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Lowering Steam Pressure Create More Condensate

A facility I work at wants to lower the High Pressure Steam pressure down from 140psi eventually down to a working pressure of 110-100 psi to run throughout hospital campus as a cost savings. An engineer said that doing so would create more condensate. I’m not sure how that would be possible. Can anymore tell me if this is possibly true? I’ve been working on this same system for 10 years and can not figure out how this could be true. Maybe I’m missing something.

Thanks

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 11,987
    Steam pressure has nothing to do with it. Condensate is measured in lbs of condensate/hour. Since a gallon of water weighs about 8.4 lbs (changes slightly with temperature), the hotter the water the less it weighs/pound but the steam it is condensed from is also hotter and since 1lb of steam=1 lb of water at the same temperature (it just a change of state) the amount of condensate does not really change in relation to the steam it is condensed from.

    What does change is the BTUs/lb of steam. High pressure steam is hotter than low pressure steam temperature wise BUT the only thing that does any work is the latent heat (change of state) so the btus/ lb of steam is lower for high pressure steam than low pressure steam.

    The lower the pressure that the steam is produced at the cheaper it will be to generate steam. Steam at 1psi is cheaper than 100psi steam so lowering the steam pressure =cost savings

    But

    There are other issues

    1. Boilers operating at 140 probably have 150 psi safety valves. You cant just lower the operating pressure, ASME code would require the safety valves be changed.
    2. Steam traps are selected at a design pressure differential. So traps selected at your current pressure say 140 out and 10psi return line pressure (say 130 diff) may not be large enough at 100 psi diff
    3. Same thing goes for the steam and condensate piping. High pressure steam can use smaller pipe than low pressure steam to carry the same load
    bud597