liquid level sensing - potential leak
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Posted by: skacur ® 11/19/2009, 13:46:39 Author Profile eMail author Edit

we are experiencing what appears to be a slow air leak in the following setup: low pressure sensor connected to a tygon tube via 1/8" hose barb; the tygon tube is submerged in a liquid; the hydrostatic pressure of the liquid compresses the air in the tube; the sensor measures the air pressure; the linear relationship between hydrostatic pressure and liquid level enables liquid level determination problem: over the course of several weeks we've noticed a slow, steady drop in pressure while a constant liquid level is maintained. of note, the small "slug" of water at the bottom of the tube climbs slowly and steadily indicating an air leak. two questions: 1 - if this is an air leak, is it through the sensor, the hose barb seam or the tubing itself (permeation)? we have tested several variations of this with no conclusive answer 2 - if this is not an air leak, what is causing this phenomenon? thank you in advance

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: liquid level sensing - potential leak
: liquid level sensing - potential leak -- skacur	Post Reply	Top of thread	Engineering Forum

Posted by: Marky ® 11/19/2009, 14:04:55 Author Profile eMail author Edit

Hi and welcome to the forum....if you have a picture of the set up that would help. Are the barbed connections clamped? With the system out of water you can simply check all of the suspect areas with soapy water. That will give you gross leaks. But if possible...Helium thru the system and a leak detector will pin point very small leaks...that looks like what you have. I would eliminate the barbs and go to a compression or push to connect fitting. Modified by Marky at Thu, Nov 19, 2009, 14:11:39

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: : liquid level sensing - potential leak
: : liquid level sensing - potential leak -- Marky	Post Reply	Top of thread	Engineering Forum

Posted by: skacur ® 11/24/2009, 10:44:18 Author Profile eMail author Edit

Thanks Marky. We tried submerging the setup in a water bath and pressurizing to 3 psi. No visible bubbles. We're also testing a clamped setup using barblock clamps but it's still too early to tell if there is an improvement. We can't use any of the connections you recommended since we are limited to the hose barb connection on our sensor. The Helium test may be the next step. Thanks again.

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: : : liquid level sensing - potential leak -- skacur	Post Reply	Top of thread	Engineering Forum

Posted by: Marky ® 11/24/2009, 10:53:29 Author Profile eMail author Edit

Cool!!! What's the sensor look like? Thank you for the update Modified by Marky at Tue, Nov 24, 2009, 10:54:07

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