Chugger pumps...impeller seizing?

[JimEb]

Thought I had the common cavitation issues, but I think its something else.

Pumping hot liquids you'll be going along fine and then hear a short squeal/buzz, motor changes pitch slightly and all flow stops. I shut the pump off and let the motor spool down. Just before the motor stops it lets out another squeal/buzz. Only then can you switch the pump back on and repeat the process again.

Pump outlet is connected to a tee with a ball valve to drain the system. When pump's acting up I can open the valve and gravity feed through the pump to drain. That makes me think the impeller isn't spinning at all despite the motor humming along. On a desperate whim I greased the impeller shaft with silicon. Bingo! Although the problem didn't completely go away, performance greatly improved. For whatever reason the impeller must be seizing up and decoupling from the magnet. The components will not recouple unless everything comes to a stop.

Ideas on why and how can I fix it?

 

[Bobby_M]

You may have some beer stone or other stubborn junk inside the impeller bore. Soak it in some PBW and run a nylon brush through it. Also check that you have both Teflon washers in the head.

 

[Bellybuster]

http://homebrewforums.net/discussion/91/chugger-pump-screeching/p1

 

[JimEb]

I have a mill and a lathe and even made new bearings on the impeller. Pretty much did everything you could possibly do on the impeller at this point, enlarged the bore, reduced the bore, adjusted axial position, etc.

Think I was chasing my tail with the impeller. It really seems as if the magnet is weak, decouples at temp and just spins free. Noticed the sound of the motor when it fails to pump is similar to the motor sound if I run it with the pump head removed.

Higher temps will reduce magnetism. Must be a luck of the chugger pump QC lottery if you get one with stronger magnets. Pump was somewhat flaking out of the box, but noticibly worsened with use. No brewing this weekend unless I can somehow conjure up a more positive couple between the impeller and motor.

 

[mabrungard]

I've experienced similar problems with my March 809HS. If the pump was turned off at any time during the main mashing and high gravity wort had been flowing through the pump, the impeller would seize to the shaft. It turned out that a thin coating of caramelized sugar developed on the shaft and I would have to disassemble the pump and scrape off the coating. It didn't take much to get the coating off, but the drag was enough that the impeller would not spin freely enough to allow the motor to restart.

My solution was to never turn off my pump until low-gravity wort had been circulated through the pump. In essence, I didn't turn off the pump until the sparging was over. I used the inlet and outlet valves to shut off the pump flow while any disconnections and reconnections are needed. The wort just spins in the pump and it does not hurt the pump to have the valves closed. Apparently, the low gravity wort helps dissolve the sugar coating on the shaft and the clearances are restored.

 

[stickyfinger]

Huh, very interesting thread. I just recently started doing a lot of high temperature mashes with mashouts and recently i've also had my HLT chugger pump start flaking out as it seems to seize up. I drilled out the impellers and played with the o-rings. I think the magnets must be the explanation. It works fine, has lots of room to spin on the shaft, but it just locks up periododically, very frustrating.


I am debating b/w replacing the impellers and washers (just to eliminate that variable) and replacing the pumps with March pumps. Has anyone tried a March impeller in a chugger pump and had good results? If the magnets in the chugger impellers are ****, maybe the March impeller would be ok in my chugger pump? maybe wishful thinking!

 

[kickflip_mj]

I have a mill and a lathe and even made new bearings on the impeller. Pretty much did everything you could possibly do on the impeller at this point, enlarged the bore, reduced the bore, adjusted axial position, etc.

Think I was chasing my tail with the impeller. It really seems as if the magnet is weak, decouples at temp and just spins free. Noticed the sound of the motor when it fails to pump is similar to the motor sound if I run it with the pump head removed.

Higher temps will reduce magnetism. Must be a luck of the chugger pump QC lottery if you get one with stronger magnets. Pump was somewhat flaking out of the box, but noticibly worsened with use. No brewing this weekend unless I can somehow conjure up a more positive couple between the impeller and motor.

