[Dsg-mvt] [New Comment] second isobutane MFC running

[beng at jlab.org]

Comments:
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 - by beng on Thu, 01/11/2018 - 22:53.

Mixing Flows - I think just keeping an eye on the tank pressures to see that if it gets over 16 psi and the system tries to reduce the pressure, if all the flows are above the minimum MFC flows the current logic can be used (at the current demanded flows).

If we change the logic we should first try to use something similar to the DC mixing system where it bounces between the pressures, but by reducing and increasing the input flow by a fraction of the output flow instead of completely stopping the input flow. This seems to work well, but also they are much higher flow rates and much bigger tanks.

I'm not sure that requesting zero flow will actually result in no flow which in turn would throw off the mixing ratios when attempting to reduce the pressure. Maybe solenoids would need to be installed to actually stop the flow to reduce the pressure?

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Logentry Text:
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Since C4H10 MFC Mix1 is going very well, we switched on the MFC Mix2. So far so good.

We should maybe find another way to scale the required flow to maintain a reasonable pressure in the tanks. It might be better to fill at full flow up to 16psi, completely stop and restart when pressure drops under 7psi. 

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