Operation of a Hydrostatic Release Unit

Overview edit

A hydrostatic release unit or HRU is a pressure activated mechanism designed to automatically deploy when certain conditions are met. In the marine environment this occurs when submerged to a maximum depth of four meters. The pressure of the water against a diaphragm within the sealed casing causes a plastic pin to be cut thereby releasing the containment bracket casing, allowing the EPIRB to float free.

EPIRB hydrostatic release mechanism

Description edit

A hydrostatic release unit is a type of pressure activated release mechanism(ARM). Some common characteristics of HRUs are:

  • Water pressure sensitive at depths not to exceed four meters or less than two meters
  • Single use only, require replacement if activated
  • Cannot be serviced; only replaced
  • Waterproof; sealed against moisture and tampering
  • Must be labeled with expiration date
  • Expiration date is two years from month of installation applies to unit and rod


Regulations and Technical Specifications Governing EPIRB, Hydrostatic Release Devices edit

  1. Corrosion Resistance Test
  2. Temperature Tests
  3. Submergence and Manual Release Test
  4. Strength Tests
  5. Technical Tests on the Membrane
  6. Performance Test

Operation Video edit

Although this demonstrates a HRU for a life raft, the EPIRB HRU works on the same principle.

Operation of a Hydrostatic Release Unit

References edit

Notes
  1. ^ Life-saving appliances: including LSA code/ International Maritime Organization (2nd ed.). London. 2010. ISBN 9789280115079. {{cite book}}: |access-date= requires |url= (help); Check date values in: |accessdate= (help)CS1 maint: location missing publisher (link)

Category:Maritime communication