Sewage Lift Station-Low Flow, High Head

[dericw]

thread407-260931
I have a similar scenario to that of Crazyhorse81 (referenced thread) where I need to come up with a sewage lift station design for 150-300 gpm at 330' TDH. The discussion about the Progressive Cavity Pump perked up my ears and I have contacted Mono. I'm hoping Crazyhorse81 will see this thread and let me know where he ended up going with his design and also for anyone else out there with experience with PC pumps to give me their thoughts.

 

[JJPellin]

We use progressive cavity pumps in sludge service. One set is in the feed to our centrifuge for dewatering the sludge and the other set is pumping the "cake" or dewatered sludge for injection back into our crude tower. Our sludge is extremely abrasive with silica sand. We were destroying rotors and stators on the original cake pumps. Then we converted to a Viton stator and a Tungsten Carbide rotor. We have had very good reliability since then.

Our pumps are manufactured by MGI Pumps (Monoflo) and Robbins & Myers (Moyno).


Johnny Pellin

 

[chris00nj]

You also could consider a rotary lobe pump. Like PC pumps, they are also positive displacement. They can run dry (unlike PC pumps), take up a lot less space than a PC pump, and the maintenance is a lot more simple.

Viking and Vogel are two manufacturers that come to mind.

 

[micalbrch]

Rotary lobe pumps can run dry? Really?

A PC pump is a good choice but as JJPellin stated you have to make sure that you get the correct rotor/stator materials. And wrapping (in case you have hair and fibres) can become a problem, too.

A piston diaphragm pump can easily handle flow and head. Properly sized and selected you will have a high availability. But the initial costs will be higher than with a PC or rotary lobe pump.

I'm not sure about centrifugals but I think they can do it as well.

 

[chris00nj]

Manufacturers claim that rotary lobe pumps can run dry. I'm sure you can if you have a sealless pump. I wouldn't want to try it with mechanical seals.


A centrifugal won't be likely to be able to handle that lower flow - high head combination. Even if they could, you'd likely be running at the back of the curve.

 

[piffer]

I am aware of a PC Pump operating OK in a sewage lift station application. As chris00nj states, "And wrapping (in case you have hair and fibres) can become a problem, too." If the PC pump becomes problematic and expensive to maintain in this installation, all of your options (pre-screening, retrofit) will be expensive.
I am also aware of a wet-pit/dry-pit station (Flygt N-Pumps in series) that is operating successfully at 400 GPM @ 280 FT TDH. 300 GPM at 330 FT TDH is within reach of their 3" N-Pumps operating in series at 2-pole speed (3600 RPM). The TDH is close to the limits on the mechanical seals, so a factory engineer should be consulted.

 

[dericw]

Thanks everyone for your input on this one. It was all very useful. As of now, a PC pump with a grinder on the intake appears to be our best option. I appreciate the comments about the stator & rotor as well.