180 GMP with a 100 PSI automatic nozzle 200 ft of 1.75 (that Is 1 3/4) Factoring in friction loss of the hose and the Engines Pre-Connected plumbing (that is a PUMPER) the pressure is 225 at the pump and the nozzle you fight fires with the 15/16 smooth bore with is a 50psi tip at 186GMP same hose same plumbing 175psi at the pump with .5% (that is 1/2%) Class A foam from the Foam Pro.
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Thread: What PSI do yall use?
04-14-2001, 08:25 PM #21lti75Firehouse.com Guest
04-19-2001, 04:09 AM #22onycsFirehouse.com Guest
180 gpm automatic nozzle at 100 psi for 200' of 1 3/4" line you should run around 180 psi engine discharge pressure. 225 is about 45 psi extra friction loss. Either your calculations are wrong or you have some lowsy pre-plumbing or bad hose. I would hate to be the nozzleman on the end of that hose. For 186 gpm 15/16" solid bore you should be around 135 psi engine discharge. Again that is a great deal of extra if you are at 175 psi. Just a thought.
I agree with the comment earlier though. Book knowledge can get you into trouble. It is important to understand hydraulics but you should also understand what your nozzleman needs to manuever the hose. A stream is only as good as it is manueverable. I usually start my guys out 10-30 psi lower than the hydraulic math says then increase it when they ask for it. This works great for our department.
04-19-2001, 04:50 PM #23lti75Firehouse.com Guest
Roger, you are right that the plumbing is poor on this rig, and you proved the point that no two rigs are the same; nor can you assume that both crosslays are plumbed the same. The point is, each pre-connect needs to be flow tested, the way it is done around here is a smooth bore and a pitot gauge the neighbors have a TFT flow meter the same hose and smoth bore on a crosslay on our Eng. 3 is pumped at 155 psi for 186 gpm. Take care of your crew and your rig STAY SAFE.
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