Vacuum Flow Meter for Compressed Air

Following are details what i got; Fluid is air but when they to empty the tank, they make sure to suck all the air so they want to install a flow meter for this

Line Sizes: 8”

Max. Flow rate: 6000 m3/h

Max. Temperature: 50 C
Max. Pressure: 10 bar g
Fluid: Compressed Air

Whats wrong with air in tank?

They never get all air out, but check vacuum pumping for information.

Install a flow meter on the outlet of the pump and you see how much comes out.

John is right, no suction needed if container has higher than atmospheric pressure.

We need more detail about what you're trying to achieve.

If the object is just to get the tank to as close as possible to 0bara, and it starts at 10barg or anything above atmospheric ~ 1bara, first thing is to vent it to atmosphere before starting any vacuum pumps.

Another one of those non-numerical posts. It's time to put it right.

Questions:

• Flowrates?
• Pipe diameters?
• Pipe materials?
• Temperatures?
• Pressures?

All the usual stuff. Plus:

• Why is air <...flow rate...> of such interest, when the pressure, or absence of it, in the <...tank...> is far easier to measure?
• Please describe the pressure rating and the volume of the <...tank...>?

_{because this quest sounds like bullshine at the moment.}

Following are details what i got; Fluid is air but when they to empty the tank, they make sure to suck all the air so they want to install a flow meter for this

Line Sizes: 8”

Max. Flow rate: 6000 m3/h

Max. Temperature: 50 C
Max. Pressure: 10 bar g
Fluid: Compressed Air

Why do you need to add another meter to this at all? There is an orifice at the junction of your tank and evacuating device. Just measure or look up the size of this orifice. The pressure differential across this orifice will allow you to calculate the flow.

If you "suck all the air out of a tank", this will happen!

Railroad tank car vacuum implosion

...if it is not rated for full vacuum, perhaps.

Perhaps the <...they...> have already thought of this, though at the moment it's impossible to tell; perhaps the original poster has disappeared up the vacuum hose never to return...

Perhaps only a small part of the original poster has been subjected to vacuum, in which case his motives are a whole new subject.

This post is illogical and not realistic. The OP is clueless. Whoever, "they" is has no idea either. "All of the air" means a hard vacuum, and the result is pictured already. Unless this imaginary tank is built to withstand 14.7 PSI external pressure.

In any case a flow meter is useless for this folly.

Until "they" explain what "they" are really trying to do this is a waste of time.

I would put a valve in the main line with a metered bypass....when the tank approaches 0 psi close the valve and measure the flow in the bypass line...

A rotameter. (Plus maybe a pressure gauge and some computation.)

Weigh the tank. You can get digital personal scales for around $10. Good for maybe 180 - 200 kg. Use a flexible hose.

When the weight stops going down, the tank is empty.

Though you may not always get the same 'empty weight', if there is condensation in the tank.

Almost right, Rel PL.

I have a medium size 2 cylinder compressor (bought 20 years ago for $95 - & running well now, as I write this. It has had an oil change, though - IIRC)

It looks to me to be about 2 cu ft volume - 0.07 kg air, at STP. The resolution on my (consumer) digital personal scales is 0.1 kg. So, more likely than not to register.

P.S. Where can I buy those lights?

P.P.S. How do you handle the pain when the sight of the vacuum hits the back of the retina?

Air at [loosely defined] ambient temperature and pressure has a weight of around 1.2kg/m³. Its effect is slight and usually swamped by other effects in everyday occurrence. However:

• for precision weighing as an extreme example, the partial buoyancy of the test weights in air has to be taken into account, as the weights will give a different outcome in a pressurised environment, in ambience, in a partial, or in a total vacuum.

If they fill the tank, shut off the fill and then empty it then you could use pressure and volume of the tank as well as exit pipe size (as this will ultimately determine flow rate if tank is large enough) to calculate the flow rate. That would just require a very inexpensive digital pressure transducer and display with minor mathematical scaling option.

"If they fill the tank." How will anyone know when the tank is "full" of air? Air is compressible. Is there a sight glass? A level indicator?

A tank with one molecule of air, still has "air" in it. How full is full?

Did you catch this?

Line Sizes: 8”

Max. Flow rate: 6000 m3/h

Max. Temperature: 50 C
Max. Pressure: 10 bar g
Fluid: Compressed Air

If they want all the air out of the tank they can just fill it completely full of water!

This thread would start better with a description of the process and an explanation of why <...they...> need all the air out of this tank and why it can't just be filled with water instead. Get writing!

I agree that the op should restate the question giving details of the process involved.

If the tank must be purged of all oxygen before refilling,then an inert gas should be used to flush the system.

Unambiguous answers require clear questions.