cvg, in this case a water main extension is required which they will pay for and deed over to us, so in this case, our design standards affect the water main extension cost (to them). If we allow them to install an 8-in main knowing that their pump would create velocities of 12-15 ft/s in our...
Thanks for your input, KoackCSR! In particular I was more concerned with pump shutdown. In other instances, we have experienced severe hammer and customer property damage from fire hydrants being closed too quickly, so its not beyond the realm of possibility based on what we've seen.
I can evaluate pressure drop and our system has no problem providing, in most cases, while maintaining 20 psi residual. The main concern was the potential for water hammer in our system when stopping their fire pumps. Also, this is for fire flow, not typical system demands. Thanks for the...
We have a maximum velocity limit of 10 ft/s used as guidance for sizing water mains in our system, which includes fire flows. It seems that when this topic is discussed, its with regard to the design fire demand. My question/concern is with regard to if a building needs a fire pump. Per NFPA...
Whats the largest water system, in MGD, that you have personally either designed or done an extensive hydraulic evaluation on that does not need elevated or ground storage?
So we tried a scenario where we slowed the valve closure down to take about 8 minutes to close from 30% to closed and there was no transient. Pressure dipped slightly to about 55 psi before bouncing back to 65 psi when feeding from the tank. I say its successful! Thanks again for the tips...
LittleInch,
Our logger and SCADA clocks aren't synced so I cant get an exact overlay (they are a few minutes off), but I am assuming the vertical drop is where the valve goes to '0'. The falloff begins about 15 seconds before that at which point the valve is anywhere from 10% to 25% open (its...
I deleted the other post. Wasnt sure if this was the right forum for hydraulic questions. Guess it was! The butterfly is already reduced smaller than the line size to take that into account. Guess it still needs some tweaking. Thanks!
LittleInch,
As you can see from the sketch, the tank is not a flow through configuration, but is fill/drain, so we need to cut off supply to lower pressure and allow the tank to drain for water quality reasons. We could possibly find a scenario where we just throttle back the valve enough to...
hydrae,
Thanks very much for your desktop analysis! About 4 miles is a straight run and about 2 miles looped. Its ductile iron pipe, so your 6 mile estimation is spot on. I will definitely look closer at the valve closure speed.
To answer your question, there is no spike when filling...
Attached is a sketch of the zone. Reservoir is one line in/out but located off of the mainline (flow can bypass it when filling).
Actuated valve is located on the plant site so its within a 1,000-ft of the pump station. Pump station is pressure controlled to maintain discharge pressure and...
