USS GRUNION After Battery Room Hatch Hatch Dog #1 Locking Rod Yoke #1 Locking Rod Locking Wheel Locking Rod Hatch Dog #2 Yoke #2 Yoke #3 Hatch Dog #3 USS COD
USS GRUNION After Battery Room Hatch Hatch Dog #1 Yoke #1 Locking Rod Locking Rod Locking Wheel Hatch Dog #2 Locking Rod Yoke #3 Yoke #2 Hatch Dog #3 Hatch Rubber Gasket/Seal
USS GRUNION After Battery Room Hatch Yoke #1 Threaded Hole for Locking Rod Yoke #2 Snapped Locking Rod Yoke #2 Snapped Locking Rod
USS GRUNION After Battery Room Hatch Stress Fractures in threaded bronze yoke allowed the Locking Rod to pull out of threads Stress Fracture Stress Fracture Stainless steel liner around hatch accessway: Liner has been stripped and mangled from inward (wrapped around ladder) CRS LINER USS GRUNNION Hatch Rim
USS GRUNION After Battery Room Hatch (2) The locking rods are threaded into the backs of the yokes (3) The yokes are attached to the hatch dogs via an eccentrically off-set hole. (1) Turning the center crank, moves the locking rods in or out. 1 2 Unused hatch dog mounting bracket; attachment lugs drilled to accept hatch dog mounting pin 4 3 (4) The hatch dogs are mounted to the inner hatch and pivot back and forth. When the locking rod moves in/out, the yokes cam the hatch dogs...out they lock hatch shut, in they unlock the hatch.
USS GRUNION After Battery Room Hatch • KEY FINDING: The Aft Battery Room Hatch locking system failed catastrophically from internal overpressure, cause as yet undetermined. • Likely chain of events (not in order); • Over-pressure/hydrostatic event • Bronze casting of Yoke #1 cracks, letting locking rod pull out • Locking rod of Yoke #2 snaps; • Dog #3 deforms (mounting flange breaks/twists?) • Hatch gasket is blown from mounting channel • Hatch blows open • Physical Evidence; • Locking Rod on Dog #1 has pulled from the threaded portion of Yoke #1 • Locking Rod on Yoke #2 has broken off at the base of the Yoke • Locking Rods (#1 &2) are lying against the inner face of the hatch, unattached to the yokes • Yoke #1 has rotated outward 180 degrees • Yoke #2 has rotated outward 90 degrees • Hatch dog assembly #3 appears deformed • Hatch gasket/seal is looped around the hatch and outer decking cover • Hatch access trunk CRS trunk liner destroyed