Manometer Question

[Jeffrey Schronce]

I have a question for you guys and am sure that you guys will have the answer. I recently picked up a down draft table from Wilke Machinery. I bought it off Ebay using the "Best Offer" function and practically stole the thing (gloat over).
I have a question on the Manometer. It is the following Mark II 25 :

http://www.dwyer-inst.com/htdocs/pdf.../mark2_iom.pdf

On their instructions there is a high and low pressure connection. The unit has the Mark II installed with 1 pressure connection as shown below.

Is this set up correctly? The unit came with no instructions. Basically the pre-filter consists of layered furnace filter material. Then below it is the 1 micron bags as found in a over head air cleaner. The motor is mounted to the bottom with the exhaust fan blowing out toward the floor.

[bigsteel15]

Looks right to me. The high connection is the one hooked up, so it looks like it's measuring the dscharge after the filters, correct?
It is only there to indicate clogged filters.
If you know what it reads with clean filters, then you'll get to know what reading indicates dirty.
If you wanted, you could hook up the low side to before the filter, but this gauge probably wouldn't be accurate enough to change a noticable amount with dirty filter then.
If you want to measure differential, I have a Capsuhelic I'll sell cheap...or maybe I just found a use for it.

[Ripsaw]

Although I am not familiar with this table, this type of manometer is used for differential readings.
In this case I am assuming it is meant to read the difference in the table draw and ambient.
Some times they are used to read diffences between two rooms, lets say a room and a hallway.
In that configuration the low port would be connected to a tube with the open end in the hall.

It is important to note that the red fluid is not just coloring, but has a certain specific gravity matched to the manometer. The required SG should be written on the face of the unit. If you need to replace the fluid this is something to consider.
There are three main SPs in use amoung manometers.
Also, it appears that the low port is just the flush opening at the top with no protection from dust or contamination.
You may want to consider putting a plastic elbow on there to limit fouling that would change the SG.

[Stytooner]

I think its okay like it is. I built a home made jobby that basiclly worked the same way.
Its a water level manometer though.
I did notice with both sides hooked up that you would get twice the movement in the water level. Therefore more accurate I think.

[Jeffrey Schronce]

Thanks guys!

It did come with the correct gravity fluid.

So, basically the numbers are not relevant to me until I determine their values, ie how dirty the filter may be at that time?

[bigsteel15]

Thanks guys!

It did come with the correct gravity fluid.

So, basically the numbers are not relevant to me until I determine their values, ie how dirty the filter may be at that time?

That's the way I would lokk at it.
Start with clean filters and when performance degrades, put a mark just before that measurement for next time.
Lee is right though, a u-tube is definitely the better system other than a magnahelic or capsuhelic that run in the hundreds. the only problem there is evaporation and water should be demin.

[Ripsaw]

You may want to to check it occasionally for zero or null without the unit running (or both ports at ambient).
Fluid evaporation, or vibration may change its attitude giving a false indication.

[Stytooner]

Thats the good thing about a home made type like I built. When its off, move the ruler to zero. Even though there is a little fluid loss, the readings will still be the same as long as you zero it.
What type fluids don't evaporate anyway? What about antifreeze? Brake fluid? Mineral oil?

Liquid mercury doesn't but not mentioning the toxicity, would you get much movement from heavy metal?

[bigsteel15]

Liquid mercury doesn't but not mentioning the toxicity, would you get much movement from heavy metal?

Yikes!!
The mercury would fluctuate with temperature, but I don't think it would move enough for the air. The specific gravity of Mercury is 13.61 so if I'm not mistaken it would take about 13.61" wc to move 1" wc on your indicator.(Those in the know please insert correction here )

[ryan.s]

Excuse my ignorance but what is the Manometer used for in your case?

[Ripsaw]

Nice job Skytooner. What you have created is called a "Slack Tube" Manometer.

Temperature will have an effect on all of these units, not just a mercury column. Another reason to adjust for zero point is if there is a significant change in temperature.

Vibration may also cause air suspension in the liquid. As temperature increases the air pockets expand causing larger errors at higher temperatures (more expansion).

This can happen to Mecury Liquid-in-Glass (LIG) thermometers. Normally caused by storing on their side or vibration through shipping.
Once gas is trapped below the surface it is difficult to remove due to the fact that it's bouyancy is not high enough to overcome the weight.

Ryan, the manometer is used to read differential pressure. When the difference in pressure drops significantly it's time to clean or replace the filters.

[bigsteel15]

Finally, another Alberta member.
Welcome aboard Ripsaw.

[Ripsaw]

Thanks bigsteel,

Been peeping here for awhile..... didn't join until I traded up to a BT from a BTS15.
A world of difference.