Counterflow failure

[edubz]

I built a counterflow chiller using 50' 3/4" soft copper and 3/8" copper tubing. I worked incredibly well for many brews. Then it got clogged. I tried unclogging it every way imaginable with no success. So I made the decision to cut it open.
The internal 3/8 copper tubing has collapsed, just past the point of entry, for about a foot. I cannot imagine how this happened. So I cut out the collapsed portion, re-soldered some fittings and went on with my life.
Three brews later it happened again. Can anyone help me figure out why this would happen? Should I scrap it and start anew? I've talked to people locally and they look at me like I'm nuts.

 

[SaltNeck]

There are a lot of causes for copper pipe failure.

1.) Too much acid flux used for soldering fittings
2.) Too high a flow rate - high velocity water
3.) Too low or high pH
4.) Not deburring or reaming the ends

There are more and a combination of those can certainly contribute but have you examined the collapsed pipe? Is it pitted or corroded in anyway on the outside or the inside? Was the chiller properly cleaned and flushed after use?

Too many things to mention but I'm sure you get the idea.

 

[Deadalus]

I built one long ago and wasn't comfortable I could get it cleaned properly so I converted it to an immersion chiller. I really liked that piece of equipment but unfortunately left it outside to dry when I started brewing outside and it froze, resulting in a couple splits. I use a plate chiller now but as far as cleanliness, I prefer the immersion chiller. Not meaning to hijack your thread at all regarding your collapse. That does seem unusual I hadn't ever seen it mentioned before.

 

[IslandLizard]

Three brews later it happened again.

Can you post a picture of that collapsed tube?
It's hard to imagine what it looks like and what could have caused it.

 

[edubz]

There are a lot of causes for copper pipe failure.

1.) Too much acid flux used for soldering fittings
2.) Too high a flow rate - high velocity water
3.) Too low or high pH
4.) Not deburring or reaming the ends

There are more and a combination of those can certainly contribute but have you examined the collapsed pipe? Is it pitted or corroded in anyway on the outside or the inside? Was the chiller properly cleaned and flushed after use?

Too many things to mention but I'm sure you get the idea.

It was very clean. No signs of corrosion or wear and tear.

 

[homebeerbrewer]

Weird. I'm wondering if there's too much pressure from the incoming water. I dunno, I've never seen that.

 

[edubz]

Can you post a picture of that collapsed tube?
It's hard to imagine what it looks like and what could have caused it.

It looks like it was steamrolled.

 

[homebeerbrewer]

Do you have a pump? Is it after the chiller? Maybe it's causing a vacuum inside, while the pressure of the chilling water is on the outside.

 

[rich5544]

There are a lot of causes for copper pipe failure.

1.) Too much acid flux used for soldering fittings
2.) Too high a flow rate - high velocity water
3.) Too low or high pH
4.) Not deburring or reaming the ends

There are more and a combination of those can certainly contribute but have you examined the collapsed pipe? Is it pitted or corroded in anyway on the outside or the inside? Was the chiller properly cleaned and flushed after use?

Too many things to mention but I'm sure you get the idea.

None of which would cause the 3/8 copper to collapse.

 

[edubz]

Here are some photos. It would take quite a bit of force to smash the copper like this. Vacuum maybe?

 

[Miraculix]

Hi I'm a hydraulic engineer from the water and environmental sector and this looks super interesting to me. I think the problem is cavitation. The faster the flow rate, the lower the pressure in the pipe, the lower the pressure, the easier to go into the gas state for the liquid. Once in gas form, pressure might change immediately, which makes the gas kind of "collaps" back into the liquid state. This can build a strong negative pressure. It all happens within milliseconds. This can cause great damage in the municipal water or waste water network, this is why I know about it.

My uneducated guess is that this happened in the inner pipe. I know... It sucks... But... I find it pretty awesome

 

[edubz]

Do you have a pump? Is it after the chiller? Maybe it's causing a vacuum inside, while the pressure of the chilling water is on the outside.

I was thinking vacuum too. The wort was being pumped with Blickman riptide, through chiller, them back into boil kettle when it happened.
The wort just stopped after about 2 minutes.

