NVIC 04-86: Hydraulic release units and float-free arrangements

NVIC 4-86 28 MAR 1986 NAVIGATION AND VESSEL INSPECTION CIRCULAR NO. 4 86 Electronic Version for Distribution Via the World Wide Web Subj: HYDRAULIC RELEASE UNITS FOR LIFERAFTS, LIFE FLOATS, AND BUOYANT APPARATUS, AND ALTERNATE FLOAT-FREE ARRANGEMENTS

Hydraulic Release Units for Life Rafts, Life Floats and Buoyant Apparatus, and Alternate Float-Free Arrangements — PURPOSE. This Circular summarizes the requirements for installing, testing, and maintaining

Coast Guard approved hydraulic release units used with liferafts, life floats, and buoyant apparatus. Alternate float-free arrangements not requiring hydraulic releases are also discussed.

Hydraulic Release Units for Life Rafts, Life Floats and Buoyant Apparatus, and Alternate Float-Free Arrangements — DIRECTIVES AFFECTED. Navigation and Vessel Inspection Circular 7-69 is canceled, along

with Changes 1, 2, and 3.

Hydraulic Release Units for Life Rafts, Life Floats and Buoyant Apparatus, and Alternate Float-Free Arrangements — DISCUSSION.

a. General Description. Hydraulic release units (also referred to as hydrostatic release units or HRUs) are mechanical devices used as -links in the lashings securing liferafts, life floats or buoyant apparatus to the deck of a vessel. If a vessel sinks before the crew can manually launch the equipment, the pressure of the water operating on the HRU automatically separates it into two parts. This action, at a depth of between 5 and 15 feet, disconnects the lashing and permits the unrestrained liferaft, life float or buoyant apparatus to rise to the surface by its own buoyancy. b. Alternate Float-Free Arrangements. An HRU is not necessary for satisfactory float-free installation of an inflatable liferaft, life float, or buoyant apparatus. Enclosure (1) shows the installation of a float-free inflatable liferaft in a crib made of removable loose-fitting stanchions and bars. The height of the enclosing stanchions will depend on the location of the raft on deck and its exposure to boarding seas. Enclosure (2) shows a stowage rack in gimbals for preventing a liferaft from being trapped if the vessel should capsize as it sinks. Apart from the details of the stowage rack, its location on deck must receive careful consideration, especially on vessels with low freeboards where green water washing over the deck could result in the loss of the raft. c. Navy/Coast Guard HRUs. The first Coast Guard approved HURs evolved from designs manufactured to a U.S. Navy specification, MIL-R-15041. Three of these stamped-metal devices received approval, although the "Arrow" unit is no longer in production. Enclosure

(3) includes details of these first HRUs, a table of their operating features, and details of the gripes for restraining the lifesaving device.

(1) The Raftgo Model C is produced by Raftgo Hendry Co. (formerly C.J. Hendry Co.) under Coast Guard approval numbers 160.062/1/0 through 160.062/1/4. Raftgo Model C releases may be used to secure a single liferaft, life float, or buoyant apparatus, or multiple devices.