Calculations Help: Working Out SF6 Usage in Litres

[Scara]

Hi Folks,

Not the best at this so hoping somebidy can help me.

I have a 67.4 litre vessel and I'm filling it with SF6 to 6Bar. Can I work out how much SF6 I'm using in litres?

Is this a dumb question? should nI be asking what weight I'm using.

I've been asked to supply usage in litres.

 

[Q_Goest]

Hi Scara. I can give you the density of SF6 if you can provide the temperature and verify the pressure is gage and not absolute pressure.

 

[Scara]

The sf 6 is at room temperature around 20deg Celsius . Pressure measured on vessel with gage.

 

[Q_Goest]

At 6 barg and 20 C, density is roughly 46.5 kg/m³. The saturation temperature at this pressure is -19 C and at atmospheric pressure the saturation temperature is -68 C.

So at this pressure and temperature, you have a superheated gas. I'm not sure why or how you could put that into liters, but I wonder if there is a liquid source and you're being asked to determine how many liquid liters are needed for this 64.7 L vessel, in which case you need to define the conditions of the liquid source.

 

[alphy]

Hello,

Calculating the usage of SF6 in litres can be done by converting the pressure and volume measurements into a more common unit of measurement, such as moles or grams. From there, you can use the molar mass of SF6 to convert to litres.

First, let's convert the 6 bar pressure to an absolute pressure in Pascals. 6 bar is equal to 600,000 Pa.

Next, we can use the ideal gas law, PV = nRT, to calculate the number of moles of SF6 in the vessel. We know the pressure (600,000 Pa), volume (67.4 L), and temperature (assuming room temperature of 25°C or 298 K). Rearranging the equation to solve for n, we get n = PV/RT. Plugging in our values, we get n = (600,000 Pa)(67.4 L) / (8.3145 J/mol*K)(298 K) = 162.66 moles.

Finally, we can use the molar mass of SF6, 146.06 g/mol, to convert moles to grams. Multiplying 162.66 moles by 146.06 g/mol, we get 23,742.5 grams of SF6.

To convert to litres, we need to know the density of SF6. According to the NIST Chemistry WebBook, the density of SF6 at room temperature and atmospheric pressure is 6.17 g/L. Dividing 23,742.5 grams by 6.17 g/L, we get approximately 3,845 litres of SF6.

I hope this helps you calculate the usage of SF6 in litres. Please note that these calculations are based on ideal gas behavior and may not be entirely accurate in real-world conditions. It may also be helpful to double-check these calculations with a trusted source or ask for clarification from your supervisor. Best of luck!