Maximizing Mixing Efficiency: Inline Mixing Pressures & PD Pump Selection

[mrmiller1]

I have two streams at controlled flow rates that will mix via an inline static mixer. Both streams will have check valves before the mixer, however, do I have to worry about fighting pressures in this situation? If the one stream is 40 psi and the other is only 20 psi, will the 20 psi line become motionless? Both lines will be fed by positive displacement pumps.



Also, does anyone have any recommendations for the type of PD pump if I'm pumping 50% caustic? I'm worried if I use a gear pump the caustic will eat the gears. Perhaps a lobe pump would suffice. Controlling the flow rate is key here, so obviously centrifugal and peristaltic pumps are out.



Thanks in advance!

 

[gmax137]

If you have a PD pump in each line the flow rates will be equal the the pump flows. For example, if the "20 psi line becomes motionless" the pressure will rise above your 20 psi (and it will rise fast). PD pumps don't have a head-flow curve like centrifugal pumps do.

 

[mrmiller1]

Thanks. That makes sense.
Any idea how much pressure a glued cpvc joint will stand?
I know the piping itself is rated to 400 psi (2" sch 80) and I suspect if I use a longer setting glue it will only take it down to around 200. My instrument flanges are rated for 150, so that's probably my limit.