Blichmann Riptide overheating?

[akpingel]

I use 2 Blichmann pumps with my HERMS setup. During the boil, i use one to re-circulate the wort. The last few brews the pump has begun to fail about 30 minutes in to the boil. The pump will make some very loud noises, and then stop spinning altogether. This last time I turned the pump off, and after about 20 minutes it was able to function again so i could recirculate a little bit more before flameout. Ive not been able to find a lot of people posting on this issue. Does anyone know if this is fixable? I rebuilt the pump right before this most recent brew.
Cheers!

 

[Golddiggie]

If it's anything like the March and Chugger pumps, check the spacing between the magnet (that spins on the motor) and the housing around it. I had that issue with one of my pumps and getting the alignment 100% was the fix. If the riptide pump doesn't have that as an adjustment, reach out to Blichmann with the issue (I would have done that already). See what they have to say. Since these pumps should be able to handle a long run time of hot liquids without issue.

 

[day_trippr]

Is the pump motor actually stopping? Or is this simply a classic case of boiling wort causing cavitation that leads to decoupling the pump rotor?

 

[TheMadKing]

I use 2 Blichmann pumps with my HERMS setup. During the boil, i use one to re-circulate the wort. The last few brews the pump has begun to fail about 30 minutes in to the boil. The pump will make some very loud noises, and then stop spinning altogether. This last time I turned the pump off, and after about 20 minutes it was able to function again so i could recirculate a little bit more before flameout. Ive not been able to find a lot of people posting on this issue. Does anyone know if this is fixable? I rebuilt the pump right before this most recent brew.
Cheers!

You're decoupling the impeller because you are pulling liquid near its boiling point into the pump and the slight negative pressure is causing it to flash boil which introduces steam/air and creates cavitation.

There's absolutely no reason to recirculate during the boil and it's really bad for your pump

 

[day_trippr]

^Agreed^, there's plenty of agitation going on just from convection currents, and there's plenty of back-end time to sanitize stuff (pumpheads, tubing, CFC or PC) if it wasn't done on the pre-boil.

Once my BK temp is ~210°F I shut off my boil kettle pump until coming down for post-boil whirlpooling. At that point it only takes a couple of degrees below boiling point (I'm 200' ASL) to avoid the flashing phenomenon...

Cheers!

 

[Golddiggie]

I don't run the wort pump when going from the BK until I'm going to whirlpool. I don't see the point in running it just to loop the wort back in leading up to boil. I get there fast enough with the new electric kettles. I didn't do it when I was using propane burners either.

 

[day_trippr]

fwiw, the inexpensive induction motors used on wort pumps typically do have a thermal cutoff element tucked into their motor field windings. So it is possible if the pump is working against abnormal loading (eg: misaligned head) the windings could self-heat to the point of shutdown. Eventually the cutoff element would cool down to where it would conduct again.

So there's still that bit of differentiating information to be gleaned in this case

Cheers!

 

[WesBrew]

Does it work ok on cold water?
-I sanitize all the tubing an recirculate through herms coil during mash.
-recirculate through the plate chiller at last minute of boil to sanitize
-when brew is complete I clean kettle , bring 3 gal water to a boil and flush everything out, but don’t leave the water boiling

 

[Vale71]

Sounds like you have severe cavitation followed by the motor overheating and shutting itself off.

To try and fix cavitation you'd have to try and place the pump much lower than where it's currently sitting in order to increse pressure at the pump inlet but as others have already pointed out recirculating during boil is completely pointless in any case.

 

[Golddiggie]

Sounds like you have severe cavitation followed by the motor overheating and shutting itself off.

To try and fix cavitation you'd have to try and place the pump much lower than where it's currently sitting in order to increse pressure at the pump inlet but as others have already pointed out recirculating during boil is completely pointless in any case.

It's common to partially close the valve on the pump out port to take care of cavitation. It you run the pump through either a plate, or counterflow, chiller in the final minute(s) of the boil, that's how to get it to work well. If you don't have either of those chillers, then running the pump for any part of the boil is pretty much useless (at best). If you think it will help you get to a boil faster consider this. You're running your hot wort through tubing that's doing a heat exchange with the brew area ambient air. Which means you're reducing the temperature of your wort (as it tries to get to a boil) thus making it take longer to get to a boil.

