gage fluid

Discussion on general flowbench design

Postby coulterracn » Fri Jun 26, 2009 4:33 pm

I measured the Inch marks on my Dwyer 36" meter with my digital caliper. They are 1.087" apart. The tube ID is 0.190" and the well is 0.750" ID. This model uses .826 red gauge oil.

Ray
"I know I'm in my own little world, but it's ok, they know me here"
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Postby johno » Sat Aug 01, 2009 6:15 am

Hi there mate, i got a manometer fluid recipie from a old flow-bench build by Peter Saueracker (this thing had 16 Grainger motors shoe-horned into it!!!!) which goes; 1 pint of distilled water with 1 drop of dishwashing liquid and 4 drops of rose/ red food colouring. :)
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Postby Eagle Eye » Thu Aug 20, 2009 10:10 am

Hello everybody. I'm going to build a vertical manometer now that asked you about months ago. I will make the resivoir 1000 times the area of the fluid in the tube as you told me to do. After reading this fluid info. I am understanding that using the same pressure will raise different fluids a different height in the tube depending on the s.g. Is that correct? My question is should I use water or marvel mystery oil and is an inch of rise really an inch? Thanks for your help everyone. Jim
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Postby 86rocco1 » Thu Aug 20, 2009 10:55 am

Normally an inch of rise isn't an inch. For distilled water (or any fluid with 1.0 s.g.), one inch of rise equals one inch + the amount of drop in the reservoir. But in your case, since the surface area of the reservoir is so big compared to that of the the tube, the drop in the reservoir will be negligible and you can happy pretend that an inch of rise is indeed an inch of pressure.

Now, if you're using a fluid other than water, you need to take the specific gravity of the fluid into account. in the case of Marvel mystery oil the specific gravity is 0.876. So, in your manometer with a 1000:1 reservoir to tube ratio, a one inch rise of MMO would be something like 0.8769 inches of pressure.
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Postby jfholm » Thu Aug 20, 2009 2:08 pm

Ed,
Since the MMO is lighter shouldn't it rise higher with the same pressure? I thought that the inch mark with MMO should be around 1.14" since MMO will rise higher with same pressure that it takes to raise water as MMO has a lighter specific gravity.

John
It is a wise man that learns from his mistakes, but it is a wiser man that learns from the mistakes of others.
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Postby 86rocco1 » Thu Aug 20, 2009 2:35 pm

You're right, my mistake, I forgot to take the reciprocal of 0.876 to should have been a one inch rise of MMO would be something like 1.143 inches of pressure.
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