Walk Me Through a Pressurized Closed Transfer Please.

[Yesfan]

Hi all. I plan on kegging a double batch I brewed about a month ago. Currently it's at 15psi at 64F. In the past, I've just bled off the pressure of the fermenter before transfer and pushed it to my serving keg at 2psi.

My thoughts are to connect a jumper gas post to gas post from fermenter to keg so the pressure equalizes between the two vessels. Then what? Connect a jumper from beer post to beer post and bleed off the keg's pressure via the prv? I've read here transferring too fast will produce foaming. If both vessels are at equal pressure, then do you use the prv valve of the keg or disconnect the gas jumper and just put a spunding valve on the keg (nothing on the fermenter) to do a slow transfer?

On another note, is there a way to see how much more days on gas a pressurized fermentation needs after transferring to a serving keg? As mentioned, it's at 15psi at 64F. If I can keg this batch tonight, how much time do I need on gas to drink it this weekend? Thanks in advance.

 

[wdavis2003]

What I do is a jumper from beer post of FV to beer post of keg and a spunding valve on the gas post of keg to release pressure while it's filling. I also apply pressure on the gas post of FV to help push the liquid out. As long as FV pressure is higher then keg pressure it should flow smoothly.

 

[day_trippr]

I have seen pictures posted by HBT folks that show connections from "beer to beer and gas to gas" with the fermentor on a bench above the keg on the floor and somehow manage to do the full closed transfer using just gravity to do the work...

Cheers!

 

[wdavis2003]

I have seen pictures posted by HBT folks that show connections from "beer to beer and gas to gas" with the fermentor on a bench above the keg on the floor and somehow manage to do the full closed transfer using just gravity to do the work...

Cheers!

Back when I was using a bucket fermenter I'd fill the keg with sani, push it out with 3-5 psi of CO2. Elevate the bucket above the keg and connect a hose from the spigot of the bucket to the liquid post on the keg. Then I would connect a hose from the gas in post on the keg and run it up to the top of the bucket and through the lid where the air lock hole was. That way as beer filled the keg, 3-5 pounds of CO2 was pushing the liquid out of the bucket (more so gravity was pushing the liquid out of the bucket but I like to think the CO2 pressure helped. Twas a semi closed transfer IMO

 

[user 338926]

Back when I was using a bucket fermenter I'd fill the keg with sani, push it out with 3-5 psi of CO2.

To the op, you made no mention of this. This is the step that is probably more important than all the other ones. There is no sense in going through any of this if you're pushing the beer into a container that is full of air.

If you're under 15 psi now, I would connect the keg after putting 12 psi in it and start the transfer. Now you don't have the degassing problem you were going to have at zero PSI or near it.

 

[Yesfan]

To the op, you made no mention of this. This is the step that is probably more important than all the other ones. There is no sense in going through any of this if you're pushing the beer into a container that is full of air.

If you're under 15 psi now, I would connect the keg after putting 12 psi in it and start the transfer. Now you don't have the degassing problem you were going to have at zero PSI or near it.

I'm not using a bucket fermenter. I think you misquoted wdavis thinking he was the op.

My fermenter is a tall 15 gallon corny that I'll be splitting to two 5 gallon cornys. It's looking like I'll have to use my co2 tank after all to push from the 15 gallon to the 5 gallon kegs. That's not a big deal. I was just wondering if there is a better way to do a pressurized transfer.

 

[user 338926]

I'm not using a bucket fermenter. I think you misquoted wdavis thinking he was the op.

My fermenter is a tall 15 gallon corny that I'll be splitting to two 5 gallon cornys. It's looking like I'll have to use my co2 tank after all to push from the 15 gallon to the 5 gallon kegs. That's not a big deal. I was just wondering if there is a better way to do a pressurized transfer.

No, what I was doing was quoting him talking about purging The Keg properly, and saying to you, that's the step you make no mention of in your procedure.

Then, if you were to actually Purge The Keg and leave some measure of pressure in it, it will mostly equalize with your FV and you don't need to worry about degassing your beer because of a massive drop in pressure. There will only be a couple PSI difference with no change in the 15psig FV pressure.

 

[Yesfan]

No, what I was doing was quoting him talking about purging The Keg properly, and saying to you, that's the step you make no mention of in your procedure.

Then, if you were to actually Purge The Keg and leave some measure of pressure in it, it will mostly equalize with your FV and you don't need to worry about degassing your beer because of a massive drop in pressure. There will only be a couple PSI difference with no change in the 15psig FV pressure.