 

[superiorsat]

I use 2 Blichmann pumps with my HERMS setup. During the boil, i use one to re-circulate the wort. The last few brews the pump has begun to fail about 30 minutes in to the boil. The pump will make some very loud noises, and then stop spinning altogether. This last time I turned the pump off, and after about 20 minutes it was able to function again so i could recirculate a little bit more before flameout. Ive not been able to find a lot of people posting on this issue. Does anyone know if this is fixable? I rebuilt the pump right before this most recent brew.
Cheers!

I had 2 new Riptide pumps I returned for the same reason, but I was not sending BOILING wort through mine. They has an issue with impellers a while back and sent me alternate impellers twice trying to fix the problem. After 2 attempts I said to heck with that and bought 2 new Chugger Pumps. You may have gotten some old stock from somewhere. Contact Blichmann about the pumps and they will probably know by color of the impeller if you have the bad ones.

 

[Vale71]

It's common to partially close the valve on the pump out port to take care of cavitation.

Putting a valve on the out port won't affect cavitation. All that matters is liquid temperature and inlet pressure.

BTW I dont' know why you're addressing me as I'm not the OP.

 

[Golddiggie]

@Vale71 Actually, using a valve on the outlet of the pump DOES control the effects of the kettle boil when it comes to a pump. I did it multiple times when using my previous generation system and pumping wort towards the end of the boil. Basically, it ensure that the pump head is filled before trying to move the wort out. I lost count of how many batches I did that with. With my current setup, it's not an issue since I don't move wort until the boil is done. Plus my pickup (in BK) is far enough from the element to not matter.

 

[Vale71]

Basically, it ensure that the pump head is filled before trying to move the wort out.

That may be the case but that's an issue of pump priming, not of cavitation.

 

[Golddiggie]

That may be the case but that's an issue of pump priming, not of cavitation.

Not going to argue with you on this. It was NOT a matter of pump priming. It was a matter of the effects of a boil on the wort impacting the flow out of the pump head. Partially closing the valve on the outlet side of the pump took care of the issue completely.

 

[Vale71]

You had trapped air. Again, this has nothing to do with cavitation but only with priming of a non-self-priming pump. I recommend you read the presentation I linked to which explains cavitation in a very concise manner.

 

[akpingel]

I recirculate to prevent scorching. I do believe cavitation would make sense as how the problem starts, but when it reaches a certain point it wont attempt to run, unless I give it time to cool down (or the wort that is in the line- both I guess). Pump seems to run fine when its at ambient temps.
Ill give the next batch a go with out so much circulation. Ill run it to sanitize so I can circulate to crash the temp when done. I use an immersion chiller.
Cheers!

 

[akpingel]

If it's anything like the March and Chugger pumps, check the spacing between the magnet (that spins on the motor) and the housing around it. I had that issue with one of my pumps and getting the alignment 100% was the fix. If the riptide pump doesn't have that as an adjustment, reach out to Blichmann with the issue (I would have done that already). See what they have to say. Since these pumps should be able to handle a long run time of hot liquids without issue.

Ill check this too!
Thanks!

 

[TheMadKing]

I recirculate to prevent scorching. I do believe cavitation would make sense as how the problem starts, but when it reaches a certain point it wont attempt to run, unless I give it time to cool down (or the wort that is in the line- both I guess). Pump seems to run fine when its at ambient temps.
Ill give the next batch a go with out so much circulation. Ill run it to sanitize so I can circulate to crash the temp when done. I use an immersion chiller.
Cheers!

I have boiled wort on a full blast 200,000 BTU propane banjo burner without scorching. Have you had some issue with this in the past? How are you heating your wort that has such a high heat loading that this is an issue?

The solution is to reduce the rate of heat loading, not recirculating boiling wort through a pump

 

[WesBrew]

you could test it by re-circulating a few gallons of room temp water into the kettle for a while. if it performs well you could at least rule out a pump failure

 

[Bobby_M]

You cannot, and should not, pump boiling liquids like that. You can pump wort immediately after shutting off the heat, but you have to restrict the output to about 25% open while the wort is still over 180F or you will cavitate and run the impellor in a pocket of steam. This prematurely wears the impeller and shaft out. There is no need to move the wort around during the boil.

