Slack tube manometer fluid?

[bimmer630]

I bought an old Dwyer manometer for testing engine crankcase vent valves. It needs fluid, and the tool says “use only mercury or green concentrate with water”.
Why does the color matter?
What is in these concentrates that’s so special? Can I just use food dye or WW fluid?
I found the concentrate on grainger and other suppliers, but it’s a 22.00 bottle which I won’t use often.. I was just wondering if there’s something equivalent for a few bucks that’s easier to get?

 

[rlitman]

https://www.dwyer-inst.com/Product/Miscellaneous/Accessories/GageFluids/GageFluids

Red Gage Fluid, .826 sp. gr., is the standard fluid for use in inclined manometers, "D" type vertical manometers and all Dwyer gages using red fluid.

Blue Gage Fluid, 1.910 sp. gr. For special instruments and Mark II Models 26 and 28.

Fluorescein Green Color Concentrate, water coloring agent. Not to be used full strength. Add 3/4 oz to a quart of distilled water. Contains a wetting agent to improve the meniscus characteristics. Use in vertical manometers only

So, for your purposes, the green is just water. In theory their dye and wetting agent either won't affect the water's density significantly, OR perhaps their gauges are calibrated around that, but in the case of the water based green, water should be more than close enough for you.

 

[ransil]

Tap water and food dye

Or you can get better water and food dye. Need wetting put a drop of dish soap in.

Sent from my SM-G960U1 using Tapatalk

 

[strutaeng]

I installed a manometer on my furnace to check pressure drop across filter and it came with the tiny little red bottle on that link. I filled it and it wasn't even 1/4 of the bottle used. Link lists it as $7.80. I would stick with the fluid they recommend, unless you can find something else with equal specific gravity.

Grainger is too darn expensive 99.999% of the time.

https://www.amazon.com/dp/B008HOWDYC/?tag=atomicindus08-20

https://www.amazon.com/dp/B009PAN3C8/?tag=atomicindus08-20

 

[rlitman]

I installed a manometer on my furnace to check pressure drop across filter and it came with the tiny little red bottle on that link. I filled it and it wasn't even 1/4 of the bottle used. Link lists it as $7.80. I would stick with the fluid they recommend, unless you can find something else with equal specific gravity....

Read my post above. Red gage fluid has an SG of 0.826 (it is a blended petroleum distillate). Green has an SG of 1.000, i.e. WATER.

edit:, looking over the SDS, the fluorescein makes up less than 1% of the green fluid concentrate (which makes sense, because fluorescein is a super powerful colorant). Most of it is water, and most of the rest is a wetting agent. One pin-head amount of dish detergent in a gallon of water will level the meniscus nearly as well (too much will risk foaming, so you can safely skip the wetting agent entirely if you prefer).

 

[strutaeng]

Read my post above. Red gage fluid has an SG of 0.826 (it is a blended petroleum distillate). Green has an SG of 1.000, i.e. WATER.

Ok, gotcha. I skipped the "green" part.

 

[BukitCase]

“use only mercury or green concentrate with water”

Does that unit have 2 different scales? If not, that statement makes NO sense; in liquid filled manometers, mercury moves 2.02 inches per pound of pressure, water moves 27.65 inches per pound... Steve

edit - nevermind, been too long since I used liquid filled manometers. The magnehelics kinda spoiled me - if you didn't already have the liquid filled type, for about the same $ as those I'd go with one of these

https://www.amazon.com/s?k=dwyer+ma...dustrial,220&ref=nb_sb_ss_organic-pltr-v2_6_6

No liquid to futz with, most of those are differential (2 ports) so you can measure ****, blow, or difference depending on how you hook it up...

 

[rlitman]

“use only mercury or green concentrate with water”

Does that unit have 2 different scales? If not, that statement makes NO sense; in liquid filled manometers, mercury moves 2.02 inches per pound of pressure, water moves 27.65 inches per pound... Steve

I was kind of assuming the same thing. But what tipped the scales towards my assumption is that there is absolutely nothing you can dissolve in water to get the SG all the way up to 13.6.

 

[bonneyman]

After my liquid manometer falling over and leaking out AGAIN I switched years ago to Dwyers low cost air gauge. It did what I needed it to do, and no fluid to leak.

http://www.dwyer-inst.com/PDF_files/2018/INTL/460.i.pdf

 

[BukitCase]

Bonnyman, what were you measuring that only runs half an OUNCE of pressure/vacuum - return air flow, or?? .. Steve

 

[bonneyman]

It turned out to be more of a novelty than anything. Didn't use it all that much, basically just wanted to be able to check CFM at the resisters.

I attended a class or two where the older tech teacher used a magnehelic for troubleshooting. I was going to get one, but then it turned into a "my eyes were bigger than my stomach" kind of deal. In the end if I suspected a real airflow problem I contracted out a air balance place to come in and do the tedious work.

 

[Milton Shaw]

It depends on what you are measuring. Natural gas/propane pressures are listed in inches of water measurements so you would use water with something to color it. Most of the things that would require mercury would be pressures a regular gauge would work on. Inches of water measurements are quite a bit lower pressures than you would normally measure. For instance 33 feet (396 inches) of water is about 15 lbs pressure or 29 inches of mercury.