Herms-loop makes system cavitate

[brick_haus]

I work with centrifigual pumps all day, every day and have for over 25 years. The cause of the discharged air can only be attributed to a couple things.
1. You have an air leak in the suction side of your system. Hoses, fittings etc.
2. You are pulling air into the suction by having insufficient liquid above the suction in your tank MLT (slurping?)
3. If the liquid is hot, it will convert to gas(steam) at a lower temperature than "normal" if the pressure is reduced enough. The required pressure to keep the gas entrained in solution is reduced as temperature increases.
4. Turbulance is a pressure reducing mechanism. Get rid of that Ell attached to the pump suction and run hose to straight barb.

Check your hoses for pin holes.
Pressure test your suction plumbing.
Make sure that you have sufficient liquid above the suction in your MLT (the air under the false bottom is curious)

Its a simple problem to fix. Proper troubleshooting is the key.

 

[Smellyglove]

What is the inside diameter of the herms coil? How long is it?

See answer a few posts up.

 

[trimixdiver1]

Even if i close the new restricting valve on the output of the pump it happens..

What? You shut the pump discharge valve and you still have flow with air in it? At this point you may want to tear everything down, redesign so there is no 90's, valves etc, within 10 plus inches of the suction, may also want to use a larger suction hose. Re tape all fittings, and move on from that point.

 

[grathan]

The latest pic you posted still has the tee and no valve.

 

[Smellyglove]

The latest pic you posted still has the tee and no valve.

What? Where?

 

[Smellyglove]

Today

View attachment 1421687530088.jpg

 

[Smellyglove]

Restricting valve on the output. Sucks air.

I've swapped every piece in the setup. I know the fix is simple but still...

 

[Smellyglove]

Also tried running a long hose so that there is no 90 on the input.

 

[Smellyglove]

For every tip on this thread I get, amd rebiild the setup... Ive tried everything.

 

[Smellyglove]

It works when set temp is reached. Thats it. Works with cold water, and set temp water. Everything between that doesnt work.

 

[grathan]

What? Where?

On the pump output. You have a tee. Perhaps this is common, but I see an opportunity for an air bubble to cavitate back into the pump if the output flow is limited. This would not explain the massive air pocket that gets created under the false bottom though (though you've only encountered this once and have not determined if the pump was cause).


I would try removing the tee and the extra priming drain hose and just have a ball valve there connected to only the main output hose. To prime, don't turn the pump on until there is at least 5 inches showing above the pump. close the output valve and turn the pump on. slowly open the output valve so that you get a flow, but not too much flow. Make sure the supply side can keep up with the output side. Look for air bubbles in the output hose/tank (there should be none).

 

[Smellyglove]

Another brewday another...

Does it tell anybody something that less water in mt equals more air in pump?

 

[mrwizard0]

Have you tried rotating the pump head 90 degrees so that the inlet is at the bottom and the output pointing up?

 

[Smellyglove]

Yes. Trust me, I've tried more or less everything.

I'm brewing right now and as I'm heating up to strike temp I removed the FB. Way less problems so far. Way less as in it takes way longer before I can hear the air, and the air-sound rises gradually instead of a close to sudden inlet of air as with the FB. But now there is a different sound. Ek ek ekek ek, or how to describe it... pop pop pop

I'm pretty sure it has something to do with the boilermaker. And low OG beers makes it more extreme.

 

[Smellyglove]

Partially solved.

I went all in an let it bleed until the I had 1/3 of the water left. Shook the BM like a person with a mental illness and its almost all gone. I guess the BM FB traps a whole lot more air than I could imagine.

 

[trimixdiver1]

Partially solved.

I went all in an let it bleed until the I had 1/3 of the water left. Shook the BM like a person with a mental illness and its almost all gone. I guess the BM FB traps a whole lot more air than I could imagine.

The Blichmann FB is very tight compared to others. Good work.

 

[RBGilbert2]

I have a similar HERMS system but w/o the Blichmann FB. I fill my mash tun from the HLT by pumping in through the kettle valve, i.e., from the bottom. Would that limit air below the FB for you?

 

[Smellyglove]

I have no idea. Maybe the bubbles would just be shuffled around under the FB, I don't know. It seems that I actualle have to lift the FB at one end and shake the kettle to effectively get rid of air.

My new technique is now placing the FB after filling water, diptube pointing up. Then reprime and shake the kettle after the herms has heated it to about +40c from initial temperature.

 

[cbhxh]

What is the inside diameter of the herms coil? How long is it?

 

[Smellyglove]

Troll?

 

[Smellyglove]

Can a mod change the topic of this thread to "Blichmann false bottom, pump sucking air" ?

I just accepted how it was, but after getting pretty fed up with this **** last time I brewed I just came to the simple conclusion that it might work if I fill up the mash-tun through the diptube... And it works!

I've tried some testing with plain water.. Fill up HLT, let gravity prime the March, then connect the output to the march to the spigot on the mash tun, so the water slowly fills from the bottom pushing trapped air under the blichmann false bottom out. Press the FB quickly some times to press out any air that might be left..It works. No air whatsoever.

