Over working chugger pumps

[awarner322]

Hey guys...been brewing on my eherms system for about six batches now and trying to improve efficiency. It was recommended that I slow down my wort extraction. My question is...is really restricting flow on the pumps bad for them? I'm guessing the answer is probably no....just seems like trickling water through them would tax the motor more our cause overheating. Can anyone confirm our deny? Thanks

 

[BlueHemlock]

Restrict flow on the output side of the pump and you'll be fine.

 

[jddevinn]

Restricting the flow on the outlet side of the pump is fine, inlet side is not fine. They are magnetically coupled pumps, so even if the impeller is moving slowly the motor is turning freely.

 

[BrunDog]

Restricting the flow on the outlet side of the pump is fine, inlet side is not fine. They are magnetically coupled pumps, so even if the impeller is moving slowly the motor is turning freely.

FYI, the impeller will not decouple normally under increased pressure. With the outlet port nearly closed shut, the impeller is still spinning at the rate of the motor - but it can only create a maximum head pressure which will limit the amount of flow through a small orifice

The magnetic coupling is there as a safety should the impeller jam. When it decouples, you will know it as the motor sound will change. When the motor spins back down, you will hear the magnets "click" as the impeller re-engages.

 

[TexasWine]

Hey guys...been brewing on my eherms system for about six batches now and trying to improve efficiency. It was recommended that I slow down my wort extraction. My question is...is really restricting flow on the pumps bad for them? I'm guessing the answer is probably no....just seems like trickling water through them would tax the motor more our cause overheating. Can anyone confirm our deny? Thanks

The short answer is yes, you can damage your pump.

For a given rotational speed, every centrifugal pump has what's referred to as a Minimum Continuous Stable Flow (MCSF). Flow rates below this will cause cavitation, and if the flow rate stays that low long enough it can result in things like impeller damage, specifically pitting of the impeller face. This happens even if you throttle the discharge.

You can tell when cavitation is happening because it sounds kind of like you're pumping gravel. The bubbles are collapsing against the impeller, making that noise.

Now, the real question is do you need to concern yourself with this? Maybe, maybe not. You probably don't know what the MCSF is for your pump nor do you have a way to measure the flow.

Personally, I wouldn't concern myself with it too much. Just listen to your pump. If it starts to sound like pumping gravel, open the valve a smidge and listen some more.

And yes, you should throttle the discharge. If you throttle the suction you're reducing the NPSHa available to the pump. This also can cause cavitation.

 

[jeschrich]

The short answer is yes, you can damage your pump.

For a given rotational speed, every centrifugal pump has what's referred to as a Minimum Continuous Stable Flow (MCSF). Flow rates below this will cause cavitation, and if the flow rate stays that low long enough it can result in things like impeller damage, specifically pitting of the impeller face. This happens even if you throttle the discharge.

You can tell when cavitation is happening because it sounds kind of like you're pumping gravel. The bubbles are collapsing against the impeller, making that noise.

Now, the real question is do you need to concern yourself with this? Maybe, maybe not. You probably don't know what the MCSF is for your pump nor do you have a way to measure the flow.

Personally, I wouldn't concern myself with it too much. Just listen to your pump. If it starts to sound like pumping gravel, open the valve a smidge and listen some more.

And yes, you should throttle the discharge. If you throttle the suction you're reducing the NPSHa available to the pump. This also can cause cavitation.

:rockin: Great definition of cavitation! I have not fired my new pump up yet as im still building my system but working at a high pressure hydraulic pump manufacture I must admit im excited to experiment.

 

[doug293cz]

...

The magnetic coupling is there as a safety should the impeller jam. When it decouples, you will know it as the motor sound will change. When the motor spins back down, you will hear the magnets "click" as the impeller re-engages.

Another (maybe the primary) reason for magnetic coupling a pump is that it eliminates shaft seals. All direct drive pump shaft seals eventually leak. For sanitary systems, leaking seals are a problem, as they are with noxious chemicals.

Brew on

 

[-CHRIS-]

Hey guys...been brewing on my eherms system for about six batches now and trying to improve efficiency. It was recommended that I slow down my wort extraction. My question is...is really restricting flow on the pumps bad for them? I'm guessing the answer is probably no....just seems like trickling water through them would tax the motor more our cause overheating. Can anyone confirm our deny? Thanks

Although I hated my chuggers at first, I have learned to tolerate them. Reducing the flow of the output as never been an issue with mine. I use my chuggers for HLT recirculation, mashing, and chilling.

I now sparge with a peristaltic pump which is much easier to control than dorking with ball valves.

Chris

 

[jddevinn]

FYI, the impeller will not decouple normally under increased pressure. With the outlet port nearly closed shut, the impeller is still spinning at the rate of the motor - but it can only create a maximum head pressure which will limit the amount of flow through a small orifice

The magnetic coupling is there as a safety should the impeller jam. When it decouples, you will know it as the motor sound will change. When the motor spins back down, you will hear the magnets "click" as the impeller re-engages.

Hmmm.... I'd never thought too much about about how the pump actually works and that actually makes a lot of sense. While they work I still want a better solution than the pumps I have, thinking either a wide range VFD or proportioning valve whenever I get to address this.

 

[BrunDog]

What is the problem you are having? What are you trying to accomplish?

 

[jddevinn]

What is the problem you are having? What are you trying to accomplish?

Are you asking me? I just don't like regulating flow with ball valves. I added flow meters and am normally within a minute or two of my calculated sparge time....but I just still don't like regulating flow with ball valves.