Link between suction and volume

[EnginE3R]

Okay guys, need a little help with a work problem. Our QC labs called me down to analyse a little problem with one of their pieces of kit and I'm scratching my head a little. I might be missing something really obvious but thought better to ask and look the fool.

So, here's a break down of the situation. They have a piece of equipment that tests the consistency of a chemical produced. They feed 50ml through a filter (by a pump at the other end of the system running at i believe 400mb) which goes through two 500ml conical flasks (the flasks are there purely to protect the pump and hold the liquid), They time it takes to draw the 50ml and it must sit within a specified bracket. Too thick and it takes too long and fails, too thin and it goes through to quick and fails. The R&D labs have a similar piece of kit except it goes through a 1000ml flask first. So QC added this to their kit.... except they have now found that the time to drain 50ml of chemical has now nearly halved.

So there's the big question. In a system such as this, would increasing the volume of the area with less than atmos pressure, have an increased suction ability, despite being kept at the same internal pressure?

P.s: I roughly threw together the drawing on AutoCAD in about 10 minutes so don't take it as a perfect representation.

 

[LittleInch]

I'm struggling to understand the operation here and your diagram.

You say the fluid comes in via a pump, but then the drawing seems to show it open to atmosphere?
The drawing shows the pump at the far end presumably drawing down the pressure inside, but the tubes stop at the bung??

Where are the liquid levels in these vessels?

Or are they empty and your "pump" is just drawing down the air pressure to -400mbar / 600 mbara??

I think I've answered my own queries, but no, the area is irrelevant to the pressure.

so something else must have changed as well? Size of the tube for the filter?

Do you have a pressure guage anywhere?

What are these mysterious "controls"??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EnginE3R]

Hi LittleInch,

Sorry for the confusion. Yes the pump sucks air out of the system to create a "negative" pressure to such fluid through the filter. The "controls" is just a series of valves and NRV and pressure gauge. I just put controls as It was just a quick sketch and didn't want to draw in each.

And as for changes, there doesnt seem to be. The tubes in and out are just on bungs and they literally just added an extra bung, which has the same hoses as the others and put it into he 1000ml flask. the pressure gauge in the controls reads the same throughout as normal, same as with just the two 500ml flasks.

Filters are uniform, all coming from the same supplier and boxes.

The flasks start empty, its just to catch the fluid as it gets sucked through the filter so that it doesn't go through the controls or into the pump. The addition of the 1000ml flask was so that they could run more tests per flask draining.

 

[LittleInch]

All I can think is that the liquid vapourise a little / somewhat?? and hence in a smaller overall volume the pressure might increase more as a percent?

If it remains as 50ml of liquid I can't see how 2000ml of low pressure is that much different to 1000?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MintJulep]

The "controls" is just a series of valves and NRV

Are they all set the same?

 

[rothers]

So what are you checking for, viscosity ?

 

[chicopee]

You have a mass transfer problem spend some time on reading a book on heat transfer that would include the topic mentioned or Perry chemical engineering handbook.
I have the same problem as LI mentioned so don't take personally and that is your OP is confusing due to the way you are describing the process and perhaps due to some grammatical errors. Also your diagram does not show the location of the filter.
Information that you should gather should include data the vacuum pump and the filter( unloaded and loaded) performance under various flow rates. The manufacturers of these two items could help. On mass transfer, the topic on vaporization should help a lot.

 

[hydtools]

I would say the larger volume at vacuum pressure changes pressure less per ml of product so that the vacuum pressure stays low longer during the draw time drawing in more product per unit time. The delta pressure remains greater providing force to draw in product.

Ted

 

[IRstuff]

Just want to clarify; you say

The R&D labs have a similar piece of kit except it goes through a 1000ml flask first.

so the R&D setup has only a single 1000-m1 flask? Where is the control in that setup and how is the control used? Perhaps a timeline/operation sequence would help, e.g.,

> control open
> pumpdown
> control closed
> filtrate valve opened

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[TheTick]

Is there a particular,reason you must draw with a vacuum instead of pushing through?

 

[LittleInch]

Also are there any records or monitoring of the actual pressure in the flasks over the sampling time?

Where is the pressure being measured?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[3DDave]

Tick,

Vacuum is trivial to set up and is naturally limited by the local pressure of the air. If a glass container explodes under pressure the fragments can be propelled to considerable velocities; failure under vacuum doesn't have quite the level of damage as the initial parts are heading towards each other; they can collide and get redirected, but again, they are limited in energy by the local air pressure. A 1 bar implosion is better than a 20 bar explosion.

The described process does seem sensitive to changes in the setup. There are better ways to measure viscosity, which this appears intended to do, so I am at a loss as to why such a complicated method was chosen.

 

[LittleInch]

Nothing about how either the filter medium is identical or temperature of all the elements is kept the same or pressure is the same or.... any other difference between R&D lab and the QC lab.

I would like to bet there is something different other than the 1000ml flask.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Metalero]

Did you verify that the filters are the same, type, material and mesh or number?

The capacity and efficiency of the pumps is also a crucial factor, is the same or proportional?