how much pressure normal Septa can handle

[jiangds06]

right now, I have around 35psi. Is this gonna cause a problem?

[dblux_]

Nope.

[rb6banjo]

35 psig? What column do you have in your GC? For a 30 m x 0.25 mm x 0.25 µm phase that's about 70 cm/s at 40 °C with a helium carrier gas and an atmospheric pressure detector. That's awfully fast.

[Consumer Products Guy]

35psi is not that much for a packed column...

[thohry]

That's no problem. My colleague runs detailed hydrocarbons analyses, and he needs about 100 psi. The column is a 100m capillary.

[rb6banjo]

Does he use a hydrogen carrier?

I realize that it may work for him but 80 cm/s (100 psig) is pretty far from the "optimum" flow for a helium carrier gas on a 100 m column. For helium, the van Deemter curve shows the smallest plate heights at about 20-30 cm/s.

[dblux_]

Does he use a hydrogen carrier?

I realize that it may work for him but 80 cm/s (100 psig) is pretty far from the "optimum" flow for a helium carrier gas on a 100 m column. For helium, the van Deemter curve shows the smallest plate heights at about 20-30 cm/s.

In turn I realize that you have not taken into account that these 100 m columns have usually 0,25 mm ID and that type of application is usually not isothermal. What if the final temperature is 250 degC (constant flow).

When assessing septum pressure tightness, maximum pressure during run is the right value.

MfG

[rb6banjo]

Ok, if you're starting at 250 °C with that dimension, then the linear velocity is more like 38 cm/s. That's a lot closer to the 20-30 cm/s that is considered optimal for helium.

I'm looking for much smaller molecules than that, hence my statements came from my paradigm.

[James_Ball]

right now, I have around 35psi. Is this gonna cause a problem?

35psi should be no problem. If you have a leak detector just check occasionally to make sure you are not leaking through the septa since the needle does slowly wear away the opening, if so then replace and you should be ok.

[jiangds06]

Thanks a lot!

right now, I have around 35psi. Is this gonna cause a problem?

35psi should be no problem. If you have a leak detector just check occasionally to make sure you are not leaking through the septa since the needle does slowly wear away the opening, if so then replace and you should be ok.