Vertical Reservoir Manometers and Marvel Mstry Oil

[1bolt]

Okay I've been searching/reading and could really use a little clarification on well or reservoir style manometers for my specific setup.

This thread answered a lot, but brought up a couple questions.

This is long but please bare with me and tell me if my assumptions are accurate or (more likely) wrong.

I am converting over from 6' tall U tubes (extra long for two way use). I have one U-tube plugged into either side of the O-plate on the tank for measuring differential. and a U-tube coming off the bottom of the stack. I use the two measurements to arrive at CFM flow in a spreadsheet I have.

The bench is an "orifice in tube" style bench (I believe you guys call it that) which consists of two/three large Shop Vacs, into an orifice chamber (a large propane tank cut in two with a steel O-plate bisecting it) leading to a PVC elbow, then a large 6" ID PVC "stack" (2' tall) connected to a bore sim. (1' long) and adaptor.

What I want to do is convert the U-tubes to reservoir style, using 1/8" ID acrylic tube. I want the zero to be about mid way up the 6 foot length so it will have 36" of drop for exhuaust and 36" raise for intake.

Assumptions: I can mount my well in the middle of the tube so the fluid level inside and thus the Zero is half way up the acrylic tube? Will the long run of tubing going to the bottom of the acrylic piece effect the accuracy? Also if this run of vinyl tube were to be say 1/4" ID would the mismatch effect accuracy in any significant way?

#2: According to that above link I need about 8 sq inches of fluid surface area inside my well, for an 800:1 ratio. because my acrylic tube is about .125" ID

#3 can I use the same mm scale (litterally two nice stainless steel metric yard sticks end to end one for down/exhaust and one for up/intake) as I used with my U-tubes and remain accurate with the spreadsheet I was using with the U-tubes?

#4 Is 36" enough? I've seen "stack" measuments over 1000mm at low to no valve lifts with my bench, which is one reason why my U-tubes are 6" (to keep surges from spitting/sucking the water out). I guess what I'm asking is will the reservoir dampen or change my "range" of fluid movement (a real newb-ish question I know). I want to keep the wide range to make the scale as fine and easy to read as possible (and also lower the impact of getting a reading off by a mm or two).

Last, can anyone confirm the specific gravity of Marvel Mystery Oil? I've seen Both Bruce and 2seater say it was .830 but also seen Bruce say .876 (most recently).

[bruce]

[color=#000000]A quick reply to one answer on the specific gravity of MMO here is the info from the MSDS from the Marvel/Turtlewax Company:

September 1,2005 Page 3 of 5
9. PHYSICAL AND CHEMICAL PROPERTIES
PHYSICAL FORM: Thin liquid
COLOR: Red
ODOR: Wintergreen
BOILING POINT: Not determined
MELT / FREEZE POINT - 60

[49-1183904562]

Bolt,

If you are going to try oil, you might look into Dot 5 as it is silicon and will 1) be less lilley to affect your tubing and 2) les likley to stick to the walls making it mre accurate Sg is .985 Close to water.



Also you might find it easier to just use a switch to change between pressure vacuum mode o your monometer they are cheep and would make your set simpler.

Search on the site many haved used them.

Rick

[1bolt]

Okay I saw some switch setups and have been contemplating that... which would leave me with shorter meters and still more available scale range... and I could forego having the reservoir in the middle. I could go with 48" or more and still be off the ground for easy reading. I like the simplicity of vertical over inclined and I don't really have the right space in my shop for inclined anyway.

I don't think MMO is any danger of messing up acrylic tubing and I already have some on hand. The lower SG gives me more sensitivity to the depression I have on hand which is just barely adequate for flowing a wide open intake or exhaust. Especially exhaust where the shop vacs are blowing and less efficient and I get less depression.

Are The assumptions I listed okay?

[49-1183904562]

Yes You should be fine, but making it a little more complicated than needed. An Incline only needs to be 6 to 10 inch's of rise so at 6" you are talking roughly 10"scale at 30 degrees and now H2O is 67% more sensitive and Using MMO you are only 13% more sensitive..

Rick

[1bolt]

Okay I'm encuraged... but why am I complicating it? Seriously I've no pretences about being a manometer expert so feel free to explain.

Am I reading right that inclined gages can be shorter and still show variations in flow as larger easier to read movements?

As I've said inclined will be problematic in my shop setup, the bench is already tall and compact, so a long inclined meter would stick out either side of the bench.

I guess I'll do some reading on inclined meters.

[bruce]

You can have a very effective inclined manometer in less than 24". Using the manometer spreadsheet in the spreadsheet area you can design a manometer to fit your bench requirements.

Yes the incline will allow you to see smaller variations in flow as larger easier to read movements.

There are some pretty indepth discussions on inclined manometer design here on the forum.



Edited By bruce on 1228093560

[2seater]

Bruce is right, all the listings I can find are for the sg that he mentioned. The information I used before came from our company MSDS database, which is apparently wrong. You can compare water and oil with two parallel U-tubes and the same vacuum or pressure applied.

I used MMO for quite a while and it has advantages and disadvantages. It doesn't freeze and being lighter than water, the scale equivalent to water is expanded, which is easier to read. Sort of like adding a bit of incline to your vertical scale. The 36" WC scale will actually cover 41" or so. It also is relatively slow to respond, so it has a natural damping effect. The color is also wonderful for contrast.

The dampened response has the downside of not being terribly responsive if you are looking for turbulence or transient events. The response can be improved some with larger diameter tubing. I would be a little concerned with using very small i.d. tubing as the film strength may make it difficult to return to zero. You may want to actually experiment with the tubing size before you commit. I actually purchased teflon tubing to keep the wetting effect to a minimum but it still exists, even after I switched back to water.

Personally, for the test pressure U-tube or reservoir type, I would make it as large as possible. Mine is over 80" and is mounted to the wall. I like the reservoir idea as you only have a single wetted leg, but the coices are yours. It doesn't cost much to experiment.

[1bolt]

Yep it is fun, making improvements, making it easier to use and better laid out really pays dividends. Also pays to ask here Thanks of the advice and clarifications. I think I'm on the right track... Mostly the only thing holding me up was the feeling that I was missing something on one key assumption... It's counterintuitive just how forgiving water gauges are to set up. Something in my mind just couldn't get passed the idea that having a bigger reservoir or 1/4 ID tube running to a 1/8 ID meter should throw things out of wack.