Ok, I see about purging. Yes, I did fill both my serving kegs with starsan (not at the same time), and pushed them out with co2. One keg, and then to the other. I pushed using 10psi a couple of weeks ago to purge and also make sure there weren't any leaks by leaving them pressurized.

Last night, I went ahead a kegged my batch. The fermenter is a 15G corny which was at 15psi. The two purged/sanitized kegs still showed 10psi, so I connected a gas jumper between fermenter to serving keg to equalize the pressure. Then I moved the spunding valve to the serving keg and connected my spare co2 tank to the fermenter. Then I connected my transfer line, beer post to beer post of the fermenter and serving keg. I backed off the pressure of the spunding valve until I heard gas escaping and watched the beer move from fermenter to keg. On average, the pressure on the spunding valve was at 10psi and the tank's regulator was 12-13psi. The serving keg was on a scale so I would know how full to get it. Repeated for keg 2.

Probably not the ideal way as I felt I wasted a lot of co2 doing it this way. The transfer for the most part went very smoothly. The only downer is the beer tasted a bit flat this morning when I sampled it, but that might be where the co2 was absorbed when I put the keg in the kegerator last night. It's on gas now.

Thanks everyone for the help, suggestions, and any more tips.

 

[wdavis2003]

Ok, I see about purging. Yes, I did fill both my serving kegs with starsan (not at the same time), and pushed them out with co2. One keg, and then to the other. I pushed using 10psi a couple of weeks ago to purge and also make sure there weren't any leaks by leaving them pressurized.

Last night, I went ahead a kegged my batch. The fermenter is a 15G corny which was at 15psi. The two purged/sanitized kegs still showed 10psi, so I connected a gas jumper between fermenter to serving keg to equalize the pressure. Then I moved the spunding valve to the serving keg and connected my spare co2 tank to the fermenter. Then I connected my transfer line, beer post to beer post of the fermenter and serving keg. I backed off the pressure of the spunding valve until I heard gas escaping and watched the beer move from fermenter to keg. On average, the pressure on the spunding valve was at 10psi and the tank's regulator was 12-13psi. The serving keg was on a scale so I would know how full to get it. Repeated for keg 2.

Probably not the ideal way as I felt I wasted a lot of co2 doing it this way. The transfer for the most part went very smoothly. The only downer is the beer tasted a bit flat this morning when I sampled it, but that might be where the co2 was absorbed when I put the keg in the kegerator last night. It's on gas now.

Thanks everyone for the help, suggestions, and any more tips.

Sounds like a good process. A lot of CO2 being used but I don't know if that's avoidable. If anybody has a better process I'd like to hear it as well.

 

[Raptor99]

I haven't tried it yet, but this looks like an interesting idea: Fermenting Under Pressure on the Cheap and Saving the Planet! | MoreBeer

I make hard cider, so I need to investigate the pros and cons of fermenting under pressure.

 

[Yesfan]

I haven't tried it yet, but this looks like an interesting idea: Fermenting Under Pressure on the Cheap and Saving the Planet! | MoreBeer

I make hard cider, so I need to investigate the pros and cons of fermenting under pressure.

Step #5 was what I kinda did. The next batch I do, I need to incorporate the serving keg(s) inline with the fermenter and utilize the off gassing from the fermenter to purge the serving keg(s).

Off topic.

First thing I thought of about the gas escaping my spunding valve during transfer is "how can this be used for the uhm 'home growers' out there/". I'm sure there's already a few within our community here that's already thought of that. It's no different than using the waste water from wert chilling to water your garden/plants or those who donate their spent grains to a local farmer.

 

[SanPancho]

Ok, I see about purging. Yes, I did fill both my serving kegs with starsan (not at the same time), and pushed them out with co2. One keg, and then to the other. I pushed using 10psi a couple of weeks ago to purge and also make sure there weren't any leaks by leaving them pressurized.

Last night, I went ahead a kegged my batch. The fermenter is a 15G corny which was at 15psi. The two purged/sanitized kegs still showed 10psi, so I connected a gas jumper between fermenter to serving keg to equalize the pressure. Then I moved the spunding valve to the serving keg and connected my spare co2 tank to the fermenter. Then I connected my transfer line, beer post to beer post of the fermenter and serving keg. I backed off the pressure of the spunding valve until I heard gas escaping and watched the beer move from fermenter to keg. On average, the pressure on the spunding valve was at 10psi and the tank's regulator was 12-13psi. The serving keg was on a scale so I would know how full to get it. Repeated for keg 2.

