Mixing by Weight?

[rjack321]

What Tobin is says is that the hose will change the force its applying to the tank and hence the scale as it pressurizes. So it will play havoc with your calculations because you won't be able to compensate for it. Every time you connect it will be in a different shape and apply different forces to the tank as it pressurizes.

 

[Superlyte27]

1. If it aint broke, don't fix it.
2. Sometimes there's no creating a better mouse trap.

With an accurate digital gauge and time on my hands... I can fill 32% within a 1/2 to 1/4 percent every time.

 

[Gilldiver]

Mixing by weight is the standard practice for specialty gas mixes. These mixes can have up to 16 different gasses and are used for calibration for automotive and stack gas testing. The weight of the fill whips is a constant but there is the problem of air drafts. That is why mix by weight is almost always done in a draft closet. A draft closet keeps air flow from affecting the scales. If you go into any lab that has a scale that goes to more then 2 decimal places it is almost always inside an enclosure for just this reason.

 

[dannobee]

Mixing by weight is the standard practice for specialty gas mixes. These mixes can have up to 16 different gasses and are used for calibration for automotive and stack gas testing. The weight of the fill whips is a constant but there is the problem of air drafts. That is why mix by weight is almost always done in a draft closet. A draft closet keeps air flow from affecting the scales. If you go into any lab that has a scale that goes to more then 2 decimal places it is almost always inside an enclosure for just this reason.

Interesting that you mention automotive. Our emissions testing machine (smog machine) uses calibrated gas, but there is a "range" of the calibration gases that must be entered into the machine when the cal gas bottle is changed. The range is wide enough that I'd have a problem using that variance as breathing gas.

 

[Gilldiver]

Interesting that you mention automotive. Our emissions testing machine (smog machine) uses calibrated gas, but there is a "range" of the calibration gases that must be entered into the machine when the cal gas bottle is changed. The range is wide enough that I'd have a problem using that variance as breathing gas.

It all depends on to what standard you are testing to, they vary from State to State. Stack gas testing can be a lot more precise. Most of the gas standards I see come with a GC-Mass Spec analysis along with the specification range, they are also mixing anything from a small 6 foot bottle up to a 200 cubic foot bottle.