Secondary Reformer Return Line Weld Failure
Secondary Reformer Return Line Weld Failure
(OP)
Dear All,
We recently observed leakage from welding joint of our Secondary Reformer return line. Mentioned below are brief details of piping:
Service: Process Air
Operating Temp= 550-560 C
Operating pressure= 36 kg/cm2 g
Pipe Material: ASTM A 312 TP321 H
Radiography: 100 % at time of commissioning
Service Life: 3-4 years ( Seen multiple startups due to gas curtailment issues)

Apologies for not being able to share additional information other than crack's actual picture as since the line was at very high temperatures during weld repairs we could not perform any NDEs.
Request your expert opinion on below mentioned points:
- Possible damage mechanisms for an in-service defect considering piping metallurgy and operating conditions
- Impact of welding practices that could have resulted in issues in weld joint microstructure, which aggravated in years to come resulting in a crack. Any special precautions that should be undertaken for welding SS 321 H in high temperature service?
- Impact of multiple startups, possibly causing fatigue failure due to cyclic stresses. Please note their is an elbow downstream of the weld joint and its weld joint was found to be in satisfactory condition during visual inspection
- Recommended inspections for next available opportunity
Regards,
Ahsan
We recently observed leakage from welding joint of our Secondary Reformer return line. Mentioned below are brief details of piping:
Service: Process Air
Operating Temp= 550-560 C
Operating pressure= 36 kg/cm2 g
Pipe Material: ASTM A 312 TP321 H
Radiography: 100 % at time of commissioning
Service Life: 3-4 years ( Seen multiple startups due to gas curtailment issues)

Apologies for not being able to share additional information other than crack's actual picture as since the line was at very high temperatures during weld repairs we could not perform any NDEs.
Request your expert opinion on below mentioned points:
- Possible damage mechanisms for an in-service defect considering piping metallurgy and operating conditions
- Impact of welding practices that could have resulted in issues in weld joint microstructure, which aggravated in years to come resulting in a crack. Any special precautions that should be undertaken for welding SS 321 H in high temperature service?
- Impact of multiple startups, possibly causing fatigue failure due to cyclic stresses. Please note their is an elbow downstream of the weld joint and its weld joint was found to be in satisfactory condition during visual inspection
- Recommended inspections for next available opportunity
Regards,
Ahsan





RE: Secondary Reformer Return Line Weld Failure
RE: Secondary Reformer Return Line Weld Failure
The is line is supported with fixed spring supports. No significant vibrations have been reported on this line in the past.
RE: Secondary Reformer Return Line Weld Failure
The key is to determine the source of the bending stresses leading to fatigue crack initiation and propagation. I would re-inspect this weld on a regular basis and review operating process conditions.
RE: Secondary Reformer Return Line Weld Failure
In addition to the advises of metengr it may be of benefits to consider the following points:-
-What was the welding metallurgy at the time of fabrication? and after 4 years of service @ 550-560 C. Typically 321H and 347H alloys have a tendency to develop some sigma phase after prolonged exposure to the above temperature range.
-As we all know welds staring ferrite typically 8 FN or above have a tendency of converting to sigma phase upon prolonged exposure and sigma reduces ductility including the Creep Ductilty.
-321H and 347H piping in thick sections (3/4" and above) could undergo Stress Relaxation or reheat Cracking in service.There had been ample evidences of this in the industry.
-If you're talking about a secondary reformer( I'm assuming for Fertilizer Plant) this unit is of tremendous importance to the plant.Hence any Hit and Miss Assessment would not be advisable.
I'm not sure about your location , however if you call a good lab for In-Situ metallurgy and then manage to cut a BOAT-SAMPLE for Lab analysis, you'll have a through picture of the root causes of the failure and effective mitigation plan, in future.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
All provided answer are personal opinions or personal judgements only. It's not connected with any employers by any means.
RE: Secondary Reformer Return Line Weld Failure
you could perform metallographic cross sections and take pictures of the opened crack.
RE: Secondary Reformer Return Line Weld Failure
I second the comments that this looks to be driven by thermal induced bending stress. You should re-evaluate the pipe supports and thermal expansion conditions.
And inspect these welds regularly! This one and others in this same run.
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P.E. Metallurgy, Plymouth Tube
RE: Secondary Reformer Return Line Weld Failure
RE: Secondary Reformer Return Line Weld Failure