What gives?īlitzfireSolo: I think that your real problem is that even if you have flow tested your deck gun plumbing with a SB and a pitot, and even if you mantain your autos properly (*coughyeahrighcough*), your auto could be regulating by 5-10psi off of normal (I believe that NFPA allows a 10% deviation - that would mean that your MS auto could be regulating at 90psi one day and 110psi the next - 20psi margin - and you would never know the difference!).Įspecially with a well-designed waterway, your deck gun plumbing should be pretty low friction loss, and 20psi could mean a pretty big difference in flow. If you open the Mosoon to 2,000 gpm something bad will happen - cavitation of some pumps, “stealing†water (a bad term in its own right), or something else. You are operating the Monsoon at 500 gpm and have other hand lines operating at 1,500 gpm (multiple hand lines, of course) for a grand total of 2,000 gpm. Consider a water supply that can deliver a maximum of 2,000 gpm. The nozzle can be operated from 300 gpm to 2,000 gpm. I am puzzled by the TFT brochure for the Monsoon nozzle where it was stated that it will not “steal†water from hand lines.
Calculate gpm using a pitot tube full#
The gauges should be recently calibrated and of high accuracy (I.e., +/- 1% Full Scale). If the monitor nozzle does not have a base of nozzle gauge, I suggest using an in-line pressure gauge at the base of the nozzle or tapping a ¼†hole at the base of the nozzle into which a pressure gauge can be attached. However, when calibrating the monitor nozzle piping for flow rates and pressure drops, larger flows are needed and thus larger diameter nozzle orifices are needed (i.e., 2â€). The base of nozzle pressure is close to the Pitot pressure when the nozzle orifice is small (I.e., 1-¼†or less in diameter). A base of nozzle pressure should be used. The Pitot pressure is a velocity pressure and the PDP is a “Normal†pressure (“Normal†in the physics sense - perpendicular to the pipe wall). The friction loss should not be determined by subtracting the Pitot pressure from the PDP. The TFT method is valid except for one point.
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