I found the formula interesting. Also, I didn't think that Brad was suggesting the fitter would modify the impeller (were you?). I assumed he was just showing that it was another possibility to explore (to be performed by pump rep). You wouldn't modify the existing impeller, but replace it with a new one.
I do know it is possible (and not entirely uncommon) to have the pump manufacturer "trim" the impeller to make small modifications to the pump curve, to dial in the pressure. Not sure if it would work for the kind of pressure differences the O.P. is looking at. If it is feasible, I think that (generally speaking) it might be considered a preferable approach to the PRV. Less parts and pieces, etc. However, the nice thing about a PRV is you can really dial in the pressure and you get that wide, flat pressure curve. But there are drawbacks as well. Kyle Montgomery Aero Automatic Sprinkler Co. 21605 N. Central Ave. Phoenix, AZ 85024 Direct: 623.580.7820 Cell: 602.763.4736 kmontgom...@aerofire.com -----Original Message----- From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] On Behalf Of John Denhardt Sent: Monday, July 16, 2018 10:36 AM To: sprinklerforum@lists.firesprinkler.org Subject: [EXTERNAL] RE: PRV after pump discharge control valve I agree with Steve. No manufacturer or Listing agency would accept this approach. This is a purely academic exercise which it my opinion has no basis for real world application. My suggestion is to move on. John John August Denhardt, P.E. Strickland Fire Protection Incorporated 4011 Penn Belt Place Forestville, Maryland 20747-4737 301.474.1136 - Office 301.343.1457 - Mobile -----Original Message----- From: Sprinklerforum <sprinklerforum-boun...@lists.firesprinkler.org> On Behalf Of Steve Leyton Sent: Monday, July 16, 2018 12:42 PM To: sprinklerforum@lists.firesprinkler.org Subject: RE: PRV after pump discharge control valve As with some of your previous posts, I've read and re-read this one and taken a few days to process it before responding. And having given this some thought, I have to ask: what is the point of undertaking this? Obviously, no fitter or service tech is going to change out an impeller - what do you think the cost of a factory-certified or an actual factory tech doing such a service might be? What cost benefit could there possibly be that justifies the hassle and risk of having someone rebuild a listed pump on site, especially when there are other "conventional" resolutions available? Unless ... you just have an uncontrollable compulsion to post equations on line? Perhaps we can (should?) change the name of this list-server to the "AFSA Sprinkler Formulae" ... Steve Leyton Keepinit Simple, CA -----Original Message----- From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] On Behalf Of bcasterl...@fsc-inc.com Sent: Saturday, July 14, 2018 1:12 PM To: sprinklerforum@lists.firesprinkler.org Subject: Re: PRV after pump discharge control valve This is very interesting Dewayne! You need a high pressure pump now--low pressure pump later, but since you have to keep the original pump you are thinking PRV on the discharge later. There might be another way: Replace the big impeller now with a small impeller later. I know how to make it work in theory but I'm not sure if it works in application, but the pump rep would. I know it works in theory because I figured out quite a few years ago how to calculate the impeller diameter based on the rated psi and rpm ONLY. I do know it is not unheard of to 'trim' an installed impeller to tamp down on the psi. v=2*pi*r*f, where, v is velocity (ft/s) calculated from feet of head (h). v=SQRT(2gh), g is 32.2 ft/s/s. r is the impeller radius (ft). f is radian/s (rpm/60). So knowing v and f, it's easy to rearange to solve for r!!! You should still install a spool piece I guess, but to pump it up only to let the air out a couple feet later never has made sense to me. Maybe Nicky in NZ knows of something in the European Code that might shed a different light? Brad Quoting Dewayne Martinez <dmarti...@total-mechanical.com>: > Is there anything that restricts the use of a PRV after the discharge > control valve on a fire pump? > > I have a ESFR storage building where I am designing to a “future” > water supply which is much higher than the existing water supply. > > The fire pump must satisfy both existing and future conditions and I > thought about leaving a space for a PRV to be installed downstream of > the pump discharge valve to account for the future higher pressures. > > Thanks, > > > > Dewayne Martinez > > Fire Protection Design Manager > > > > *TOTAL* *Mechanical* > > *Building* *Integrity* > > > W234 N2830 Paul Rd. > Pewaukee, WI 53072 > > dmarti...@total-mechanical.com > > Ph: 262-522-7110 > > Cell: 414-406-5208 > > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.total-2Dmechan > ical.com_&d=DwIGaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3b > n8etxB7nLN8OBJwQd9A&m=FU1ekxtEezMunTSmi6Q7K68HzkOxQ8TohV5jBLKF6mw&s=bx > fEUpUsyf9DVMeiFuKDDoGheRtiHWc6jtv2vKtqIWE&e= > > > > [image: A close up of a sign Description generated with high > confidence] _______________________________________________ Sprinklerforum mailing list Sprinklerforum@lists.firesprinkler.org https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.firesprinkler.org_listinfo.cgi_sprinklerforum-2Dfiresprinkler.org&d=DwIGaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3bn8etxB7nLN8OBJwQd9A&m=FU1ekxtEezMunTSmi6Q7K68HzkOxQ8TohV5jBLKF6mw&s=CnrCn1hZdkdLJl9g9My8X3gWvSN2uJ1DXkqStfBxCNk&e= _______________________________________________ Sprinklerforum mailing list Sprinklerforum@lists.firesprinkler.org https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.firesprinkler.org_listinfo.cgi_sprinklerforum-2Dfiresprinkler.org&d=DwIGaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3bn8etxB7nLN8OBJwQd9A&m=FU1ekxtEezMunTSmi6Q7K68HzkOxQ8TohV5jBLKF6mw&s=CnrCn1hZdkdLJl9g9My8X3gWvSN2uJ1DXkqStfBxCNk&e= _______________________________________________ Sprinklerforum mailing list Sprinklerforum@lists.firesprinkler.org https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.firesprinkler.org_listinfo.cgi_sprinklerforum-2Dfiresprinkler.org&d=DwIGaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3bn8etxB7nLN8OBJwQd9A&m=FU1ekxtEezMunTSmi6Q7K68HzkOxQ8TohV5jBLKF6mw&s=CnrCn1hZdkdLJl9g9My8X3gWvSN2uJ1DXkqStfBxCNk&e= _______________________________________________ Sprinklerforum mailing list Sprinklerforum@lists.firesprinkler.org http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
