Diving Bell Bailout Manifold Failure

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Questions and Answers

What was the likely sequence of events that led to the lifeboat detachment?

The master link handles, being incorrectly oriented, impacted the hook safety latch, releasing the hooks; the lifeboat then swung, releasing the painters. (correct)
The lifeboat was lowered, the falls slacked, and both master links disconnected simultaneously, after which the crew lost control of the lifeboat.
The lifeboat swung 180 degrees, causing the aft painter to disconnect first, which was followed by the forward master link releasing the hooks.
The forward painter disconnected first, followed by the aft painter, then the master links, leading to the lifeboat drifting away.

What primary factor contributed to the failure of the bailout manifold assembly's nuts?

Lateral force introduced by inappropriate securing mechanisms likely led to stress corrosion cracking and material ingress, causing internal corrosion over time. (correct)
The nuts were made from a copper alloy CW614N, which is known to resist stress corrosion cracking and dezincification under pressure.
The securing strap holding the bottles together was too tight, causing the nuts to fail.
The system was over-pressurized beyond its design limits, causing immediate failure of the nuts.

Why did the lifting trunnion cover plate fall off, and what erroneous assumption contributed to the problem?

The cover plate was not properly welded and the assumption that excessive force would not be applied during the lift.
The lifting trunnion was struck by equipment, causing the bolts to shear and the cover plate to fall off due to over-tightening of the securing screws.
The lifting trunnion was manufactured incorrectly, causing the cover plate to detach under normal operating conditions.
The lifting trunnion cover plate fell off because the securing screws were not tightened enough and the assumption that sideways forces were introduced in the center of the lug cover. (correct)

What critical oversight led to a crew member experiencing burns during the cleaning of grouting equipment?

<p>The Safety Data Sheet lacked information regarding the hazard of grout dust mixing with water and becoming corrosive, resulting in insufficient risk mitigation. (A)</p> Signup and view all the answers

What was the primary cause of the hose contamination incident, and what action could have prevented it?

<p>The hose previously contained a cooling agent (Antifrogen) and was not properly flushed; flushing the hose after each use and proper storage could have prevented the incident. (C)</p> Signup and view all the answers

Flashcards

Bailout Manifold Failure

Failure of a diving bell bailout manifold due to stress corrosion cracking and material ingress, leading to internal corrosion.

Lifeboat Master Link Release

Master links disconnected due to handles incorrectly orientated towards the hook latch, causing unintentional release.

Lifting Trunnion Bolt Shear

Sheared bolts on a lifting trunnion cover plate, due to incorrect assessment of side forces, causing the plate to fall.

Hose Contamination Incident

Hose containing residual cooling agent (Antifrogen) caused a reaction when used, due to improper flushing and storage after previous use.

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Grouting Dust Chemical Burn

Burns caused by a chemical reaction between grouting dust and water, due to lack of information on corrosivity in the Safety Data Sheet.

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Study Notes

Bailout Manifold Failure

A diving bell bailout manifold failed due to pressure while no divers were in the bell
The bell was being readied for diving, and the bell trunk was isolated at 31 msw, with the system at 32 msw
A dive supervisor detected a gas rush and visible misting via the bell internal camera
Investigation found four pieces of a failed nut from the bailout manifold assembly
Diving operations were halted so both bells could be surfaced and bailouts inspected
Uneven rubber boots on each cylinder likely stressed one side when moved
The securing strap holding the bottles was loose
This bailout manifold had a less robust design compared to others
Forensic testing suggested lateral force from incorrect securing caused stress corrosion cracking
Material ingress led to internal corrosion over time
The specific bailout manifold assemblies were replaced with more robust versions
Increased awareness of bailout alignment, integrity, and boot maintenance is needed
Nuts were made from copper alloy CW614N, prone to stress corrosion cracking and dezincification

Master Links Came Free from Lifeboat Release Hooks, Releasing the Lifeboat

A vessel was waiting on weather and decided to do annual checks, including a lifeboat launch
The lifeboat launch was unmanned
The fore and aft master links connecting the lifeboat to its falls became disconnected
No injuries occurred, but there was slight damage to the lifeboat
The lifeboat was lowered, and falls slacked as expected
Shortly after, the forward master link disconnected, with crew monitoring the movements
The aft master link disconnected while assessing the forward link
Incorrect orientation of master link handles faced inboard towards the hook latch and lifeboat
Movement of the handles impacted and released the hook safety latch

Three Bolts Sheared on a Lifting Trunnion

After installing an offshore renewables Transition Piece (TP), the crew found the cover plate of the lifting trunnion had fallen off
The cover plate weighed 44kg and fell about 0.5m from the lifting trunnion to the hatch cover
Three securing screws were nearby, sheared
The cover plate was secured by three screws
Damage was noted on a survey beam and a GNSS positioning equipment antenna
The method of verifying the screws securing the cover plate to the lifting trunnions was incorrect
The side forces on the cover plate exceeded what the screws could handle
A permit to work was used with a toolbox talk referencing the Job Hazard Analysis and last-minute risk assessment, and the installation task plan was followed
Welding the cover plates to the lifting trunnions can mitigate the risk

Hose Management and Chemicals: Crew Person Felt Ill

While filling a bucket from a hose, a person was affected by the contents
The individual started coughing as the bucket was being filled so was told to get fresh air
Upon returning that individual still felt unwell
Yellow/brown liquid was observed in the bucket, indicating it was not water
Gloves were not worn due to the assumption it was only water
The hose likely contained stagnant water and cooling medium, as it had been coiled in a cupboard for two years without dripping dry
The hose was previously used with Antifrogen (cooling agent) in July 2019 but not flushed properly afterward
The hose was disposed of and two new hoses were prepared
Hoses should be flushed and left to dry after use

Chemical Reaction: Person Injured During Grouting Operations

After grouting an offshore wind farm transition piece, a team began cleaning equipment with high-pressure water jets
A team member received first-degree burns to the knees and left calf, with minor irritation elsewhere
The injured person had grouting dust on their coveralls and got soaked with water, creating a corrosive solution
The Safety Data Sheet lacked information on the hazard of grout dust mixing with water
The lack of hazard identification resulted in no risk mitigation measures in the risk assessment