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AUGER Lifeboat No. 6

This incident occurred on FPS AUGER, a Tension Leg Platform (TLP) at Garden Banks Block 426 in the Gulf of Mexico, on June 30, 2019 and resulted in the untimely deaths of two personnel and injury to a third person. The incident occurred when Lifeboat 6 released from the fall cables during recovery after a routine launch and perceived U.S. Coast Guard requirements.

Our condolences go to the families of the two men that lost their lives during this incident.

The USCG formal investigation has been completed and endorsed by the District Commander, Coast Guard District Eight, but is still under review for Commandant actions at USCG Headquarters. The information on this page is associated with USCG Safety Alert 03-20 that was issued as a result of findings/concerns during the investigation, until such time that the Report of Investigation for this incident is made available to the public.


Use the tabs above to view the following information related to the safety alert:

1) Context/Summary;

2) Presentation and Videos detailing observations related to Safety Alert 03-20;

3) Graphical depictions and accompanying explanation detailing observations related to Safety Alert 03-20; and

4) U.S. Coast Guard recommendations from the safety alert.


 

Safety Alert Overview

Photo of damaged control cable with broken conduit and linerSafety Alert 03-20 was published on February 5, 2020, after observations and testing revealed that a damaged/compromised hook control cable could fail in a manner that would allow a hook to open, essentially defeating the safety features that are incorporated into the design of a lifeboat release gear system. Prior failures with these types of control cables were assumed to be 1) a seized cable or 2) a severed cable. Shell Offshore, Inc. and USCG investigation team members observed that another failure mode was possible, as summarized in the safety alert:

"During post-incident laboratory testing the Coast Guard observed that if a control cable, similar to that shown in the image above, is damaged all the way through the outer layers, leaving the traveling inner member exposed, forces applied directly on the separated outer layers can cause the traveling inner member to pull on each of its ends. As the separated outer layers pull apart, the cable’s end rod at the hook can move, which in turn can rotate the locking shaft inside the hook. If the locking shaft rotates enough, the hook can release, even without an operator touching the release handle or overriding the interlocks. The Coast Guard has no indication that a damaged control cable alone can cause a hook to release or open on-load. However, the Coast Guard believes that damaged control cables pose a significant safety risk and should be replaced before attempting to launch a boat that incorporates control cables into the on-load release capability of a hook release system."


Presentation and Videos

Safety Alert 03-20 and the observations from CG-testing were presented during the September 30, 2020 National Offshore Safety Advisory Committee (NOSAC) meeting (video teleconference). The presentation and individual videos (mp4 format) are available below. Note that the presentation is a large file size (30mb), as the videos are embedded within the presentation, but can also be downloaded separately. Microsoft PowerPoint or a compatible viewer will be needed to view the presentation.

  • Introductory Video: Separated Cable Conduit (2.5mb)
    • This video shows what happens if the conduit is extended between the fixed connections at the release unit and the hook. See the graphics below for details on the various control cable conditions and the related effects on the hook.
  • Video #2: Subsequent Cycling (after conduit/liner separation; 5.6mb)
    • Testing video 2 documents the observations of open and close cycling of the release unit after the control cable conduit (and liner) have separated.
  • Video #3: Effect of an Increasing Load (12.3mb)
    • Testing video 3 documents the effect of additional loading to a hook with the locking shaft in a partially-closed (i.e., almost-open) position due to a compromised control cable/separated conduit. As shown in the video, additional load can force the locking shaft to open and release the hook, but it has to be very close to the open position to be forced open. USCG testing showed that if the compromised control cable leaves the locking shaft in a position closer to the fully closed position, the locking shaft will not be forced open under increasing load.

 

Discussion of Observations and Findings

Please note that testing was conducted on Schat-Harding LHR-series release gear. As such, the descriptions of components and operation relate to that make and series of release gear. Other manufacturer's release gear designs, functions and component terminology could vary, but the ​control cable is the area of focus in these findings and could pose a similar vulnerability in other designs.

Generally, the system works in the following manner:
When closing or resetting a hook, an operator positioned at the release unit pulls up on the safety lock and pushes forward on the control handle, locking it into place. Consequently, the end rod on the hook extends. This extension causes the hook's locking shaft to rotate to the closed or locked position. When opening the hook, the opposite actions and forces apply.

