Incident Date:

11/05/2010

Summary:

The incident occurred while breaking down bailer sections of a dry environment ( Auger/Helix) type cleaner when trapped pressure escaped resulting in personnel being sprayed with moist debris. Although the Cleaner has breather holes on both ends of the bailer section the pressure had become compartmentalised and was being held in pockets by the packed up debris.

Incident consequences (potential or actual):

Injury

Cause of accident or incident:

Release of a harmful substance

Activity Location:

Fixed Installation

Activity Type:

Well services / intervention

Description:

Description of what happened: Following Run 2 of the Cleaning Tool string, there were positive indications on surface that the 3 Bailer Sections had successfully been filled. (An increase in tool weight and visual indication) The tool string was then rigged down sectional, splitting the tractor and cleaner vertically and laying both sections down on the Cat Walk. At that point the Risk Assessment specified that the personnel don the agreed level of PPE for the task. The bottom nose of the Cleaner was then broken off exposing the chamber to atmospheric pressure, visual inspection of the debris in that section showed there was no pressure evident thus personnel removed their secondary PPE. (slick suits, rubber gauntlet style gloves, rubber Boots, and face shield) and reverted to standard PPE used offshore. The debris recovered was confirmed moist debris with a “play dough” like consistency. The personnel then moved on to break off the bottom bailer section, whilst unscrewing the bailer section a trapped pocket of gas then escaped and blew debris in a 360° pattern over personnel and equipment. Operations at that point were ceased.

Specific Equipment:

Dry environment cleaner

Lessons Learnt:

Until all bailer sections are empty assume there can be trapped pressure.

Secondary PPE (slick suits, rubber gauntlet style gloves, rubber Boots, and face shield) worn until bailer sections are empty.

Bailer sections have been modified to reduce the risk of pressure pockets.

Risk assessments for this task have been modified to cover this new found risk.

Task Description:

The tool string was rigged down sectionally, splitting the tractor and cleaner vertically and laying both sections down on the Cat Walk.  At that point the Risk Assessment specified that the personnel don the agreed level of PPE for the task. 
The personnel then moved on to break off the bottom bailer section, whilst unscrewing the bailer section  a trapped pocket of gas then escaped and blew debris in a 360° pattern over personnel and equipment.   

Recommendations:

Recommended practices to follow when breaking apart Dry Environment bailer sections:

Barrier off the area.

Wear the required PPE at all times as agreed by the risk assessment.

Until all bailer sections are emptied assume there can be pressure pockets.

Reduce number of personnel in the immediate area.

Only relevant personnel should be present when dismantling the equipment.

Before disassembling the bailer sections tap them with a rubber mallet from top to bottom this will assist trapped pressure to percolate.

Drape weighted sand bags over the connections whilst unscrewing

Pour water onto vent holes in order that get air bubbles reveal if trapped pressure is present.

Where possible keep clear of vent holes in case pressure suddenly releases.

Be alert for unusual sounds such as hissing and popping during disassembly of components as this indicates trapped pressure.

Unscrew connections slowly and wiggle the connection to allow for pressure dissipation

If trapped pressure is observed, leave tool to naturally dissipate the pressure.

Contact Details:

Martin Watt&

Figures:

Usage details:

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