centrifugal into lobe pump line

[pdvl]

I havve a question that I need help / opinions on please:

I have to mix two liquids and control the volume ratio of one to the other to get the right mix. Liquid 1 is from a silo, pumped with a centrifugal pump.

Liquid 2 is currently being pumped by a lobe pump as it is leaving an upstream proccess, going into a silo, and I need to put a tee into the line on the positive side of this pump and use a control valve arrangement to bleed some of the liquid into my new tee line (the flow is variable and i only need some of it for mixing, the rest goes into silos as current. This tee then goes into the Liquid 1 line (ex the centrifugal pump) to allow the two fluids to mix. The liquid then goes through a static mixer, then into a tank.

My question is: will this work - i.e. can a positive displacement type lobe pump discharge effectively into the discharge side of a centrifugal pump? or will the centrifugal pump dead end due to the pressure of the P.D. pump? Should I use a constant pressure valve on one of the lines?

Any help would be most appreciated. I have attached a simplified sketch to this post. Thanks.

 

[pdvl]

any feedback at all would be most appreciated guys.

 

[Compositepro]

As far as your drawing goes it should work okay. The backpressure on the centrifugal pump has little to do with the other pump but more to do with the pipe and valves to the tank. Silo normally means a vessel for solid materials.

 

[pdvl]

thanks Compositepro... we have had trouble in the past when lobe pumps and centrifugal pumps discharged into a common line, as depending on how the pumps and line is sized, the lobe pump sometimes "wins out" in terms of flow as lobe pumps do not reduce flow rate much in response to higher pressure (within reason), while centrifugal pumps do, but considering I am bleeding off only some of the lobe pump flow (1/3rd to half), it should be ok.

re silo for solids - I know! but in the food industry here we use silo for liquid and bin for solids, and now i have that habit as well.