DROWNED DETECTORS CAN BE AVOIDED..

Drowned Detectors can be Avoided

Copyright by Alan Hassell all rights reserved

Ever experienced a drowned underwater metal detector? For some reason, owners of underwater metal detector's are under the impression their waterproof machines wont leak. Manufacturers work to fine tolerances creating control housings capable of withstanding water pressure at various depths. Manufacturers have no control over their products once it is in the hands of an individual.

Coming from a hot country such as Australia, we learn quickly why U/W machines for no apparent reason develop a leak. I have heard of individuals going overseas and their machines leaked ruining what could have been a pleasant holiday.

The reason machines leak is partly the blame of the owner, who is unaware that heat is the main culprit. Law of Physics state heat expands, cold contracts. Heat causes control boxes to expand, once that control box is submerged in cold water it immediately contracts creating a vacuum sucking in a certain amount of water shorting out the circuit board.

Prevention is always better that the cure and only takes a few second's time. Car windows act like magnifying glass increasing heat inside car causing control housing to expand, Cover detector in car with blanket or towels to keep sunlight off machine during transit. Wrap a damp cloth or tissue around the control housing once detector is out of car exposed to sunlight.

At the water's edge, cup your hand and gently pour water over coil and control box to cool everything down to normal temperature. Allow a few minutes for machine to contract during cooling process and you should never experience a drowned detector again. Care should also be taken with "O" rings, clean with mentholated spirits and re-apply a thin film of Silicon grease or Vaseline to ensure watertight seal.

On the Surfmaster PI make sure the clips fastening the top to the control box are secured evenly. Make a visual inspection to ensure the O ring is squeezed evenly around the top of the control box. It was only after hearing of surfmasters leaking in Spain that I decided to write this little tip. Detectors seldom leak in winter owing to cooler conditions. However it is always possible to do something stupid like accidentally pulling a cable out of the control box.

Happy hunting,

Alan Hassel

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Thanks, Alan.  This is going in my "Save" file for my next trip to the coast and for when I go to Hawaii next fall.

BA

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Thanks, all good advice.  I think the best advice you gave is about making sure the seal is clean and that you  put Vaseline on the seal before putting your detector back together.   This is very important to do, everytime you change batteries or do anything inside of the control box.  A little sand on the seal will let water in.  It is most important to clean the seal and then put a silicon grease or Vaseline on the seal before fasting the top to the control box.

About leaving ANY detector in you car while it's hot outside or even leaving your detector in a car when it is freezing outside.  Both are no No's.  You don't like to be in a hot car or a cold car, neither does your detector.  Why would you spend 100's or 1,000's of for a detector and then treat it like a piece of junk.  Take care of your detector and it will take care of you!!

Best Regards,
Ringfinder
Keep you coil to the soil

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Thanks for the good info have a Cobra Beach Magnet ready to take it to the water this summer.  Have been using it out of the water this winter think I will put silicone lubercatnt on oring before submerging it.

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I must take issue with this article. The article refers to the laws of physics then states facts that are in contradiction to the laws of physics. I have no dought that the leaking boxes have been observed when going from hot to cold, but a shrinking control box creating a vacuum is physically impossible. A shrinking control box alone would cause an increase in pressure and thus prevent a leak, but since we are not dealing with a temp constant simple physics of shrinking and expanding boxes don't explain the situation correctly. I have not done the calculation on any of the water machines, but the information below should help if you would like to spend the time to do it. The problem would more than likely be the air inside the machine shrinking as it is cooled. Air shrinks 12% when the temp is lowered from120degF to 60DegF.

The reason I am posting this is to say I would cool my detector for a sufficient amount of time to allow the air inside to cool this means the electronics must be cool also.

All that being said and O-ring seal should be able to handle pressures anywhere from an absolute vacuum all the way up to thousands of PSI. The temperature changes should not cause enough pressure change to cause a leak. Uneven cooling of the box could cause distortion and thus a leak, but at the temps we are talking about I think that would be unlikely.

Is it possible that this problem has been link to the temp change because almost 100% of the time a water detector is taken from a hot environment into the cool water?

Here are the shrink rates of some common materials. All units are inches per inch per degF
Aluminum shrinks 0.0000123? per inch per degF
ABS Thermoplastic 0.000041
Magnesium  0.0000123

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