Probably not the ideal way as I felt I wasted a lot of co2 doing it this way. The transfer for the most part went very smoothly. The only downer is the beer tasted a bit flat this morning when I sampled it, but that might be where the co2 was absorbed when I put the keg in the kegerator last night. It's on gas now.

Thanks everyone for the help, suggestions, and any more tips.

Late to the party but you’ve now seen the drawback of fermentation under pressure. Lots of wasted co2. Avoiding foam means pressurizing keg towards the ferm pressure, as well as keeping ferm pressure stable. All of that gets wasted.
there may be other ways but the one process I’ve used with decent success is to crash it as low as possible, towards 30f if you can. Get your keg ice cold as well, and then slowly blow off residual pressure on ferm until you’re down around 5psi or so. Then transfer, slow and steady. You’ll get a bit of foam but not bad at all As long as you slow and steady.

another option someone noted above is to get Keg like 2-3psi under the ferm, position it below ferm, connect your purged gas jumper to only one of the kegs, then connect the beer posts. As soon as the beer starts flowing into keg, then you quickly connect the gas jumper to equalize pressures. At that point you’re siphoning the beer by gravity, in closed system.

 

[Bobby_M]

If you want to transfer carbonated beer and not have it lose any carbonation at all, or foam in the process, you have to have an adjustable PRV on the gas port of the receiving keg. If you carbed the beer to 15psi, that's the vent pressure you set on the PRV of the receiving keg. Then to make the transfer happen, you apply about 20psi on the donor keg. That 5 psi differential will move the beer quickly. The PRV maintaining the same pressure that the beer is currently carbed to does not allow CO2 to break out of solution.

Any other solution to this is going to yield sketchy results and you'd be better off just holding off carbonation until it's in the final keg in that case.

 

[Yesfan]

If you want to transfer carbonated beer and not have it lose any carbonation at all, or foam in the process, you have to have an adjustable PRV on the gas port of the receiving keg. If you carbed the beer to 15psi, that's the vent pressure you set on the PRV of the receiving keg. Then to make the transfer happen, you apply about 20psi on the donor keg. That 5 psi differential will move the beer quickly. The PRV maintaining the same pressure that the beer is currently carbed to does not allow CO2 to break out of solution.

Any other solution to this is going to yield sketchy results and you'd be better off just holding off carbonation until it's in the final keg in that case.

Does temperature matter in this Bobby? I had 15psi on my fermenter, but that's at 64F. Instead of pushing at 20psi, I was pushing at 12-13. A bit lower than what the fermenter had showed, but the serving keg's prv was at 10psi.

Late to the party but you’ve now seen the drawback of fermentation under pressure. Lots of wasted co2. Avoiding foam means pressurizing keg towards the ferm pressure, as well as keeping ferm pressure stable. All of that gets wasted.
there may be other ways but the one process I’ve used with decent success is to crash it as low as possible, towards 30f if you can. Get your keg ice cold as well, and then slowly blow off residual pressure on ferm until you’re down around 5psi or so. Then transfer, slow and steady. You’ll get a bit of foam but not bad at all As long as you slow and steady.

another option someone noted above is to get Keg like 2-3psi under the ferm, position it below ferm, connect your purged gas jumper to only one of the kegs, then connect the beer posts. As soon as the beer starts flowing into keg, then you quickly connect the gas jumper to equalize pressures. At that point you’re siphoning the beer by gravity, in closed system.

I agree, but most of that co2 was from fermentation. In a sense, it's going to be wasted anyways, right? In the future, I've thought about adding another cleaned/sanitized keg in the chain so as to "save" (for lack of a better word) more of the co2 from fermentation.

Maybe with the transfer, I could just use the pressurized fermenter to push more of the beer instead of trying to keep it at 10-15psi during the entire transfer via co2 bottle. With all the various ptc fittings, I could always rig up an extra regulator to monitor the fermenter's outgoing pressure vs the serving keg's out going pressure. If I get to a point to where there's not enough pressure left from the fermenter to keep the beer moving to the keg, then I could just connect my co2 bottle to the fermenter to finish the transfer.

