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So here's a pic of my pump configuration right at the moment. I have QDs to hook up and get rid of that long copper pipe, I just haven't done it. The problem is the pump cavitates (right term?) while the kettle is boiling. I'd like to recirc the wort for the last couple minutes of the boil to sterilize the pump head and lines if possible. I assume this is due to the pressure drop at the pump head causing the wort to boil in the pump head thus not allowing it to pump. Moving forward when I get around to building a rig of some type I'd like to design this issue out if possible.
How much lower will I have to mount the pump to overcome that pressure drop? If I add a pickup point for the recirc at around the 5-7 gallon level will that help?"On it. I hate software." ~Cpt Snarklepants -
There is a mathematic formula to solve this problem. I think you gain 0.46 psi for every 10' of head.Sign here______________________________
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A ball valve to throttle the discharge will help.Sign here______________________________
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jeepinjeepin said:
A ball valve to throttle the discharge will help.
Yeah... I've tried nearly every option here. Cutting it back to 10% still does nothing."On it. I hate software." ~Cpt Snarklepants -
My pump was doing the same thing, I was drawing into the pump via my lower port which also has a dip tube pointing down attached, during a full boil the bubbles coming off the bottom were simply being drawn into the pump causing cavitation at best, completely stopping pump flow at its worst. I tried it with water to confirm, nixed the downturn on my pickup and it solved my problem.Jesus didn't wear pants
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Lakewood said:
Where the outlet is located on the tun will not effect the head pressure.
Only the height of the top surface of the liquid above the pump will matter.
What pump are you running?
It should by a foot or so, wouldn't it?Sign here______________________________ -
Scoob, so using a port located at the 5 gallonish level that is turned horizontal should work?
Lake, March 80whatevereveryoneelseuses. Also, I thought as much about head pressure being relative to the top surface of the liquid.
The diptube may be the cause?"On it. I hate software." ~Cpt Snarklepants -
You just need to be a few degrees below where you are, or reduce vacuum by getting a smaller pump. Upping your pipe size might help (might). Using more copper pipe so things cool more before the pump might help."I don't have TP, but I do have ammo."
-Some guy in Ohio -
C_B said:
Scoob, so using a port located at the 5 gallonish level that is turned horizontal should work?
Lake, March 80whatevereveryoneelseuses. Also, I thought as much about head pressure being relative to the top surface of the liquid.
The diptube may be the cause?
dip tube can help if its actually picking up vapor. really depends on the temp going in to the pump. they will cavitate if the temp is near boiling.The only thing between me and a train wreck is blind luck..... - Kenny -
Lakewood said:C_B said:
Scoob, so using a port located at the 5 gallonish level that is turned horizontal should work?
Lake, March 80whatevereveryoneelseuses. Also, I thought as much about head pressure being relative to the top surface of the liquid.
The diptube may be the cause?
dip tube can help if its actually picking up vapor. really depends on the temp going in to the pump. they will cavitate if the temp is near boiling.
So if its near boiling it will cavitate period? Regardless?
"On it. I hate software." ~Cpt Snarklepants -
C_B said:Lakewood said:C_B said:
Scoob, so using a port located at the 5 gallonish level that is turned horizontal should work?
Lake, March 80whatevereveryoneelseuses. Also, I thought as much about head pressure being relative to the top surface of the liquid.
The diptube may be the cause?
dip tube can help if its actually picking up vapor. really depends on the temp going in to the pump. they will cavitate if the temp is near boiling.
So if its near boiling it will cavitate period? Regardless?
Unless it's not pulling that hard."I don't have TP, but I do have ammo."
-Some guy in Ohio -
Dr_Jerryrigger said:
regardless of the pressure, the pump will add some heat so you'll have to be somewhat below boiling to use the pump.
that's not really the thermodynamic principal at work here, but the resulting advice is still the same, so yeah, close enough.The only thing between me and a train wreck is blind luck..... - Kenny -
C_B said:Lakewood said:C_B said:
Scoob, so using a port located at the 5 gallonish level that is turned horizontal should work?
Lake, March 80whatevereveryoneelseuses. Also, I thought as much about head pressure being relative to the top surface of the liquid.
