Yeast stalled from pressure?

[refect]

I brewed up a west coast style IPA last week and decided to test out my new spunding valve with this batch (First time ever spunding a batch). I didn't want to start with pressure right off the bat because I'm not spunding to lower ester producton. I just wanted to capture co2 and preserve hop aromas.

About 48 hours into fermentation I was having some pretty good activity, so I decided to close the valve on my blow off arm and wait for pressure to build naturally. I was trying to achieve 15 psi, but it seems the yeast could only get it to about 13ish psi before it seemed to stop building pressure. After a few hours of waiting to see if pressure was going any higher (it didn't), I called it good an started to open my spunding valve until it started bubbling. I then dialed it back a bit so that I was holding a steady 13 psi on the pressure guage.

After I did this, the bubbling in my spunding valve seemed to come to a hault quite fast (within a few hours). Especially after how much I was getting just a few hours prior to closing the valve on my blow off arm. I am now at the end of day 3 of fermentation, and it is still holding a steady 13 psi, but no co2 bubbling out. This makes me think no more co2 is being produced by the yeast. I also raised fermentation temp to 72 F to help keep it moving since I understand pressure can slow yeast down.

Is this normal activity when spunding, or did the yeast possibly stall out from the pressure?

I'm fermenting with WLP001. I've used this yeast many times and I've never seen it finish in just a few days. However, I've also never spunded before, so I am not sure if this all it's pretty normal?

I'm going to take a sample in a few days to check gravity and pH and see what is really going on, but I figured I'd see if anyone could give some input. There should be no leaks in my fermenter either because I was holding it at 15psi for a few days prior to putting the batch in.

 

[RM-MN]

I don't think you have a problem, I think the yeast have reached the portion of their life cycle where they cease production of CO2. Read through this article and notice the time line of the yeast.

http://www.brewgeeks.com/the-life-cycle-of-yeast.html

 

[refect]

I don't think you have a problem, I think the yeast have reached the portion of their life cycle where they cease production of CO2. Read through this article and notice the time line of the yeast.

http://www.brewgeeks.com/the-life-cycle-of-yeast.html

Thank you! That was a good article. It is probably safe to assume they have stopped producing co2, but I was only able to capture the last remaining co2 coming out of solution. That is likely why it capped at 13 psi as well. I'll have to remember this timeline for next time I use my spunding valve. Maybe start spunding earlier if I want to capture more co2.

 

[Bassman2003]

Refresh your timeline on this brew. It seems you closed down the spunding valve at 48 hours after pitching? In my experience that is pretty early and yeast produce CO2 all the way to the bitter end. Just less and less as activity slows down.

What needs to be stated is pressure fermentation does put more stress on yeast, so the health of your yeast and size of your pitch come more to the forefront. My SOP these days is to ferment IPA at 30PSI from the start. I just compensate with more fresh yeast to get a complete fermentation. The high pressure really accentuates the hops.

"Normal" spunding practice is to close the valve with 3-5 gravity points left in the fermentation to generate carbonation. You can close it earlier if you want. But yeast most certainly keep putting off CO2 or this method would not work...

 

[MicroMickey]

I talked with a guy who actually did some pressurized fermentation experiments while working for Coors. Yeast didn't start to stall out until the pressure got up to 60 or 70 psi (lager yeast). This experiment was mainly done to check the effect of hydrostatic pressure in VCTs. The box fermenters at Coors run 9 to 12 ft. vertical depth of liquid while at Budweiser, it'll run about 40 ft. in a VCT. Both are vented to atmosphere but do develop hydrostatic pressure to a varying degree. He didn't check for health of the yeast or beer quality.

 

[refect]

Refresh your timeline on this brew. It seems you closed down the spunding valve at 48 hours after pitching? In my experience that is pretty early and yeast produce CO2 all the way to the bitter end. Just less and less as activity slows down.

What needs to be stated is pressure fermentation does put more stress on yeast, so the health of your yeast and size of your pitch come more to the forefront. My SOP these days is to ferment IPA at 30PSI from the start. I just compensate with more fresh yeast to get a complete fermentation. The high pressure really accentuates the hops.