 

[Miraculix]

I was thinking vacuum too. The wort was being pumped with Blickman riptide, through chiller, them back into boil kettle when it happened.
The wort just stopped after about 2 minutes.

Pumps abruptly starting and stopping can indeed create a short vacuum in the pipe, which could lead to collapsing pipes.

 

[edubz]

Hi I'm a hydraulic engineer from the water and environmental sector and this looks super interesting to me. I think the problem is kavitation. The faster the flow rate, the lower the pressure in the pipe, the lower the pressure, the easier to go into the gas state for the liquid. Once in gas form, pressure might change immediately, which makes the gas kind of "collaps" back into the liquid state. This can build a strong negative pressure. It all happens within milliseconds. This can cause great damage in the municipal water or waste water network, this is why I know about it.

My uneducated guess is that this happened in the inner pipe. I know... It sucks... But... I find it pretty awesome

Interesting. Thank you. It

Hi I'm a hydraulic engineer from the water and environmental sector and this looks super interesting to me. I think the problem is kavitation. The faster the flow rate, the lower the pressure in the pipe, the lower the pressure, the easier to go into the gas state for the liquid. Once in gas form, pressure might change immediately, which makes the gas kind of "collaps" back into the liquid state. This can build a strong negative pressure. It all happens within milliseconds. This can cause great damage in the municipal water or waste water network, this is why I know about it.

My uneducated guess is that this happened in the inner pipe. I know... It sucks... But... I find it pretty awesome

Interesting, so steam from the hot wort would turn back to liquid and cause this collapse? I think one of my mistakes was I put valves on the outer water pipe so I could control incoming and outgoing. Unintentionally, I have the outgoing water valve off.

 

[micraftbeer]

So thinking along the lines of pressure drop here, like @homebeerbrewer was asking about the pump. The pressure of your cooling water looks like it was crushing your beer line. So thinking through that would be:

1. Was the crushed potion at the end where your cooling water comes in? That would be highest pressure on the outside.

2. Looking at your picture, it appears it's right after a right angle bend. Maybe you've got some venturi flow phenomenon going on where you're getting a pressure drop right around that corner.

3. Related to the pump question would be if you have any flow restriction ball valves or anything to slow the beer flow. If so, ideal location would be at outlet of your CFC, not at the inlet. That would keep the pressure higher in the chiller, while still achieving the slower flow rate through.

4. And of course, if that's the part where hot wort meets cold chilling water, you'll have the contraction effect of your wort dropping in temperature so fast. This of course is present in every chiller, but maybe a combination of some of the above left you susceptible at this weakest spot.

5. Maybe some copper welding process put in too much heat to your inner pipe, reducing the copper's mechanical properties.

 

[Miraculix]

Interesting. Thank you. It

Interesting, so steam from the hot wort would turn back to liquid and cause this collapse? I think one of my mistakes was I put valves on the outer water pipe so I could control incoming and outgoing. Unintentionally, I have the outgoing water valve off.

So you had high pressure from the outside due to the closed valve and pump pumping against it, negative pressure from the inside because the higher flow rate due to the right angle bent could have caused cavitation (the bent limited the diameter of the pipe so the wort has to flow faster through this narrow part, which lowers the pressure).

All of this at elevated temperatures which increase the chance of cavitation to occur.

This is such a cool experiment!

 

[Indian_villager]

Where are you throttling your cooling water, before or after your chiller? If your valve for the cooling water is after the chiller you are putting up as much of the supply pressure on the pipe as possible as you have thermal contraction on the inside of the pipe from the wort cooling off. Additionally are you on city water? What is your measured water pressure in the house? Looks high enough that I'd be worried about other things. Do you possibly have a blown water pressure regulator?

 

[rich5544]

Hi I'm a hydraulic engineer from the water and environmental sector and this looks super interesting to me. I think the problem is cavitation. The faster the flow rate, the lower the pressure in the pipe, the lower the pressure, the easier to go into the gas state for the liquid. Once in gas form, pressure might change immediately, which makes the gas kind of "collaps" back into the liquid state. This can build a strong negative pressure. It all happens within milliseconds. This can cause great damage in the municipal water or waste water network, this is why I know about it.

