# Getting an exact amount of Methane out of a cylinder

• mkbent
In summary, this method of filling a tedlar bag with methane requires a water tank, a clear bottle, and a valve for the methane supply. Methane is charged into the bag through the top port while water is pushed out the bottom valve.
mkbent
TL;DR Summary
I want to fill a tedlar bag with an exact amount of methane from a cylinder.
Hello,

I am currently working on a research project that involves filling a 10L tedlar bag with about* 8 liters of methane gas from a compressed gas cylinder. I'm trying to work out the best way to fill the bag with a reasonable degree of accuracy while also minimizing (or hopefully avoiding altogether) the leakage of methane into the air. I do have access to mass flow controllers that maybe we could calibrate and use, but was wondering if there was a more precise way of filling them since the mass flow controller would fill the bag for a bit with lower flow while it gets up to the set point. I also could use a 1L gas syringe to fill the bag manually... but I am going to be filling a lot of these bags and that would give me a bit more of an arm workout than I was hoping to get for the next few months. Does anyone know of a better solution than either of these two methods?

Thanks,
Mike

Last edited:
Welcome to PF.

mkbent said:
Summary: I want to fill a tedlar bag with an exact amount of methane from a cylinder.

involves getting filling a 10L tedlar bag with exactly 8 liters of methane gas from a compressed gas cylinder.
8L at what temperature and pressure? How will you control the temperature?

https://www.supplymylab.com/Supplie...CMP7jkK-M8Wto6fvWYTO17NbF_hxA9UwaAm-TEALw_wcB

Welcome!
Could you place the empty bag inside a graduated recipient and measure the increase of liquid level equivalent to a volume of 8 liters?

Lnewqban said:
Welcome!
Could you place the empty bag inside a graduated recipient and measure the increase of liquid level equivalent to a volume of 8 liters?
That's a pretty good idea if I can find a graduated recipient big enough, thanks for the help!

mkbent said:
That's a pretty good idea if I can find a graduated recipient big enough, thanks for the help!
It could be any recipient with regular shape, if you can calculate the proper level differential for 8 liters or 8000 cubic centimeters, or 488 cubic inches.

mkbent
Lnewqban said:
It could be any recipient with regular shape, if you can calculate the proper level differential for 8 liters or 8000 cubic centimeters, or 488 cubic inches.
True I could just put marks in a trash can for 22 L and 30 L and technically would be fine. Gotta see if my boss / the sponsors would be OK with it but it seems cheap fast and easy.

Lnewqban
Lnewqban said:
It could be any recipient with regular shape, if you can calculate the proper level differential for 8 liters or 8000 cubic centimeters, or 488 cubic inches.
Or make two marks: one before you add the measured extra 8 liters of water and one after !

hutchphd said:
Or make two marks: one before you add the measured extra 8 liters of water and one after !
That's what I was saying, thanks again for the idea!

hutchphd
If you really only need 5% precision then you could measure the buoyancy in air. At STP 8 liters is ##\frac 8 {22.4} mole## and methane has a molecular mass of 16 while dry air is 28.97. So you would have about 4 grams buoyancy to work with.

This is how I would do it.
1. Set up an 8 litre clear bottle in a water tank, open neck at the bottom, two valves at the top. One top valve is for methane supply, the other for a tedlar bag.
2. Sink bottle into water tank with a top valve open, it fills with water through the neck.
3. When the bottle is full of water, close the top valve.
4. Open the methane supply valve at the top, as the bottle fills with methane, water is pushed out through the neck at the bottom. Raise the bottle as it floats up.
5. When water is at the 8 litre mark inside the neck, and water outside is at the same level, then methane is at atmospheric pressure in the bottle.
6. Connect tedlar bag to top port, open valve to bag, sink the bottle pushing all 8 litre of methane into the bag.
7. Close top valve as bottle is now full of water, ready for next methane charge.
8. Seal and remove the previous tedlar bag.
9. Go to step 4, filling the bottle with methane for the next bag.

## 1. How do you measure the exact amount of methane in a cylinder?

To measure the exact amount of methane in a cylinder, you will need to use a gas chromatograph. This instrument separates and analyzes the different components of a gas mixture, allowing for accurate measurement of methane levels.

## 2. What factors can affect the accuracy of methane measurement from a cylinder?

Some factors that can affect the accuracy of methane measurement from a cylinder include temperature, pressure, and the presence of other gases in the mixture. It is important to control these factors and calibrate the instrument properly for precise measurements.

## 3. How do you ensure the safety of handling methane in a cylinder?

When handling methane in a cylinder, it is important to follow proper safety protocols, such as wearing protective gear and using appropriate tools. It is also crucial to store and transport the cylinder in a well-ventilated area to prevent buildup of potentially dangerous levels of methane gas.

## 4. Can the exact amount of methane in a cylinder change over time?

Yes, the exact amount of methane in a cylinder can change over time due to factors such as leakage or evaporation. It is important to regularly check and monitor the levels to ensure accuracy and make any necessary adjustments.

## 5. How can the exact amount of methane in a cylinder be used in scientific research?

The exact amount of methane in a cylinder can be used in various scientific research studies, such as studying the effects of methane on the environment or using it as a fuel source. Accurate measurement is crucial in these studies to ensure reliable and valid results.

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