"Normal" spunding practice is to close the valve with 3-5 gravity points left in the fermentation to generate carbonation. You can close it earlier if you want. But yeast most certainly keep putting off CO2 or this method would not work...

I always thought that they would produce co2 all the way through as well, but just less and less like you stated. That is why I wasn't sure if i stalled them out becsuse i stopped seeing bubbling shortly after starting to spund. My thought process was to start spunding when it was down in the 1.020 range, which I assumed it would be after 48 hours from previous experiences.

I made a starter using homebrew dads calculator a few day prior to brewing. My yeast should have been healthy with the correct pitch rate according to the calculator. I had activity in less than 12 hours of pitching. The OG was 1.062. Nothing crazy high, I also aerated with pure o2 at 1 liter p/m for about a minute and 20 seconds. No yeast nutrient was used. Post boil pH was 4.8. I'll be doing a hefty dry hop so I dropped pH low to compensate for the change after dry hopping.

Should I be building my starters with significantly more yeast than the recommend amount if I will be spunding? Has anyone had yeast stall out once they started to spund?

As I mentioned before, I'll let it sit and pull a sample in a few more days to see if I've reached terminal and see how it is tasting. Beer Smith predicts an FG of 1.013.

If I did stall them out, should I make a small starter of WLP001 and pitch that under pressure?

 

[Bassman2003]

Thanks for the info. Tough to say if the yeast was really finished or if it pooped out. Any major yeast impact would be from starting at a higher pressure which inhibits growth in the early phase due to higher amounts of CO2 which is harmful to yeast cells. Once the growth phase is completed, the main fermentation begins. Pitch plenty of yeast and the growth phase is shorter and less important because you already have a lot of cells. Underpitch and the growth phase drags out longer while the yeast are replicating. This also depletes them of resources for the long journey.

Yeast calculators probably do not account for pressure fermentations.

It is tough to think you hit terminal gravity in 48 hours from 1.062 but it is possible. Ales can be quick which makes spunding more of a challenge. When I moved to spunding I missed the window a few times which prompted me to buy a Tilt so I could track the progress of the fermentation. If your gravity is 1.020 then the yeast just finished before completing the job. Which may or may not be due to the increased pressure towards the end. If it is 1.013 they were just done and you missed the window for spunding. One fix is to add some sugar and maybe a little cask yeast (CBC) and get a little more activity going to spund.

Remember:

Fermenting under pressure (with CO2) is an effort to mimic large cylindroconical tanks that due to their size, create hydrostatic pressure. We can not have hydrostatic pressure so we have to use CO2 based forced pressure. They are not exactly the same, but similar. The benefit of hydrostatic pressure is that it is less harmful to yeast compared to CO2

Spunding is trapping CO2 in the beer for natural carbonation. This is typically done towards the end of fermentation, even for beers that were not fermented under pressure. German lager is actually often spunded in the lager tank. Slow with a lot of trust!

 

[refect]

Thanks for the info. Tough to say if the yeast was really finished or if it pooped out. Any major yeast impact would be from starting at a higher pressure which inhibits growth in the early phase due to higher amounts of CO2 which is harmful to yeast cells. Once the growth phase is completed, the main fermentation begins. Pitch plenty of yeast and the growth phase is shorter and less important because you already have a lot of cells. Underpitch and the growth phase drags out longer while the yeast are replicating. This also depletes them of resources for the long journey.

Yeast calculators probably do not account for pressure fermentations.

It is tough to think you hit terminal gravity in 48 hours from 1.062 but it is possible. Ales can be quick which makes spunding more of a challenge. When I moved to spunding I missed the window a few times which prompted me to buy a Tilt so I could track the progress of the fermentation. If your gravity is 1.020 then the yeast just finished before completing the job. Which may or may not be due to the increased pressure towards the end. If it is 1.013 they were just done and you missed the window for spunding. One fix is to add some sugar and maybe a little cask yeast (CBC) and get a little more activity going to spund.

