Pump Sucking Air During HERMS

[BadNewsBrewery]

I tried posting this over in the all-grain sub, but maybe I'll have more luck with my fellow e-brewers.

So I find myself in a bit of a pickle... I run a full electric HERMS setup, and use the standard 10 gallon igloo cooler w/ NorCal - jBird fals bottom in my mash tun. Calculating for the deadspace beneath the FB, I still end up mashing slightly thin to try and accomodate the flow through the HERMS coil.

Here's the issue I've been having - unless I run my HERMS pump (a Chugger) at 1/4 to 1/8 open on the discharge valve, I wind up sucking air into the system somehow. I have made entirely sure that all the fittings are tight and nothing leaks water anywhere, but after a period of time with the pump running I can see air in the line running from the MLT to the pump. If I kill the pump power and let the air run back into the MLT, I get quite a few large bubbles. Even after getting the entire system fully clear of air, if I run it again for a while, it starts getting air in the line.

Now from a logical standpoint, it seems only one of 2 things can be happening. 1 - the FB is causing such a restriction that cavitation is occuring within the line somewhere. This is highly unlikely, as such low pressure would cause other issues, and the air pocket wouldn't sustain in such large volumes. 2 - the FB is causing such a restriction that the pump is somehow causing one of the fittings to leak air, but only under the low-pressure scenario. Under normal operation, there's not enough of a vaccum to cause a leak to appear.

Otherse with a similar setup have claimed the ability to run their pump full-bore. Where would you focus your efforts? Rice-hulls to help keep the FB from getting jammed up? Tripple check all the valves and fittings? Devise some sort of system to stir / scrape the FB to keep it free and clear? Get a new FB? I thought the NorCal FB was suppose to be the bee's knees... I don't mill my own grains, but I've had this problem on multiple occasions with multiple LHBS / mill combos.

Thanks for the help,
-Kevin

 

[ChuckO]

I'm using a RIMS system, but have had the same problem of sucking air into the system. One entry point on my system is the sight glass. As my system runs I can watch the level in the sight glass slowly go down until it's empty and air is entering the mash. Capping the sight glass during pump operation solved that part of the problem although it makes it impossible to measure volume until I stop the pump and remove the cap on the sight glass. Obviously you only need to look for leaks on the input side of the pump, so I would check hoses and fittings for any looseness.

I start my pump with the output throttling valve shut off and then slowly open the valve. Once the grain bed has set I can open the valve all the way. If I open the valve completely to start with I find that there is a much worse situation and I get a stuck mash.

 

[augiedoggy]

I run mine at full bore but its only a 12 liter per minute 12v pump so that might be why I havent had issues...

 

[BadNewsBrewery]

I don't have a sight glass on my mash tun, though that's a fairly interesting find ChuckO. I always run my pump with the valve mostly shut until things get going, but it doesn't seem to make a difference - if I open it up much more than 1/4 valve, the whole thing winds up with air in the system.

 

[ebstauffer]

Funny you post about that. I no-sparge brew and therefore heat my strike water via RIMS directly in the MLT (a picnic cooler). Last weekend my chugger started cavitating for no apparent reason. For the life of me couldn't get it to stop. Swapped to another pump and it picked up just fine. I wonder if adding an auto-vent to the input side of the pumps (I have the center input stainless head) would help out. Subscribed!

 

[processhead]

I can confirm that a system that has water-tight plumbing and fittings is definitely not necessarily air tight.

My RIMS was pulling air in through what were water-tight threaded fittings and hose barb fittings with hose clamps. These leaks were all on the suction side of the pump between the pump and my MLT

After tightening the all the threaded fittings, and cranking down on the hose clamps, the air bubbles in the liquid line were eliminated.

Check-em all again.

 

[ChocolateMaltyBalls]

If checking the hose connections doesn't fix it, I'd look at the pump head, start by using your other pump (if you have one) and see if the problem persists. I doubt the FB itself is an issue.


Sent from my iPad using Home Brew

 

[BadNewsBrewery]

I think I'm going to have to basically fill the MT with some water, fire up the pump, and start plugging / pinching off different parts of the system to see if I can figure out where the leaks may be occuring. I'll double check all my fittings and connections to make super sure. If that doesn't bring anything, I can look into the pump, but I don't think that's what's causing the issue.

-Kevin

 

[ChuckO]

It might be messy, but what about putting a drop of food coloring on the outside of each connection on the suction side of the pump? Do one connection at a time and watch the return to the mash tun for slight color. If you can suck air through a fitting you might also suck the food color in. You would have to cover part of your false bottom with something to artificially create sufficient suction.

