Hammar A1 HRU Re-Arming Head

This inflation mechanism requires both water and pressure combined to activate automatically. It requires full immersion in water to a minimum 10 cm depth to activate fully. At this point the hydrostatic valve opens and lets the water meet the water sensitive element that in turn releases a stainless steel coil spring. The spring then drives a cutter into the end of the gas cylinder to pierce it and release the gas through the sealing ring aperture in the bladder and inflate the lifejacket.

The Automatic system is backed up by a manual override, which allows the user to pull the toggle and activate the cutter to pierce the gas cylinder in order to inflate the lifejacket alternatively.