Remember:

Fermenting under pressure (with CO2) is an effort to mimic large cylindroconical tanks that due to their size, create hydrostatic pressure. We can not have hydrostatic pressure so we have to use CO2 based forced pressure. They are not exactly the same, but similar. The benefit of hydrostatic pressure is that it is less harmful to yeast compared to CO2

Spunding is trapping CO2 in the beer for natural carbonation. This is typically done towards the end of fermentation, even for beers that were not fermented under pressure. German lager is actually often spunded in the lager tank. Slow with a lot of trust!

This is all some good info here. Thanks everyone for the response. When I pull a sample I'll report back if it finished or not and go from there.

It looks like timing would be everything when spunding an ale towards then end. I have a Tilt myself, but I stopped using it. It worked great the first 2-3 times. I even used it in a lager with great success to know when to start my d-rest, but for some reason the gravity readings and temperature readings have been all over place. Either way too low, or way too high compared to my hydrometer readings. Even with calibrations it's all over the palce. I haven't used it lately because of this.

For my future ale spunding attempts it looks like timing will be everything. When spunding towards the end of an ale, do you let yours build pressure naturally like I did on this attempt, or hook up co2 and get pressure to where you want and start spunding?

I'd like to spund some lagers in the future as well. If co2 is detrimental to yeast growth/health, would it be better to pitch and pressurize to the desired psi with an air pump of some sort if spunding right at pitching time?

All my spunding will be done in an ss unitank with ss spunding valve. Not sure if that info matter or not...

 

[Bassman2003]

I only add tank CO2 when I am starting at a desired PSI - like an IPA with a starting pressure of 30 PSI. I oxygenate, close the fermenter then add tank CO2 to 30PSI. The fermentation proceeds and keep the valve on to maintain 30 PSI throughout. All other situations I let everything happen naturally. That is the main point of spunding - all natural 100% pure CO2. Tank CO2 contains small amounts of oxygen.

Yes, you can pressurize with an air pump or let it naturally build from the start. These approaches are easier on the yeast. In the end, the different approaches are just different levels of CO2 trapped inside the fermenter, earlier or longer.

 

[refect]

I only add tank CO2 when I am starting at a desired PSI - like an IPA with a starting pressure of 30 PSI. I oxygenate, close the fermenter then add tank CO2 to 30PSI. The fermentation proceeds and keep the valve on to maintain 30 PSI throughout. All other situations I let everything happen naturally. That is the main point of spunding - all natural 100% pure CO2. Tank CO2 contains small amounts of oxygen.

Yes, you can pressurize with an air pump or let it naturally build from the start. These approaches are easier on the yeast. In the end, the different approaches are just different levels of CO2 trapped inside the fermenter, earlier or longer.

This is all good info that I will certainly need to consider as I venture on with my spunding journey. That is exactly the reason why I wanted to spund on my recent IPA. I was trying to trap all pure natural co2 to limit as much o2 as possible and further help preserve the hop aromas. Also, to try and have the beer pretty much carbed up by the time it goes into the keg. I'd like try and spund a lager on one of my next batches as well and try to get it to finish really clean.

 

[Bassman2003]

It gets really simple when you ferment at your final carbonation pressure. Just transfer and your done.

 

[DuncB]

I suspect the reason you couldn't build beyond 13 psi was because you have a leak.
As stated above, can easily build to 30 psi with 5 or 6 gravity points from final and I often see the pressure continue to rise after the SG is stable ( measured with Ispindel ).
Check the lid seal, posts, the PRV and the spunding valve. My first spunding valve was a metal one and that had a hairline crack in it, this meant it spunded fine during active ferment and then pressure dropped away once rapid gas production ceased.

 

[refect]

I suspect the reason you couldn't build beyond 13 psi was because you have a leak.
As stated above, can easily build to 30 psi with 5 or 6 gravity points from final and I often see the pressure continue to rise after the SG is stable ( measured with Ispindel ).
Check the lid seal, posts, the PRV and the spunding valve. My first spunding valve was a metal one and that had a hairline crack in it, this meant it spunded fine during active ferment and then pressure dropped away once rapid gas production ceased.

