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15 psi high pressure steam?

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Jayymayy95
Jayymayy95 Member Posts: 2
in Strictly Steam

What is the deciding factor of 15psi being the number that separates high pressure and low pressure steam? My teacher gave us a table of properties of saturated steam and told us the answer would be found on the sheet. Thinking it has something to do with the volume or 15psi being over 14.7 (atmospheric) pressure

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  • Jamie Hall
    Jamie Hall Member Posts: 23,418
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    Before we go any farther… are we talking 15 psig (gauge) pressure here, or 15 psia (absolute) pressure. It rather makes a difference.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Mad Dog_2
  • Jayymayy95
    Jayymayy95 Member Posts: 2
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    15 psi gauge

  • Jamie Hall
    Jamie Hall Member Posts: 23,418
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    O. Then the fact that the number 15 in regard to the dividing line pressure happens to be similar to the absolute presssure of the atmosphere is quite irrelevant.

    What is relevant is that there needs to be a definite line for the various code requirements for high pressure steam — which is quite lethal in an enclosed space, and which can do sever harm from even a relatively small leak — and low pressure steam which, while it can still blow up under some conditions, and do a lot of damage isn't quite so hazardous.

    Why 15 psig was chosen, however, I honestly don't know. Hopefully someone here can!

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Mad Dog_2
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,544
    edited May 2
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    The National Board of Boiler and Pressure Vessels sets the parameters.

    There is also medium-pressure steam (15 -150 psig) but we stopped using that term in heating. It applies to turbines. In the heating world, we now call anything over 15 psig high-pressure steam.

    Retired and loving it.
    WMno57
  • ChrisJ
    ChrisJ Member Posts: 15,767
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    https://forum.heatinghelp.com/discussion/comment/1800837#Comment_1800837

    Do you know the history of how or why they came up with 15 PSIG?

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,544
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    it goes back to 1919, when too many boilers were exploding. That’s when the National Board was born. It was a good thing.

    Retired and loving it.
    pecmsgSuperTech
  • jumper
    jumper Member Posts: 2,282
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    Talking through my nose here. Factor of safety test low pressure boiler at twice 15 psia. Well if it passes then 15 psig is probably okay? I've seen "atmospheric boilers" operate at over 10 psig indefinitely. Very often you see heating boilers operate at such high pressures to "blow the condensate through traps". Intelligent experienced folks can have misconceptions.

  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,095
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    HP steam needs to be worked on like High Voltage wire...Like your life depends on it. Mad Dog

    Consulting by Mad Dog & Matt Jr.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,605
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    HP steam is used for one of two things . Distribution or temperature.

    Distribution like in hospitals or for district steam and industrial plant where the steam lines are very long you can use much smaller pipe with HP steam

    Temperature some processes need more heat than 15 psi steam can provide. Kitchens, sterilizing, brewing, drying etc.

  • Sylvain
    Sylvain Member Posts: 146
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    It seems in 1900 in Belgium, the "effective pressure" (gauge pressure) for domestic heating was limited to "1/4 d'atmosphère " which was 3.673…. psig.

    "low pressure" is actually 1/2 bar or 7,251887 psig. The testing pressure is 1.5 bar.

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