My uneducated guess is that this happened in the inner pipe. I know... It sucks... But... I find it pretty awesome

That would be an amazing amount of vacuum to collapse 3/8 copper tube. Compressors run near 30 inches of vacuum and I have never seen one collapse any of its copper components. Although, much of it is steel.

 

[Miraculix]

That would be an amazing amount of vacuum to collapse 3/8 copper tube. Compressors run near 30 inches of vacuum and I have never seen one collapse any of its copper components. Although, much of it is steel.

Cavitation can create huge forces. These huge forces work on a relatively small surface area.

 

[SaltNeck]

None of which would cause the 3/8 copper to collapse.

Actually high velocity water or wort does create low pressure in a pipe. Bernoulli's Principle.

He's pumping wort from 1/2" (maybe more?) tubing to 3/8" tubing using a very powerful pump. This creates an area of low pressure directly inside the copper tube at the point of entry accelerating the wort to 1.33 times the velocity it was in the 1/2" tube. What happens from here depends on what the OP did. Did he have both input and output cooling water valves closed and just pumping hot wort through the chiller, for example to sanitize? Was the output cooling water valve closed and the input open? If both valves were closed then residual cooling water in the outer chamber would have turned to steam pressurizing the chamber. When did the pipe collapse before it was noticed? We don't know for sure but opening the cooling water input valve on a chamber filled with steam would certainly have imposed a positive pressure on top of the negative pressure already exerted on the inner pipe.

Is the input cooling water on the same end as the input wort? In a counterflow chiller they should be on opposite ends.

I'm sure the conditions are reproduceable but my point is that everything I've listed can contribute to pipe failure.

Counterflow-Chiller-Connection-Kit-Pump-Fed-1548972879013.pdf (shopify.com)

fluid dynamics - How does high velocity cause low pressure? - Physics Stack Exchange
pressure - Why does Bernoulli's principle work? - Physics Stack Exchange

 

[passedpawn]

No way that happened from vacuum or any pressure event from brewing equipment. IF the pressures could be created, something else would go way before that pipe. At least that's my intuition.

 

[SaltNeck]

Water hammer - Wikipedia

Column separation is a phenomenon that can occur during a water-hammer event. If the pressure in a pipeline drops below the vapor pressure of the liquid, cavitation will occur (some of the liquid vaporizes, forming a bubble in the pipeline, keeping the pressure close to the vapor pressure). This is most likely to occur at specific locations such as closed ends, high points or knees (changes in pipe slope). When subcooled liquid flows into the space previously occupied by vapor the area of contact between the vapor and the liquid increases. This causes the vapor to condense into the liquid reducing the pressure in the vapor space. The liquid on either side of the vapor space is then accelerated into this space by the pressure difference. The collision of the two columns of liquid (or of one liquid column if at a closed end) causes a large and nearly instantaneous rise in pressure. This pressure rise can damage hydraulic machinery, individual pipes and supporting structures. Many repetitions of cavity formation and collapse may occur in a single water-hammer event.[35]

 

[Miraculix]

Water hammer - Wikipedia

Water Hammer seems to be the word I was looking for, thank you. In German it is simply "Druckstoß" (roughly translates to "pressure push"). It can also be caused by pumps instantly shutting down.

 

[Miraculix]

No way that happened from vacuum or any pressure event from brewing equipment. IF the pressures could be created, something else would go way before that pipe. At least that's my intuition.

Yes and no. Yes, because the regular pumps would not be able to create such a pressure in a normal way. And no, because the pressure is just created localy and for a very short amount of time, this is why the affected surface area is so small and the pipe ultimatly colapses undeneath the force. So it is kind of created with the normal brewing equipment, but not in the usual way that one might think of.

 

[rich5544]

Actually high velocity water or wort does create low pressure in a pipe. Bernoulli's Principle.

He's pumping wort from 1/2" (maybe more?) tubing to 3/8" tubing using a very powerful pump. This creates an area of low pressure directly inside the copper tube at the point of entry accelerating the wort to 1.33 times the velocity it was in the 1/2" tube. What happens from here depends on what the OP did. Did he have both input and output cooling water valves closed and just pumping hot wort through the chiller, for example to sanitize? Was the output cooling water valve closed and the input open? If both valves were closed then residual cooling water in the outer chamber would have turned to steam pressurizing the chamber. When did the pipe collapse before it was noticed? We don't know for sure but opening the cooling water input valve on a chamber filled with steam would certainly have imposed a positive pressure on top of the negative pressure already exerted on the inner pipe.

