Monday, September 17, 2012

[MW:15325] hot tap welding-branch weld

Please clarify the following.

Query 1
Clause 1.1 of DEP 30.10.60.30 quoted as below.
"This DEP specifies requirements and gives recommendations for the welding of fittings,
sleeves, branches or attachments onto pressurised carbon steel pipelines (X70 or lower
strength) and on-plot piping using SMAW welding only."

Why welding process is limited to SMAW only. In case of  small branch(1" dia x 4mm thk)  why can't  be  GTAW process  applied?

Query 2
For welding of set-on type branch weld in  new construction, hot pass will be deposited after completion of root pass for entire circumference, where as for same in hot tapping , the first pass in the throat of fillet shall not be extended beyond one electrode  run out length  before being reinforced by deposition of hot pass.  What could be the reason?

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