 

[Vale71]

Cavitation does not create any "pocket of steam". Cavitation bubbles are short-lived (milliseconds) and their imploding is what causes the awful racket you hear while this is happening. As a matter of fact no pocket of steam can exist as long as the pump is below the surface level of the liquid being pumped as this would require the liquid in the pump head to reach a temperature that is higher than the local boiling point which is impossible as the liquid can only cool as it leaves the kettle. Throttling the outlet will not affect cavitation in any way.

If there is any gas trapped in the pump head that is just air (though water vapor saturated, obviously) and this means there is an issue with priming of the pump but that is a completely different issue.

 

[day_trippr]

Boiling points of water as a function of pressure...

 

[Bobby_M]

Cavitation does not create any "pocket of steam". Cavitation bubbles are short-lived (milliseconds) and their imploding is what causes the awful racket you hear while this is happening. As a matter of fact no pocket of steam can exist as long as the pump is below the surface level of the liquid being pumped as this would require the liquid in the pump head to reach a temperature that is higher than the local boiling point which is impossible as the liquid can only cool as it leaves the kettle. Throttling the outlet will not affect cavitation in any way.

If there is any gas trapped in the pump head that is just air (though water vapor saturated, obviously) and this means there is an issue with priming of the pump but that is a completely different issue.

You're getting into semantics that go beyond the practical advice I'm trying to give the the OP. The vacuum pulled on the inlet plumbing due to the unrestricted output lowers the boiling point and causes localized boiling and that is the definition of cavitiation. Those bubbles work their way into the pump head and it loses prime. Whether you want to call that steam or air is irrelevant.

Throttling the output absolutely drops the incidence of cavitation because it lowers the inlet suction. Opening up the cross section of all the plumbing between the kettle and pump inlet would also help assuming the output throttling to stop the cavitation is a lower flow rate than you require.

Semantic aside, I stand by my statement that there is no reason to pump actively boiling wort but if you HAVE to, it will only work with the output significantly throttled back. If you don't believe me, try it for yourself. Put a sightglass on the pump input, run the pump full bore open on the output. Observe bubbles in the sightglass. Restrict output flow, observe bubbles diminish.

 

[Vale71]

If you see air going into the pump then you should tighten the leaky connection that is sucking in air at high flow rates. But whatever, I'm done wasting time here...

 

[DavidWood2115]

All that matters is liquid temperature and inlet pressure.

Thank you for the pointer to the presentation above; I found it very interesting as I had never studied pump cavitation. That said, if you re-read your linked presentation, you will quickly see that your quoted statement is only (partially) true for the Available Net Positive Suction Head (NPSHA). Slide 8 clearly shows that the Required Net Positive Suction Head (NPSHR) is strongly dependent on flow rate; for the example pump NPSHR stays below 2 ft for flows under 30 gpm but jumps to almost 8 ft for 60 gpm. Thus throttling the flow rate can absolutely affect whether NPSHA > NPSHR, the criterion to prevent cavitation.

Furthermore, NPSHA also decreases as flow rate increases because the greater flow results in increased frictional loses on the input side (Hf). Bottom line is that decreasing flow rate both increases NPSHA and decreases NPSHR, thus decreasing flow rate can indeed help prevent cavitation.

 

[Bobby_M]

I rebuilt the pump right before this most recent brew.

Make sure the impeller spins freely on the shaft. Sometimes a layer of beer stone will build up and creates extra friction on the impeller. Also, did you remember to put the stainless thrust washer between the head and the impeller?

 

[BarryBrews]

There are two phenomenas being discussed here. For brewers it's the flash boiling due to the pressure drop at the pump inlet when near boiling wort enters. When the pressure is lowered the boiling point is also lowered, hence the wort flash boils. The steam produced could break the pump prime? This is easily resolved by the back pressure produced when the pump outlet valve restricts the flow. I personally start the pump/plate chiller at the end of the boil clock leaving the heating element on until the wort returns to a boil before proceeding with the cool down.

Then there is cavitation which is the result of the pump turbine force and the inlet pressure producing a vacuum which then quickly disappears with a bang. Riptide pumps are not that powerful, thankfully!

 

[day_trippr]

[...]For brewers it's the flash boiling due to the pressure drop at the pump inlet when near boiling wort enters. When the pressure is lowered the boiling point is also lowered, hence the wort flash boils. [...]

simple physics...