Is the input cooling water on the same end as the input wort? In a counterflow chiller they should be on opposite ends.

I'm sure the conditions are reproduceable but my point is that everything I've listed can contribute to pipe failure.

Counterflow-Chiller-Connection-Kit-Pump-Fed-1548972879013.pdf (shopify.com)

fluid dynamics - How does high velocity cause low pressure? - Physics Stack Exchange
pressure - Why does Bernoulli's principle work? - Physics Stack Exchange

All that may be true, but that Blickman is by no means a high pressure pump. With 1/2 inch lines it is rated, (in a perfect world) at 7 gallons/ minute. 3/8 inch copper lines are rated around 2gpm. So how many gpm do you think the Blickman is pushing thru the 3/8 lines. I also am not sure why there would be valves at both inlet and outlet for the fresh water cooling. Even so, the circulating wort is most likely far below boiling before circulating thru the cfc. I could definitely be wrong, but I see no way recirculating hot, not boiling, wort would cause the damage to 3/8 copper line.

 

[SaltNeck]

All that may be true, but that Blickman is by no means a high pressure pump. With 1/2 inch lines it is rated, (in a perfect world) at 7 gallons/ minute. 3/8 inch copper lines are rated around 2gpm. So how many gpm do you think the Blickman is pushing thru the 3/8 lines. I also am not sure why there would be valves at both inlet and outlet for the fresh water cooling. Even so, the circulating wort is most likely far below boiling before circulating thru the cfc. I could definitely be wrong, but I see no way recirculating hot, not boiling, wort would cause the damage to 3/8 copper line.

The Bernoulli Principle is based on velocity not pressure. 2 gpm in a 1/2 in. tube is 3.27 fps, which when it hits the 3/8 tube increases velocity to around 5.81 fps. The Blichmann Riptide pump is a capable pump, see the competition chart.

While the specific circumstances of the event aren't clear, you haven't presented your thoughts on why it happened?

 

[Bobby_M]

The one thing I've learned over the years is that there are aspects of physics that cannot be appreciated by common sense. Do you know how many people think a 55 gallon closed head barrel "should be able to handle 10psi"? The second most common one is that it's easier for a pump to fill a tank by throwing the hose over the top of the tank wall than it is to pump in from the bottom.

 

[passedpawn]

The one thing I've learned over the years is that there are aspects of physics that cannot be appreciated by common sense. Do you know how many people think a 55 gallon closed head barrel "should be able to handle 10psi"? The second most common one is that it's easier for a pump to fill a tank by throwing the hose over the top of the tank wall than it is to pump in from the bottom.

I guess common sense doesn't know the difference between pressure (PSI) and force. 10psi in a large tank is FAR more force on the walls than in a 3/8" copper tube, due to the surface area.

 

[sibelman]

No disrespect to the cavitation theory, but: could the tubing have been stressed and partially flattened during construction of the chiller (including the rebuild agreed the first incident)?

Intuition is often wrong, but it tells me copper isn't that soft. Seems like there "has to" be something more at work here than "just" local cavitation and inferred consequent partial vacuum. I wonder if the tap water pressure at OP's (but over - pressured) chiller is unusually high? Also, a valve at the chill water outlet seems, erm, unexpected.

Seems like... Of course I have no clue.

 

[CuS.S. Brewing Equipment]

Do you store the CFC in an area that has freezing temperatures?

 

[coolitfast]

To expand on Miraculix's post. You mentioned having a valve on both ends. Is it possible you closed them simultaneously locking hot wort in the tube and let the chilling liquor continue to run through the shell, chilling the wort causing a contraction. If you want to simulate the problem, take a cheap plastic water bottle and 1/4 fill it with with 160° hot water seal it. Now chill it down to 55° (chilling liquor temp) and watch the contraction collapse the bottle. I think you may caused a vacuum with thermal contraction? Just an idea hope it helps.

