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  • water pressure and volume

    i have a situation at a surgical center that is a catch 22

    the center purchased a rebuilt 1200# sterilizer that uses a steam generator that sterilizes the surgical instruments. the problem is the rep had "his people" connect it to the existing location of the older smaller unit. the steam generator has a pressure booster built in to keep up with demand. the actual sterilizer uses another source of water to create a vacuum in the sterilizer chamber. it calls for 8-10 gallons per minute at 50psi residual pressure. the 3 story large medical complex has a 3'' water main with 90psi inlet side and 60psi on the outlet side of the regulator station. seems low as the total height is approx. 40' for the top suites. the sterilizer is on the ground floor, 60psi static. the water feed is only a 1/2'' line with a reduced pressure back flow preventer feeding the unit.

    since i can't run this machine to actually get a flow test and a static test without the rep being there, how would i figure the max pressure and volume without running the machine? i do own a real nice digital flow meter and pressure gage. i guess i can disconnect the 1/2'' line and divert it into the floor sink. i also think that the building pressure is set way to low.
    is 8-10 gpm with 1/2'' pipe through a rp valve possible with only 60 psi and a drop of 10psi max? the water is used to pull a vacuum using a venturi principal. the machine is only pulling 19'' of mercury and needs 25'' of mercury to operate.

    i know there are a lot of variables, but is it just asking too much with these set numbers. if the building ups the regulators to 70psi, can i get 8-10 gallons in your opinion.

    i have not tried any real test yet. just a static pressure reading.

    the rep who sold this machine to the center, didn't take the water requirements into account. they already spent good money on a 3 phase 50 amp power supply to run the steam generator.


    i know there are a lot of unknowns, but the doctor is on the verge of sending it all back. i told him i will see what i can do without the help of the building issues or rep.

    so here are the questions:

    is 8 to 10 gallons possible at 60psi with a drop of only 10psi and residual of 50psi.

    will upping the regulators to 70psi fix the problem? this will affect the entire 3 story complex and i don't know what the extra pressure can affect in the rest of the suites and bathrooms.

    or is running a larger 3/4'' line with a new rp valve the only solution?

    what would you do?

    thanks for your suggestions.

    let the debate start

    rick.
    phoebe it is

  • #2
    Re: water pressure and volume

    will the equipment be damaged if you test it at the increased water pressure, without the proper volume. If not , I would start there. If it can be , I would over size and be done with it. Also even if you increase the psi ,will it meet peek demand if all the suites are running.
    THE GLASS IS ALWAYS HALF FULL

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    • #3
      Re: water pressure and volume

      the minimum requirements call for 8 to 10 gpm at 50# residual pressure. boosting to 70#static should be fine. it's the 8-10 gpm that flows through a venturi to create the vacuum.

      what gets me is that the surgical center has piped in med gas along with vacuum piping. why are they wasting water just for vacuum. why not just pipe med. vac. into the unit, or purchase a unit with a vac. connection

      rick.
      phoebe it is

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      • #4
        Re: water pressure and volume

        Rick,

        I would make the Rep meet you out there to eliminate the back and forth. I'm sure the unit cost enough that they would be glad to meet you out there. Also remember the 10 psi at the RP is for a new unit to pass the USC test not necessarily the real drop.

        Mark
        "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

        I never lost a cent on the jobs I didn't get!

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        • #5
          Re: water pressure and volume

          I'm confused.

          This sterilizer has a pressure booster to make steam but not on the side that needs 8-10 gpm through a 1/2 connection?

          Just curious...how does it discharge the water? does it dump 200 degree water down a floor sink?

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          • #6
            Re: water pressure and volume

            Originally posted by plumberscrack View Post
            I'm confused.

            This sterilizer has a pressure booster to make steam but not on the side that needs 8-10 gpm through a 1/2 connection?

            the steam generator has the pressure booster. doesn't make sence, but it's there.

            Just curious...how does it discharge the water? does it dump 200 degree water down a floor sink?
            i would think that the generator would auto flush x amount of hours after it shuts off. just like a small unit would do in a shower.

            rick.
            phoebe it is

            Comment


            • #7
              Re: water pressure and volume

              Rick,

              As time permits today, I will try to explain my answer to your question in more detail.

              To flow 9 gpm of water through a 1/2" pipe, you will need a velocity of about 12.5 fps (feet per second), thats insane.

              The short answer to your question is: No, you dont even want to attempt this by raising pressure. You will end up eroding the pipe.

              Not trying to be short, but will try and explain the formulas later in the day.

              To keep velocities low, I would recommend that you run a 1" line to the unit. I know this sound big, but as a mech. engineer, I am always in the "CYA" mode.

              Also, making a quick calculation, I came up with a pressure drop of 78 psi to flow 9 gpm through a 1/2 inch pipe at 12.5 feet per second.

              Regards,
              Last edited by biscuit; 05-17-2007, 07:50 AM. Reason: I am stupid and typed too darn quickly, FUBAR some designations.

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              • #8
                Re: water pressure and volume

                biscuit, thanks for the quick response. looking forward to the entire formula. thanks for the help.

                rick.
                phoebe it is

                Comment


                • #9
                  Re: water pressure and volume

                  Originally posted by PLUMBER RICK View Post
                  the center purchased a rebuilt 1200# sterilizer that uses a steam generator that sterilizes the surgical instruments. the problem is the rep had "his people" connect it to the existing location of the older smaller unit.....

                  i can't run this machine to actually get a flow test and a static test without the rep being there...

                  the rep who sold this machine to the center, didn't take the water requirements into account...

                  the doctor is on the verge of sending it all back....

                  i told him i will see what i can do without the help of the building issues or rep...

                  what would you do?
                  I think I'd contact the upper management of the outfit that sold the unit and scream bloody murder. This is inexcusable. A complaint should be made to the Board of Consumer Affairs in Sacramento, too.

                  There is no way that this doctor should have to pay a plumber to do what should have been done right in the first place.



                  How long ago was it installed? What does the warranty say?

                  Al
                  America:
                  The land of the free
                  Because of the brave

                  Comment


                  • #10
                    Re: water pressure and volume

                    al, all fixed. installed a 3/4'' line from a 2'' main in the ceiling.

                    then the 2'' floor sink was too small to handle all the water.

                    took care of that too.

                    the dr. paid me real fast. don't know if the dr. was repaid for this work

                    in fact they emailed me 2 days ago thanking me and saying all well so far for 2 weeks

                    rick.
                    phoebe it is

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