Materials & Welding

Dear All, We would appreciate your technical opinion regarding a leakage issue observed in stainless steel piping after several months of operation. Background: Line sizes: 2" and 6" 361L Stainless Steel (Schedule 10S) NDT coverage: 10% completed as per project requirements Hydrostatic test: Successfully passed without any leakage Records related to line preservation after reinstatement are not available, as the system was under the control of the Pre-Commissioning and Commissioning teams The line has been in service for approximately 4 months Issue: Leakage has recently been observed at several locations, including: Weld joints Pipe body/base material   Considering that the line successfully passed hydrotesting and has been operating for several months before the leakage occurred ,    Could you please share your views on the potential reasons Thank you in advance for your valuable inputs. Bes...

Hi Karupa samy, Yes — the pattern you described strongly suggests a post-hydrotest localized corrosion problem rather than a simple pressure-test failure, especially because the line held during hydrotest and leaked only after months in service. Most likely reasons Residual hydrotest water left inside the line. Stainless steel systems can fail weeks or months later if test water is not fully drained and dried, especially in low points, dead legs, and crevices. Chloride pitting / crevice corrosion. Chlorides in hydrotest water, cleaning water, or trapped contamination can break down the passive film and create pinhole leaks, often first seen at welds and local stagnation points. MIC after stagnant water retention. If untreated/raw water remained trapped after hydrotest and the line sat idle before/after commission...

The Primary Cause for failure shall be Chloride-Induced Stress Corrosion Cracking (SCC). Contributing Factors:   - Post-Hydrotest Preservation: Evidence suggests improper or missing preservation procedures following the hydrotest.   - Weld Integrity: Residual stresses remaining in the welds.   - Contamination: Likely chloride contamination during or after testing. Required Preventive Measures:   - Water Quality: Utilize low-chloride hydrotest water, ideally maintaining levels <50 ppm Cl⁻.   - Post-Test Protocol: Ensure immediate draining followed by thorough drying using air blowing or nitrogen.   - Surface Treatment: Apply a formal passivation treatment and ensure all weld heat tint is removed via pickling and passivation.   - Material Specifications: Evaluate the use of SCC-resistant materials, such as Duplex SS, for critical service components.   - Documentation: Maintain strict preservation records for all future assets. Regards,   ...

I agree with the MIC process as the main failure mechanism.  M Nunes Senior Materials Engineer  On Sat, 27 Jun 2026, 3:19 am Karuppa Samy, < samyqc08@gmail.com > wrote: Dear Sridhar, Thank you for your kind response and valuable inputs on this matter. We are currently analyzing the root cause of the issue, and your insights will be highly beneficial to our efforts. We truly appreciate the time you have taken to share your thoughts with us. Thank you once again for your support. Regards, K. Karuppasamy On Fri, Jun 26, 2026 at 9:39 PM sridhar cn < sridharcn305@gmail.com > wrote: Dear Mr. Karuppasamy. Please refer to the issues you have faced in your SS 316L pipes both on the weld joints and base pipe. Since the media is 'utility water', and the leakage occurred after 4 months in service, the probable...

Dear all, Kindly advise on the appropriate repair method for the corroded pipe spools. Specifically, please confirm whether the following repair options are acceptable: Can the corroded bottom portion of the pipe spool be cut out and replaced with a new section of the same material, using the approved WPS and qualified welding procedure? Alternatively, is it acceptable to insert a pipe of the same diameter inside the corroded section and perform internal fillet welds as a repair method? As I am not a welding specialist, I would appreciate your technical guidance on the most suitable repair approach. Please also provide a detailed repair procedure, including inspection and testing requirements, so that the repaired spool can be accepted and handed over to the client. Since this project is located at a major airport, the repair method must comply with the international procedures, and relevant codes and standards. Warm Rega...

 Dear Mr. Sharafudden, You have not mentioned the type of material used, its thickness, application, Standards followed and other  details.  In our view,  repair should comply with internationally accepted practices such as ASME B31.3  (Process Piping). Cut out the defective portion and replace it with a new pipe. Inserting a new pipe within the existing pipe and fillet welding is  not a good idea, as it may create stress concentration.  Also, cannot be accepted as a  permanent  repair process under the code. Hence, a.    Identify and mark the defective areas by VT, and  UT (if possible)  for pipe  thickness measurement. b.   If pitting extends beyond the visible leak, extend the cut until only unaffected material remains. c.  Fabricate a new replacement section after PMI, and use a suitable welding process. d. ...