I think you mean to say the main purpose is to avoid entrained air from entering the pump, especially when the tank level has become low. The pump might act like there is cavitation but it would be more the result of entrained air than having flow turbulence near the suction. Turbulence at the suction prevents a vortex from forming, which ironically does pipe air down into the pump suction. At some degree turbulence is a good thing. I wonder how turbulent the water would have to be as it enters the suction before all the required suction piping on the way to the pump cannot straighten it out enough for proper performance and even if it practically possible to create that condition.
Allan Seidel St. Louis, MO > On Feb 28, 2019, at 10:23 AM, Prahl, Craig/GVL <[email protected]> wrote: > > Of the most recent tanks we’ve done the refill nozzle is on the outside of > the tank, located high and was on the physically opposite side of the tank in > relation to the suction flange and these were very large volume tanks. > > The reason being that in a low volume scenario with tank refill occurring > while the fire pump was drawing from the tank, in-fill water flow could > cause turbulence at the suction and result in pump cavitation. Now the > argument could certainly be, what is the acceptable separation distances in > tanks between the suction and refill points since they come in various > diameters. > > Craig Prahl | Jacobs | Group Lead – Fire Protection | 864.676.5252 | > [email protected] <mailto:[email protected]> | www.jacobs.com > <http://www.jacobs.com/> > > From: Sprinklerforum <[email protected]> On > Behalf Of Kyle.Montgomery > Sent: Thursday, February 28, 2019 10:42 AM > To: [email protected] > Subject: [EXTERNAL] Suction Tank Question > > NFPA 22 states the following: > > 14.4.10.1 Pipes for the automatic filling of suction tanks shall discharge > into the opposite half of the tanks from the pump suction pipe. > > Does that mean that the fill line has to be directly across (opposite) the > tank from the pump suction? If I’ve got a tank with a diameter of 90 feet, do > I really need to run the fill line all the way around to the other side or is > there an acceptable minimum distance? It seems like overkill to require the > fill line to be 90 feet away from the suction. I mean, if it was a small tank > with a diameter of 20 feet, then only 20 feet away would be acceptable, right? > > Any thoughts? > > Kyle Montgomery > <image001.png> > Aero Automatic Sprinkler Co. > 21605 N. Central Ave. > Phoenix, AZ 85024 > Direct: 623.580.7820 > Cell: 602.763.4736 > [email protected] <mailto:[email protected]> > > > > > NOTICE - This communication may contain confidential and privileged > information that is for the sole use of the intended recipient. Any viewing, > copying or distribution of, or reliance on this message by unintended > recipients is strictly prohibited. If you have received this message in > error, please notify us immediately by replying to the message and deleting > it from your computer. > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
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