Two spunding valves one fermenter?

[McMullan]

Is it okay to daisy chain two spunding valves? The problem, being relatively new to pressure fermenting, I forgot to plan to link an empty sanitised keg to my latest pressure fermentation, but I want to purge air from a sanitised keg using CO2 from the fermentation then bring the pressure up to equal the 10psi in the FV. I'm using BlowTie spunding valves so the tube 'out' push fitting makes it very easy to connect a second valve via a length of EvaBarrier tubing. But is it okay to do this? I'm thinking it should be fine as long as the second valve downstream on the keg is set at a lower pressure than the primary valve on the FV. Am I missing anything?

 

[GilSwillBasementBrews]

I would jump the fermenter gas port to the kegs gas port and put the spunding valve set to the pressure you require in the beer out of the keg.

 

[McMullan]

I would jump the fermenter gas port to the kegs gas port and put the spunding valve set to the pressure you require in the beer out of the keg.

The problem is fermentation started about 36 hours ago, so If I move the primary spunding valve to the keg (which is where I'd normally fit it, at the start, after pitching the yeast) there is going to be a big drop in FV pressure, which might spook the yeast.

 

[GilSwillBasementBrews]

If that is your concern, I don’t see any problem with using another spunding valve downstream of the first

 

[McMullan]

Sorry, I think I've confused myself thinking about it. I'm not going to daisy chain the valves at all, just link the pressurised FV and the unpressurised keg:

FV spunding - keg 'in' disconnect - keg 'out' spunding

 

[DuncB]

@McMullan
I do what @GilSwillBasementBrews suggests with nearly all of my pressure ferments. However I'm normally flushing out a keg filled with starsan so I connect ferment gas to gas on keg. Then liquid out via tube to the vessel to recollect the starsan, or liquid out to liquid in of the next keg and then either have an open ball lock on the gas or a spunding valve.
If you are doing one keg only when connected you don't get a great equalisation of pressure ie dropping to 0 psi in fermenter because it is pushing against the liquid. Once the liquid is transferred out then put the spunding valve on the keg gas out and the pressure rises pretty quickly.

I accidentally due to ignorance put a non return ball lock connector on my spunding valve and discovered this on day 5, fermentasaurus was tight as a drum leaking out thru PRV with a psi of 35. It was still bubbling away and not spooked at all. I did over a period of time bring the pressure down but don't do it all at once otherwise you end up with a fire extinguisher.
If you aren't going to flush starsan out just put the other keg on the pressure equalises but won't drop to zero or shock the yeast too much.

 

[McMullan]

@McMullan
I do what @GilSwillBasementBrews suggests with nearly all of my pressure ferments. However I'm normally flushing out a keg filled with starsan so I connect ferment gas to gas on keg. Then liquid out via tube to the vessel to recollect the starsan, or liquid out to liquid in of the next keg and then either have an open ball lock on the gas or a spunding valve.
If you are doing one keg only when connected you don't get a great equalisation of pressure ie dropping to 0 psi in fermenter because it is pushing against the liquid. Once the liquid is transferred out then put the spunding valve on the keg gas out and the pressure rises pretty quickly.

I accidentally due to ignorance put a non return ball lock connector on my spunding valve and discovered this on day 5, fermentasaurus was tight as a drum leaking out thru PRV with a psi of 35. It was still bubbling away and not spooked at all. I did over a period of time bring the pressure down but don't do it all at once otherwise you end up with a fire extinguisher.
If you aren't going to flush starsan out just put the other keg on the pressure equalises but won't drop to zero or shock the yeast too much.

That sounds like a better way to put things back on track. I even have a bucket full of fresh starsan to hand and it's only a 9L keg so no problem filling it

 

[DuncB]

@McMullan
Wanted to add this photo to my post but couldn't access the server with the picture on.

Two kegs both flushed with starsan and pressuring up.
Once the kegs are at pressure and have had some time with pass through to remove every last oxygen molecule I disconnect them and move spunding valve back onto the fermenter.
I do aim for my final vols in the fermenter towards the end / during the diacetyl rest and boost the keg pressure to that level as well. THen cold crash and the pressure will drop in the fermenter.
Come the closed transfer pressure in keg will be higher vent this into the keg and use the pressure excess to drive the transfer, using other keg if needed.