 

[Red over White]

I found a gravity closed xfer to be ideal. Most times I am at 25 psi when I xfer, but the key I believe is to size the length and diameter of the jumper lines exactly as you would for serving. I don't have co2 breakout with balanced lines. It takes a while to xfer, but runs tickety boo. I clean the jumpers, Sanitize them and use the fermenter to purge them with co2 before pulling the prv and cleaning the fermenters. Hopefully this helps.

 

[SanPancho]

if you use ferm gas to purge, you're not "losing" any gas there (i.e. buying gas in a tank), that's correct. but the ferm itself needs to maintain its pressure, and then what do you do with that gas? just wasted, unless you're gonna hold onto that ferm under pressure and wait for another keg to free up and try and use the gas to purge another keg.
you can do it, definitely. but its kind of a pain and what if it takes a few weeks before you're ready to purge a new keg? your ferm is gonna be crusty and nasty. all technically doable, just not practical in most regards for home brewing.

DO NOT believe the BS above about there being only "one way" to do this. everyone who's ever bought a growler from a brewery has more than likely had it filled at low temp, very slowly, and its holds carb just fine. the majority of your local micro/nano breweries dont have automated canning/bottling lines with full 100% counterpressure and it comes out just fine. hell, you cant have 100% counterpressure in bottling or canning, as there's no way to get the lid/cap on. they all get opened to ambient after filling and before capping/lids. if the beer is cold, and you're being gentle/slow, its fine. the automated machines dont want to do "slow" so they need to do the counterpressure to avoid foam.
and i wish i knew where to find it, but somebody here on this forum has taken photos if not a video of their setup where they do the gravity/siphon method i talked about and it works just fine.

 

[day_trippr]

Just a little over the top there.
The proffered posit was conditional.
Ie: "not have it lose any carbonation at all, or foam in the process".
Sans counterpressure any transfer will assuredly lose carbonation to some degree.
Perhaps not enough to matter to anyone, but that wasn't the point of the posit...

Cheers!

 

[ITV]

if the beer is cold, and you're being gentle/slow, its fine. the automated machines dont want to do "slow" so they need to do the counterpressure to avoid foam.
and i wish i knew where to find it, but somebody here on this forum has taken photos if not a video of their setup where they do the gravity/siphon method i talked about and it works just fine.

Sounds like how I do my transfers: Spike CF10 - closed transfer without pressure?

 

[SanPancho]

Just a little over the top there.
The proffered posit was conditional.
Ie: "not have it lose any carbonation at all, or foam in the process".
Sans counterpressure any transfer will assuredly lose carbonation to some degree.
Perhaps not enough to matter to anyone, but that wasn't the point of the posit...

Cheers!

sure man, over the top. just like crying about technicalities of hypothetical theoretical 0% loss of carb AND zero foam posits that dont exist in reality. because that's what homebrewing is all about, demonstrating how using ultra-precise lab-quality equipment is used in processes to generate empirical results approaching theoretical limits.

 

[day_trippr]

lol!

 

[SanPancho]

Sounds like how I do my transfers: Spike CF10 - closed transfer without pressure?

ah, cool. not the post i was talking about earlier, that one's keg to keg. but same idea, and thats a nice setup. only question is whether you've run into issues with filter clogging? i guess if you dump enough prior to transfer it shouldnt be an issue, right?

 

[ITV]

ah, cool. not the post i was talking about earlier, that one's keg to keg. but same idea, and thats a nice setup. only question is whether you've run into issues with filter clogging? i guess if you dump enough prior to transfer it shouldnt be an issue, right?

Correct I dump the trub through the dump port. For beers that I dry hop, I do several dumps, a few days apart, and after cold crashing. This has worked out very well for me for batches that I dry hop loose (no bag). I have not had any issues with the filter clogging but I use a coarser bazooka screen in my filter.

I find that I need at least 5 PSI to push the beer through the filter and into my keg, otherwise there is close to 1 quart of beer left in the filter and beer line.

 

[SanPancho]

yeah, thats about what i assumed. no way around the restriction of the filter except to just use force and push. being able to dump makes everything downstream so much easier, even if i'm too lazy alot of times to do it.

 

[Bobby_M]

Does temperature matter in this Bobby? I had 15psi on my fermenter, but that's at 64F. Instead of pushing at 20psi, I was pushing at 12-13. A bit lower than what the fermenter had showed, but the serving keg's prv was at 10psi.

If the beer being transferred is at equilibrium at 15psi, the receiving keg needs to vent at 15 to keep 100% of the carbonation regardless of the temperature of the beer.

