side. Slowly
zigzag your way along the open root for the first section of the pipe until you have to change your position.
12 Inter pass temperature shall not exceed the limit specified in the WPS (normally, interpass temperature will be
250°C maximum for carbon steel base metal.
13 Think of the pipe in terms of a clock face, and divide it up into sections. Start at the 12 0’ clock position, and
work round to 3 0’clock then stop and make sure you’re comfortable and prepared for the next section, and
repeat this process until you’ve completed the entire weld.
14 Stagger these welding start and stop points for each weld layer rather than keeping them all at the same point
around the pipe.
15 Perform and complete SMAW / GTAW welding process welding as per the WPS with appropriate current,
voltage, travel speed for the respective electrode filler meta sixes and respective weld passes (root, hot,
intermittent and fill passes) within the permissible heat input limitation as specified in the WPS for the respective
weld passes as per WPS.
16 In case of TIG / GTAW welding, shielding gas flow rate shall be maintained as per WPS.
17 Ensure that welding is performed with proper fusion and penetration. Excess penetration more than 1.5mm
shall be avoided.
18 Similarly welding shall be completed without excess weld reinforcement (In general - 2mm maximum weld
reinforcement.) At the same time welding shall not be under-flush with pipe base-metal surface.

19 Perform visual inspection and sent for necessary NDT and mechanical testing (destructive test).

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CITS : C G & M - Welder - Lesson 33 - 43