Reversible Pump

[H2O101]

I'm having a horrible time trying to find a pump for my application:

~3 USGPM @ 20' TDH
low maintenance
instantaneously reversibly (no modification required to make it so)

All the lobe manufacturers don't go low enough in flow. I'd like to avoid labour intensive units like peristaltics and rotary vane pumps. There is SAWA out of Switzerland who makes a reversible centrifugal pump, but the cost is outside of my intended price range. Any thoughts?

 

[hydrae]

H20101

Reversible centrifugal? If you spin a centrifugal backwards it produces water in the forward direction with marignally less head and significantly less flow. The only way to make a centrifugal reversible is with a network of valves or a reversing valve ...

Hydrae

 

[btrueblood]

Why are rotary vane or lobed-impeller pumps labor-intensive? What is the fluid?

Gear pumps and flexible-vane rotor pumps are reversible too.

 

[H2O101]

Hydrae - Oh we questioned it too, but it extists, and works, there technical information is rather limited though, and it's hard to get a handle on exactly how. It's not a typical end suction pump. In theory, it's more like a vane type but with a slight clearance, so no typical wear...that's all I could get.

btrueblood - Lobed aren't, but I can't find one small enough. We don't want to maintenance (or operating costs) of replacing the vanes. Gear pumps may be an option, but there's a concern about the lack of lubricity as we're only pumping water. If by "flexible-vane" you are refering to a flexible impeller, like what ITT Jabsco provides, we have experience with them, however, to reverse them, the impeller needs to be removed and "twisted" in opposite direction. If you're refering to something else, please explain.

Thanks

 

[hydrae]

H20101

Ok you take the progression of centrifugal to mixed flow to turbine to propellor pump, in each case the head per stage drops and the flow increases, when you get to the propellor pump it is reversible I agree, so to get 3 gpm at 20 tdh it would need have many stages, more moving parts, yes it could be built but at what cost?

Is two pumps and check valves a posibility (one pump for each way)?

Hydrae

 

[JStephen]

I was just going to suggest two pumps and check valve on each- and see the person above has. Seems the simplest approach.

 

[H2O101]

A two pump system is our current standard for this type of process. However, a reversible pump simplifies things much more, and eliminates a complete series of automatic valving.

I may ultimately have to revert to that route, but I'm trying to explore my options.

 

[JStephen]

A stupid question from a non-pump person- what happens if you connect two pumps outlet-to-outlet, and just turn on one or the other? Would pressure drop through the "dead" pump be too excessive? I suppose the unpowered pump would just freewheel a bit as you pumped. But this would eliminate any check valves. I know they sell "trash" pumps that have larger-than-normal free openings through the pump; perhaps something like that would also allow better backflow.

Now that I think about it, with two pumps and two check valves as I mentioned above, flow from one pump would just circle back through the other pump- hadn't thought of that.

 

[25362]

There is one article in the ChE issue of Jan. 26, 1981 titled Using centrifugal pumps as hydraulic turbines by Fred Buse (Ingersoll-Rand) that may interest you.

 

[btrueblood]

H20101,

You're right about the ITT/Jabsco pump, but there are other versions out there that can reverse just by twisting the shaft. Don't know if they'll meet your head/flow requirements.

If a vane pump will wear out (even with carbon vanes) in your application, then yes, gear pumps are probably ruled out too. But there are a lot of vane pumps and gear pumps used in clear water with pretty long service lives.

A rotary lobe pump would work, but is subject to abrasive wear also (it just doesn't degrade as badly in performance). But, you are right that it's tough to find a manufacturer, much less a model in the "right" size. A gear pump with loose tolerances on the pump gears, and external timing gears (like a lobed rotor pump) would work as well, and maybe you could fabricate one to suit your needs.

Check

http://www.fristam.com

- they have a rotary p.d. piston pump that is advertised as reversible.

 

[btrueblood]

Huh, as soon as I sent that last post, the dang web browser finally woke up and gave me the following (via Google search):

http://www.boergerusa.com

They have a rotary lobe pump, with helical lobes (reduces pulsation), and with hard metal or soft elastomer impellers. These last would work great in a condition with potential for solids ingestion (tends to cause major malfunctions in hard-metal rotors). Their 25 frame size pump peaks at about 12 gpm, so it would work well in your application (just run the pump at lower rpm).

Another possibility is

http://www.pump-manufacturers.com/suppliers/vogelsangusa.html

They have a 45 frame size pump that goes up to 69 gpm, a little big...