Skip to content

Diving helmet: Failure of sealed pull pin

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. 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 recommend that the tender, stand-by diver, or at least a second person, ALWAYS perform 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
Helmet sealed pull pin slot after failure
Pull pin
Pull pin
Parts of failed sealed pull pin (l-r) Plunger, with breakage point at right; knob; Nyloc lock nut
Parts of failed sealed pull pin (l-r) Plunger, with breakage point at right; knob; Nyloc lock nut

The following actions were recommended:

  • 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

  • Pull Pin Overhaul procedure;
  • 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.

Safety Event

Published: 23 September 2013
Download: IMCA SF 15/13

IMCA Safety Flashes
Submit a Report

IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of all. The effectiveness of the IMCA Safety Flash system depends on Members sharing information and so avoiding repeat incidents. Please consider adding [email protected] to your internal distribution list for safety alerts or manually submitting information on incidents you consider may be relevant. All information is anonymised or sanitised, as appropriate.

IMCA’s store terms and conditions ( apply to all downloads from IMCA’s website, including this document.

IMCA makes every effort to ensure the accuracy and reliability of the data contained in the documents it publishes, but IMCA shall not be liable for any guidance and/or recommendation and/or statement herein contained. The information contained in this document does not fulfil or replace any individual’s or Member's legal, regulatory or other duties or obligations in respect of their operations. Individuals and Members remain solely responsible for the safe, lawful and proper conduct of their operations.