![]() It then moves the baffle in or out to maintain a particular tip size necessary to keep the nozzle pressure at 100 psi. The pressure-control spring senses any increase or decrease in pressure within the nozzle. A highly dependable spring, connected to the baffle that forms the discharge orifice, is balanced against the water pressure in the nozzle. The automatic nozzle uses a principle very similar to that of a pumper relief valve. This sets the flow being supplied to the proper nozzle pressure and correct velocity for maximum extinguishing capability. With an automatic nozzle, the discharge orifice continually adjusts depending on the flow to the nozzle. ![]() Second, too much water flow creates excessive nozzle pressure making the hose line more difficult to handle and potentially jeopardizing the safety of the nozzle crew. First, inadequate flow provides a weak, ineffective stream that fails to reach the seat of the fire. There are two possible results when the conventional nozzle is not supplied with the rated or selected flow. For example, a selectable gallonage nozzle with settings of 30, 60, 95 and 125 gpm will only deliver those flows of 100 psi of nozzle pressure. In order for a conventional nozzle with a fixed opening to operate at the correct nozzle pressure of 100 psi, the proper gpm flow must be supplied. ![]() These settings correspond to a particular discharge orifice, or tip size. Teamwork, communication, experience and constant training make nozzle firefighters most effectiveĬonventional fog nozzles have a fixed or selectable gpm setting.
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