The diptube may be the cause?
dip tube can help if its actually picking up vapor. really depends on the temp going in to the pump. they will cavitate if the temp is near boiling.
So if its near boiling it will cavitate period? Regardless?
if its a couple degrees below boiling you should be fine. if it's actually boiling in the kettle it's gonna cavitate in the pump.
The only thing between me and a train wreck is blind luck..... - Kenny -
you can gueestimate your gauge pressure at the impeller to be somewhere in the neighborhood of -2 to -5psi depending on flow rate, of course if you have a very large static head from mounting the pump a few feet below the fluid level, you could conceivably offset that by a couple psi.The only thing between me and a train wreck is blind luck..... - Kenny
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So like I've been saying, reduce the vacuum and or reduce the temp at the pump. You have a ball valve just after the pump. Turn that nearly off so that only a little trickle gets by. Add a longer hose before the pump, or find some way of cooling it a little (like a bucket of cool water).
"I don't have TP, but I do have ammo."
-Some guy in Ohio -
The only thing between me and a train wreck is blind luck..... - Kenny
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Dr_Jerryrigger said:
So like I've been saying, reduce the vacuum and or reduce the temp at the pump. You have a ball valve just after the pump. Turn that nearly off so that only a little trickle gets by. Add a longer hose before the pump, or find some way of cooling it a little (like a bucket of cool water).
interestingly, with this type of dynamic pump, even shutting the outlet flow off completely wont result in a 0 psi drop. it's still spinning the fluid around really frikin fast and that results in a static pressure difference that will induce flow within the pump head and result in a slight negative pressure at the center-most point of the rotating machinery.The only thing between me and a train wreck is blind luck..... - Kenny -
Lakewood said:Dr_Jerryrigger said:
So like I've been saying, reduce the vacuum and or reduce the temp at the pump. You have a ball valve just after the pump. Turn that nearly off so that only a little trickle gets by. Add a longer hose before the pump, or find some way of cooling it a little (like a bucket of cool water).
interestingly, with this type of dynamic pump, even shutting the outlet flow off completely wont result in a 0 psi drop. it's still spinning the fluid around really frikin fast and that results in a static pressure difference that will induce flow within the pump head and result in a slight negative pressure at the center-most point of the rotating machinery.
Thus resulting in the cavitation regardless how far closed the valve is."On it. I hate software." ~Cpt Snarklepants -
Dr_Jerryrigger said:
and why are you doing this?
To clean and sanitize the lines and pump head. That I've already cleaned."On it. I hate software." ~Cpt Snarklepants -
C_B said:Lakewood said:Dr_Jerryrigger said:
So like I've been saying, reduce the vacuum and or reduce the temp at the pump. You have a ball valve just after the pump. Turn that nearly off so that only a little trickle gets by. Add a longer hose before the pump, or find some way of cooling it a little (like a bucket of cool water).
interestingly, with this type of dynamic pump, even shutting the outlet flow off completely wont result in a 0 psi drop. it's still spinning the fluid around really frikin fast and that results in a static pressure difference that will induce flow within the pump head and result in a slight negative pressure at the center-most point of the rotating machinery.
Thus resulting in the cavitation regardless how far closed the valve is.
if its really 212 deg F at the pump, yes. but it's unlikey that you will have 0 heat loss, so it's kinda sorta possible to run it slow enough to not cavitate at boiling...
The only thing between me and a train wreck is blind luck..... - Kenny -
In conclusion, either let it come off boil before pumping or run a large copper drain from near the bottom of the kettle straight down to the pump 2' below.Sign here______________________________
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Lakewood said:Dr_Jerryrigger said:
So like I've been saying, reduce the vacuum and or reduce the temp at the pump. You have a ball valve just after the pump. Turn that nearly off so that only a little trickle gets by. Add a longer hose before the pump, or find some way of cooling it a little (like a bucket of cool water).
interestingly, with this type of dynamic pump, even shutting the outlet flow off completely wont result in a 0 psi drop. it's still spinning the fluid around really frikin fast and that results in a static pressure difference that will induce flow within the pump head and result in a slight negative pressure at the center-most point of the rotating machinery.
