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  • Users: Xalii
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  1. Xalii

    Surge Pressure due to sudden valve closure

    The value of the head surge, assuming a steel pipe, is about 25 bar, then I guess the software assume that the pump is a dead end and thus double the surge at the reflection giving the ~50 bar (or 200 tonnes for 28 inch). How correct is that is another question, if there is a quick NRV is might...
  2. Xalii

    Flow rate in a gravity fed water pipeline

    If I am not mistaking, a 450 OD, PE100 PN8 is a 407 internal diameter. With this diameter if you want to avoid negative pressure in your pipe, the maximum flow you can pass is about 180 l/s. The maximum flow for this pipe would be about 230 l/s but only if you have a flat (or concave) profile...
  3. Xalii

    Flow rate in a gravity fed water pipeline

    In deed the more flow you have, smaller can be the difference of head to have a requested minimum velocity. Attached you can find those values for a min velocity of 0.5 m/s. With this velocity you will still need to tackle the problem with air blockage. Would be good also to clarify which type...
  4. Xalii

    How would you estimate peak water demand?

    I think we have to be careful when we are speaking about peaking factor. There is two different things: 1) the peak flow of the daily average demand of a large population that can range from 150% to 400%. This figure is used to design main pipes and tanks serving at least 200 to 500 households...
  5. Xalii

    How does the specific gravity affect the pressure output from a pump?

    For a given system, if you only change the density of the fluid, but not viscosity, the flow will almost be the same (a change might come from the specification of your motor, but not from your pump). I will try a simple explanation: if you don't change the geometry, nor the losses, you will...
  6. Xalii

    Pump Seizing

    From my experience, the biggest problem for centrifugal pump is the notion of "safe side". The working point should be as close as possible to the BEP (best efficiency point), but often engineers tends to exaggerate head losses, and take some "safe side" for the head, and the pump is...
  7. Xalii

    Find an object in a class collection

    Thanks a lot Zigenz, this is exactly what I wanted. I have found some further information on the Web, now I can proceed to use my class object. Best regards
  8. Xalii

    WESTCO PUMPS

    Application Boiler Feeding - Water supply to High Building, Temporary water supply Features The horsepower of the motor is decided by the boiler’s operating pressure (kg/㎠). The water is supplied at a temperature range from 90℃ to 95℃. (only when Fu-jet is installed) Compact and easy to install...
  9. Xalii

    Find an object in a class collection

    I have defined a class module : clPipe with several properties. I have then defined a collection aLinks to contains my pipes I would like to know if I can define the stID as a default Value and then be able to look for an item of my collection so that I can find quickly a item of my collection...
  10. Xalii

    maximum water depth / diameter in open channel flow

    At 67% depth you are at 80% of the max flow. At 75% depth you are at 91% of the max flow... (max flow is at 82% depth) Then passing from 67% to 75% you divide by 2 the security margin... With the forecast of stronger storm in coming years, I let you make the calculation of damage versus...
  11. Xalii

    Booster Pump Schematic

    Usually you have two possibilities: 1) use a ground storage tank with a booster pump and a pressure vessel to smooth the flow and without PRV, in this way the water can be protected form the sun and would be cooler. 2) use an elevated tank with a gravity flow distribution (possibly with PRV)...
  12. Xalii

    Stop time for a pump after an electrical shut down

    Thanks for this Lyle, but I will try to check (when I am back home, in a month time) with the university were I have studied as they are specialized in hydraulic machines. Best regards
  13. Xalii

    Stop time for a pump after an electrical shut down

    Dear Lyle, I guess with a short steel pipe, your assumption is valid, which is not my case however, the equations are quite close as you are calculating losses in the system and I should calculate the one of the pump. Cam you share the "standard solution" so see if they could be applicable in...
  14. Xalii

    Location of Strainer and its orientation

    The problem of the Y strainer is that is getting quickly choked, even more if you install it backwards. A basket strainer would be more adapted but it usually only installed horizontally, maybe you can find one for vertical flow... I would still suggest to try to install an intake screen or...
  15. Xalii

    Stop time for a pump after an electrical shut down

    Thanks to all for your valuable inputs. For precision, my aim is to demystify a bit the water hammer phenomena and to develop a spread sheet able to calculate simple cases, where the project doesn't worth to ask a special transient analysis. Basically in simple conditions, the end section of the...
  16. Xalii

    Stop time for a pump after an electrical shut down

    Interesting and nice approach, would be a very neat result. Unfortunately, according to my understanding the "block" assumption is abusive as what I want to calculate is the water hammer, and in your case we assume that the water is in-compressible? Let me know if I am wrong.
  17. Xalii

    Power factor/efficiency measurement of motor

    I have the impression you are mixing your powers. Pelec: W=1.73*V*I*PF= 2.5 kW (pf for this size, 2 poles, should be ~0.86) cf attached doc Pmec = Pelec/effmotor = 2 kW (eff motor this size 2 pole should be 79%) Then Phydro= Pmec/effpump Phydro 2.i*746=1.57 kW Therefore I conclude that you...
  18. Xalii

    Stop time for a pump after an electrical shut down

    Does it mean that the main factors are the RPM and the diam of the impeller ?
  19. Xalii

    Stop time for a pump after an electrical shut down

    That's what I fear... 8<((( Usual setup is a pipe dumping into an open tank... Any other suggestion ???
  20. Xalii

    Stop time for a pump after an electrical shut down

    I am not looking for a specific case but a formula for general situation, we could limit the cases with the following specifications: L: between 500 and 5000 Pipe Diam from 75 to 300 mm (PE or PVC) RPM: 1450 & 2800 Q: flow from 15 to 350 CMH Specific speed (Ns) between 20 and 60 (low head or...

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