Large through-wall defect on a 36” Sulphur Degassing Unit

Problem Summary

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Anomaly Description:
Visual inspection found through-wall damage on a section of the line. Damage was located near tie-in 6” nozzle attachment weld of exhaust gasses line from Sulfur Degassing Unit. UT scanning was performed to determine the condition of the area of damage and 6” nozzle. In accordance with inspection results, wall residual thickness in the area of damage was ≈4.7mm, in the adjacent areas. Т-min was 5.0mm, nominal thickness was 7.9 mm. Wall residual thickness of 6” nozzle was 5.8mm, nominal thickness was 7.11 mm.

Root causes:
The probable cause of this damage was occurrence of wet acid corrosion mechanism due to missing of heat tracing on 6” nozzle tie-in of exhaust gasses line from Sulfur Degassing Unit.

Integrity concerns:
The length of through wall damage was ≈200mm and consists approximately ⅓ of nozzle attachment weld length, and may result in catastrophic failure of the nozzle.

Technical Details

Service:
Line Diameter:
Design Pressure:
Operating Pressure:
Design Temperature:
Operating Temperature:
Material:
Line Class:
Technical AirR H2S
36” to 6”
14.5 BAR
1 BAR
100°C
90°C
A671 – CC60
On-Line Leak Sealing Repair Case Study
On-Line Leak Sealing Case Study

The Beruseal Solution

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Clamp Design:
A T-clamp was designed according to the ASME PCC2 specifications with a strong back system to hold the 6” Nozzle in place in the case of catastrophic failure. In the process of the clamp design a lead patch was installed over the hole in the pipe and set down with BELZONA1111 to stop the H2S leak while the clamp is being manufactured.

Seal:
The 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.

On-Line Leak Sealing Case Study
On-Line Leak Sealing Case Study
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