Regardless of pressure drop, a spinning thing will add heat. At my place of work we make one product that uses 25kg of butter, if not heated enough; we soften it by mixing it for a long time in a massive blender. It's a crappy way of heating things if you're trying to heat, but it has an effect that shouldn't be ignored. If just the pressure drop was to blame a closed valve would cause bubbles that quickly condensed.
And with out movement any where is that 1/6th hp(give or take a lot) going? Really a variable speed thing would be best.
Yeah like i said a wile back, to sanitize, just let it run into a bucket with out the pump running. To pump it somewhere; let it cool down a little."I don't have TP, but I do have ammo."
-Some guy in Ohio -
I run my march pump at boiling temps all the time. (Not accounting for temp loss in the hose to the pump). Just make sure the out valve is facing straight up (I find even a slight tilt will have a large impact on cavitation). I run wort through my pump and plate chiller for the last 15-20 mins of my boil.BJCP A0936 National Beer Judge and Mead Judge
Cicerone Certified Beer Server
AHA Member
CRAFT Homebrew Club
Sons of Liberty Homebrew Club
HBT "mors" -
mors said:
I run my march pump at boiling temps all the time. (Not accounting for temp loss in the hose to the pump). Just make sure the out valve is facing straight up (I find even a slight tilt will have a large impact on cavitation). I run wort through my pump and plate chiller for the last 15-20 mins of my boil.
Interesting. I suppose having the outlet stright up would help remove the vapor quickly. I might have to try experimenting.The only thing between me and a train wreck is blind luck..... - Kenny -
Outlet straight up.IMAG0944.jpg2560 x 1440 - 575K"On it. I hate software." ~Cpt Snarklepants
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Mors, what configuration do you have in the kettle? False bottom? Dip tube? Straight inlet? 1/2" ball valve?"On it. I hate software." ~Cpt Snarklepants
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It's a 1/2" ball valve with 1/2 silicone tubing. I have a 1/2" coupler on the inside of the kettle but nothing screwed into it so no dip tube atm (I just tilt it when it gets lower).BJCP A0936 National Beer Judge and Mead Judge
Cicerone Certified Beer Server
AHA Member
CRAFT Homebrew Club
Sons of Liberty Homebrew Club
HBT "mors" -
I should note I do have some restriction due to the shitty QD I use. I have these atm...
http://morebeer.com/products/kent-male-qd-12-mpt.html
But if anything they should make it more likely to cavitate...BJCP A0936 National Beer Judge and Mead Judge
Cicerone Certified Beer Server
AHA Member
CRAFT Homebrew Club
Sons of Liberty Homebrew Club
HBT "mors" -
mors said:
I should note I do have some restriction due to the shitty QD I use. I have these atm...
http://morebeer.com/products/kent-male-qd-12-mpt.html
But if anything they should make it more likely to cavitate...
Ha! Those are the cheapos I have to install. I think the problem with mine is the diptube. I think I'll install a couple recirc ports and plan on drawing off the topish and returning at the bottomish."On it. I hate software." ~Cpt Snarklepants -
Then pulling off the bottom to run to the fermentor."On it. I hate software." ~Cpt Snarklepants
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yeah the Kent disconnects 'work' but they do restrict flow alot... Need to drop a good $200 and get some stainless and end my suffering though.BJCP A0936 National Beer Judge and Mead Judge
Cicerone Certified Beer Server
AHA Member
CRAFT Homebrew Club
Sons of Liberty Homebrew Club
HBT "mors" -
mors said:
yeah the Kent disconnects 'work' but they do restrict flow alot... Need to drop a good $200 and get some stainless and end my suffering though.
I would like full bore cam locks, but I'm not dropping that kind of cheddar on a hobby.
"On it. I hate software." ~Cpt Snarklepants -
I'm a gadget whore. What's the point of a hobby if you can't immerse yourself fully in it lol ;-)BJCP A0936 National Beer Judge and Mead Judge
Cicerone Certified Beer Server
AHA Member
CRAFT Homebrew Club
Sons of Liberty Homebrew Club
HBT "mors" -
mors said:
I'm a gadget whore. What's the point of a hobby if you can't immerse yourself fully in it lol ;-)
Yay, toys!The only thing between me and a train wreck is blind luck..... - Kenny
Pump cavitation help.
