Vacuum breaker on MLT for setting recirculation flow rate

[Truman42]

Has anyone used a vacuum breaker to set and control their re-circulation flow rate?
Ive had a lot of problems getting a stuck mash with my brews. Initially I played around with my mill gap setting but the trade off was poor efficiency. Part of the problem was my drill was too fast even when set at slow speeds so Ive since setup a wiper motor to keep things consistant.

So now Im turning my attention to my flow rate. After doing some reading on the subject I found out that your flow rate should be set to the same rate as if you were draining from your MLT via gravity and you wont get a compacted grain bed and stuck mash.
I came across and idea where you use a vacuum breaker to set this.
Basically you fit a T piece between your MLT wall and the ball valve. You then connect some hose to the T just like a sight tube setup basically. (Although some brewers fit a vacuum gauge instead)

If your grain bed causes restriction because your pump is sucking faster than the wort can drain through, the wort in the tube will suck down and allow air in. So you close your valve a bit on the Inlet side of the MLT.
You keep adjusting your inlet valve until you dont suck down the wort in the tube anymore and allow air in.
Also its better to use a gate valve on the MLT inlet as it allows you more precise control of your flow rate compared to a ball valve.

 

[Yob]

Interesting.

My flow rate is much faster than my drain rate, if it wasn't, ramp speeds would be ridiculous,

I'm on gravity power for fly sparging so my pump is off by then.

Got some links on these dohickys?

 

[pk.sax]

If recirculating, monitoring the level of liquid in the mash tun will give you the same benefit.

However, need to have the lid open.

 

[WarmBeer]

Now I'm HERMS-ing, I dough in at 3.5 lt/kg, just to keep my mash nice and wet (TWSS!)

Never had a stuck sparge, even with 60% wheat, but I think the main reason is the BB false bottom I use.

 

[razz]

I have a sight glass on my mashy and mark the appropriate level during sparging. A vacuum breaker would work quite well.
Truman, have you tried a gate valve on your rig? Somethings come to mind that make me think a ball valve is better. Can you pull a gate valve down to clean it, like a ball valve? I understand where your'e coming from with precise control during sparging but a ball valve does the job easily. It doesn't take long to adjust flow from HLT and MLT to get them balanced. I also mark my valves with a felt tip pen and then set them at that.

 

[dicko]

If that system allows air into the pump inlet side then you will have prime problems if using a magnetic drive pump.

Just throttle the outlet of the pump to control the flow through the mash. If a gate valve does this better than a ball valve then use it..

$0.02

 

[dent]

The trouble with the gate valve is you can't see at a glance what opening it is set to.

 

[Truman42]

@ Yob..No link it was just a post on another forum.

@Razz... The Op mentioned using a gate valve but you do have a point about sticking with a ball valve and thats what I have so would probably stick with that.

@Dicko... The point of the sight tube is to adjust the inlet valve so the wort in the tube drops down to just above the T. If you open the inlet valve too much and the pump sucks too hard to cause air to be sucked in youve gone too far. Some brewers use a vacuum gauge instead and after some trial and error know what vacuum pressure works for them.

@PF..I dont think you would have enough wort past the false bottom and through the coil to show up as a difference in your level in the MLT.

@....Warm beer...What was your mill gap again?? I tried .9mm went up to 1.3mm but suffered with only 60% efficiency. Now that Im using a slower motor I hope I can get the gap back to around .9-1mm and 70% efficiency at least. But I think another part of my problem was my flow rate. Im trying to get the fastest flow rate whilst still not slowing down ramp times too much. I have my pid set so that it wont start the next step until the set temperature is reached.

 

[dicko]

Wash some rice hulls and throw them into the mash and circulate at 1 litre per minute....if you still have troubles then it will probably be a tube collapsing between the false bottom and the pump or just the design of the false bottom and tun kettle.

I know some will say that 1 litre per minute is too slow for ramping but it will do for the experiment/test although I found that rate spot on for my Herms when I had it.

Or you can just continue the way you are going with the vacuum breaker.
Not much help to you but you will find out what is causing your mash problems..

 

[WarmBeer]

@....Warm beer...What was your mill gap again?? I tried .9mm went up to 1.3mm but suffered with only 60% efficiency. Now that Im using a slower motor I hope I can get the gap back to around .9-1mm and 70% efficiency at least. But I think another part of my problem was my flow rate. Im trying to get the fastest flow rate whilst still not slowing down ramp times too much. I have my pid set so that it wont start the next step until the set temperature is reached.


Yep, 0.9mm gets me nice consistent 75% efficiency.

The BB falsie has a large surface area compared to the bottom of my MT, so the comparative 'suction' from my pump per square cm is low. I recirc the entire length of the mash, with the pump un-throttled.

