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Up Topic Welding Industry / Technical Discussions / API 5L X60 subsea pipeline welding
- - By Jayesh Date 09-13-2007 07:40
We need to weld a subsea pipeline of API 5L X 60 ,24" dia x  12.7 mm thk.
The service is in sour environment.
As company requirement, cellulosic SMAW electrodes are only permitted for root and hot pass.
Q1. which electrode can be used for fill and cap passes?(another condition is weld direction shall be downhill except for repairs.)

Test requirements:
1. Hardness : shall not exceed 248HV10
2.Impact: Charpy V notch at
+32 degree F  minimum average value 37 ft-lbs and minimum individual  value 30 ft -lbs
3.All weld metal tensile - yield strength shall excedd pipe SMYS by 10ksi  to a maximum of 30ksi. Maximum tensile stregth shall not exceed the pipe specified  UTS plus 30%.

Please advise the alternate options .
Thanks

Jayesh
Parent - - By dbigkahunna (****) Date 09-13-2007 14:42 Edited 09-13-2007 14:45
Are you sure the company requirement requires a cellulosic SMAW electrode for root and hot pass for sour service? One of the problems with sour service is delayed stress corrosion cracking which can be caused by using a cellulose coated electrode. This is me just raising the issue as I have not seen the job specs. My experience with high sour service is LH is required for the weld. However, if the spec is for a cellulose  rod, I would recommend a 5/32 E70+ ran straight keeping the travel speed between 8-12 IPM, a 5/32 Hot pass of E70+ reverse with a travel speed of 14-20 IPM. A maximum of 5 minutes between the bead and hot pass. A 3/16 hot fill of E70+, and fill and cap with 3/16 70+ all reverse.
I have set procedures with this fro X country pipeline and if the bead hand keeps the speed down and the starts and stops get feathered, you can put in a nice, clean even bead. You will want to have 4 welders at the bead and HP station and keep the grinding on the bead to a minimum. Use 1/4 wide disk. Just enough to knock the top off the weld and open it up. This keeps from pushing the bead in with the hot pass.
BABRT's  
Parent - - By Jayesh Date 09-15-2007 20:06
Cellulosic electrodes are only permitted in root and Hot passes. Low hydrogen  electrodes are to used with downhill progression.

Which is advisable low hydrogen electrode to weld 12.7 mm thick, 24 " API 5L X60 pipe and 6" dia API 5l x 42 pipe. Both are subsea lines to be welded on pipelay barge.
Parent - - By dbigkahunna (****) Date 09-15-2007 21:58
I am sorry but that goes against everything I know about welding in sour service. DH using LH is beyond hard. I could understand using LH UH for the bead and hot pass and DH out as this is a fairly common practice in sour service. The issue is delayed stress corrosion cracking and hydrogen embrittlement. By using the cellulose coated rod for the bead and hot pass, you will be causing a problem. And running LH downhill on this thin of pipe is bazaar. Slag out the wazzoo. But this is jmho, You need to talk to the project engineer or a welding engineer. I may be wrong but something is not right with this.
BABRT's
Parent - By CWI555 (*****) Date 09-16-2007 14:37 Edited 09-16-2007 14:39
Think I'd have to agree with you on this one. To me, a corrosive environment is "sour" when H2S is present. There is some disagreement on what "sour" is, as H2S is not the only possible source of corrosion based cracking.
So the first question I'd ask is what they are defining as sour.
"NACE TM0177 - laboratory testing of metals for resistance to sulfide stress cracking in H2S environments" calls the kind of cracking your speaking of sulfide stress cracking. (SSC)
While others call it hydrogen induced cracking (HIC), stress corrosion cracking (SCC).

Whatever you choose to call it, the concern remains, I learn something new every day, but I don't think 5P is the right answer on this.

Regards,
Gerald
Up Topic Welding Industry / Technical Discussions / API 5L X60 subsea pipeline welding

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