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  1. Bjegovic

    Volute design

    labirynth rings serve as seal between impeller and the casing, reducing the loss of fluid. are you designing a new pump? or you are an user trying to modify the existing one? in any case, this is a very complex and interesting issue, so be more specific!
  2. Bjegovic

    Flushing and Dechlorinating Large Diameter Pipe

    large qty of chlorine (water is super-chlorinated for flushing, right) will adversely affect most of biological waste water treatment plants! bisulfite ('scavanger') is commonly used on RO plants to remove active chlorine and protect membranes. this sounds like the best option to me!
  3. Bjegovic

    Well Pump Control & Surge Protection

    first of all, transient analysis shall be done independently of the pump operating mode in the design stage, considering worst case scenario (stop can occur due to power failure, for example - don't expect that VFD will help you there). For this system, you shall go with start/stop mode to...
  4. Bjegovic

    Well Water : Manganese Removal

    increasing ph up to cca 9 will give immediate good results. if this is potable water, high ph is not acceptable. chlorination + filtration (greensand) will work ok, but you need 3-4 times stechiometric chlorine dose for manganese. 0.02 mg/l mangane is quite low, we had this tested with Mn...
  5. Bjegovic

    Arsenic Removal/Filter

    this makes little sense because you are discharging the same water you are taking from wells. but yes, regulations can be tricky! 70 ppb of arsenic however is quite usual concentration in raw water. however, if you have to reduce it to 10 ppb prior to discharge, I reccomend 2 stage filtration...
  6. Bjegovic

    Can you control centrifugal pump flow with a flow meter?

    'The use of VFD's aren't pratical in my case because operators may not be present to adjust the pump speed'.... You can program the VFD to meet the specified set point (given that it receives pressure and flow input signals which all of them can do) so it can operate automatically. all...
  7. Bjegovic

    Effect on atm pressure for Cavitation

    not too big. don't bother to think about it in most normal applications. (hope your pumps are not on the top of the world!)
  8. Bjegovic

    Water Storage Tank - Feedpipe

    as pointed above, it saves energy if you are pumping against actual water height in the tank, instead to the top of the tank. other issue is if the pumps can stand varying head? if you don't have VFD, and pumps are pumping mostly against static head, it is not vise to put inlet on the bottom...
  9. Bjegovic

    pumping in parallel

    one big pump will probably have better efficiency than two smaller pumps delivering same Q,H; but this effect is not important compared to other design issues (proces demands, reliability...and commercial offers!) usually we consider that by increasing pump size, relative dimensions of gaps and...
  10. Bjegovic

    Shut-off pressure of pump

    last time this issue was discussed in thread 'pump cavitation' started by airbus a few days ago.
  11. Bjegovic

    How to size a Water Meter

    many types are available on the market. some thoughts from the top of my head: 1) calculate peak flows. check that the foreseen flow meter can meet min/max flow demands. having smaller water meter can save you some money (not much on that diameter) and remember that you need pipe reductions...
  12. Bjegovic

    Thermal insulation for steel potable water tanks - do we need it?

    I did some calculations and @ -25C and tank of cca 500m3, water will start to freeze after 3 days without turnover at all. since the raw well water is usually above 10C, it seems there is no problem with at least a minimal consumption. Now i have to address the problem of potential surface...
  13. Bjegovic

    Pump Cavitation

    Artisi is right. note also that 'immediate' effect of cavitation is loss of power/head accompanied with noise, vibrations, etc. but for pump itself (regarding the damage inflicted), cavitation is a long term process with cummulative effects, which may or may not be connected to loss of...
  14. Bjegovic

    Thermal insulation for steel potable water tanks - do we need it?

    Hi all. My company is dealing with water treatment and supply. We are trying to introduce above ground steel tanks for potable water, instead of most common concrete tanks that are installed below ground. The problem at hand is do we need to include thermal insullation? Climate is moderate...
  15. Bjegovic

    Holding suction after pump shuts down

    centrifugal pump? no.
  16. Bjegovic

    Double Volute vs Single Volute

    @ PUMPDESIGNER: as I was mistaking and referring my post to double suction pumps ; the explanation would be that uneven flow distribution can create axial disbalance which bearings are not designed for, leading to premature failure. (assumption is that in normal conditions double suction pumps...
  17. Bjegovic

    Double shaft deflection in a BB pump

    I am sorry that my posts (both here and in thread 407-142821 ) were confusing, ignorant and written in a hurry. I agree with in general with definitions that Artisi offered. I also have tried to give specific codes reffering to API610 (8th, 1995) of Hydraulic Institute standards (14th...
  18. Bjegovic

    Double Volute vs Single Volute

    I am sorry that my posts (both here and in thread 407-144831) were confusing since I was reffernig to double suction pumps. sorry again!
  19. Bjegovic

    Double Volute vs Single Volute

    I will try to find out how I got that information, and provide the reference. I had a similar double vs single volute problem a long time ago and i remember this as an argument against double volute pumps, but don't remember the source....
  20. Bjegovic

    Double shaft deflection in a BB pump

    my guess is: 1) BB layout is much less succeptible to deflection than overhung. 2) BB shaft usually supports double impeller (double volute pump) which very vell balances hydraulic loads in complete range of operating conditions. therefore, shaft deflection is not a big issue in BB pumps.

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