 

[Assoc]

Make sure you have enough space between the dip tube and the bottom of your kettle.

 

[Beernik]

I'll reiterate my original question to the OP: are you sure it's cavitation? Does it sound like there is gravel in your pump. If it doesn't, its likely that it's air and not cavitation.

Cavitation causes are on the suction side of the pump. It's either not enough net suction head or a flow restriction on the suction side. When either of those happen, the suction can cause a phase change from liquid to vapor and make a bubble. As soon as that bubble hits the pressure side, it implodes, usually on the impeller or pump housing and causes that gravely-crunching-hammering sound.

If you are seeing bubbles in the flow on the pressure side, it's not cavitation.

Also, if there is a sound and it's more of a high pitched whine, it's likely air bound instead of cavitation.

 

[Smellyglove]

No its' air.

But it was another false alarm that it works now. Whenever the water temp rises it starts pulling air again. So I'll just start heating my strike water in the HLT to get rid of the air, and then pump it over to the MT.

 

[Smellyglove]

This time I'm positive it's been solved!

Heat strikewater in HLT to get rid of all gasses in the water, fill MT from bottom after a good prime, no air, tried three times now.

 

[Beernik]

Sorry @smellyglove. I meant that I was asking @chjgj the same question.

 

[Smellyglove]

Aha!

 

[Smellyglove]

I have spent almost nine hours trying to figure out why I get cavitation in my system. I've narrowed it down to the herms-loop, but that's it.

You seem like being in my situation until I figured it out. What's you setup?

Haha, bogus post. That was my first post in my thread. A bot?

 

[Smellyglove]

Just the tap of it is longer than your dick, that's for sure. How do I ignore people on this forum? MF bots.

 

[Smellyglove]

I'm back and im just as frustraded as before.

7.5G boilermaker this time. It happens whenever the herms fires. Any way of resolving this besides of heating up the mash water to let the air get out of solution before I dough in?

 

[jddevinn]

I'm back and im just as frustraded as before.

7.5G boilermaker this time. It happens whenever the herms fires. Any way of resolving this besides of heating up the mash water to let the air get out of solution before I dough in?

What do you mean by "whenever the HERMS fires"? Do you mean whenever the heating element is actually active?

Is it possible that you have the HERS coil too close to the element and are heating the liquid in the coil directly too hot? You are recirculating the HLT water?

Do you still have the small ID tubing? If so the water coming out of the HERMS coil has an expanded flow area as soon as it exits, meaning that it's velocity and pressure decrease. Are you somehow flashing in here? What's the inside of the mash look like?

Can we get a picture of the current system? Where are the temperature transducers located? What is your set point for the HLT?

 

[Smellyglove]

I wrecked my pump so I stowed it all away waiting for a new SS head before I took any pics. But, I tried it as straight as possible. Boiler maker - pump - boiler maker. Hose straight on barbs. The air just magically appears. I can see bubbles coming out of the barb from the BM. It's amazing! Where does that air come from? Even with the diptube above the FB. Even with the valve on the directly on the output on the pump almost closed, everything from full open to almost closed = air. Where does it come from? It seems like it just magically just appears somewhere inside the BM.

 

[jddevinn]

If there is no air leakage you are flashing the water/beer into steam somehow through a pressure drop.

 

[Smellyglove]

If there is no air leakage you are flashing the water/beer into steam somehow through a pressure drop.

I see air bubbles coming from the Blichmann-kettle. I use 10mm ID hoses, throttling the output valve on the pump way back just makes it happen slower. I don't get it. Even without the FB.

 

[jddevinn]

Into the kettle?? That wouldn't be steam it has to be water. We need some pictures and maybe video. Where are you at? Maybe you'll get lucky and be near someone that'll come take a look with new eyes.

 

[Smellyglove]

Into the kettle?? That wouldn't be steam it has to be water. We need some pictures and maybe video. Where are you at? Maybe you'll get lucky and be near someone that'll come take a look with new eyes.

From the kettle, or.. mash tun. Not into it.

I had some minutes to spare today and found two other barbs. The ones I've been using haven't been 1/2" ID. So I swapped them with one fat ass (20mm OD) and one which seems like it's 1/2" ID. The result was that I could run the pump with the restriction valve half open before I could hear any air. Which is better than it has ever been with this setup.

I'll try uploading some pics when I have the time.

 

[jddevinn]

I guess im sucking air. Does this point have to be before the pump, or can it be after also?

Your images are not showing up.

Sucking air has to be before the pump. After the pump the line is pressurized and a leak would spray water OUT not let air leak IN.

 

[The_Bishop]

He was a copy/paste spammer.

 

[jddevinn]

He was a copy/paste spammer.

I had a suspicion when I saw the link address for the "photos"

 

[Smellyglove]

I started from scratch to day. No QDs, just hose barbs. That worked so in with the QDs. That worked too. So in with the HERMS-loop, that worked too, for maybe an hour and then I shut it off. So lets try with the heating element ON.... Does NOT work, a while after the HERMS starts I can hear air in the pump head.

Test-scenario today: