dkelly wrote:
Carrier gas: He
Desired Flow: 114.9 mL/min
Pressure: 55 psi from cylinder
Col Dem: 30m x 25mm x .25um
Oven temp: 190
Split Ratio: 50
I hope that is 0.25mm diameter. If so according to my calculator which maxes out at 100ml/min flow it would take 287psi to achieve the flow, so you would need over 300psi to reach 114.9ml/min helium.
If the total flow is 114.9 with a split ratio of 50:1 then you have a column flow of 2.298 which is more achievable. At 114.9ml/min column flow and 50:1 split you would have 5745 ml/min at the split vent which would empty your helium cylinder in a day.
With a column diameter of 0.25mm and flow of 2.298ml/min you require a head pressure of 31.1psi to maintain that flow rate so it could be you need more than just 55psi from the cylinder to keep the head pressure up and flow that much to the split vent.