description on the 10 th october 2010 at 22:30hrs, an axle retaining block weighing 2lbs fell 51ft...
TRANSCRIPT
Description
On the 10th October 2010 at 22:30hrs, an axle retaining block weighing 2lbs fell 51ft to the rig floor from the Pipe Racking System (PRS3i) in the derrick. It came to rest in
the mouse hole area within the “Red Zone”.
There was no harm to personnel although three floormen were standing 3 to 4m away, outside of the ”Red Zone”.
Photo taken from the stbd side of the rig floor, looking port. It shows the Pipe Racking System (PRS) with its upper & lower grabs retracted, facing aft
The axle retainer fell from this assembly. (Note in the photo, it is shown at the upper end of its travel – it can move up/down the track and was 15m up when the retainer fell..
PRS3i Upper Carriage
Close up of closed roller arms with the retainer block missing.
Retainer Block
Grip Jaws
Stop
Axle Retainer
Roller Arms
Photo of upper carriage on PRS3i with jaws and rollers open. Axle retainers on top of roller arms which also prevent the roller arms extending beyond the grip jaws
The job was stopped and a Time Out for Safety held with a dropped object inspection of the PRS taking place. Of the two securing bolts for the dropped retainer block, one appears to have backed out while the other was sheared, possibly due to a clash between the partially secured block and the roller arm itself (not the stop) overloading the fastener thus allowing the block to fall.
Red Zone & Personnel Positions
Position of Roughneck
#2
Position of Roughneck
#3
Impact
Position of PRS
Resting Place
Position of Roughneck
#1
Incident ClassificationFrom the outset the incident was investigated and reported as a high potential, but on completion of the incident investigation that classification was down graded.
•The reasons for this are: •The dropped axle retainer fell from the PRS3i which is within the “Red Zone”.
NOTE: The introduction and use of the “Red Zone” was a requirement of the Norwegian PSA (Based on OLF/NR-081) which was introduced in 2009, prior to the rig going to work in Norway. The Safety benefits of ensuring people are not working below moving equipment that has the potential to drop objects was seen as very positive and a conscious decision was made to continue the practice when the rig returned to work in the UK.
•As per established rig practice, nobody was in the “Red Zone” while the remotely operated equipment was being used therefore it was not possible for a person to be directly hit by the dropped object falling vertically from its source. There is the potential for the retainer to have deflected off other equipment or bounced back off the rig floor & struck an individual but it is likely that the majority of the energy would have been dissipated & injury potential decreased accordingly. This reduces the potential from “Single Fatality” (P2) to “Lost Time Injury” (P3).
Findings / Actions• The risk of an issue with the roller arm and retaining block had been
identified by Varco in 1999 & Product Bulletin PRS-98-01 was issued with the recommendation to fit a revised design that eliminates the overloading of the fasteners.
• The Varco Product Bulletin had not been identified by the rig owner, therefore had the revised design had not been installed. A “One Page Flyer” was prepared & distributed to other rigs with similar equipment.
• All of the Technical Bulletins for all of the equipment on the rig which have the potential for dropped objects causing harm to people are currently being reviewed & a detailed review of the structure & execution of the rig maintenance system (vs OEM recommendations) will also be undertaken.
Varco Bulletin