1. #1
    Member

    Join Date
    Aug 1999
    Location
    First Strike Technologies, Inc.
    Posts
    72

    Default Measured or Calculated Flow?

    I'm curious as to how many people are actually measuring their flows versus calculating them.

    For those that are measuring them, were you flowing what you expected or not? Did you discover any problems, such as excessive pre-connect FL or bad hose?

    For those not measuring them, how are you ensuring your compliance with the NFPA guidlines for a required flow of 300-gpm minumum, assuming your department follows NFPA guidlines?

    It seems that in my travels flowing water all over the country there is still a great number who depend on calculations, which do not account for crappy plumbing, thus lower than expected flows.

    A recent test reflected 50-psi of FL in the plumbing of a brand new Quint for a flow of only 200-gpm.

    Looking for your input.

    Thanks
    Last edited by KirkAllen; 03-08-2003 at 01:53 AM.
    Kirk Allen
    First Strike Technologies, Inc

  2. #2
    Forum Member
    Bones42's Avatar
    Join Date
    Mar 2001
    Location
    Pt. Beach, NJ
    Posts
    10,694

    Default

    Kirk, we went with the "measured" method and kept it KISS. We used our tank size (450gal) on one truck and tried different pressures on our 1 3/4" hose. We attempted to get the tank empty in 3 minutes. That "should" leave us at 150gpm roughly. We then followed this procedure with out other trucks and now know our Preconnect pressures.
    "This thread is being closed as it is off-topic and not related to the fire industry." - Isn't that what the Off Duty forum was for?

  3. #3
    Junior Member

    Join Date
    Nov 2000
    Location
    Moncton,NB,Canada
    Posts
    17

    Default

    Kirk
    What method would you recommend we use to determine flows? We recently tried to determine exact pumping pressures for our handlines and first did the mathematical calculations for the attack lines then tested them using a flowmeter from TFT (small palstic screw on type). The results were quite close to the calculations but we did find some differences with certain lays.
    What does the NFPA recommend?
    Brian

  4. #4
    Member

    Join Date
    Aug 1999
    Location
    First Strike Technologies, Inc.
    Posts
    72

    Default

    Brian,

    I believe that the best way to determine flows is with a calibrated UL listed flowmeter and inline pressures gauges. FRC is the only company that makes a UL listed flowmeter. The spring loaded site gauge flow devices can not be calibrated in the field and over time are not accurate.

    NFPA guidlines only state that the evaluator shall determine that effective pressure and flows are provided at each nozzle. The only way to do this is with flow meters, and inline pressure gauges. If your using smooth bores all you would need is a handheld pitot and use the physics formula to determine flow.

    I suggest using aninline pressure gauge at the hose connection in the crosslay, an inline pressure gauges at the nozzle, and a UL listed calibrated flowmeter on the intake side.

    With the flowmeter on the intake side ensure that tank to pump is closed, tank fill closed, and cooling/recirculation line closed. That way the water coming in is only going to one place, the nozzle being used.

    The hose connection pressure gauge will reflect a measured pressure for what is going into the hose/out of the plumbing. Subtract this number from the panel gauge reading and you now have a measured FL for your plumbing. This information is more of an educational item that can be used for future specs. on your engines unless you find that its excessivly high. I have seen plumbing FL as high as 110-psi. If you find excessive plumging loss let me know. There are some simple fixes for that problem.

    The pressure gauges on the nozzle is a MUST. This is an absolute necessity to determine if the nozzle is operating within its limits.
    This gauge pressure can also be subtracted from the hose inlet pressure with the result being your MEASURED FL in the hose for whatever flow you have.

    Hope this helps.
    Last edited by KirkAllen; 03-11-2003 at 12:06 AM.
    Kirk Allen
    First Strike Technologies, Inc

  5. #5
    MembersZone Subscriber

    Join Date
    Aug 1999
    Location
    Winfield, IL
    Posts
    137

    Default Measured!

    We have flow tested each and every line off all of our engines and built pump charts for each one. Before we did that we used the same pump pressures for all of our engines. Once we did the flows with a flow meter and we saw how much of a differance between there was using measured vs. calculated flows everyone was shocked.

    I would suggest that everyone flow test their engines.

    Patrick

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts

Log in

Click here to log in or register