 

[augiedoggy]

Well looks like I lied...

I brewed a batch of begian strong yesterday and noticed my pump to is pulling air but only when used to pull from the bottom of the mashtun... theres no water leaks and it doesnt do it when theres less resistance on the pump like whaen pushing wort through a plate chiller...
I believe ist a bad seal where the camlock fittings screw on or the hoses seal to the camlocks or perhaps its the camlock fitting seals themselves in my case.

 

[BadNewsBrewery]

I don't think the food coloring will help - I don't see it sucking in enough food coloring to cause a noticable color change. If the leak was that extreme, it'd probably be leaking liquid out as well, but it's a good thought.

I'm banking on the issue being at the bulkhead through the plastic cooler. That's the only area where the setup isn't a true 'gorilla tight' seal. If that's not it, then it may be at the actual camlock fitting connection, which would be difficult or impossible to troubleshoot unless I can find thicker / better seals.

 

[yogensha]

I had a similar problem and I suspect it was, as you suggest, cavitation below the FB. No matter how slowly I recirculated, eventually the flow would stop and I'd see a large pocket of air start slowly expanding down the line coming out of the HLT. If I closed the pump output valve and stopped the pump, it would stay there for several minutes. When I'd finally open the valve, it would suck a bunch of liquid back up into the HLT.

I've made it through my last 2 batches with a healthy flow rate mainly by paying very close attention to the crush.

 

[BadNewsBrewery]

So I tightened all the fittings, filled the MLT with some water, hooked up the hoses, fired up the pump, and did my best to restrict the flow and create suction on the pump intake side. I even 'pulsed' my finger over the opening, causing the hose to jump about from the pressure changes.

In no way was I able to recreate the issue, and gave up after about 10 minutes of trying and my arm going numb... Which led to a few possible conclusions.

1 - The water was cold (48*), normally the wort is 100+* hotter - perhaps the heat is causing the fittings to flex or expand, and I can't recreate the scenario.
2 - It does have something to do with the FB, and I wasn't able to recreate the issue.
3 - By tightening the fittings I fixed it and the problem is solved.

I'm hoping for #3...

One question though - for those using a similar setup with a bulkhead fitting in your MLT (I don't use a dip tube, but no matter), a T on the outside to house your temp probe, and then a valve, and then a camlock fitting - do you find that the whole assembly outside the MLT is fairly long and unsupported? I'm thinking about trying to come up with a way to build a little stand that will take some of the weight of the equipment (and hose when it's attached) off the bulkhead fitting that's squeezing against a relatively thin piece of plastic. That stress can't be good, and may be another cause of possible failure. Anyone build their own little support?

-Kevin

 

[yogensha]

One question though - for those using a similar setup with a bulkhead fitting in your MLT (I don't use a dip tube, but no matter), a T on the outside to house your temp probe, and then a valve, and then a camlock fitting - do you find that the whole assembly outside the MLT is fairly long and unsupported?
-Kevin

It was bad enough on my drink cooler MLT that I used a roll of duct tape to support it to keep it from leaking. Haven't had issues with it since I switched to a Boilermaker. I used the recirculation problem as justification to buy it

 

[lschiavo]

So I tightened all the fittings, filled the MLT with some water, hooked up the hoses, fired up the pump, and did my best to restrict the flow and create suction on the pump intake side. I even 'pulsed' my finger over the opening, causing the hose to jump about from the pressure changes.

In no way was I able to recreate the issue, and gave up after about 10 minutes of trying and my arm going numb... Which led to a few possible conclusions.

1 - The water was cold (48*), normally the wort is 100+* hotter - perhaps the heat is causing the fittings to flex or expand, and I can't recreate the scenario.
2 - It does have something to do with the FB, and I wasn't able to recreate the issue.
3 - By tightening the fittings I fixed it and the problem is solved.

I'm hoping for #3...

One question though - for those using a similar setup with a bulkhead fitting in your MLT (I don't use a dip tube, but no matter), a T on the outside to house your temp probe, and then a valve, and then a camlock fitting - do you find that the whole assembly outside the MLT is fairly long and unsupported? I'm thinking about trying to come up with a way to build a little stand that will take some of the weight of the equipment (and hose when it's attached) off the bulkhead fitting that's squeezing against a relatively thin piece of plastic. That stress can't be good, and may be another cause of possible failure. Anyone build their own little support?