I have had the same exact experience. Drilled the old impeller out, purchased a march impeller, drilled that out. still same garbage issue on 2 pumps. It only happens when temps rise. I am tempted to purchase a replacement magnet that is attached to the motor. except for the fact that they are 30 bucks a piece.

 

[mabrungard]

I have had the same exact experience. Drilled the old impeller out, purchased a march impeller, drilled that out. still same garbage issue on 2 pumps. It only happens when temps rise. I am tempted to purchase a replacement magnet that is attached to the motor. except for the fact that they are 30 bucks a piece.

Oh come on you guys! Did you see my post above? Don't turn off these pumps if they are handling high gravity wort (essentially every mash) or they will seize up due to the sugars collecting on the impeller shaft. Just close valves and keep the motor always running until you have run the pump with really low gravity wort or water.

After I learned about that problem and its solution, I've never had the pump stick again in the 15 years I've had it.

 

[kickflip_mj]

Oh come on you guys! Did you see my post above? Don't turn off these pumps if they are handling high gravity wort (essentially every mash) or they will seize up due to the sugars collecting on the impeller shaft. Just close valves and keep the motor always running until you have run the pump with really low gravity wort or water.

After I learned about that problem and its solution, I've never had the pump stick again in the 15 years I've had it.

Sadly this happens even when I'm moving strike water on a bottom drain kettle. I wonder if 25 gallons of water on a bottom drain is to much force for these?

 

[stickyfinger]

Sadly this happens even when I'm moving strike water on a bottom drain kettle. I wonder if 25 gallons of water on a bottom drain is to much force for these?

The worst problem I've had is on my HLT, so it's only water.

 

[kickflip_mj]

The worst problem I've had is on my HLT, so it's only water.

Yeah well 25 gallons of RO water that has been heating for an hour is a huge waste.

 

[stickyfinger]

Yeah well 25 gallons of RO water that has been heating for an hour is a huge waste.

it's totally annoying. however, it dispels the idea that it's only thick wort that is causing the problem. i am wondering if my magnet in my pump is going bad now.

 

[Bobby_M]

Make sure the magnet is centered and that the set screw on the cup magnet hasn't loosened up allowing it to fade too far away from the head.

 

[stickyfinger]

Make sure the magnet is centered and that the set screw on the cup magnet hasn't loosened up allowing it to fade too far away from the head.

I'll try that first. Thanks!

 

[RocketBrewer]

I have the same issue with both my Chugger pumps to some extent, one is worse than the other. I'm not sure if cavatation is causing it to decouple, but higher temps obviously increase the problem. I've found that if I throttle the output a little it stops the issue (after stopping the pump to let it recouple of course).

 

[stickyfinger]

I also found that it has a tendency to decouple at higher flow rates, makes sense. I'll see if I can get just enough flow to keep my HLT homogenized.

 

[mabrungard]

Higher temperature fluid does increase the pump's tendency to cavitate. Cavitation is essentially the implosion of tiny steam bubbles and it often sounds like you are running gravel through the pump. I suppose its possible that the cavitation is causing the impeller to decouple.

 

[Bobby_M]

I get a lot of calls from people that have restrictive plumbing on the inlet side and are also trying to pump full bore at 210F. No pump will do that. At high temps you need to throttle back on the output.

 

[stickyfinger]

I get a lot of calls from people that have restrictive plumbing on the inlet side and are also trying to pump full bore at 210F. No pump will do that. At high temps you need to throttle back on the output.

whatever is happening on my pumps started after like 10 months of use. i don't think it's something external to the pump. the problem is in the pump somewhere. i'll try to check alignment. for now, i hope to get by with throttling back the flow.

 

[lumpher]

never mind. Different problem

 

[stickyfinger]

I moved the magnetic ring out toward the impeller so that it just barely has clearance on my HLT pump. At least it will work now without completely seizing every time I try to use it at any flow rate! It still seizes. I noticed that it kept seizing, so I decided to try it full flow in exasperation, and it worked fine for like an hour at least. Then, I turned the flow down to sparge, and it kept seizing, but I kept restarting it, and finally it ran, though it threatened to decouple several times.

