How Water Resistance is Tested

[Librarian2]

Authored by Isthmus

 
This page discusses how water resistance testing is supposed to be done:

http://www.watchrepairer.co.uk/Water%20Resistance.html

Here is what one type of water resistance testing machine looks like (this is a bergeon model - picture from Casker):

[bigbonsai]

Oh dear- the link doesn't work, i was looking forwards to finding out whether the watches are flooded when they fail the test, i thought they weren't actually tested in water but i'm not sure

John

[KenS]

John
Great question. If a watch fails the test, flooding isn't usually a problem. The main malfunction I encounter is a watch that will fill with air, quickly, when pumped up but won't release the air when submerged. You think the watch is water resistant but when it is pulled out of the water; or even, sometimes under water, the pressure becomes too much and the crystal will blow out, and the dial will blow off taking the hands and hour wheel with it. What I do is to remove the watch from the water before the pressure goes to 1ATM so if there is a leak it won't get water in it. Hope this helps.


Ken

Oh dear- the link doesn't work, i was looking forwards to finding out whether the watches are flooded when they fail the test, i thought they weren't actually tested in water but i'm not sure

John

[George Novak]

There is a good description of the procedure in this link
http://watchtalkforums.proboards.com/index.cgi?board=general&action=print&thread=1378
 
The author also does some preliminary testing above water to see if trapped pressure could blow out the crystal.
 
 

[trailboss99]

Yup, the Standard calls for a dry run above the water before the submerged test to take care of crystal blow outs.
Up to pressure (usually between 3 and 4 ATM in a Bergeon like above , pushing too high regularly is not good from them), wait 2 minutes
and slowly release the pressure. If the crystal doesn't blow repeat and lower the watch into the water. A slow release again down to aprox 1ATM whilst looking for bubbles. You will get some air escaping from under the bezel if so equipped and from the bracelet but a leak should be easy to spot as a continuous stream of bubbles. Note that the air may escape from a different location from it's entrance point. Crystals tend to provide an easy escape rout as the seal is designed to cope with pressure from the outside, not from within.

In most cases the leak is the pushers on a chrono or the stem seal. A simple change of O rings and a grease will fix the problem in 99% of cases. It's also important to check for corrosion or dirt build up on the sealing surfaces as even the smallest amount can prevent a good seal. I have serviced diver's watches where there was a tiny spot of discolouration on the case back sealing surface that was enough to prevent a successful test. I also recommend the test be repeated at 1.5ATM as at times a higher pressure can produce a false seal and the watch will still leak at lower pressures.



Col.

[Adriano]

In a "swiss model" workshop, we just use that Bergeon or Bergeon kind of tool for finding the leak when alreay detected, but not for definitive test.

The standard test is made in a dry equipment, usually the Witschi ALC 2000. Here is an example of a Ti Samurai being tested in a ALC 2000, before and after the test:






This equipment is composed by a chamber with a sensor where we put the watch in. The sensor touches the crystal of the watch. The other part of the equipment, not shown here, is a air compressor. The test is made subjecting the watch to pressures, positive or negative (vacuum) and measuring how much it deforms under those situations. Under vacuum, the watch expands and under pressure it shrinks. So the pressure is applied, the watch starts to deform, the equipment start to measure the deformation (which is not subtle) and wait until the deformation stabilises. Once it stop to deform, the equipment wait for a time, usually 60 second or sometimes a bit more to see if the watch can keep that deformation. If yes, this means it's watertight. If it cannot keep the deformation, this means the watch is leaking.

Of course different watches performs a little different. For example, dive watches, due to it's robust construction, tends to deform much less than a "social" watch. This way, the equipment can misunderstood that little deformation and think it's leaking, when it's not. That's why we can choose an option of "hard case", so the equipment can make the right reading even in watches that deforms very little under pressure.

Also, the results to decide wheter it is good or bad, are matematically based on a ISO norm. As the ISO just preview the test resistance in one specific depth, the equipment can calculate the same proportion for any depth between 1 and 9 bars. You can also choose if you want to use the same proportion of watch resistance, wich is a leakage of 1%. Usually we use a stricter tolerances from the norm, using a maximum leakage of 0.5%. This basically doubles the safety of the results.

The equipment make two tests: one with vacuum, usually at -0.5 bar, folowing a pressure test up to 9.0 bar. The vacuum teste is actually more decisive than the pressure one, because it tests the watch in a relaxed situation. Because worn, old, deformed or incorrect gaskets can work when pressed against the parts, but can fail when relaxed. So the vacuum ensures the gaskets are in condition of being water tight in any condition, and also ensures that any part is correctly fitted. So we keep an eye much more on the vacuum than the pressure test.

In regular watches, this is sufficient to say the watch is watertight.

But for professional dive watches, above 150m of resistance, we have to follow the water test. This is a simple equipment with a chamber fiiled with water. You just put the watch inside, close it, and build up the pressure to 125% of the rated pressure. This means that a 200m watch must be tested at 250m, a 300m watch muste be tested at 375m, and a 1000m must be teste at 1250m. The watch must be kept to that depth for two hours. After that, you remove the watch from the chamber and make a condensation test. You have to heat the watch up so it becomes entirelly warm. If any water got in, it will evaporate. Then you put a drop of cold water over the crystal. If water got in and evaporated with the heat, it will condensate under the crystal. If everything is ok, the watch just passed the test. This is a definitive test.

This is the same Samurai on the test:











And for curiosity, this is an Omega Seamaster Planet Ocean being tested at 750m...









But this is a destructive test, to it can only be carried out if the watch was assembled by a professional and trained watchmaker, if the gaskets and other parts are original and new, and if it succesfully passed the dry test. Otherwise it can be disastrous.

To finish, that Bergeon equipment we just use to find where is the leakage when a what does not pass the dry test. If the leakage is not obvious, then we use that equipment so by the bubbles we can see if the leakage is on the crystal, or on the case back, or on the crown, etc.

Hope you liked!

Best regards,

Adriano