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Copper Erosion

ZmanZman Member Posts: 3,590
I thought I would throw this one out there as is is a new one for me.
This is a domestic recirc pipe that has run at excessive velocity for 20ish years. The building has had many leaks where you would expect on 90's and tee's.
It is also pin holing on straight sections of pipes. Check out the inside of the pipe.
"If you can't explain it simply, you don't understand it well enough"
Albert Einstein

Comments

  • Big EdBig Ed Member Posts: 896
    Turbulence of the moving water , How the Grand Canyon was carved ...
    I have enough experience to know , that I dont know it all
  • ZmanZman Member Posts: 3,590
    The gouges are the interesting part. They are noticeable and deep. One theory would be that there where inconsistencies in manufacturing resulting in weaker areas in pipe. The high velocity exposed the weakness and stripped this material first.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • flat_twinflat_twin Member Posts: 83
    How excessive was the velocity in this example?
  • ZmanZman Member Posts: 3,590
    I am putting together a proposal to balance the system. My best guess is that the water is presently moving at 8-10 fps.
    The original circulator is no longer in place. I suspect the water was moving even faster originally.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RayWohlfarthRayWohlfarth Member Posts: 243
    Zman I have been told that velocities faster than 6 fps would cause erosion inside copper. I have never seen it though. Either that or its a remake of Tremors.
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • JUGHNEJUGHNE Member Posts: 3,626


    This is 40 YO hard L copper that was in a return on a recir line.
    It was just downstream of a ball valve that was partially closed for balancing. There was no copper left in the ball valve socket.
    This was only noticed because of the pin hole that was spraying water.
    I suspect the "tumbling" effect of the water coming out of the partly closed ball valve.
  • RayWohlfarthRayWohlfarth Member Posts: 243
    wow thats amazing how erosion is so powerful
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • GordyGordy Member Posts: 7,191
    Carl are the erosion areas at the bottom, or top of the pipe when in place?

    Water temperature, TDS level, PH all play into this.

    To me it seems as you say manufacturing. Maybe the extrusion process of the pipe, , and material inconsistency.. wall thickness maybe thinner in the eroded area.
  • hot rodhot rod Member Posts: 7,286
    Big Ed said:

    Turbulence of the moving water , How the Grand Canyon was carved ...

    Cavitation from a rough surface in the spillways almost took out the Glen Canyon dam above the Grand Canyon in 1983.

    A rough surface caused by a concrete defect allowed the water to erode through a 3 foot thick reinforced concrete pipe in the spillway.

    Here is a great read about the canon and a handful of river guides the sneaked on to the river during that high water season.



    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • hot rodhot rod Member Posts: 7,286
    Zman said:

    I am putting together a proposal to balance the system. My best guess is that the water is presently moving at 8-10 fps.
    The original circulator is no longer in place. I suspect the water was moving even faster originally.


    I think that is just the flow pattern from the excessive velocity and caviation.

    Here is a fitting I cut out years ago. High velocity and extremely hot water leads to this type of pin hole.

    The un-reamed copper tube may have played a big part also.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Larry WeingartenLarry Weingarten Member Posts: 1,197
    Hello, You might want to consider using PEX and plastic fittings where possible. PEX stands up to erosion corrosion much better than copper. Also, anything you can do to reduce run-time of the pump will have multiple benefits, from limiting erosion to cutting utility bills. A rough rule of thumb is that constant recirc triples you water heating energy use. :o

    Yours, Larry
  • HomerJSmithHomerJSmith Member Posts: 16
    What's the quality of the water? It's obviously a velocity problem.
    Ball valves don"t balance a line worth squat. I usually use the other 's' word, but it's Sunday.

    Use a real balancing valve or (a globe valve if you have to).
  • HomerJSmithHomerJSmith Member Posts: 16
    That looks like type L Copper. Recirc lines have a pump on it, maybe you should resize it and make sure it has a flow check on it if there is a possibility a larger pump in the system could push thru it in reverse. If that's the case a larger pump could just close off the flow check when it is running.
  • ZmanZman Member Posts: 3,590
    Gordy said:

    Carl are the erosion areas at the bottom, or top of the pipe when in place?

    Water temperature, TDS level, PH all play into this.

    To me it seems as you say manufacturing. Maybe the extrusion process of the pipe, , and material inconsistency.. wall thickness maybe thinner in the eroded area.

    @Gordy
    Water temp is around 130
    PH ~7.6
    TDS 150
    I believe the water likely has high levels of entrained air which adds to the issue

    Building has all types of erosion. Some are the classic ones like hot rod pictures. Others are on the bottom of pipes in areas where there are several fittings, flux may have been over applied. The one that surprised me was the one that looked like gouges.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ZmanZman Member Posts: 3,590
    @HomerJSmith
    Agreed, I am planning on Caleffi Quicksetter with temp gauges.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ZmanZman Member Posts: 3,590
    I like this feature of Siggy's software. You need very little flow in recirc lines. This is one of the most misunderstood subjects in plumbing/heating.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot rodhot rod Member Posts: 7,286
    Zman said:

    I like this feature of Siggy's software. You need very little flow in recirc lines. This is one of the most misunderstood subjects in plumbing/heating.

