Diving helmet: Failure of sealed pull pin
- Safety Flash
- Published on 23 September 2013
- Generated on 4 December 2025
- IMCA SF 15/13
- 2 minute read
A Member has reported an incident without injury in which the knob of a sealed pull pin assembly (p/n 505-110) on a Kirby Morgan diver’s helmet came apart.
What happened?
The incident occurred after an air dive, when the dive team was assisting the diver to remove his helmet. On the block side of the hat, the sealed pull pin came apart whilst undressing the diver. Upon inspection, the dive team found that the threaded part of the shaft on the plunger, at the base of the threading, just above the square key, had broken and the knob had separated from the pull pin assembly. The Nyloc lock nut was connected to the top threaded section and still in the end of the knob. All parts of the pull pin assembly were recovered. Both sealed pull pin assemblies on the helmet were removed and replaced.
Our Member contacted Dive Lab to discuss the incident. From photographs and information sent by our member, it was determined that the pull pin shaft had crevice corrosion.
Kirby Morgan strongly recommends that the tender, stand-by diver, or at least a second person, ALWAYS performs a pre-dive check that includes checking the sealed pull pins to ensure that both are functioning correctly and are fully engaged and latched in the closed position prior to each and every dive.
helmet sealed pull pin slot after failure
pull pin
parts of failed sealed pull pin (l-r) plunger, with breakage point at right; knob; Nyloc lock nut
swipe for more figures
Actions
- Pre-and post-dive checks.
- Regular careful inspection of pull pin assemblies, in accordance with Dive Lab checklist appendices A2.1, A2.2 and A2.23.
- Regular check of pull pins for signs of leakage and corrosion, and to ensure that pull pins are operating properly.
- All torque specifications for fasteners (10-15 inch/lbs for the Nyloc lock nut on the pull pin assemblies) should be strictly followed.
Kirby Morgan notes that the following further information is available at www.kirbymorgan.com:
- Pull Pin Overhaul procedure https://divelab.com/download/supplemental_training_information/
Pull-Pin-Procedure-7-14-2010.pdf - Bulletin #2 of 2013: Sealed Pull Pin Inspection & Maintenance
- Bulletin #6 of August 23, 2011 New Kits Part Numbers 425-090, 425-099, 525-211, 525-373, 525-385 and 525-718
- Bulletin #7 of December 1, 2010 Change to Product Bulletin 530-110 Lock Nut Replaces 330-320 Lock Nut.
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