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Drew,

What is the sensitivity of that method? Long time ago I successfully used halogen leak detector to find leaks in high vacuum systems pumped down with a leak to 10-3 - 10-5 torr. The special sensor has been installed in the fore-line at the mechanical pump inlet flange and the vacuum chamber and pumping system were blown with freon or other halogen contained gas (even cigarette smoke works fine). All other was exactly like you described. It was very inexpensive ( as far as I remember less than $1000 a brand new one) small portable device and its sensitivity was high enough - for vacuum coating applications it worked no worse than helium leak detector.

Now I can't find such a device anywhere on sale...

Regards,

Vladimir Chutko


On 1/27/2014 9:53 AM, Andrew Aurigema wrote:

I came up with one but it is not fast or environmentally friendly.

Get yourself a digital Freon ( halogen ) sniff detector off Ebay ( $20 ). Put a sock over the output of your vacuum pump so the discharge does not spit oil vapor. Put the detector in the discharge stream so it is sniffing. Set it to most sensitive. pump down your system to get vacuum in there. I go down to 5 torr. Just crack your vent valve so that there is a tiny leak of air into the chamber...... so there is actually some air flowing into the chamber and that air can be pumped out via the pump. The detector should be silent thru all this pumping as there is no halogen gas in the discharge.

To test the detector, put a plastic bag over the vent and put a puff of "caned air" in the bag. Compressed air is really Freon 134a ( a halogenated gas ) so in a few seconds the halogen gas will be sucked into the system via the valve you have cracked and exhausted via the pump. The detector will go crazy for a few seconds. Just put a short blast of the gas in the bag and let the system run for a minute to clear out the chamber of test gas.

Eventually ( like in 30 seconds ) the detector will be silent again. Retest to make sure your system is working. Let clear 30 seconds each time to clear the chamber ( with fresh leaked in air ). Now you are ready to test. Put the compressed air baggy over any part you are suspecting and give that new suspect volume a blast of caned air. If your detector goes off 30 seconds later you have a very very large leak.

It is not fast, but it is a very good way to find leaks.

Every so often check your test by putting a puff of caned air into the calibrated leak and make sure the detector goes off.

Any brand of "caned air" will work. Just look on the can to see that it is a halogen gas. Check your freon detector against the can before you start to get a feel for the amazing sensitivity of the machine. Any freon sniffer will work so dont be fooled into buying an expensive one.

Hope it helps.

Drew in sunny Florida

On Mon, Jan 27, 2014 at 11:18 AM, Guy Brandenburg <gfbrandenburg@...> wrote:

Anybody have any nice cheap easy reliable leak/detection methods other than
1. Deduction by logic by compartmentalizig
2. Stethoscope
3. Squirting acetone at suspected joints to see if pressure rises
?

Guy Brandenburg
so full of hilarious errors... ;-}}