Fall Through Deck Plate at Bldg 983 Z-Machine High Bay by ezw15872

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									Fall Through Deck Plate at Bldg 983
        Z-Machine High Bay
        NA—SS-SNL-1000-2007-0021

hinge




             Trapezoidal deck plate.
                                       Veronica Martinez
                                       Sandia Site Office
What happened?

Monday, December 3, 2007


   A worker stepped on one of the trapezoidal deck
    plates to reach for a damaged rod nearby....
   the trapezoidal deck plate flipped and fell into the
    tank……
   the worker then fell into the opening. Luckily he
    was able to grab onto a nearby flexible cord and fell
    approximately 4 feet……though the potential fall
    distance was 10 feet to the first platform.
What is Z-Machine?
   Z-Machine is a radially configured pulsed power
   accelerator consisting of 36 modules arranged
   around a central experiment vacuum chamber.


                                   Center
              Water Section
                                   Section/Vacuum
Oil Section



  20 ft



                 108 ft diameter
Background……
July 27, 2006 - late September 2007
Z-Machine was refurbished.


                                      The old
                                      equipment and
                                      components
                                      within the tank
                                      were completely
                                      removed from the
                                      tank!
Background/History
July 27, 2006 - late September 2007
Z-Machine was refurbished.


                                      The oil/water
                                      barrier wall
                                      starting to be
                                      installed!
Background/History
July 27, 2006 - late September 2007
Z-Machine was refurbished.


                                      The water
                                      section and the
                                      platforms
                                      starting to be
                                      installed.
                                      Notice the
                                      trapezoidal
                                      plates!
Critical Decision 4 was granted on September 24, 2007.
Normal operations commenced.

                                        The top of the
                                        machine is covered
                                        by deck plates for
                                        walking and
                                        working.

                                        In 18 areas, around
                                        the center of the
                                        machine, are
                                        trapezoidal deck
                                        plates that are
                                        hinged for access to
                                        the water tank for
                                        component removal
                                        if necessary
Normal operation of the trapezoidal plate being lifted
open by its’ hinge.
                                    33.1”

Dimensions:
The hinged plates were
originally designed to facilitate
removal of large components
from the water section.

                                            49.5”
6 of the 18 trapezoidal plates
had their hinges removed
where structure or utilities
prevented them from being
completely raised.




                                    15.5”
           Z-Machine – Water Section




On the day of the incident, the water had been drained from the tank.
       Worker sustained minor injuries, a small
        laceration on the wrist and some minor
        swelling

           Categorized
           Significant Category 3
           10(3) Near miss

Injuries could have been much more significant !!!!
Series of events….
   Sept 20, 2007 a worker noticed that one of the plates did not
    fit properly.
        The A/E firm was contacted about the problem. There was
         not a recognition that other plates could become loose.
   Nov 21, 2007 manager inspected the other deck plates and
    they appeared to be in place and holding up well.
   Nov 30, 2007 the hinge pin material was received from the
    A/E.
   Nov 30,2007 Z-Machine fired a shot.
   Nov 30, 2007 The suspect plate was seen loose by a person
    walking through the area. The person was not part of the
    Operations crew and assumed they would address the issue.
   December 3, 2007 11:45 am Worker fell into tank!
Root Cause

   Removal of the hinge pins.

   The decision was made during the installation of the deck
    with the intent of improving the safety of dive operation.

    The decision did not take into account system issues with
    the potential for the plates to fall due to movement of the
    deck was not recognized.
Contributing Cause

   The workmanship of the decking appears to be less than
    adequate. The decking is showing gaps both vertical and
    horizontal that were not evident after initial installation.

   After each shot there is a post-shot assessment of the area
    performed for emergency conditions.
        However, there is no systematic walk-down of the
         walking/working surfaces looking for worker hazards.
    Lessons Learned:
•   Prior to CD-4, numerous readiness activities took place. A Pulsed
    Power Class III review was performed. Four hazard focus areas were
    selected to be reviewed/walked-down. One of focus areas was dive
    operations.
     •   The focus was testing each of the sub-systems, interfaces
         between the various systems of the machine and the associated
         hazards.
•   Focus was given to the diving hazard. Divers were expected to dive
    within the water tank. The focus was to minimize that hazard.
          The design of the floor structure (trapezoidal deck plates) was
          changed. One hazard was minimized while another hazard was
          introduced.
The End

   Questions?

								
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