I'll certainly have to check for leaks after this batch. I pressurized my fermenter to 15psi with the spunding valve completely closed and it held fine for the few days prior to this batch. I'll try to pressurize it to 20+ psi and open the valve to hold at that pressure to see if it's dropping once it is opened. As of now it is holding just around 13psi on the pressure gauge with no bubbling on the spunding valve.

 

[DuncB]

What fermenter are you using?
What spunding valve?
If the fermenter is rated higher than 15 psi and you can take the spunding valve off do this for about 6 hours.
Then test the pressure with a gauge or your spunding valve. If it has built then it shows the issue is with your spunding valve.

 

[refect]

What fermenter are you using?
What spunding valve?
If the fermenter is rated higher than 15 psi and you can take the spunding valve off do this for about 6 hours.
Then test the pressure with a gauge or your spunding valve. If it has built then it shows the issue is with your spunding valve.

My fermenter is a 7 gallon ss brewtech unitank 2.0, and the spunding valve is the ss brewtech adjustable prv (non etched marking version). I have it attached to my blow off arm just above the ball valve, so that I could close the blow off once I was ready to spund. It was holding 15 psi empty prior to this batch, but I'll definitely do some leak testing.

I've seen fermentation be just about done in 3 days with a lot of english strains that I've used, but I'm using a Chico strain for this batch, which I've always seen to be pretty active still at 4 days in. That's why I wasn't sure if the pressure might have stalled them out.

 

[DuncB]

The equipment answers the question.
The Fermenter has a PRV set for 15 psi.

That's your leak!!

 

[refect]

The equipment answers the question.
The Fermenter has a PRV set for 15 psi.

That's your leak!!

Well, it is a good thing I went back and checked. I always thought it was good for up to 30 psi. Looks like I read it wrong when I got it. Its max pressure rating is 30 psi, but it says working pressure 15 psi. I must have had a few too many beers when I was reading up on the specs a year ago prior to my purchase. Looks like I won't be spunding anything over 15psi in the future.

I currently do not have the large 3-inch safety prv that it comes with attached, so I know it was not bleeding off any pressure prior to reaching 15 psi. If there is a leak, then the only place I can think of is either the ball valve on the blow off arm or the spunding valve itself.

 

[DuncB]

Always a good idea to have the PRV and the spunding valve on.
If for any reason the spunding valve sticks ( which has been reported on this forum ) then you are making a potential danger.
As to why a stainless steel fermenter costing a 1000 dollars is rated to only 15 psi and my 60 dollar pet fermentasaurus is rated to 35 psi ( and used to that pressure ) I do not know.
On the brighter side a Lager spunded to 15 psi and cold fermenting at 9 C would be about 2.4 vols.

Not so good for an ale fermenting warmer.

 

[mashdar]

Second for a safety PRV. If you are using something as a primary pressure control, it is not providing emergency pressure relief. These are by definition two devices. Commercial setups frequently have multiple emergency devices.

edit: Also, I'm confused by the setup with the blow off. Is the spunding valve paralleled with the blow off valve?

 

[DuncB]

@mashdar
Having read the manual to find out about the 15psi, I think the spund is on the blow off tube for the 7 gallon fermenter. Somewhere different on their bigger fermenters. I was skimming through the 16 page manual.

 

[mashdar]

@mashdar
Having read the manual to find out about the 15psi, I think the spund is on the blow off tube for the 7 gallon fermenter. Somewhere different on their bigger fermenters. I was skimming through the 16 page manual.

Blow off goes through the spund?

@refect mentions closing the blow off. That could mean closing a ball valve ahead of the spund, which would leave the spund at a fixed pressure while the fermenter pressure increases unchecked.

 

[DuncB]

Blow off goes through the spund?

@refect mentions closing the blow off. That could mean closing a ball valve ahead of the spund, which would leave the spund at a fixed pressure while the fermenter pressure increases unchecked.

Not sure exactly how the spunding valve was fitted but this is an image from the manual for the 7.0 gall unitank

 

[mashdar]

I see, so probably popped it onto that upward-facing TC flange where the gauge is shown.