 

[Miraculix]

To expand on Miraculix's post. You mentioned having a valve on both ends. Is it possible you closed them simultaneously locking hot wort in the tube and let the chilling liquor continue to run through the shell, chilling the wort causing a contraction. If you want to simulate the problem, take a cheap plastic water bottle and 1/4 fill it with with 160° hot water seal it. Now chill it down to 55° (chilling liquor temp) and watch the contraction collapse the bottle. I think you may caused a vacuum with thermal contraction? Just an idea hope it helps.

Pretty easy, but entirely possible. Maybe I'm doing the classical overlooking the obvious while searching for way too complicated explanations thing?

 

[RufusBrewer]

That kind if collapse makes me think it would be from a change in pressure due to quickly changing temperatures due to quick cooling or quick heating.

If it were my CFC, I would cut the length down to 25 feet. I know longer is better, but that comes with diminished returns. Most if your cooling happens in the first few feet of tubing. As the wort travels along the cooling lessens.

If you are pumping the wort through the CFC, return the wort to the kettle and you can make multiple passes through the CFC to chill your wort.

 

[SaltNeck]

Meh, I was going to say that I said the same thing as @coolitfast in post #20, but then reconsidered as it may or may not be interpreted the same and didn't want to start a ruckus about it.

How far is the inner pipe collapsed? Is it collapsed back to the T or even further back to the inlet of the wort? What is the integrity of those joints? Did the collapse affect the integrity of the wort inlet joints?

As usual, too many questions not enough answers. Let's all go over to @edubz so we can over analyze his equipment and processes, maybe he'll be nice and give us a homebrew!

 

[Miraculix]

Meh, I was going to say that I said the same thing as @coolitfast in post #20, but then reconsidered as it may or may not be interpreted the same and didn't want to start a ruckus about it.

How far is the inner pipe collapsed? Is it collapsed back to the T or even further back to the inlet of the wort? What is the integrity of those joints? Did the collapse affect the integrity of the wort inlet joints?

As usual, too many questions not enough answers. Let's all go over to @edubz so we can over analyze his equipment and processes, maybe he'll be nice and give us a homebrew!

Great Idea, let's meet at five!

 

[homebeerbrewer]

Great Idea, let's meet at five!

I'm gonna be a little late, I get out of work at five. But, I'll be there as soon as I can.

 

[rich5544]

The Bernoulli Principle is based on velocity not pressure. 2 gpm in a 1/2 in. tube is 3.27 fps, which when it hits the 3/8 tube increases velocity to around 5.81 fps. The Blichmann Riptide pump is a capable pump, see the competition chart.

While the specific circumstances of the event aren't clear, you haven't presented your thoughts on why it happened?

Blickman does make a nice pump. Just not high velocity. I guess I was misinformed because I thought Bernoulli said that with an increase in velocity, there is a corresponding decrease in pressure. And what fun would it be if I came right out with the answer to the collapsing pipe mystery?
I think Bobby from New Jersey has presented some interesting questions.

 

[Bobby_M]

If the crush happened outside of the brew day, I would have sworn it was trapped water turning to ice and crushing the inner tube. That was ruled out.

If the wort path has valves on the inlet and outlet, and hot wort was inside the tube, and the valves were closed, and then the cooling water was turned on, the tubing imploded due to rapid vacuum. That's a long shot too but it would make sense.

 

[edubz]

Do you have a pump? Is it after the chiller? Maybe it's causing a vacuum inside, while the pressure of the chilling water is on the outside.

The water flowing through is straight tap water. No chiller. Pump on the wort side. Water pressure is 90 psi

 

[edubz]

Meh, I was going to say that I said the same thing as @coolitfast in post #20, but then reconsidered as it may or may not be interpreted the same and didn't want to start a ruckus about it.

How far is the inner pipe collapsed? Is it collapsed back to the T or even further back to the inlet of the wort? What is the integrity of those joints? Did the collapse affect the integrity of the wort inlet joints?

As usual, too many questions not enough answers. Let's all go over to @edubz so we can over analyze his equipment and processes, maybe he'll be nice and give us a homebrew!

The collapse only was about 6" or so and didn't affect the solder joints.