strange bubbles

[twosoc]

Hey, I got my laser working well today so I ran it for a good few hours as I had a job waiting that really needed to go out. I leave my water circulating 24/7 as its awkward to lean over and chase bubbles out, plus I'm quite lazy. Normally, there is no trouble whatsoever, the tube remains clear even when its been standing for over a week when I went away there were no bubbles whatsoever in the tube. After running at 10ma or so for a few hours, the exit end of the tube had a few bubbles catching on the shoulder of the tube where it narrows. I can only assume these must have been crated whilst the laser was running.

I have had this problem before and asked on a different forum, and was told it was cavitation caused by the pump, I'm pretty sure its not though as the pump has been running for over two months and has not produced them before. I just can't work out why the tube being run would produce bubbles. Maybe I'm missing something obvious.
any ideas guys?
cheers, Tim.

[waltfl]

that's happen ones in a while I believe nobody really can figure this out.
I always use the pump only when the machine is running and check every time before starting the first job for bubbles if there is any I push them out with tube loosen and lifting till its out. sure it takes a little while and you have to realigned but its cheaper then a new tube. this bubbles will prevent the water from cooling the cathode and this will desroy the tube very fast.
greetings
waltfl

Hey, I got my laser working well today so I ran it for a good few hours as I had a job waiting that really needed to go out. I leave my water circulating 24/7 as its awkward to lean over and chase bubbles out, plus I'm quite lazy. Normally, there is no trouble whatsoever, the tube remains clear even when its been standing for over a week when I went away there were no bubbles whatsoever in the tube. After running at 10ma or so for a few hours, the exit end of the tube had a few bubbles catching on the shoulder of the tube where it narrows. I can only assume these must have been crated whilst the laser was running.

I have had this problem before and asked on a different forum, and was told it was cavitation caused by the pump, I'm pretty sure its not though as the pump has been running for over two months and has not produced them before. I just can't work out why the tube being run would produce bubbles. Maybe I'm missing something obvious.
any ideas guys?
cheers, Tim.

[twosoc]

cheers walt, just wondered if there was anyhting I could add to the water to stop it, or if I used another container and ran them as an input output system.

[waltfl]

Hi there
no there is nothing you can ad to the water. you just need to force the bubbles out and then watch that all parts pump - inlet - outlet are all full under water. this would prevent pretty much all bubble.
greetings
waltfl

cheers walt, just wondered if there was anyhting I could add to the water to stop it, or if I used another container and ran them as an input output system.

[twosoc]

yeah but its bubbley foam that generates whenever I cut for a long time or do mdf at a higher power. I just thought it was odd and wondered if it was created in the tube, as there seems to be no other reason. Could the electrical current be creating bubbles? CAn it drive the O out of the H2o? Sorry if thats a really dumb question, I'm not too hot on chemistry.

[Tech_Marco]

Try to use distilled water instead of tap water. Even boiled water (of course after cool off) is better as most oxygen removed during boiling.
Other thing to watch is the return of the water tube. Make sure it is submersed into the water and not 'htting' water that cuased bubbles and got suck into the water pump. I guess you may have the outlet placed above the water surface, wasn't it? Last thing to do is to raise up one side of the laser tube by 5' degree up so bubble will be guiding out from inside of the laser tube through the host.

Marco

[medicdude]

Gasses coming out of solution where the cooling water gets hottest. Gas solubility decreases as water gets hotter. You can prevent this by boiling the cooling water before filling the cooling system, obviously make sure it's cooled back down before using the laser.

If you have any sort of air/water interface then gasses will slowly creep back into your cooling water from atmosphere. Minimize this air gap, or just close it off completely with a value. If you're really worried about an expansion volume I would just use a large upsidedown syringe at a low point in the piping, tape the plunger halfway before filling then take the tape off once it's sealed up (if you don't tape the static pressure may push the syringe out while filling) . A 'reservoir' is bad because it allows gas to creep back into the system from atmosphere. You shouldn't need a reservoir anyways, there shouldn't be any leakage.

Fill point should be at the highest point in the system. Chase all the bubbles out while the water is still hot from the fill, then close the valve to seal it from atmosphere. No more bubbles, ever.

Fill with distilled water so you don't corrode the copper pipe on your heat exchanger. Some heat exchangers may tolerate tap water, but most copper ones will slowly corrode over time due to the contaminants present in tap water.