Fine and good into you have a fire with only one had that activates. Therefore I say unto you, Take no thought for your life, what ye shall eat, or what ye shall drink; nor yet for your body, what ye shall put on. Is not the life more than meat, and the body than raiment? MAT 6:25
Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. JHN 3:5 > On Jan 17, 2017, at 3:16 PM, Steve Leyton <st...@protectiondesign.com> wrote: > > Okay, great and wonderful but you what that does is flatten the curve and > potentially makes higher flow rate residual pressures plot HIGHER than they > would otherwise be. Soooooooo … as a designer-of-record charged with (among > myriad other things) anticipating worst case scenario, methinks it makes > sense to keep as much tilt in that flow data curve as possible. > > Steve L. > (My opinion only, based on numerous cases served as an expert witness and > somebody who buys a lot of liability insurance every year.) > > From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] > On Behalf Of Dewayne Martinez > Sent: Tuesday, January 17, 2017 1:13 PM > To: sprinklerforum@lists.firesprinkler.org > Subject: RE: Static pressure after backflow preventer > > Ames got back to me and said “Yes there is a pressure loss at static flow. It > will depend on which type backflow youre looking at. A RPZ will usually show > a 10-15 PSI drop. A double check is usually 8-10.” > > > From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] > On Behalf Of Brad Casterline > Sent: Thursday, January 12, 2017 12:51 PM > To: sprinklerforum@lists.firesprinkler.org > Subject: RE: Static pressure after backflow preventer > > Matt, > > I think your example of sliding friction is excellent. Pressure is force > divided by area, and force is mass times acceleration. > With sliding friction the force required to give a mass an acceleration is > greater than the force required to keep it going a constant velocity. > With fluid friction viscosity comes into play and is actually related to > sliding friction in that the constant force required to slide a steel plate > across the surface of a fluid, imparting a certain constant velocity to the > plate is a measure of the viscosity of the fluid. > > But the question is regarding friction loss when the flow is 0 GPM, and at 0 > GPM the velocity of the water = 0. > Near the end of what I pasted you see: > mgh=1/2mv^2. > This is the Conservation of Energy formula for going from Potential Energy > (static), to Kinetic Energy (residual). > In a closed system no mass is gained or lost (it is the same on both sides so > it cancels out), so, > h=v^2/2g, and, > v=SQRT(2gh). > But if the velocity is 0 on both sides the only way to get a different force > measurements is with different h measurements (elevations). > > I know you and others know all this, so please excuse my didactic tone. > > Brad > > <image001.jpg> > <image002.jpg> > > From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] > On Behalf Of Matt Grise > Sent: Thursday, January 12, 2017 6:33 AM > To: sprinklerforum@lists.firesprinkler.org > Subject: RE: Static pressure after backflow preventer > > Of course – if you are super close to a pressure limit – the BFP might also > lock in some unusually high pressure spike that occurs in the system. Then > the sprinkler system could sit around locked at a pressure that is greater > than even the typical measured static. > > Matt > > > From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] > On Behalf Of Matt Grise > Sent: Thursday, January 12, 2017 6:30 AM > To: sprinklerforum@lists.firesprinkler.org > Subject: RE: Static pressure after backflow preventer > > Just to think out loud – I don’t have a perfect understanding of how very low > flow works through backflows… but: > > It seems like the system static that is locked in is usually pretty close to > the flow test static. I wonder if the noticeable pressure loss to initially > open the BFP, that goes down once flow starts, if that pressure drop might > approach zero as the flow goes from positive back to zero. > > That is – the pressure drop seen at a flow that is just barely over zero > depends on whether you are approaching that flow from zero, or from [more > than zero]. > > For example: if you slide a block across a table – the force it takes to move > the block at a very low speed will depend a lot on whether you start from a > standstill, or a faster speed. (that illustrates a different principle, but > shows how the approach could change) > > Thoughts? > > Matt > > From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] > On Behalf Of Roland Huggins > Sent: Wednesday, January 11, 2017 6:07 PM > To: SprinklerFORUM > Subject: Re: Static pressure after backflow preventer > > I'm flying by the seat of my pants (with no lights) but until I prove to > myself otherwise (or am beat into submission by the technical committee), I > don’t see why we should beat ourselves up and default to what ever seems to > be the most conservative. Our supply curve is a straight line relationship > from static to some lower residual pressure. We now incorporate a device > that has a crazy high initial pressure loss that then drops back into a more > normal curve. In looking at SYSTEM DEMAND are we well served by ignoring the > actual available pressure that was otherwise lost due to accounting for a > wiggle at the front end. > > For now, I’ll stick with my mantra: Lead the way, Mr. Custer. I’m right > behind you. > > > Roland Huggins, PE - Senior VP Engineering > American Fire Sprinkler Assn. > Dallas, TX > http://www.firesprinkler.org > > Fire Sprinklers Saves Lives > > > > > On Jan 11, 2017, at 12:27 PM, Dewayne Martinez > <dmarti...@total-mechanical.com> wrote: > > I have used the static without the backflow loss in the past but I noticed > with the SprinkCad software I am running it uses the mfg curves and it was > showing less static than I had figured. If I take into account the BFP loss > I can eliminate 6 pressure reducing hose valves…..Looks like I will err on > the side of caution and design them in. > Thanks, > Dewayne > > > _______________________________________________ > Sprinklerforum mailing list > Sprinklerforum@lists.firesprinkler.org > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
_______________________________________________ Sprinklerforum mailing list Sprinklerforum@lists.firesprinkler.org http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