 

[Bobby_M]

DO NOT believe the BS above about there being only "one way" to do this. everyone who's ever bought a growler from a brewery has more than likely had it filled at low temp, very slowly, and its holds carb just fine. the majority of your local micro/nano breweries dont have automated canning/bottling lines with full 100% counterpressure and it comes out just fine. hell, you cant have 100% counterpressure in bottling or canning, as there's no way to get the lid/cap on. they all get opened to ambient after filling and before capping/lids. if the beer is cold, and you're being gentle/slow, its fine. the automated machines dont want to do "slow" so they need to do the counterpressure to avoid foam.
and i wish i knew where to find it, but somebody here on this forum has taken photos if not a video of their setup where they do the gravity/siphon method i talked about and it works just fine.

The only BS is trying to compare two completely different things and act like they're the same. Did the OP ask about filling a can or growler?

IF the beer is in the mid 30s or colder, AND the beer is run through balanced serving lines gently into the container, AND you don't mind the time it takes for that beer to move AND it's acceptable to lose some carbonation.... it's fine. The issue is that most FVs, even glycol cooled ones, bottom out at 38-40F and many people are trying to do this at room temp (See OP in this case).

There are tons of pro brewers who fill kegs fast and loose off the brite and they ARE losing carbonation and dumping buckets of foamy beer in the process.

 

[Bobby_M]

20 dollar solution

 

[StayThirsty]

If your donor keg is at 15 psi equilibrium you want to do the entire transfer without letting the donor keg fall below 15 psi. Otherwise, CO2 bubbles will be forming within your trub layer and they will spew yeast and/or hop particulate into your previously clear beer. (Bobby's technique in post 13 avoids this).

I used to ferment in Fermzillas (crystal clear PET) and I learned this lesson when I was watching in horror as CO2 bubbles would emerge from the carbonated trub layer, each one creating a little mushroom cloud as it burst out of the trub layer. This all goes away if you use your CO2 tank to keep the FV at least slightly higher pressure than it was carbed at.

 

[Red over White]

If your donor keg is at 15 psi equilibrium you want to do the entire transfer without letting the donor keg fall below 15 psi. Otherwise, CO2 bubbles will be forming within your trub layer and they will spew yeast and/or hop particulate into your previously clear beer. (Bobby's technique in post 13 avoids this).

I used to ferment in Fermzillas (crystal clear PET) and I learned this lesson when I was watching in horror as CO2 bubbles would emerge from the carbonated trub layer, each one creating a little mushroom cloud as it burst out of the trub layer. This all goes away if you use your CO2 tank to keep the FV at least slightly higher pressure than it was carbed at.

I've done a couple hundred xfers with all rounders and have not had this issue.

With lager yeast pasted to the bottom I can leave a couple shot glasses of clear beer in the fermenter after it's kegged. We are getting different results.

 

[doug293cz]

If the beer being transferred is at equilibrium at 15psi, the receiving keg needs to vent at 15 to keep 100% of the carbonation regardless of the temperature of the beer.

The question might be: "at what pressure would the beer be in equilibrium?" If you for example ferment at 64°F and 15 psi (1.81 volumes of carb), and then cold crash to 32°F, the beer with 1.81 volumes will be in equilibrium with a CO2 partial pressure of 16.7 psia or 2 psi gauge pressure. As time passes the beer will absorb some CO2 from the headspace (since the pressure will be higher than 2 psig) and the equilibrium pressure at 32°F will increase from 2 psig.

If you leave the spunding valve (with gauge) on during cold crash, you will have a better idea of what pressure is needed for a foam free transfer, but unless you crash for an extended period of time (many days), the gauge will indicate higher than the actual equilibrium pressure. The actual equilibrium pressure can be calculated from the starting conditions and the current gauge pressure and temperature, but it's late, so I won't go into that now.

Brew on

 

[doug293cz]

The question might be: "at what pressure would the beer be in equilibrium?" If you for example ferment at 64°F and 15 psi (1.81 volumes of carb), and then cold crash to 32°F, the beer with 1.81 volumes will be in equilibrium with a CO2 partial pressure of 16.7 psia or 2 psi gauge pressure. As time passes the beer will absorb some CO2 from the headspace (since the pressure will be higher than 2 psig) and the equilibrium pressure at 32°F will increase from 2 psig.

