Well, we had a serious problem, a weld corroded on a High Pressure Gas Pipe Line to Leak, the corrosion was on the bottom part of the weld inside the Pipe, Imagine a rough area of about 2 cm X 2 cm which is directly centered above the root of the weld which is totally corroded till Leak, We re-viewed the Radiographic Film and no deffect at all in this portion, the root pass is nearly of the same hight with no indication of any depression that may make a trap, also the gas contains a high precent of water cut with salts, but thickness measurements on other parts show that the Line it totally protected and no - any - corrosion on other areas, - the line is perfect except for this severly corroded part - we are going to re-radiograph the whole Line - but what about other lines ????????????
DO ANY ONE HAVE ANY IDEA OF WHAT DID MAKE THIS HAPPEN AND HOW COULD WE AVOID IT ?
sounds like you may have excessive bead causing turbulence at that area. If the bead was put in SMAW B31.3 UH, then you can bet there is plenty of bead sticking up. The bead causes erosion which causes a trap for water, which accelerates the corrosion, and the erosion continues. This happens frequently in wet and high H2S pipelines except you can get HIC with the erosion/corrosion.
Look downstream of where the line changes elevation or where the flow would be interrupted. Ells, tees and reducers. I would recommend UT rather than RT especially if the line is operating. I would get corrosion people looking at this after you determine the extent of the corrosion.
What size is the line?
BABRT's
I'm having a little difficulty with the idea that the radiograph of this particular weld gives no indication of trouble yet the decision is to radiogaph everything else.
What type of material ? What about the welding procedure does it meet requirements to max. hardness acc. to NACE
which are max. 248 HV10 or 22 Rockwell C.
If the HAZ are more than the described above there can occour corrosion in the HAZ and adjacent areas.
best regards
Jan Jensen
Denmark
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