-Kevin

Your pump is creating a vacuum at the bottom of your MLT. To get air in, it has to be somewhere between the inlet of your pump and the outlet of the MLT. Igloo style coolers are dual wall. The seal on the output needs to be tight to the inner wall of the cooler. Any cracks on the inner wall or a bad seal at the top of the cooler between the walls "could" let some air in. Maybe you could fill the MLT with water, backpressure the MLT outlet with a few psi and look for bubbles in the water. Also, spray the seal between the walls at the top with some soapy water and see what happens.

 

[ChuckO]

I have been suspecting the seals in the camlocks. Some of mine are o-rings and others are silicone washers. The next time that I brew I plan on paying attention to which type are on the suction side of the pump.

 

[BadNewsBrewery]

It was bad enough on my drink cooler MLT that I used a roll of duct tape to support it to keep it from leaking.

That's not a bad fix... I think I'll go for something a little more custom / fabricated, plus I need mut duct dape elsewhere!

Your pump is creating a vacuum at the bottom of your MLT. To get air in, it has to be somewhere between the inlet of your pump and the outlet of the MLT. Igloo style coolers are dual wall. The seal on the output needs to be tight to the inner wall of the cooler. Any cracks on the inner wall or a bad seal at the top of the cooler between the walls "could" let some air in. Maybe you could fill the MLT with water, backpressure the MLT outlet with a few psi and look for bubbles in the water. Also, spray the seal between the walls at the top with some soapy water and see what happens.

Not a bad idea to try reversing the flow and plugging the line so it creates a possitive pressure in the line. Then I can check to see if water is leaking out anywhere. Of course, a vaccum leak and a leak from over-pressurization won't necessarily be the same. I'm really hoping that cranking down on the fitting was the fix.

I have been suspecting the seals in the camlocks. Some of mine are o-rings and others are silicone washers. The next time that I brew I plan on paying attention to which type are on the suction side of the pump.

I know I have one hose that I've somehow lost the washer in. I got all my fittings from Bobby_M and I believe he replaces all the o-rings with the flat silicone washers. It seems like a good enough seal, but what do I know.

 

[BadNewsBrewery]

Got a brew in yesterday, and I have to say, total success, but I threw the scientific method out the window so who knows what the exact fix was.

1 - Added a half pound of rice hulls to the mash. I added some early while heating the water / recirculating through the HERMS and a few got through and clogged my HERMS valve which killed me flow and had me totally worried until I diagnosed and fixed it. The majority were added to the grains and mixed in.

2 - I let it sit a while before starting up the HERMS, mainly because I was dealing with the clogged valve, so things had a little time to settle.

3 - I had tightened the fittings earlier.

I have to say, I was able to run the HERMS pump at full volume for the entire mash, no issues. Thanks for all your help, HBT!
-Kevin

 

[cjkline]

I've been having the same issue, and after reading this post stirred along the bottom of my MLT against the false bottom. Voila, my pump volume immediately increased to normal operations. It makes sense that I don't have the issue early on in the mashing process - it doesn't begin to happen until the grains start to expand.

I'm still left with the question - how do I fix it? Should I change my crush, or get a different FB? I don't know the brand, but it is dome style for a 10 gal orange cooler. Any ideas?

 

[LarMoeCur]

Your pump is creating a vacuum at the bottom of your MLT. To get air in, it has to be somewhere between the inlet of your pump and the outlet of the MLT. Igloo style coolers are dual wall. The seal on the output needs to be tight to the inner wall of the cooler. Any cracks on the inner wall or a bad seal at the top of the cooler between the walls "could" let some air in. Maybe you could fill the MLT with water, backpressure the MLT outlet with a few psi and look for bubbles in the water. Also, spray the seal between the walls at the top with some soapy water and see what happens.

winner...winner...beer for dinner! I'd bet the pump is compressing what little air is in the Cooler MLT. Have your tried running it with the lid open?

 

[cjkline]

I don't mash with the lid on. While I agree that I may be getting air in from between the walls, I'd like to fix the problem of low flow first and see if that's still an issue. I don't have a problem of sucking air (or having cavitation) until I have wet grain - so I'm sure the issue is grain plugging the FB holes. Besides, this issue is making my pump work much harder than it should, possible decreasing the life of the equipment. I'd like to fix this first, and if it's still an issue, deal with any air leak issues if they still exist. But since I never have flow problems until I have a wet grain bed, I think the sucking air issue will go away if I fix the FB issue.

 

[Bobby_M]

Add one pound of rice hulls to the mash.