How to efficiently fill U-tube manometers - I don't want a red mouth, HELP!!!

[FPV_GTp]

Wooooooooooo nice info , I have a lot of reading to do thanks guys


cheers

[Moparsled]

As I have been reading up and trying to understand all the intricacies of the fluid manometers, (I'm not there yet) I think I have decided that Marvel Mystery Oil is the way to go for my bench build. I also really like this approach to the vertical gauge. So, my question-

If I build a single tube/reservoir gauge, and use MMO, is the scale still 1", or does it change because of the fluid SG, or the tube/reservoir diameter?

[106-1194218389]

[slracer]

[color=#000000]OK John, Somewhere you lost me. Remember that I am a Pitot Bench kinda guy!

As I understand it, the specific gravity of the fluid in the manometers doesn

[106-1194218389]

Doug,
What I was going on was Ed's spreadshhet to calculate the incline manometer setup. Using that it said that my delta p with water was 13.15" and if I used MMO it would only be 10.86" H2O". The delta p being the difference in pressure above and below the test orifice in the orifice flow bench. So if you test pressure is 28" H2O which is measured on the head (or in my case above the orifice) and the delta p is 13.15" when using water then my vacuum motors would have to be able to pull 28" + 13.15" = 41.15" H2O. Now if change to MMO which is less as far as SG then it takes less pressure to get it to the same 100% mark hence the lower delta p. That is why the delta p drops to 10.86" when using MMO. So now if I test @ 28" and the delta p is 10.86" my motors only have to pull 28"+10.86"= 38.86" H2O to get to the 100% reading on the manometer. This gives me a net gain of 2.29" H2O in usable test pressure. But you are right, now my orifice at 100% calibrates to a lower cfm. When I said performance gain I was refering to just test pressure.

I also notice that the id of the tube for the manometer and the well id also play a part in this so I have decided to design wisely.

Now on the verticle manometer you have answered a question for me. You "DO" have to correct scale to correspond to inches of water when using MMO.

Thanks,
John

[slracer]

Ed, Where are you?

John, I think you are using the numbers in the wrong way. It doesn't say that you NEED less delta P to test, it says that you CANNOT HAVE as much delta P to test. I put the incline rise to 36 in Ed's sheet (i.e., a vertical manometer) and got the 30.68 answer I had calculated above so I think my calcs are OK. What it says is that at a depression of 30.68 with MMO, you are at the top of the scale. With water at a density of 1.00, you could go on to 37.15 inches of depression before reaching the top of the SAME scale. With a fixed depression, the MAXIMUM delta P on the same inclined is 10.86 inches of water using MMO before you reach the end of the manometer. If you were flowing 13.15 inches with water in the gauge, you will be overpressuring when you change to MMO, so have to change the incline to near 16 to compensate. I hope that someone else will join in here as I am going to have to start all over understanding how these things work! -- Doug

[bruce]

Ok, the easiest way to do this on an orifice style bench is this; determine your Dp you want to use say 8,10, 12 etc machine your plates, using a calibration plate that flows XX% @ 28" (or a static pressure you choose) set your incline scale to read that XX% against your Dp orifice plate.

So lets say you have a 200cfm@10" inside your bench and you put a 160@28" cal plate on your bench you would set your incline to read 80% . . . simple as that.

If you make the pivot point of your inclined scale online with the gauge tube you will be able to tweak in right in. I found the numbers from the spreadsheet gets you close but you will have to tweak it on the flowbench. Ideally the pivot point should be at your zero mark otherwise you might have to do this a couple of times till it is right.

[106-1194218389]

Here is a post where I am asking Ed about this same issue. Bruce has stated a very good way to make sure your inclined is right on.

Quote (jfholm @ Sep. 18 2008,22:28)
Even though I input 12" as the scale vertical height it shows the delta P WC as 14.25". Can anybody give me a clarification there?

Delta P is the actual pressure difference that the manometer is measuring expressed in inches of water. It's different from the vertical rise on the manometer scale because you need to account not only for the vertical rise along the manometer tube but also the corresponding vertical drop in the reservoir. In your particular case, as the fluid moves up manometer scale changes through 12" vertical height, the fluid in the reservoir moves down 2.25" giving you the total delta p of 14.25"

[Moparsled]

question #2 about a well type vertical Manometer using MMO---

using 1/8" ID tube, looking for a reservoir diameter;

dia=.125
radius=.0625

Pi(R squared)= area of a circle

R squared= .00390625

Pi (.00390625)= .012265625 (square inches area inside tube)

1000x= 12.265625

12.265625 divided by Pi= 3.90625

round 3.906 up to 4, square root of 4 is 2,

2" radius x2= 4"diameter

I need an approximately 4" inside diameter round tube for a well.

that right?

[Tony]

Yes that sounds about right.
For a 1,000:1 area ratio, that requires a 33:1 diameter ratio.

But the well does not need to be very deep, because the fluid level in the well hardly changes.

[106-1194218389]

So if I have this correct, If I go to MMO then I have to change my vertical scale if I want my read out to correlate directly to inches. In other words since MMO SG is .876 and water is 1.0 then I would divide 1.0 by .876 and that would give me 1.142". So on my scale to read the same as water my graduations would be 1.142" apart instead on 1"?

I assume that is correct since it is lighter the same pressure would raise MMO higher? Is that correct?

EDIT: Ok my math skills suck! I found another thread where they did the correct just by subtracting the .879 from 1.00 to get the correction. In this case would that be what I do and the correction would be .124 so I would calibrate my scale to 1.124" MMO = 1.0" water? I was dividing 1.0 by .876 to get the correction factor before of 1.142" - which way is correct?

John

[49-1183904562]

John;

I am getting in on this late and do not wnat to confuse anyone but please tell me what is your motivation for going to MMO as a Fluid? If i understand this I might have some insight.

Rick

[1bolt]

I believe the motivation is that MMO doesn't freeze (good for unheated garages and shops) it's red and stays red so its high contrast, and because it has a lighter specific gravity it moves more with the same depression pressure, and it moves more when you make a small change to a port... In other words its a little more sensative and shows small changes a little better.

Some other side benefits I can think of are, its available at any auto parts place. for about 2 bucks a quart.

Also It does not grow algae inside your manometers like water can. Ask me how I know this :laugh:

[slracer]

John, I'd like to read the other thread, but as far as I know, you divide the water specific gravity (1.00 by definition) by the SG of the new fluid. That means the first way is correct. I was trying to figure out how the subtraction would work with the SF Blue fluid (about 1.92)? 1.00-1.92 equals -0.92 so SFBlue would be -0.92 inches @ 1 " H2O. Dividing by 1.92 says about 0.52 " SFBlue equals 1 " H2O. Makes more sense dividing! -- Doug

PS - Is MY race track totally under water?

[49-1183904562]

[color=#000000]As i had said on another post I'm not sure if the 1/8 inch/inch more sensitivity is really that much especially when you talk about the wall wetting and drain back error. All the trouble with the calculations etc It might just be better to go to the motorcycle shop and get some dot5 brake fluid, there are several colors ( I like the purple ) depending on who makes it and its SG is .958 +- depending on manufacturer. This equates to roughly .040 in an inch or a little more that a 32nd (not even the meniscus). With the thermal expansion of pure water being .00021ml/deg-c and the specific gravity of tap water being closer to .985, Correct me if I