Has anyone had success with replacing the magnet in the Chugger with a March magnet? I have a feeling that is the problem. It could be the impeller I guess. I could try a new one in that pump. it is really loud now that i've drilled out the impeller, which is really annoying. My MLT pump impeller is much quieter even though it is also drilled out.

 

[atliens21]

Depending on your pump ability, there is a pressure delta across the impeller. Increased fluid velocity decreases pressure and if you're at hot temperatures, it will cause the fluid to superheat into vapor and cause cavitation. Here's an example: Assuming no additional losses due to plumbing length, fittings, etc..,and your pump can push 17 feet of head pressure. Looking at temp/pressure thermo charts for water, it will super heat at 80 deg C. Basically it's the same principal for why water boils at lower temperatures in the mountains. If you can increase back pressure after the pump, you can help decrease that delta P and keep the pump from superheating the fluid. Hope this helps.

 

[atliens21]

Thermodynamics. Pump creates significant pressure drop causing hot liquid to super-heat (vapor). Kinda like running the pump dry. Same reason why water boils at lower temps in the mountains and CO2 liquefies when pressurized into a tank. The typical Chugger pump has 17 ft head pressure which will cause super-heating with water over about 80 deg C (rough numbers, don't correct me). Take a look at temperature-pressure charts for water and you can see how a specific pressure drop will change the boiling point. Increasing pump outlet back-pressure (valve, plate heat exchanger, etc..) will help raise that boiling point up.

 

[stickyfinger]

Why did it work fine for 9 months and then start giving problems, though.

 

[atliens21]

I'm not sure. I'm not familiar with your system layout. Nothing at all has changed in the 9 months? Maybe you changed tubing size, have your HLT in a new location vertically, temps are slightly different, you moved to a place higher in altitude?

I have a system where after the boil I try to recirculate in my normal free flowing loop where everything had been heat soaked for an hour and a small amount of liquid comes out and then pump changed pitch and no flow. But if I throw my 3 way valve to recirculate through my 30 plate heat exchanger, no problem. Delta P changes across pump and no longer superheats. I've chased this problem for a while including reaming out impeller but every time, same issue occurs. Then it hit me.

 

[stickyfinger]

The only thing i've changed is i now recirculate at closer to 170F for a lot longer than i used to.

 

[atliens21]

If I were you I'd put a valve on the outlet and restrict the flow as much as I could to see if that will stop your issue. There's so many variables here. My advantage is I can consistently recreate the problem by just turning the pump on. It doesn't happen after 30 minutes or inconsistently throughout a process.

 

[stickyfinger]

If I were you I'd put a valve on the outlet and restrict the flow as much as I could to see if that will stop your issue. There's so many variables here. My advantage is I can consistently recreate the problem by just turning the pump on. It doesn't happen after 30 minutes or inconsistently throughout a process.

i already have valves after both pumps. i've tried lots of things. it used to stop when going full speed. last brew, it stopped unless i kept it full open. i tried adjusting the magnet housing. i'll see if that helps.

 

[stickyfinger]

I've now adjusted two things, and it seems to have fixed my impeller problems:

1) I loosened the drive magnet set screw, and slid it out so that it is almost flush with the motor connecting bracket, just a little bit of room to keep the rear housing from rubbing on the magnet.

2) I played with the motor connecting bracket to try to position it so that the gap between it and the drive magnet is exactly the same all around (use my sight as the gauge.)

Item 1 made some difference, but item 2 seems to have completely removed the problem of the impeller losing magnetic contact with the magnet. The HLT impeller still rattles around on the shaft louder than I would like, but at least it works fine now at all flow rates with no seizing (so far....)

A huge thank you to Bobby_M and his excellent video.

 

[stickyfinger]

One last update: I did a beer this weekend, and it only seized up once, when I was sparging at low flow rate. It then kept going. The complete rest of the brew it worked. It tried to seize up a few times but didn't. I suppose that's good enough for now. I wonder if I adjusted the bracket so that the magnet pulled down on the impeller on the shaft more if it would work even better due to gravity?