gioarmani Posted October 6, 2006 Author Report Share Posted October 6, 2006 Cool. Thanks again. Quote Link to comment Share on other sites More sharing options...
TJGladeRaider Posted October 6, 2006 Report Share Posted October 6, 2006 Maybe I can help -- I have one of those testers too, and I have tested a LOT of my watches so far. I hope you read this before testing, or you will be unnecessarily depressed. Before we start, this is a bit complicated and people may choose to weigh in with different opinions and explanations. If you choose to invest the time and effort necessary to follow this, it is not wasted. I am a Dive Master with something in excess of 3000 HRs underwater, and my second academic pursuit was Mechanical Engineering. I understand Boyles Law perfectly well, PV=NRT is very basic to me, and I am perfectly well qualified to teach this. I say that because there were some differences of opinion last time this was discussed. Here we go. Understand that there is pressurized air inside your watch. If you are standing at sea level, it should be at about 14.7 psi - but we will say 15 to keep the math easy. It doesn't seem pressurized to us because everything is at 15psi - standard atmospheric pressure. If you took that watch into outer space while stuck inside a skin tight balloon, and popped the stem (or otherwise compromised the structural integrity of the case), air would come rushing out to expand the balloon. If you can understand that -- everything else that follows will be simple. Meanwhile, back at the oasis . . . put the watch in the device just like you are doing. Feel free to use paperclips, or whatever you need to help suspend the watch if you prefer to leave the bracelet on. Pump the pressure up to TWO of atmospheres. Now, if you are really following along, you would know that you have added two atmoshperes worth of pressure (30 PSI) to the cylinder outside the watch for a total pressure outside the watch of 45 PSI (since everything started at 15 psi). Now, LET THE WATCH SET A FEW MINUTES TO EQUALIZE IF IT IS GOING TO (Hopefully, it won't) If the watch equalized while up in the air, that means it is not airtight. In other words, and this is the part to understand, there was a small volume of air at normal atmospheric pressure inside the watch going into the chamber (say for example purposes on cubic inch of air at 15 PSI) If you add two atmospheres of pressure, you have tripled the pressure from 1 to 3, but if the watch is airtight, NOTHING happens inside. That's why men can spend forever in a submarine at significant depths with no decompression issues, but if the watch was an airtight balloon, you would watch it shrink to a third it's size which is exactly what you do see if you take a balloon down underwater about 66 feet. If the watch is not airtight, the pressure will equalize inside the watch and that means that the amount of air inside the watch will triple - three times the pressure means that three times the volume of air fits into the same space, so what we need to know is, do we have one cubic inch of air inside that one cubic inch case at 15 PSI, or three cubic inches of air at 45PSI. Lower the watch into the water. SLOWLY release the pressure -- did I say SLOWLY!!!!!! DO NOT - NOT - NOT dump the pressure. SLOWLY releasing the pressure releases the pressure on the enitre system - the air, the water, and the watch. As the pressure releases, NOTHING happens inside the airtight watch - like the men in the submarine, they don't know the difference. On the other hand, if our little experiment packed three cubic inches of air into a one cubic inch space, releasing the pressure makes that air want to come right back out. At this point, let me focus you on something - think about the inside of the watch case - including the space between the dial and the crystal. Even though the watch is filled up with a movement, there is still a LOT of airspace in there. If you take that volume and add twice that volume to it - twice the volume of airspace inside that watch is a LOT of air. When you release it, it isn't going to be a few bubbles. More on that later. If air come's pouring out of that watch as you are SLOWLY releasing the pressure -- DO NOT STOP. DO NOT STOP, but even more importantly, DO NOT - NOT - NOT let the pressure go to zero. NO, NO, NO, NO, NO! Pull that watch up out of the water while the pressure is slowly dropping and before it hits zero. IT MUST NOT GO TO ZERO while a leaky watch is under water becasue once the positive air pressure bleeds out, water can get in. No water can get in that leaky watch while the air pressure inside is bleeding out. Now, back to my point about volume. If you test your watches with bezels before reading this, you will report back that they all leak. Not so. When you pressurized the system, you did that by pumping in air. You stuffed three times the air into that system that was originally there so you pumped three times the air into the space beneath the bezel, where the lug holes are, etc that would be there without all that pressure. That little airbubble trapped under the bezel, or inside the lug hole, or wherever, is going to expand to three times its size as the pressure released and as it does, it won't fit there anymore. In other words, a few little bubbles are perfectly normal. Remember, when you pump in six atmospheres of pressure, you are compressing all the air inside that cylinder, forcing every space to hold seven times as much air as it held to start with. That is a HUGE differential. Watch the springbars and you will see bubbles coming from them, as well as from under the bezel, lug holes, from the underside of lugs . . . anywhere a tiny bubble could cling. When that bubble gets seven times as large, it will float up. Believe me, when seven times the vollume of air normally inside a watch case comes rushing out, nobody will have to tell you it leaked. If it passes just fine at two atm, repeat the process at five or six. As for the obvious question that you will have - "Did I damage my watches doing it the wrong way," I don't know, but you could not have damaged them unless they leak and no matter what you may have heard, these reps do not generally leak. If you test a watch and find that it does leak very badly, you should probably have it serviced. Good luck, Bill Quote Link to comment Share on other sites More sharing options...
gioarmani Posted October 6, 2006 Author Report Share Posted October 6, 2006 Bill, you rock. Thanks again. Quote Link to comment Share on other sites More sharing options...
Linder Posted October 7, 2006 Report Share Posted October 7, 2006 Bill, please make a new thread so this can be moved to the knowledgebase! Great info! POM material! Quote Link to comment Share on other sites More sharing options...
TJGladeRaider Posted October 7, 2006 Report Share Posted October 7, 2006 Bill, please make a new thread so this can be moved to the knowledgebase! Great info! POM material! I don't know how to move it to the knowledge base, but I can reporst as a new thread Coming up. Bill Quote Link to comment Share on other sites More sharing options...
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