A previously unknown vulnerability in the system was identified during the course of the investigation that was referenced in Safety Alert 03-20: if all three layers of the conduit of a hook cable separate or break during a reset, the locking shaft may not return to the fully-closed position. Rather, the locking shaft may come to rest at an "almost-open" position (see the various positions on the following graphics). In such a position, the hooks can support the weight of the boat and its occupants during retrieval. However, testing has revealed that an additional load can cause the locking shaft to rotate to the open position, releasing the hook.


Release Mechanism Arrangement

A typical dual-fall/hook release mechanism is comprised of two hooks, a hook release unit (located inside the lifeboat adjacent to the helm), a hydrostat unit, and three control (push-pull) cables. One control cable connects the hook release unit to the aft hook, the second control cable connects the release unit to the forward hook, and the third control cable connects the release unit to the hydrostat unit.

Graphic depicting a typical dual-fall lifeboat release gear arrangement; Click to enlarge


Closed/Reset PositionGraphic depicting hook and control cable positions in the closed/reset condition; Click to enlarge

This graphic shows the positions of the control cable and the hook when the release unit handle is in the closed, or reset, position.
 


Open/Released PositionGraphic depicting hook and control cable positions in the open/released condition; Click to enlarge

This graphic depicts the actions of the control cable and the hook when the release unit handle is moved into the open, or released, position.


Graphic depicting hook and control cable positions: closed w/damaged conduit; Click to enlargeClosed/Reset Position with 
compromised cover and steel layers

With the conduit cover and steel reinforcement compromised but the liner still intact, the system continues to function. In this condition, the liner is subjected to compression and tension forces that correspond to the open and close motions of the release handle that is transmitted through the control cable.


Graphic depicting hook and control cable positions: closed w/separated conduit; Click to enlargeClosed/Reset Position with 
separated conduit (broken liner)

The conduit tends to separate after the liner breaks. This separation causes the conduit to lengthen and results in the inner member moving the locking shaft arm toward the open position. During testing, it was observed that the:

  • liner separated during the closing motion of the release handle (the liner is under tension during this motion);
  • locking shaft stopped rotating toward closed when the liner separated and remained in a partially-closed position; and
  • conduit separated during the remaining closing action of the release handle (less resistance require to separate the conduit than to rotate the locking shaft).

Graphic depicting the effects of increasing load w/separated conduit; Click to enlargeEffects of Increasing Load with
a separated conduit

Testing confirmed that the locking shaft can be in a partially-closed position that will support the weight of the boat and occupants, but can rotate to the open position with an increasing load/additional weight (such as the additional load that can be imparted to the hooks as a boat is pulled against the davit bumpers).


Graphic depicting hook and control cable positions: cycled after conduit separation; Click to enlargeClose/Reset Position with
separated conduit after additional cycling

Additional cycling (opening and closing) of the release handle during testing showed that the cable conduit would separate before any rotation was transferred to the locking shaft. This condition leaves the hook in an open position that will not support any weight.


 

USCG Recommendations

Based on these observations, the USCG strongly recommends the following in Safety Alert 03-20:

  • Conduct thorough inspections of control cables between the release handle station and release hooks;
    • Inspect any other similar cables communicating between the release station and the hydrostatic interlock, if installed, and
    • Look for current damage and for potential hazards or other conditions that might compromise the cables in the future;
  • Photo showing an in-service (at the time it was taken) control cable with a compromised conduit (outer layers)Replace cables that show signs of wear or damage to any layers (photo to the right shows a release mechanism control cable that was in service (at the time the photo was taken) with a compromised conduit);
  • Implement an inspection regime that allows for cable damage to be identified and replace cables identified to need replacement in a timely manner.
  • Consult the lifeboat and release mechanism operations manual(s) prior to conducting launch and recovery drills.

The safety alert also noted that:

  • Photo of a Palfinger Marine Safety pins (photo to the right shows a Palfinger Marine "Training Lock" installed in a LHR-series hook) can be used during drills to prevent the hook-locking shaft from rotating, when they are approved as part of the release mechanism;
  • Although safety pins may provide an extra level of safety during drills and training, operators should ensure that lifeboats are stowed in the "ready to launch" condition without safety pins in place; and
  • Operators should ensure that lifeboat crews understand that safety pins will prevent a lifeboat from releasing from the fall wires during a real emergency if they are not removed after routine training evolutions or maintenance.