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The importance of pH in steam-boiler water

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HeatingHelp
HeatingHelp Administrator Posts: 650
edited February 2017 in THE MAIN WALL
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The importance of pH in steam-boiler water

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  • mdilling2wmsdist
    mdilling2wmsdist Member Posts: 4
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    Isn't it interesting. Way back in high school there were kids sitting in chemistry class thinking they didn't need to know this stuff because "I am going to be a plumber and heating man!" If we could just get through to kids today just how important this knowledge is and how that knowledge can bring them much higher incomes than what the average "plumber and heating man" will earn. I often wish I could get some of my friends that know these things to go with me into the high schools and demonstrate to the next generation what the mechanical fields offer. But no, these kids have to go to college and get a degree in medieval music history and come out of college with $50k of student loan debit. The challenge and the solution to our employment problems lies in our ability to explain how technical and skilled our industry truly is. Dan, I love reading your writing and simple, clear explanations. Even as you retire I hope to still continue to research, learn and teach as best you can. Oh, and by the way, thanks for that picture of "The lovely Marianne". The adjective you use to describe her is so very accurate.
    SWEI
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,545
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    Thanks for the good thoughts and kind words. And I'll keep writing!
    Retired and loving it.
  • Pumpguy
    Pumpguy Member Posts: 663
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    3 comments:

    1) A very high pH, say much above 10 or so, is corrosive to bronze and copper; especially bronze impellers and rotors in condensate and vacuum pumps. This is why when we sell a vacuum pump to a power plant for main condenser vacuum service, it must be "all Iron" construction. In a power plant you can often experience an Amonia smell, which is from the Hydrazine or other similar alkaline boiler water treatment chemicals.

    2) On 2 pipe vacuum return systems, high condensate temperature is detrimental to vacuum pump performance. Our recommended maximum returning condensate temperature is 175 *F, or be less than 25 *F below the flash point of the operating vacuum.

    3) Very high temperature condensate can cause cause cavatation damage to condensate pump impellers and vacuum pump rotors. Severely hot condensate may prevent a condensate pump from pumping and require a special "Two Foot NPSH" type pump. This pump uses a conventional centrifugal impeller along with an upstream axial flow prop and intermediate straightening vanes to handle the very hot condensate. Special high temperature seals are also needed to prevent early shaft seal failure.

    Condensate temperature plays an important role in pump life and performance and should always be considered when troubleshooting a pumping problem.
    Dennis Pataki. Former Service Manager and Heating Pump Product Manager for Nash Engineering Company. Phone: 1-888 853 9963
    Website: www.nashjenningspumps.com

    The first step in solving any problem is TO IDENTIFY THE PROBLEM.
    Jackmartin
  • SWEI
    SWEI Member Posts: 7,356
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    Excellent info. Those old systems with the radiators in the condensate line may have been on to something. A few feet of fin-tube would surely cost less than an upgraded pump?
    MilanDJackmartin
  • Pumpguy
    Pumpguy Member Posts: 663
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    @SWEI, Yours is a modification I frequently suggest. A building that has a lot of domestic hot water usage can install a shell and tube heat exchanger in the return line and use the hot condensate to preheat the DHW.
    Dennis Pataki. Former Service Manager and Heating Pump Product Manager for Nash Engineering Company. Phone: 1-888 853 9963
    Website: www.nashjenningspumps.com

    The first step in solving any problem is TO IDENTIFY THE PROBLEM.
    SWEIJackmartin
  • Billo
    Billo Member Posts: 6
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    Which is the lesser of 2 evils. Cold water feed or hot. My mechanic changed my feed to hot when he put in the new boiler.
  • Abracadabra
    Abracadabra Member Posts: 1,948
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    Billo said:

    Which is the lesser of 2 evils. Cold water feed or hot. My mechanic changed my feed to hot when he put in the new boiler.

    imho, cold water feed is better, properly piped into wet return header
  • Larry_52
    Larry_52 Member Posts: 182
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    Pumpguy said:

    3 comments:

    1) A very high pH, say much above 10 or so, is corrosive to bronze and copper; especially bronze impellers and rotors in condensate and vacuum pumps. This is why when we sell a vacuum pump to a power plant for main condenser vacuum service, it must be "all Iron" construction. In a power plant you can often experience an Amonia smell, which is from the Hydrazine or other similar alkaline boiler water treatment chemicals..

    That statement is misleading. The pH of above 10 does not by itself drive the corrosion of bronze or brass. It is a strictly all volatile treatment with ammonium hydroxide that introduces NH3 to any copper bearing metal and corrodes by reducing the copper. A high pressure power plant using only caustic or equilibrium phosphate or cordinated phosphate treatment would not have the copper corrosion issues you mention. I have never heard nor recommend any house hold boiler treatment with ammonia hydroxide as it would, besides corrode any copper like the vents, but smell like someone poured windex out in every room.

    Canucker
  • Jackmartin
    Jackmartin Member Posts: 196
    edited October 2017
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    Great advise. As for the kids attending college for courses that will never lead to a career you are correct. My youngist son attends the U of M and he is a really good mathmatican his training in computer science and math makes him an exceptional observer. He sees things in a equation based way and I always take him with me if I have a difficult control problem he reads the information and comes up with the correct ratios for air intake exhaust or any other parameter the system uses. I am glad the boys ( my other son is an is an electrical engineer) inherited their mom's brains. As far as cooling the condensate down for DHW that will cool the condensate down and as Dan said cooler water adsorbs more co2 therefore you are producing more carbonic acid he wants you to insulate the pipes to prevent absorbtion of co2 back into the return water. All the best Jack Winnipeg Manitoba
    Henry
  • jumper
    jumper Member Posts: 2,289
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    Pumpguy said:

    3 comments:

    1) A very high pH, say much above 10 or so, is corrosive to bronze and copper; especially bronze impellers and rotors in condensate and vacuum pumps. This is why when we sell a vacuum pump to a power plant for main condenser vacuum service, it must be "all Iron" construction. In a power plant you can often experience an Amonia smell, which is from the Hydrazine or other similar alkaline boiler water treatment chemicals.

    2) On 2 pipe vacuum return systems, high condensate temperature is detrimental to vacuum pump performance. Our recommended maximum returning condensate temperature is 175 *F, or be less than 25 *F below the flash point of the operating vacuum.

    3) Very high temperature condensate can cause cause cavatation damage to condensate pump impellers and vacuum pump rotors. Severely hot condensate may prevent a condensate pump from pumping and require a special "Two Foot NPSH" type pump. This pump uses a conventional centrifugal impeller along with an upstream axial flow prop and intermediate straightening vanes to handle the very hot condensate. Special high temperature seals are also needed to prevent early shaft seal failure.

    Condensate temperature plays an important role in pump life and performance and should always be considered when troubleshooting a pumping problem.

    Informative but I've seen exactly opposite situation. The boiler feed is heated to degas it. Then of course the problem you describe arises. I had clients who tested various sorts of low NPSH solutions.