As somebody else mentioned, is it possible you're getting vacuum on some other part of your plumbing setup? If so, adding all the rice gulls in the world won't help...

 

[Truman42]

The wort exits from the bottom of the MLT (I have bolts screwed into the bottom of the keg for legs) So there are no hoses to crush inside the MLT. The rest of the plumbing is fine and its definitely grain compaction. I even broke a spoon trying to stir it up again. Was stuck like concrete.

Ive used rice hulls a few times now. In my last brew the mash stuck 3 times and each time I kept putting in more rice hulls but I also started with the valve open just a crack and eventually opened it fully again over 6 mins or so.
The last stuck mash I kept the valve open halfway and it flowed no problems but I dont know if it was due to now having enough rice hulls in the system or that I wasnt pumping as fast anymore. Im trying to get the flow at a decent rate to allow good ramp times throughout the entire mash but also not compact the grain bed.

@Dicko..So what test did you do to see that 1 litre p/min was suitable? Did you measure the temp of the wort at your MLT outlet and compare the time it took to get to your mash step temp? I was working on needing around 4 litres per min flow rate at a minimum so my 21 litre mash would take just over 5 mins to do a full cycle through the herms.

@ Warmbeer. My false bottom is the keg king type. Its about 300mm diameter so only around 40mm gap to the edge of the keg. I would like to know how your managing to get full flow without a stuck mash. Are you using a march pump or a LBP?
We will have to discuss it more on Saturday.

 

[Camo6]

What plumbing are you using at your MT drain Truman? And how is your FB secured?
Just brainstorming but is it possible grain is getting past and collecting here, restricting flow?
Sounds like we run pretty similar setups except for the outlet. Once my grainbed sets and I slowly open the taps I can pump at full flow for the whole mash.

 

[Truman42]

What plumbing are you using at your MT drain Truman? And how is your FB secured?
Just brainstorming but is it possible grain is getting past and collecting here, restricting flow?
Sounds like we run pretty similar setups except for the outlet. Once my grainbed sets and I slowly open the taps I can pump at full flow for the whole mash.

My false bottom isnt secured at all. I have an elbow at the bottom of the keg and then a compression fitting into some stainless pipe out to the edge of the keg then another compression fitting onto my ball valve.

On one occasion when I used torrified wheat I had a blockage in that area and had to blast it out with the garden hose on the end of the ball valve. I do get some grain particles in the boil kettle but whenever I stir the grain bed my flow is fine so its definitely a compacted grain bed.

 

[TSMill]

Have you considered using a grant, so there is no suction pressure on the bottom of the grain bed?

 

[Yob]

Heres one for you Screwy..

If you recirc, dont stir. It'll cause it to stick (at the very least wont help)

My system is a bit of a hybrid, I use a sheet of voille over my manifold and if I stir it, it causes the finer particulate to condense furhter down the bed, only once it happened, but the particulate clogged the sheet and it started to pull from the sides getting air in.. was a PITA and the last time I stirred the mash.

since ive stopped playing with it, I dont get the issues with that problem. I should add, I use the sheet as I still use a 24V LBP and was always concerned about particluate blocking it, I do have an 809 waiting in the wings but figure why fix what aint broke (for now)

 

[Truman42]

@TSMill...Yes considered a Grant but if it works for others without one it should work for me.

@ Yob.... I dont stir at all after dough in...usually. The only reason I do stir is when I get a stuck mash so I can loosen the grain bed again.

Just to add when I crush at around 1.3mm and Im using a fairly regular grain bill. (No wheat) I can recirculate at full speed and I dont have any problems with a stuck mash at all. But my efficiency is only around 60-62%. Now that I have a consistant motor speed on my mill I want to try and adjust crush and flow rate to get me up to at least 70% without risking a stuck mash.

 

[Truman42]

I did some tests on my pump flow tonight using water.
With the inlet valve on the MLT fully open I am getting a flow rate of 5 litres per minute. With it closed up around half way and what I had to keep it set at to avoid a stuck mash on my last brew it's flowing at 3 litres per minute.
It was interesting to note that the flow rate doubled if I bypassed the hex coil so there is a fair bit of restriction in the hex coil.

But this test was with water only and with grain I'm assuming my flow rate will be even less due to greater restriction.

So in conclusion with a 1mm grain mill gap I have to set my fow rate at around 3 litres per min (which is probably 2 litres a minute with grain restriction) or I pull on the gran bed too hard and cause a stuck mash.
2 litres a minute is going to stuff my ramp times right up.

 

[Truman42]

Bump..anyone? Curious to know what sort of flow rate you guys are getting?

 

[Yob]

Way more than that with a 24v LBP.. What's the head height of your pump?

 

[Truman42]

It's only about 1-1.2 metres at most although the hex coil adds a bit of resistance. You can see in the photo below how high it is.