    The Circuit Simulator is another great module, the 3rd one.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ZmanZman Member Posts: 3,590
    I agree, I found it useful even on cirs that are not in the system. You can graph the system curve by trying different circs and noting the head loss and gpm.
    I used it the other day to size pool pumps
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • JUGHNEJUGHNE Member Posts: 3,626
    Hot Rod, I did watch the webinar on Legionella Disease 11-16-17, the one you mentioned.

    One thing I did come away with was in some major projects they raised the flow rates of recir pumps in order to increase the return rate of the water to get some of it back into the 140 degree tank. Hopefully to kill the Legionella if there.

    So there has to be a happy medium somewhere.
    I have a gravity recir system in my house and wondering if I might be cooking a stew in the recir line as the water comes back pretty lukewarm.
  • Mark EathertonMark Eatherton Member Posts: 5,617
    A couple of things about hydrolysis.

    1. Horse always walk up stream.
    2. . The CDA discovered that many (most) of their previous diagnosis related to copper erosion, were incorrect. Most erosion problems relate to the acid in the flux used during the soldering of the pipes.

    Lastly, the long striations I see in your examples look like they had their extrusion presses set too tight. In my 40 years, I've never seen hydraulic erosion that looked like that, and I always cut failed pipe and fittings apart to see what's going on inside. Most cases look like the ones HR showed, and are probably flux related. True hydrolysis has u shaped tracks (horse shoes) and as noted, horses always walk up stream.

    I have seen a small ding in 3/4" type K soft pipe erode out a hole. Water flowing is a strange beast to follow... Just look at a stream.

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Mark EathertonMark Eatherton Member Posts: 5,617
    edited December 5

    Hello, You might want to consider using PEX and plastic fittings where possible. PEX stands up to erosion corrosion much better than copper. Also, anything you can do to reduce run-time of the pump will have multiple benefits, from limiting erosion to cutting utility bills. A rough rule of thumb is that constant recirc triples you water heating energy use. :o

    Yours, Larry


    If you do choose to use PEX and there is chlorine in the water, make certain it has a high resistance to oxidizers. Most people don't know that there are different degrees of antioxidants used in PEX. Pipes used in circ return systems need to have a higher antioxidant package than pipes not seeing circulation.

    As it pertains to tripling the energy consumption, I guess one needs to look at the resource that is being conserved, and the trade offs associated with that conservation effort. Having a good and properly controlled circ return system will completely eliminate the waste of water purging tepid water out of a given circuit to get hot water. At the expense of fuel consumption. If fuel is cheap and readily available, but water isn't, then it makes sense to do circulation. Water is our MOST valuable resource, no?

    The key words here are "properly controlled" circ return system. Most circ return systems are NOT controlled. We need to start addressing this by the use of sensor (electric and or non electric) to restrict flow when hot water is readily available at the furthest end of the system, instead of waiting for the return to come back hot. If we apply off shelf technology (Grundfos Alpha for example) and use the European non electric flow modulating technology with the temperature sensing bulbs on the FAR ends of the system, the DHW circ return system will begin modulating, wasting minimal energy(s) while reducing the waste of the most critical resource, that being water.

    The only thing an out of control circ return system saves, is time... and a little bit of water.

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • hot rodhot rod Member Posts: 7,286
    Also, proper sizing of the recirc circulator is critical to the operation. It's rare to see an under-pumped recirculation system, most are over pumped or grossly over-pumped.

    Regardless of using a smart pump or smart control, the pump size should be calculated.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • hot rodhot rod Member Posts: 7,286

    A couple of things about hydrolysis.

    1. Horse always walk up stream.
    2. . The CDA discovered that many (most) of their previous diagnosis related to copper erosion, were incorrect. Most erosion problems relate to the acid in the flux used during the soldering of the pipes.

    Lastly, the long striations I see in your examples look like they had their extrusion presses set too tight. In my 40 years, I've never seen hydraulic erosion that looked like that, and I always cut failed pipe and fittings apart to see what's going on inside. Most cases look like the ones HR showed, and are probably flux related. True hydrolysis has u shaped tracks (horse shoes) and as noted, horses always walk up stream.

    I have seen a small ding in 3/4" type K soft pipe erode out a hole. Water flowing is a strange beast to follow... Just look at a stream.

    ME

    Pretty much all the flux nowadays is water soluble, it should wash out when water flows?

    I think the wear marks in my ell was related to not reaming the tube AND excessive velocity. The ridge on the tube is obvious in the cut a way. I'd guess that lack of de-burring to be more common of a mistake or oversight compared to flux.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GordyGordy Member Posts: 7,191
    I'm still thinking extrusion malfunction in the manufacturing process.
  • ZmanZman Member Posts: 3,590
    Gordy said:

    I'm still thinking extrusion malfunction in the manufacturing process.

    I agree, It may have never surfaced if not for exposure to to high velocity DHW...
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • GordyGordy Member Posts: 7,191
    Very true.
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