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Permalink Reply by John Carl Roat on November 4, 2010 at 9:26am

OGP Safety Alert
SUBSEA OXYARC CUTTING - RISK OF EXPLOSION
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Country: ---
Location: OFFSHORE : Specialist vessel eg diving, construction, survey
Incident Date: --- Time: ---
Type of Activity: Diving, Subsea, ROV
Type of Injury: Explosion / Burn
Function: Exploration
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Subsea Oxyarc cutting utilises an energising current supplied by a welding generator. There is a potential for leakage current to be present in the circuit if industry standard single pole isolation is used. This increases the potential for hydrogen gas to be produced as a product of electrolysis, these can become trapped in pockets inside the oxyarc torch and burning rod subsea. Hydrogen pockets introduce a risk of explosion when mixed with the oxygen.

What Went Wrong?:
Common Industry practice is to use a single pole isolation as a break in the circuit and this can result in leakage current still flowing through the Oxyarc torch and Rod while the diver believes it fully isolated.

Corrective Actions and Recommendations:
Double Isolations that perform a complete break in both poles of the circuit should be used between the surface generator and the diver. These will form a more effective and dependable isolation.

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safety alert number: 227
OGP Safety Alerts http://info.ogp.org.uk/safety/

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Permalink Reply by John Carl Roat on November 4, 2010 at 6:16pm

Dale I have been raising the issue for over 5 years in a public way and at least 5 years before that just asking quietly. You will note it is not the ADCI or IMCA that did anything about it but the oil companies.

The ADCI and IMCA just can't understand why no diver has has any faith in them. Believe the Coast Guard is getting the picture.

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