Have we created a pressure booster?

[baatsman32]

I came across a hydraulic system at work which I need to understand fully. We are pumping out electrolyte from a small tank (~20" diameter) with pressurized nitrogen at 20 psi. The electrolyte leaves the tank in a 1/2" pipe. The outgoing electrolyte shows a pressure of 50 psi. I think the original intention was to have the same pressure on the outgoing electrolyte as the nitrogen that we use to push the electrolyte with.

My guess is that we see an increase of pressure of the electrolyte because we are creating a pressure booster since we are pushing with a smaller pressure (20 psi) but with a larger area. Can this be the case? As you probably can tell, I do not have much experience within piping and hydraulics.

Thanks!

 

[Compositepro]

You cannot get a pressure boost by pushing a fluid with a fluid. A couple of principles that apply to fluids is that they conform to the shape of the container and that the fluid pressure at at point is the same in all directions. Pressure amplification requires solid pistons so that the force of one piston can be applied to another piston of differing area. Fluid inertia can also be converted to pressure, resulting in water-hammer.

 

[EdStainless]

There can also be effect of fluid momentum and elevation differences.
But in your case I suspect gauge errors.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[3DDave]

Some basic error in measurement is being made.

The volume coming out of the tank has to equal the volume displaced in the tank. Since, as a first approximation, Work is pressure times volume and the volume change at each location is the same, then more Work would be coming out than going in. If that was true, you could feed the outlet back into the tank and build a bomb by increasing the 20psi->50psi->80psi->110psi and so on.

Obviously this cannot be true so a closer examination of the setup is required.

 

[LittleInch]

Well first off you're not "pumping" out, but flowing out, unless there is a pump in this system you haven't told us about.

~So unless your tank is about 20m tall and full of your electrolyte, one or other of your pressure readings is incorrect.

Static height between the top of the liquid and your measuring location will add to the Nitrogen pressure if the location is lower than liquid level and reduce the pressure f it is above the liquid level.

Try ad draw this out noting the elevation of the top of the liquid and the pressure guage location as a minimum. Then it might, just might, make some sort of sense.

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

 

[baatsman32]

Thank you for your answers. This is why I don't understand the system. I drew a quick sketch of how the tank containing the electrolyte and the nitrogen (gas) are connected. The outgoing electrolyte (50 psi) enters into a smaller tank of which the level is being regulated by demand. The height difference in the system is negligible. I would estimate the height of the tank to about 1m.

 

[LittleInch]

There are a few possible explanations.

1) If these are flowing pressures - Your gauges are wrong (try fitting new ones) or badly calibrated
2) There are some Non return valves in the system somewhere and your downstream equipment is at a higher pressure than your tank ( no forward flow fro the tank)
3) You have a locked in section and your pipe contents are at a higher temperature than the tank and you are seeing the effect of increased temperature of the fluid (also no flow from the tank)

You have not managed to create energy / change the laws of physics, but if you have then I want a share.

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

 

[SwinnyGG]

The above posters are all correct with regard to the fluid power at various parts of the system.

There two possible causes as to why you could be seeing this behavior in your system:

1) Your gauges are wrong.

2) Your system diagram is incomplete.

This is what you've given us so far. Normal lead is knowns (to us) and red is unknowns:

Is there an unaccounted for check valve in your system somewhere?

Where exactly are you measuring 50 psi?

What are the temperatures in the lines and tanks? Is it possible that you're seeing a heating effect upstream of a device which prevents backflow (and thus pressure signal transmission) into the N₂ pressurized tank?

 

[SwinnyGG]

Apparently, LIttleInch, great minds think alike.

 

[IRstuff]

At some point in time, you'll have emptied the tank; do you still see the same pressure readings if there's only N2 in the system? That'll pretty quickly reveal that one or both of the readings is incorrect.

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

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[Compositepro]

Are you reading 20 psi with a 500 psi gauge?

 

[baatsman32]

Here is a better system diagram. We have two equal designed systems with electrolyte/nitrogen-tanks going into the L-port valve just before the 50 psi gauge. This is also why I cannot check the gauge when the tank is empty, because it switches over to the other tank. The motorized valve before the smaller tank regulates the level of electrolyte in the smaller tank depending on demand. There are no check valves in the system and I know for a fact the there is no back flow, since we are depleting the electrolyte tanks.

I just don't understand the increase of pressure, it doesn't make any sense. The thing is, we have two systems like this and there is an increase of pressure in both of them at the same location. What are the odds that the gauges in both of the systems are faulty?

 

[SwinnyGG]

How does pressure on the gauge showing 50 psi change when the 3-way valve is closed to switch between tanks?

Does the E-lyte solution have a dissolved gas component?

You may not have a separate check valve anywhere... but are any of these valves equipped with internal backflow prevention?

20m is a relatively long tube run for a lab setup. What's the temp of the fluid before and after this run, and are there any potential heat sources in/on/near that 20ft tube run?

 

[itsmoked]

I could easily see the 50psi if both those motorized valves blocked off the gauge section, especially with 20 meters of pipe involved.

Sure be nice to have a gauge service valve installed at the 50psi gauge.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IFRs]

What is the liquid density and height under the N2 blanket?

Can you shut off the N2 feed, let the 20 psi go to zero, open a vacuum relief on the supply tank and watch the pressure at the 50 psi gauge as demand continues to exist?

 

[IRstuff]

20 meters of water = 28 psi weight pressure + 20 psi from trapped N2 or air in the 2nd tank = 48 psi

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

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[IFRs]

IRStuff - correct but the OP stated that "The height difference in the system is negligible."

I'm not expecting the liquid head to add much pressure since the OP also stated "the height of the tank to about 1m"

Looks like gauge error, gas generation inline, heat input between tanks or dark matter from another universe affecting his reality.

I wonder if one is reading psia vs psig or if one is reading a pressure differential while the other is reading a system pressure?

 

[IRstuff]

No height difference from the 1st tank to the meter, but there's a 20-m difference between the 2nd tank and the meter.

Lots of checks could be done, like emptying the 2nd tank and seeing what the pressure is, or making sure that the 2nd tank has no entrained/trapped N2.

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

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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[baatsman32]

The ~20 m pipe is located about 1 m above the 50 psi gauge. Could this really be the cause of the 30 psi pressure increase?

I don't see how emptying the 2nd tank would change anything since there is a valve in front of it which is closed all the time except when the tank needs refill (which is not that often).

 

[SwinnyGG]

The ~20 m pipe is located about 1 m above the 50 psi gauge. Could this really be the cause of the 30 psi pressure increase?

Unless it runs 20m vertically, no, it isn't the cause of the pressure rise.