Page 8: of Marine Technology Magazine (January 2023)

Letters to the Editor

We received some terri? c comments and experiences from the last

Lander Lab “Underwater Releases” bit.ly/3j2KBkZ

Patrick Lahey, Triton Submarines, on Frangibolts More on Galvanic Releases:

Patrick Lahey, Triton Submarines (Sebastian, Flori- Galvanic (bimetallic) releases are better used to release a recovery da), spoke of their use of Frangibolts for an emergency buoy rather than to drop the anchor weight and free a lander. Even with drop weight release in their hadal class submersible 1% accuracy, at 7 days the time variability is +/- 1.7 hours, or a total time

Triton 38000/2 (s/n 001 named DSV Limiting Factor). window of 3.4 hours. Time the release to have the buoy on the surface

The EBAD Frangibolt® Actuator is a simple and effec- before dawn during the week when the winds are light and boat traf? c tive way to support and release loads up to 20,000 lb. in the area is minimal. A high strength, low stretch, non-hockling, buoy-

Actuation occurs when power is applied to a Shape ant line, such as Samson’s Amsteel-Blue Dyneema AS-78 single braid is

Memory Alloy (SMA) cylinder until it reaches its transi- preferred. The AS-78 1/8” diameter has a 2,500-lb breaking strength. At tion temperature. As the SMA cylinder heats up, it ex- 20% breaking strength (500-lb load), the stretch is 0.7%. A battery pow- pands to its elongated length, producing strain on a bolt or stud until frac- ered capstan will be a big help to the deck crew if line lengths measure ture occurs at a predetermined notch, achieving separation of the anchor, 100’s of meters. Net weight of the buoyant lander with a negative anchor manipulator, or other load from the submersible. The cold temperatures weight should be around 40-lbs, so a lightweight capstan will suf? ce. The of deep water are not enough to affect the operation of the Frangibolt. capstan should be mounted rigidly to the boat frame to allow for dynamic

Standard Fastener sizes range from #8 to ¾” bolts.” More information at loading with roll, pitch and heave.

From Rob Morris, EdgeTech: Exploding Bolts, Pyrotechnic Cutters, and

Kevin, please remind your readers that EdgeTech is expanding their

Pyrotechnic Pin Pullers code structure to offer additional unique codes for their acoustic releases.

Other release devices I missed mentioning are explosive bolts, pyro-

The change increases the number of possible commands from 12,000 technic cutters, and pyrotechnic pin pullers. In my early days at Scripps to 131,000 per tone pair for a total possible 786,000 commands. we used exploding bolts down to 5km. These devices are generally ex-

All new low frequency (LF) releases purchased after September 2022 will pensive and somewhat hard to ship, especially by air. (Class-1 Explosive, have the expanded new codes. If your group uses an existing EdgeTech

Division 1.4) They do work in fresh water. Pre-launch testing options are deck unit that is less than 10 years old and wishes to use that deck unit with able to con? rm integrity.

your existing releases and the new releases please contact Rob so he can

Exploding bolts mechanically arrange to upgrade your deck box. If you are unsure of the age of your deck secure two objects together, then box you can send Rob the serial number and he will check the age of it.

fail on command at a weak band,

Deck units sold as of December 2021 will have the new expanded code with a minimum of loose debris, structure. New deck units can be used with existing acoustic release units releasing the anchor or other and the factory-new releases.

object. Some bolts are designed

[email protected] speci? cally for marine critical ap- plications where rapid structure separation is required. In-line tensile strengths from 200-lbs to

From Bart Chadwick, SubSeaSonics: 1,000,000-lbs are available.

Bart writes: “Take a look at the EvoLogic S2C Acous-

A Pyrotechnic Cut- tic Release Device. It says they are hydraulic, but it’ll ter uses a gas gen- be interesting to take a closer look at how they work. erating charge and

Based on the specs they are roughly compatible with a cutting blade to the output of the AR60 link voltage and current.” sever objects. When https://evologics.de/components/acoustic-release initiated, the cutter (Kevin: “Thanks, Bart, we’ll take a look and discuss.”) will sever a multi- tude of materials

Back when… and cross-sectional

Scripps Institution’s Frank Snodgrass, Chief Engineer for Walter Munk shapes including in the 1960’s and early 1970’s, always believed in dual release systems, electrical or ? ber op- a primary and a back-up, but also believed in using two different release tic cables, steel wire rope, bolts, tubes and woven or braided ? ber cords, types, such as a solenoid on one side and an exploding bolt on the oth- lines and straps.

er. His reasoning: if the same release type is used for both primary and

A Pyrotechnic Pin Puller is used to toggle latch releases, pull locking back-up, and a mistake is made arming one, the same mistake might be pins or move mechanisms to perform work.

made arming the other. Detailed checklists help reduce that possibility,

For more information, go to the PacSci EMC website: https://psemc.com.

but something to consider in system design.

8 January/February 2023

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