 

[DuncB]

I see, so probably popped it onto that upward-facing TC flange where the gauge is shown.

I think so.
A three inch to 1.5 converter with a T on it fitted to the top with the prv and a separate gauge could be a good mod for safety.

 

[refect]

QUOTE="DuncB, post: 10402907, member: 265668"]
I think so.
A three inch to 1.5 converter with a T on it fitted to the top with the prv and a separate gauge could be a good mod for safety.
[/QUOTE]

Yes that is correct. The ss spunding valve attaches on the blow off arm in-between the ball valve and the blow off arm via a T and a 90 degree elbow. You simply close the ball valve when you are ready to spund, or keep it closed the entire time if you are spunding from the start. This is a pic of how I have mine setup...

 

[mashdar]

That's a very nice setup!

On the emergency PRV theme, the SSbrewtech website says in regards to spunding "Lastly, a final note on safety, always leave the fixed-pressure PRV included with the Unitank in place".

There's another manufacturer that throws best safety practices to the wind in this regard...

 

[refect]

That's a very nice setup!

On the emergency PRV theme, the SSbrewtech website says in regards to spunding "Lastly, a final note on safety, always leave the fixed-pressure PRV included with the Unitank in place".

There's another manufacturer that throws best safety practices to the wind in this regard...

Thank you!!

Yeah I definitely agree with having a safety prv attached. The ss brewtech comes with a big 3 inch tri clamp that attaches to the top port. The only reason why I left it off is because I use that top port for o2 free dry hopping. Once I close the butterfly valve and switch back on the I prv, I have no way to purge the space of oxygen before opening it back up. For that reason, I decided to leave it off and just monitor it like crazy, checking on it quite obsessively. In the future, if I am spunding something that won't be dry hopped then I'll use the safety prv it came with for sure. However, I am currently putting together something else to be used as a safety release for dry hopped beers that are spunded.

 

[refect]

Decided to take a sample today. It looks like it didn't stall out after all. FG was 1.013, and post fermentation pH was 4.15. I'm expecting final pH to be in the 4.3 range after dry hop. Everything landed right where I wanted.

I guess I just missed that window to start spunding and capture a bit more co2 as mentioned earlier, or I do have a leak somewhere. After I keg this batch, I'll be doing pressure tests to find out if it was just the fact that the yeaat stopped producing co2 and couldn't get it up to 15 psi, or I do in fact have a leak somewhere.

Thanks everyone for the responses! This has all helped as I start my spunding journey!

Edit:
I also don't know if it is just me, but I feel like the hop aroma from my whirlpool addition was jumping out of the glass while the sample was just sitting on my table. I typically don't get that until I dry hop. I definitely noticed a difference with spunding on hoppy beers. I feel like a lot more of the hop aroma from the whirlpool addition remained in the beer.

 

[DuncB]

If you fit a T to the top 3 inch with the side to say the left you can fit the prv to that. Put your hop dosing thing on the top of the T.
Then you can keep the whole system closed for your dry hopping.
Might need a 2 inch T for that.

 

[refect]

If you fit a T to the top 3 inch with the side to say the left you can fit the prv to that. Put your hop dosing thing on the top of the T.
Then you can keep the whole system closed for your dry hopping.
Might need a 2 inch T for that.

That is one way I was thinking of doing it. I'm just not sure how big and bulky a 3 inch T would be on top of that. I'll probably get a hold of one to see how big it will be in person and decide how I want to do it. My main concern is making the FV too top heavy since it is on the smaller side at 7 gallons. It's pretty stable, but it can easily rock if you push on it with a little bit of force (especially if you push from the back since a lot of weight is on the front from the valves). It will take a very very hard push to knock it over, so it's not going anywhere, but if the 3 inch T is too big and bulky then I may consider the other option.

The other option I was thinking is to buy another one of the smaller 1.5 inch T's that my spunding valve is attached to, and mount it under the spunding valve with a safety valve coming off of the side of that. This would be a bit more cost because I'd have to purchase another safety prv.

I'll have to see what will work best, but I think both would certainly work. The second one would just cost more than the fitst option.