How do I remove air bubble in oil-filled compass?
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Jack Hammer
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I just buy a new compass at that point.
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Why?
Jack Hammer
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Every one I've had the bubble get big in began sticking and giving false readings. If you are handy enough you could drill a hole, top off with mineral oil, reseal, and be happy with your bubble free compass. I just buy a new one every 3 or 4 years.
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GJC
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I tried fixing one once. Despite filling it and sealing, the next day there was a bigger bubble. Then I learned you have to have the fluid in a vacuum for a while before sealing to remove air that is dissolved in the fluid before you seal it. Not worth my time and effort. Bought a new compass.
I always used the bubble like a level since the diver is a substitute for a gimbal.
A bubble is usually an indicator that the compass has a leak.
The bubble will only get bigger and after a while the compass will start to stick.
A bubble in my compass is a replacement indicator for me . . . . .
The bubble will only get bigger and after a while the compass will start to stick.
A bubble in my compass is a replacement indicator for me . . . . .
broncobowsher
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A sealed compass is like a scuba tank you leave in your car in the summer. What's inside expands and contracts with the temperature.
The bubble is there so the silica oil can expand in the heat without bursting the glass. That expanding silica oil has to have somewhere to go under pressure.
Air is "squeezable", Liquid is not. Remember?
So if you had a compass that was sealed and had no air in it, and say you left it lying on the dive boat seat in august in the noon sun, the liquid has room to expand without increasing the pressure very much inside the globe.
Military-style dive compasses are built to withstand pressure changes. Most dive compasses just have cheap plastic cases. Plastic doesn't handle pressure changes very well.
If the bubble grows to the point it's causing the needle to not function properly, then that's a leak. Otherwise an air bubble is normal.
My boat compass has a dime-sized bubble in it. The temperature in my garage in February is a lot different than the temperature is when I'm beached at Radio Island in August. That bubble allows the oil in the compass to expand and contract without increasing the internal pressure very much. On most boat compasses, there's a little brass screw you can remove on the bottom and turn it upside down to add more liquid silicon to it. Wrist mounted scuba compasses don't have that feature. They're made cheap and intended to be replaced when they start leaking.
The bubble is there so the silica oil can expand in the heat without bursting the glass. That expanding silica oil has to have somewhere to go under pressure.
Air is "squeezable", Liquid is not. Remember?
So if you had a compass that was sealed and had no air in it, and say you left it lying on the dive boat seat in august in the noon sun, the liquid has room to expand without increasing the pressure very much inside the globe.
Military-style dive compasses are built to withstand pressure changes. Most dive compasses just have cheap plastic cases. Plastic doesn't handle pressure changes very well.
If the bubble grows to the point it's causing the needle to not function properly, then that's a leak. Otherwise an air bubble is normal.
My boat compass has a dime-sized bubble in it. The temperature in my garage in February is a lot different than the temperature is when I'm beached at Radio Island in August. That bubble allows the oil in the compass to expand and contract without increasing the internal pressure very much. On most boat compasses, there's a little brass screw you can remove on the bottom and turn it upside down to add more liquid silicon to it. Wrist mounted scuba compasses don't have that feature. They're made cheap and intended to be replaced when they start leaking.
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