Crude Oil leaks on numerous 4″ Ball Valves

Client: Esso Exploration Angola

Problem Summary

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Anomaly Description:
Numerous 4” ball drain valves situated underneath an HP oil separator vessel sustained leaks on the neck of the valve body.

Root causes:
The current cause of the leak is not known. NDT inspection was performed and found that there was no internal corrosion. This leads us to believe that holes in the valve body were due to manufacturing defects.

Integrity concerns:
Further deterioration of the defect could result in possible shutdown of equipment
Due to the unknown cause of the defect, integrity of the piping is a concern. Loss of containment of hydrocarbon content poses a possible safety and environmental risk.

Technical Details

Line Size:
Design Pressure:
Operating Pressure:
Design Temperature:
Operating Temperature:
Material:
Line Class:
4″
21 BAR
16 BAR
110°C
110°C
Cast Carbon Steel, ASTM A216 GR WCB
300
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The Beruseal Solution

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Clamp Design:
A straight-line flange clamp was designed according to ASME VIII Div 1 to enclose the entire body of the ball valve. An integrated strongback system was designed with the enclosure to maintain the structural integrity of the valve (due to the unknown causes of the leak). The strongback also acted as a restraint to keep the enclosure in the vertical position. An FEA analysis was performed on the strongback to analyse total circumferential failure of the valve body.

Seal:
A successful seal was obtained by injecting a PTFE based sealant into a sealing groove that runs throughout the seem and bores of the enclosure. The groove was designed to allow the flow of sealant into the flange gap and bolt holes to eliminate future leaks due to gasket failure.

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