Case Study: Mixed Sour Gas Manifold-Weld-O-Let Cracks

Problem Summary

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Anomaly Description:
Axial orientated cracks were found in one butt weld and one fillet weld on a 2” pipe with RT on the U300 Mixing Manifold.

Root causes:
Probable cause of the defects is availability of wet chlorides causing stainless steel chloride cracking

Integrity concerns:
There was a high risk for the further growing of the known defects and it is not improbable that further defects may develop.

Technical Details

Service:
Line Diameter:
Design Pressure:
Operating Pressure:
Design Temperature:
Operating Temperature:
Material:
Line Class:
Sour Gas
20 to2”
85 BAR
66.7 BAR
190°C
95°C
SA-358
900P21
On-Line Leak Sealing Case Study
On-Line Leak Sealing Case Study

The Beruseal Solution

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Clamp Design:
An analysis of an on-line leak sealing clamp for a sour gas line was made for the cracked weld-o-let. The design was to firstly seal the whole area to prevent leakage without putting any additional stress into the already cracked weld, and secondly, support the drain should the weld crack through completely. The Beruseal design department designed a strong-back clamp and used FEA (Finite element analyses) technology to determine stress levels that would be imposed on the clamp in the event of catastrophic failure of the weld. The design was made according to ASME PCC2 and underwent stringent analysis by Client engineering house Department and found to be acceptable.

Seal:
The on-line leak sealing clamp was a multi medium system where the use of PTFE based compound was inject into a precut groove around the clamp and bores of the large diameter pipe to create an outer seal. Surface preparation was made to the 20” line and the inside of the clamp to ensure adhesiveness of the resin, the clamp was then filled with a two part high temperature epoxy resin. The resin is resistant to hydrocarbon attack and highly adhesive which also acted as additional support for the cracked weld.

On-Line Leak Sealing Case Study - Mechanical Design
On-Line Leak Sealing Engineering Design
On-Line Leak Sealing Case Study

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