degausing

mickyc123
5th October 2008, 08:46
can anyone tell me about degausing vessels. i was on one in 1965 it was called DGV 403. iwas 15yrs old, she was ex inshore minesweeper in portsmouth.

BillH
5th October 2008, 12:20
can anyone tell me about degausing vessels. i was on one in 1965 it was called DGV 403. iwas 15yrs old, she was ex inshore minesweeper in portsmouth.
in very simplistic terms the degaussing vessel passes electric current through the other vessels hull and effectively changes the magnetic polarity thus reducing or eliminating the risk of triggering magnetic mines.
No doubt some more knowlegable person onboard will put meat on this skeleton

trotterdotpom
5th October 2008, 12:39
Degaussing is a method of neutralising a ship's magnetic field in order to protect it from magnetically activated mines. An explanation is at http://www.eaglespeak.us/2007/11/sunday-ship-history-degaussing-ships.html

Degaussing coils are placed round the screen end of cathode ray tubes in colour TVs - at switch on, a strong magnetic field is created round the tube. The current in the coils reduces rapidly and the magnetic field decays in sympathy, leaving a negligable magnetic field to interfere with the electron beam arriving at the screen. The perceptable noise at switch on of a TV is caused by the degaussing coil operation. See what you can learn by tuning in to Ships Nostalgia!

John T.

lesbryan
5th October 2008, 13:17
The perceptible noise at switch on of a TV is caused by the degaussing coil operation
I remember when we used to degauss in the dockyard what an operation that was ! cables all over the place .But you do learn something everyday i did not know that with the telly(K) (K) (Cloud)

David Davies
5th October 2008, 16:37
Running over the degausing range at Weymouth in the late 50s we were told that the modern magnetic mines had pressure, acoustic as well as magnetic triggers. With this advancement in mine technology, degausing would no longer give protection and was to be discontinued. About a year latter we were proceeding up the swept channel to Nagoya, Japan, without degausing, the pilot on being told this, hissed as only a Japanese can and informed us that the batteries in the WW2 mines had lasted much longer than anticipated, there had been a mine related incident. Apparently the anti rolling horns on the mines had corroded away and the mines were rolling down the sides of the deep water channel. Needless to say, we didn't tell the engineers of this development

senior pilot
5th October 2008, 17:01
i did my first sea trip on same ship as cabin boy 1962 alex

benjidog
5th October 2008, 18:16
There is an article about degaussing in the SN Directory here:
http://www.shipsnostalgia.com/guides/Degaussing

robandbarbara
5th October 2008, 19:53
Between about 1956 and 1963 there were (at least) four Degaussing Vessels working from the Royal Dockyards.
DGV 400 (ex MMS 1002)
DGV 401 (ex MMS 1003)
DGV 402 (ex MMS 1004)
DGV 403 (ex MMS 1011) ... Portsmouth Dockyard.
all being converted Motor Minesweepers.

I am uncertain when they were disposed of.

Rob

trotterdotpom
6th October 2008, 00:51
Were ex minesweepers used because they were made of wood and therefore not magnetic themselves?

John T.

Baulkham Hills
6th October 2008, 01:52
Degaussing is also used on rotating machinery to eliminate residual magnetism
otherwise currents may flow causing sparking on bearings leading to failure. Earthing devices on the shaft is to prevent this sparking problem.
While my ship was in dry-dock in Bahrain in about 1998, I was visiting the electrical workshops and the electrical mechanics showed me a breaker for a degaussing system which they were repairing for a U.S. warship, the frequency of the supply was 400 hz, I was surprised that this system was still in use, but I seem to remember that the U.S. navy was very short on minesweeping capacity in the first gulf war.

Cheers

mickyc123
6th October 2008, 17:21
i did my first sea trip on same ship as cabin boy 1962 alex
hi alex i was on 403 in 1965, great days we went upto london docks i was the boy. we degaused big cargo ships right through to east india dock up there six weeks, we were in india dk when the blind beggar shooting hapend some of the crew were there. so u were p a s alex was the skipper captain harris and the cook bob briges Mick

Don Matheson
6th October 2008, 20:31
Someone should tell the Royal Navy about degaussing as they dont seem to know much about it. Few years ago I went to overhaul a couple of engines on a MINESWEEPER (note the type of ship). Took hours to get clearance to get onboard, part of a large submarine base on the Clyde.
Get started on the engines but there is a cable that looks like a garden hose running round and under each engine. It has to come off, so we ask the ER rating what it is, he does'nt know, but on prompting is sure the ER Petty Officer will know. He does'nt and despite me asking if its degaussing gear he thinks the Electrical PO will know. He does'nt but is sure the Weapons Officer will be bound to know. Down he comes to find out but despite me asking again, he does'nt know what it is. This crew had been on the ship for 6 months, having just completed a tour in the Med. I ask him if its degaussing gear and he says " It could be, disconnect it and we will see if an alarm goes off." I explain its nothing to do with us so they have to find out and remove it. No response, so I rip it off and sure enough the degaussing gear alarm goes off.
Second day there we are told to stop all work as they dont have the spares, so could we rebuild what we have stripped. Hard to do when you have no spares but we managed to get it running again.
My point is, the crew were great with us and could not do enough to help, but this is a very good navy, what happens in the navy of Sierra Leone or Suriname to name but two?
Don

JimC
7th October 2008, 17:37
I don't know when they stopped fitting them but degaussing cables were fitted to some merchant ships in the 1950s. The first time I saw them was on the Denholm ore carrier 'Ormsary'. They were ususally quite visible running round the inside of the shell plating attached to a cable tray. If I remember rightly there were four heavily insulated cables arranged verticaly side by side within a cable tray and running right round the inside of the ship. They were very visible under the forecastle. I think, but am not sure, they ran on the inside of the maindeck bulwarks where they were fitted with protection covers.

As for how they worked; well that's been explained elsewhere in this thread. Actually, I have a similar system fitted to the screen I'm using at present to de-magnetise it.

Cheers!

senior pilot
8th October 2008, 00:04
hi alex i was on 403 in 1965, great days we went upto london docks i was the boy. we degaused big cargo ships right through to east india dock up there six weeks, we were in india dk when the blind beggar shooting hapend some of the crew were there. so u were p a s alex was the skipper captain harris and the cook bob briges Mick

that was the same trip i did went to tilbury docks spent one night there then was sent back to pompey by train sorry cant remember anyone in the crew, i was on the kinterbury in65 then left to go home to rosyth alex