Hydrogen compressor snubber vessel nozzle welding issues
Hydrogen compressor snubber vessel nozzle welding issues
(OP)
We are seeing repeated failures near the toe of the SS nozzle weld in Stainless snubber vessels in hydrogen service lately. The vessel shell is SS 316H while the small bore nozzle material is 1" SS 316L schedule 40S as in the data report. The nozzle is only about 6-8" long. The recent crack is at the toe of the weld in the pipe segment closer to vessel. This failure occurred within a few hours of starting up. Roughly a week prior to this event, we had another failure on this sch 40 nozzle but in that case the failure was near the toe of the fillet weld closer to the Class 1500 socket weld flange side. There are lot of vibration issues with the compressor as well which we are trying to mitigate. To strengthen the nozzle we have now used sch 160 piping and replaced with weld neck flange to bring the critical compressor back up again. What could be the possible cause for this failure to recur? The OEM is troubleshooting his design but we want to get to the root cause and not just have a temporary fix.





RE: Hydrogen compressor snubber vessel nozzle welding issues
RE: Hydrogen compressor snubber vessel nozzle welding issues
Regards
r6155
RE: Hydrogen compressor snubber vessel nozzle welding issues
RE: Hydrogen compressor snubber vessel nozzle welding issues
Regards
r6155
RE: Hydrogen compressor snubber vessel nozzle welding issues
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Hydrogen compressor snubber vessel nozzle welding issues
Option (i) is more difficult, requiring isolation of the compressor (expensive and difficult), or changing to a unit that causes less vibration (ditto).
Option (ii) has several possibilities that are fairly easy and inexpensive to implement (best, good, not so much):
(1) Attach brackets to stop the bending vibration that is driving the crack;
(2) Blend the weld toe. I'll wager the crack runs from the toe into the pipe base metal, so increasing the weld size is useless and in fact could make things worse;
(3) Increase the pipe wall thickness. This has limited effectiveness as you have already learned. This kind of fatigue is strain-controlled.
"Everyone is entitled to their own opinions, but they are not entitled to their own facts."
RE: Hydrogen compressor snubber vessel nozzle welding issues
Be careful, gong heavier will significantly increase the stress on the welds. IT may not help at all.
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P.E. Metallurgy, Plymouth Tube