If you leave the spunding valve (with gauge) on during cold crash, you will have a better idea of what pressure is needed for a foam free transfer, but unless you crash for an extended period of time (many days), the gauge will indicate higher than the actual equilibrium pressure. The actual equilibrium pressure can be calculated from the starting conditions and the current gauge pressure and temperature, but it's late, so I won't go into that now.

Brew on

The equilibrium pressure for the current carb level of the beer is the minimum CO2 pressure that needs to be maintained in the receiving keg to guarantee no carbonation loss during a counter pressure transfer. The information in the previous post is about the equilibrium pressure. If you transfer with higher than equilibrium pressure in the receiving keg, you won't have any carbonation loss, or foaming. So, higher than equilibrium pressure is perfectly ok to use. If the receiving keg has lower than equilibrium CO2 pressure, then you will lose some amount of carbonation during transfer, and most likely have some level of foaming.

Brew on

 

[Yesfan]

Thanks for the suggestions gang. A lot to take in for the next batch.

 

[StayThirsty]

I've done a couple hundred xfers with all rounders and have not had this issue.

With lager yeast pasted to the bottom I can leave a couple shot glasses of clear beer in the fermenter after it's kegged. We are getting different results.

Just to clarify: you've been transferring carbonated beer from all rounders and letting the pressure drop during the transfer process?

One possible explanation of our different results is that you were brewing lagers and presumably let the yeast cake compact significantly (you said "pasted to the bottom"). My experience was based on brewing ales and I would transfer off the yeast after 1-2 days of cold crash. I'd transfer into another all rounder for dry hopping and would keg after the hops had settled for a couple of days. In neither case was the trub layer very compact. It's in that context that I learned of the importance of keeping the source all rounder at its equilibrium pressure during the entire transfer.

 

[Cherokee6]

Back when I was using a bucket fermenter I'd fill the keg with sani, push it out with 3-5 psi of CO2. Elevate the bucket above the keg and connect a hose from the spigot of the bucket to the liquid post on the keg. Then I would connect a hose from the gas in post on the keg and run it up to the top of the bucket and through the lid where the air lock hole was. That way as beer filled the keg, 3-5 pounds of CO2 was pushing the liquid out of the bucket (more so gravity was pushing the liquid out of the bucket but I like to think the CO2 pressure helped. Twas a semi closed transfer IMO

This is my process now and it seems to work fine. I purge the keg using the CO2 from the fermentation and when fermentation is done, I make a closed loop between that keg and the FV. My FV is elevated above the keg so gravity does the work.

 

[olie]

Hi all. I plan on kegging a double batch I brewed about a month ago. Currently it's at 15psi at 64F. In the past, I've just bled off the pressure of the fermenter before transfer and pushed it to my serving keg at 2psi.

My thoughts are to connect a jumper gas post to gas post from fermenter to keg so the pressure equalizes between the two vessels. Then what? Connect a jumper from beer post to beer post and bleed off the keg's pressure via the prv? I've read here transferring too fast will produce foaming. If both vessels are at equal pressure, then do you use the prv valve of the keg or disconnect the gas jumper and just put a spunding valve on the keg (nothing on the fermenter) to do a slow transfer?

On another note, is there a way to see how much more days on gas a pressurized fermentation needs after transferring to a serving keg? As mentioned, it's at 15psi at 64F. If I can keg this batch tonight, how much time do I need on gas to drink it this weekend? Thanks in advance.

I know this is an ancient thread, but it didn't have an answer, so here goes:

* I keep the fermentor pressurized "as normal" for the style of beer.
* I add CO2 to the TOP of the beer in the fermentor (so as not to blow bubbles in the beer!) to hold "normal" pressure.
* I have an adjustable valve on the keg that I leave shut at the start of transfer.
* Once the flow begins to slow (I weigh my kegs to know when they're approaching full), I crack the valve to allow about 1lb of beer every several [3-5, depending on "feel"] second.

If beer goes into the keg too fast, you'll get a lot of foam on top, it'll blow out your valve, make a mess, and you won't have a full keg (unless you blow a LOT of foam!)

If beer goes into the keg too slow, you just end-up sitting there for a loooooooong time doing the transfer. No real harm, other than the extra time.

5 gallons of beer is ~42-43lbs, depending on the FG of the beer; I do (8.345 x FG x gallons) to get my final weight. (Don't forget to tare the keg weight!)

Heh. And now that I've typed all that, I see that there *ARE* answers, they just took a while to load on my slow internet. Ah well, now you have mine, too.