Counterflow failure

[SaltNeck]

Tap water pressure @ 90 PSI is way too high. It should be regulated down between ~30 - 80? Have you had any other plumbing failures in your home?

 

[rich5544]

90 psi seems pretty high for tap water.

 

[edubz]

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.

The defect wasn't at a 90 bend, it's at the end, at the tee. The only valve to slow the wort would be at the pot, and there is one built into the pump. The defect happened where the hot wort was entering and the cold water is exiting.

 

[RufusBrewer]

I am going to believe there is no water and wort pressure difference that can cause the flattening of that tube. Your tap pressure and your pump cannot have enough pressure difference to cause that. Building up heat and steam and expanding and contracting gas? Yes, I will buy that.

Try it with only one valve, at the water in side. The place where a valve is least likely to cause an issue is the valve that makes up the hose bib. May not be the most convenient place to have a valve. If you are trying to be cooling water conservative, it will be more wasteful. But so is a failed CFC. How much water do you use when the CFC choked.

Do not restrict the water exhaust end of things. Same goes for the wort out. Let flow free and fast.

I will say it again, you are not helping the problem with a 50 foot CFC. All you are doing is creating more restriction to water and wort. Virtually all the transfer of heat happens in the first 6-12 feet of the CFC.

 

[SaltNeck]

Water hammer can create pressures in the 1,000-psi range in small equipment and in excess of 10,000 psi in large systems with long runs.

water velocities should be limited to 5 ft/sec unless special considerations are given for controlling water hammer

When a valve is closed suddenly, the momentum of the fluid immediately downstream tends to continue downstream. This creates a high pressure drop that can actually boil the liquid and cause vapor to form in the vacuum. When the vapor re-condenses to liquid, the bubble collapses and the separated liquid columns slam back together, creating a sudden high rise in pressure.

Hydrodynamic Design, Part 11: The Water Hammer – WCP Online

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.

The defect happened where the hot wort was entering and the cold water is exiting.

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

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

Right now, given what's known, I'm sticking with my theory that a water hammer occurred in the outer pipe. Given the op's very high tap water pressure and the conditions present it makes the most sense.

 

[passedpawn]

Hydrodynamic Design, Part 11: The Water Hammer – WCP Online

Right now, given what's known, I'm sticking with my theory that a water hammer occurred in the outer pipe. Given the op's very high tap water pressure and the conditions present it makes the most sense.

I agree it's the most feasible explanation, but I still think it's VERY unlikely.

In order for water hammer to create a problem, there needs to be significant mass of moving water (at a significant rate of flow). We experimented with it a lot at fire school in Baton Rouge LA, where I did a lot of training. With a large-diameter hose moving water, slam it closed and watch the hose jump off the ground. But do that with a thin hose, and reduced velocity due to the restrictions in the tubing, and I'd suggest that that the momentum of the water in there doesn't add up to enough to cause this problem.

 

[SaltNeck]

But do that with a thin hose, and reduced velocity due to the restrictions in the tubing, and I'd suggest that that the momentum of the water in there doesn't add up to enough to cause this problem.

I think it's the column separation and resulting collapse that caused the damage, not the actual water hammer event, though that increase in pressure would have contributed on collapse. The actual water hammer calculations place the increase in pressure between 100 and 200 psi depending on how fast the valve was closed.

 

[rich5544]

I think it's the column separation and resulting collapse that caused the damage, not the actual water hammer event, though that increase in pressure would have contributed on collapse. The actual water hammer calculations place the increase in pressure between 100 and 200 psi depending on how fast the valve was closed.

I think the crush pressure for 3/6 annealed copper tube is around 800 psi.

 

[rich5544]

I think the crush pressure for 3/6 annealed copper tube is around 800 psi.

Sorry, 3/8

 

[rich5544]

I used 3/8 copper inside 3/4 to cool 12 gallons for over 10 years with no particular attention to flow rates. Just varied cold water to obtain lowest wort temperature. Never had a problem. I never heard of this kind of problem and was wondering if anyone else has or knows of any problems with CFC.

 

[SaltNeck]

I think the crush pressure for 3/6 annealed copper tube is around 800 psi.

True, however the pressure in a column separation and collapse combined with the increased pressure from the water hammer event could easily exceed ~1000 psi.

 

[rich5544]

Really. What would you think the pressure in the column is

 

[SaltNeck]

A lot. I haven't done the calculations, but you can imagine the weight and force of the entire column of water in the outer pipe being forcefully separated by at least a foot, most probably much more than a foot, (I think the OP said a foot of crushed pipe.) and then collapsing and slamming back together.

There are spreadsheets and calculators available online to do these calculations.

There are some really fascinating stories online about the damage caused by these phenomena.

Something I don't understand is why the OP hasn't mentioned hearing any thumping noise or anything out of the ordinary. Maybe they weren't in the area or the area was too noisy itself. Perhaps they're just used to the thumping in their pipework due to the high water pressure.

I'm always open to hear other theories or speculation on the subject.

 

[rich5544]

Agreed. 90 psi is way too high for a residence. To male constant repairs, I would think he is a plumber or has a very good friend that is. But he also said he was not turning the tap water on and off rapidly, so there should be no hammering. There should be no air in the system and it is odd that it crushes at the same place both times. Something is missing here.

 

[thefigure5]

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

@edubz - I thought you implied that the outgoing cooling water valve was inadvertently in the closed position when the damage occurred. If the valve was closed when you started the cooling process, the cooling water would have been static and heating up as the hot wort was circulating through the 3/8-inch pipe.

The water hammer effect occurs when a valve is shut off quickly and derives from the momentum of the water abruptly dropping to 0. If a valve wasn't shut off during the chilling process, I don't see how the water hammer effect occurred.

Anyway, your counterflow chiller worked well for many brew days. Can you clarify what was different when it failed?